Wetland Plant of the Week #15

Batis maritima

"Saltwort"

Obligate, succulent herb found throughout coastal Florida. Leaves are cylindrical, fleshy and oppposite. Often found in mangrove swamps, tidal areas and salt marshes.

This one was photographed last week - adjacent to Wetland Plant of the Week #14 in Levy County, Florida.

Impressive morphology – I’m lichen it!

A couple of snapshots from earlier in the week showing a highly filamented foliose lichen - Parmotrema perforatum. (Found in proximity to the scorpion posted previously)

Lichens have traditionally been referred to as a prime example of a symbiotic relationship. Each lichen consists of an intimate association between a fungus and a species of algae. The algae within the lichen photosynthesize, providing food for both symbionts. The fungus protects the alga from harmful light intensities, produces a substance that accelerates photosynthesis in the algae, and absorbs and retains water and minerals for both organisms. There is physiological and ultrastructural evidence that suggests the fungus parasitizes the algae in a controlled fashion and, in some instances, actually destroys the algal cells. There are about 25,000 species of lichens known and they are capable of living in environmental conditions that kill most other forms of life.

Although lichens can reproduce sexually, they are predominantly asexual reproducers. In the latter case, small powdery clusters of hyphae and algae, called soredia are formed and cut off from the thallus as it grows. These soredia are dispersed by wind or water and take up residence elsewhere. Sexual reproduction occurs when the fungal ascomata produce spores which germinate and parasitize independently living algae upon contact with them. Lichen algae reproduce by mitosis and simple cell division.

[Lichen overview from the Encyclopedia of the Earth]

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As a side note, one lichen has been in the news recently- "newfound lichen species named for Barack Obama" - Caloplaca obamae

How Discriminating Ants Choose

In addition to merging sci-fi art with the reality of science ('tagged ant' image below), researchers at the School of Biological Sciences within the University of Bristol have demonstrated that the ‘irrationality’ associated with contextual decision making is avoided in the ant Temnothorax albipennis as it chooses between alternative nesting sites.

Tagged Ant!

As the article "Do ants make direct comparisons?" explains, Temnothorax albipennis makes a collective decision when a colony emigrates to a new nest. Scouting ants that discover new nests assess them on the basis of multiple attributes. Some of these scouts subsequently recruit nest-mates to the new nest using tandem-running, where an informed ant leads a second ant to her destination. When the number of ants in the new nest reaches a quorum, scouts begin rapid transport of the rest of the colony by carrying nest-mates and brood. Colonies are able to choose the best of several nests. Two individual-level mechanisms for this collective choosiness have been identified. Some ants visit both nest sites, and subsequently recruit only to the better site, which has been taken as evidence for direct comparison. However, ants that visit only one site still contribute to the colony decision, by starting to recruit earlier (i.e. using a shorter recruitment latency) when a nest is of higher quality.

According to Elva Robinson, "Each ant appears to have its own 'threshold of acceptability' against which to judge a nest individually. Ants finding the poor nest were likely to switch and find the good nest, whereas ants finding the good nest were more likely to stay committed to that nest. When ants switched quickly between the two nests, colonies ended up in the good nest. Individual ants did not need to comparatively evaluate both nests in order for the entire colony to make the correct decision.

On the other hand, animals – including humans – who use comparative evaluation frequently make 'irrational' decisions, due to the context in which options are compared or by inconsistently ranking pairs of options, (for example option A preferred to B, B preferred to C but C preferred to A).

The ants' threshold rule makes an absolute assessment of nest quality that is not subject to these risks, and circumvents the necessity for memorization and comparison of every site visited. Thus, simple individual behavior substitutes for direct comparison, facilitating effective choice between nest sites for the colony as a whole."

Specimen: CASENT0173192Species: Temnothorax albipennis

Photographer: April NobileDate Uploaded: 08/09/2007

Copyright: California Academy of Sciences, 2000-2007

Specimen: CASENT0173192Species: Temnothorax albipennis

Photographer: April NobileDate Uploaded: 08/09/2007

Copyright: California Academy of Sciences, 2000-2007

Robinson, E., Smith, F., Sullivan, K., & Franks, N. (2009). Do ants make direct comparisons? Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.0350

Hyperbolic Geometry and Corals

This video relates to the coral bleaching post made yesterday - Resilience in Acropora Corals


Margaret Wertheim: The beautiful math that links coral, crochet and hyperbolic geometry

Snapshots from the Field

A couple of the ecosystems visited this week, and a representative inhabitant from each...

Pine Flatwoods

Centruroides vittatus - the "striped bark scorpion"

Same specimen in both pictures; on the left she's sitting on my map, and to the right she's demonstrating her camouflage ability.

Salt Marsh

Menippe mercenaria - the "stone crab"

Resilience in Acropora Corals

Great news - local management of water quality and other factors may significantly contribute to the survivability of coral reefs that have been negatively impacted by climate change.

A massive bleaching event took place on the Great Barrier Reef approximately three years ago and devastated a huge number of inshore reefs, but the Acropora corals made an unprecedented comeback – in only a year’s time!

According to Guillermo Diaz-Pulido, three critical factors contributed to this unprecedented turn around, “first was exceptionally high re-growth of fragments of surviving coral tissue. The second was an unusual seasonal dieback in the seaweeds, and the third was the presence of a highly competitive coral species, which was able to outgrow the seaweed. But this also all happened in the context of a well-protected marine area and moderately good water quality.”

Sophie Dove of the Centre for Marine Studies and Australian Research Council Centre of Excellence for Coral Reef Studies points-out that, “The exceptional aspect was that corals recovered by rapidly regrowing from surviving tissue. Recovery of corals is usually thought to depend on sexual reproduction and the settlement and growth of new corals arriving from other reefs. This study demonstrates that for fast-growing coral species asexual reproduction is a vital component of reef resilience.”

Coral recovery following algal overgrowth

(Images from Artcle)

Branches of Acropora corals died after bleaching and were subsequently colonized by a variety of benthic algae. Remnant coral tissue at the base of the coral colonies regrew upward and deposited new skeleton along the old dead coral branch, overgrowing

A) algal turfs (arrows). B) fleshy seaweed Lobophora variegata.

C) crustose coralline algae. D) Coral tissue has all but completely overgrown the colonizing algae.


E) Thin section of coral showing benthic algae sandwiched between old coral skeleton and a thin layer of new skeleton. Examination using a compound microscope showed that coral tissue overgrew a range of algal types.

Ove Hoegh-Guldberg of CoECRS and The University of Queensland suggests, “...that managing local stresses that affect reefs such as overfishing and declining water quality can have a big influence on the trajectory of reefs under rapid global change.”

Read the Article from PLoS One - HERE

Diaz-Pulido, G., McCook, L., Dove, S., Berkelmans, R., Roff, G., Kline, D., Weeks, S., Evans, R., Williamson, D., & Hoegh-Guldberg, O. (2009). Doom and Boom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery PLoS ONE, 4 (4) DOI: 10.1371/journal.pone.0005239

Wetland Plant of the Week #14

Salicornia virginica

"Glasswort"

Obligate, succulent plant with rounded leaves fused to a fleshy jointed stem, salt tolerant and found in salt and brackish marshes.

Photographed earlier this week in Yankeetown, Florida.

Apis mellifera

Apis mellifera

Wing veination ditinguihes Honey Bees from Bumble Bees. This one was next to my mail box; common, but cool none-the-less...

The Fire Gene Described

A lengthy introduction during the initial post on this topic (available Here) contrasted a harmonious view of nature with the perspective of nature as a series of oppositional organisms struggling to gain a competitive edge over rivals. As a model of this outlook, the ecotone boundaries between various sets of differing plant communities were offered as a case study. More specifically, the prairie, savanna and hardwood hammock ecosystems of the Big Cypress Preserve were forwarded along with the proposition that members of these communities actively challenged each other for limited resources. In staging this proposition the question was asked, “Why don’t trees invade - and take over – the prairie communities currently occupied by grasses?” After eliminating the likelihood that densely growing stands of grass crowded-out young saplings by denying them access to sunlight, cyclic wildfire were explained and presented as an alternative explanation. Moving forward with this production, a profile of one of the previously introduced characters is in order – the conifer tree Pinus elliotti.

Slash Pine Growing from a Log

Slash Pine is a species of the genus Pinus (pine tree) which branched from genus Picea (spruce tree) during the Cretaceous Period, somewhere between 87 and 193 million years ago. There are two distinct varieties of slash pine, variety elliotti and variety densa, although there are several important distinctions, for purposes here both varieties can be considered one and the same. Pine and spruce trees are grouped together with cycads, gnetophytes and ginkgo as gymnosperms, which had a start back in the Pennsylvanian Period of the Carboniferous more than 300 million years ago. The long history of the pine trees, and the slash pine in particular, is significant because these trees have one of the largest and most complex genomes of any organism on the planet today – a result of varied evolutionary forces. Of specific interest in regards to evolutionary history is that gymnosperms arose from the Carboniferous swamps during a period of rapid plant adaptation. In addition to the advent of the bark fiber “lignin,” plants during that period underwent a multitude of morphological changes - many of these changes were adaptations to wildfire. Unlike the 21% atmospheric oxygen present today, the carboniferous boasted 35% oxygen content, this in conjunction with an abundance of herbaceous material (remember Carboniferous = “coal age”) resulted in frequent – and intense – wildfires.

Wildfires…

So, do wildfires prevent trees, such as slash pine, from invading prairie strongholds held by grasses? Not really, some especially intense (“intensity” being a measure of a fire’s maximum temperature and duration) wildfires may destroy slash pine, but fires capable of doing so are relatively rare. The typical “fire seasons,” as described in the first post, may have sufficient intensity to kill some young saplings, but remember - slash pines also have “initial rapid growth genes” which provide a solid head start in defending themselves. Essentially, any sapling greater than two years old has a good chance of getting through the “average” wildfire. As for the periodic “non-average” wildfire, one that is of an unusually high intensity, slash pines may need to rely on evolutionary adaptations other than “initial rapid growth genes” – they may need to lean on morphological phenotypes resulting from a “fire gene.”

A fire gene is a genetic compliment possessed by an organism that is expressed in such a manner that the presence of fire improves the likelihood of that genotype being passed on to future generations. In other words, if a population of trees exists in which some members have a genotype that provides phenotypical resistance to fire, and that population is then exposed to fire, killing a certain percentage of the population, those trees with fire gene advantage will have higher survivability and greater measures of fitness than will those not possessing a fire gene. Through this process of “selection by fire,” the fire gene would become more prevalent in the population, eventually becoming so common as to be called characteristic.

This is precisely what has occurred with the pine trees of the Big Cypress. Through millennia of “trial by fire,” only those trees expressing the most fire tolerant phenotypes have survived. Morphological features such as thickly armored plates of bark shield the trunk from heat, scale plated meristems guard against flames and the pine’s reproductive strategies take into account spring fires by germinating in the fall and producing periodic mast crops. However, these products of natural selection are merely defenses, what is truly remarkable is that another aspect of the fire gene contributes to offensive maneuvers.

As a thought experiment only, image being a tree with the cognitive function of a human and the knowledge that you have an inherit resistance to fire; a resistance that many of your competitors do not posses. If locked in a battle for survival, and you had a match in hand, (or rather, a match in “branch”) would you start a fire?

Of course, matches are of little use to trees outside of thought experiments, but what if there was an adaptation that would provide not only defense, but also allow trees to harness naturally occurring fires to their advantage? Genes don’t exist in isolation; frequently they form partnerships to gain mutual advantage. Epistasis, the interaction between genes, has occurred in pine trees to accomplish the same goal. Not only do the trees have defensive morphologies, they have also adapted the chemistry of their leaves (i.e. pine needles) such that while on the tree the leaves produce flame resistant chemicals, but when wildfires are absent for extended periods of time leaf chemistry changes. In the absence of wildfires leaves are randomly shed, accumulate in the area around the tree and - as opposed to being flame retardant - they become easily ignited at low temperatures and burn at an intensity that, well… An intensity that only a slash pine would love…

Some fires do adversely affect slash pine, but the presence of a “fire gene” provides both defensive and offensive adaptations that can –and have been – utilized to survive. So, why don’t trees such as slash pines invade prairies? It’s a “one-two punch.” Through heat stressing the trees, fires slow down advancing slash pines; however it is what happens after the fire season that stops them cold in their tracks – flooding. Summer rains pile on additional stress to what has already accumulated due to fire defense investment. Grasses are in the same boat, but due to a better water tolerance they can bounce back more readily. The slash pine can survive fires or flood, but taken together these two modes of environmental disturbance overwhelm the trees and limit their prairie-ward charge. This is, however, a function of seasonality, climate and cyclic wildfires; with climate change and alteration of these natural processes all bets are off. (But that’s a topic for another time…)

Beckage, B., Gross, L., & Platt, W. (2006). Modelling responses of pine savannas to climate change and large-scale disturbance Applied Vegetation Science, 9 (1) DOI: 10.1658/1402-2001(2006)9[75:MROPST]2.0.CO;2

Nordlund, D., & Lewis, W. (1976). Terminology of chemical releasing stimuli in intraspecific and interspecific interactions Journal of Chemical Ecology, 2 (2), 211-220 DOI: 10.1007/BF00987744

Morse, A., Peterson, D., Islam-Faridi, M., Smith, K., Magbanua, Z., Garcia, S., Kubisiak, T., Amerson, H., Carlson, J., Nelson, C., & Davis, J. (2009). Evolution of Genome Size and Complexity in Pinus PLoS ONE, 4 (2) DOI: 10.1371/journal.pone.0004332

Platt, W. J., J. M. Huffman, M. G. Slocum, and B. Beckage. In press. Fire regimes and trees in Florida dry prairie landscapes. In: Noss, R. & Singh, S. (eds.) Land of fire and water: The Florida dry prairie ecosystem. Avon Park Air Force Range and Department of Defense, Avon Park, FL,

US.Kabrick, John M.; Dey, Daniel C.; Gwaze, David, eds. Shortleaf pine restoration and ecology in the Ozarks: proceedings of a symposium; 2006 November 7-9; Springfield, MO. Gen. Tech. Rep. NRS-P-15. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 28-32.

The Fire Gene: One Organism’s Ability to Exploit Fire

Gazing across the tranquil landscape of the Big Cypress Preserve, nature seems to be in balance, unchanging and at peace - picturesque beyond any poetic description. Here, anthropogenic throngs of sharply angled concrete and glass edifices suspend their battle for roadside dominance and yield themselves to a sea of sparsely treed savanna, rolling prairies of grass, and randomly scattered islands of thickly vegetated hammocks; the perfect environment for a relaxing stroll, a picnic, or even a quick nap. All may appear calm within this enchanting panorama; however, the perceived tranquility is but a chimera. A mere illusion of serenity resulting from shortfalls in the ability of Homo sapiens’ photoreceptors to see beyond the narrow range of the electromagnetic spectrum called visible light, an inability to hear sound outside of 22000 Hertz, and the failure of the human olfactory system to nose its way into the vast chemo-landscape of pheromones and other volatile chemicals in which it is continuously assailed. If the sensory apparatus of Homo sapiens was keener - more finely calibrated – the landscape of the Big Cypress would appear very different.

Very different indeed, imagine the ecological interplay that could be interpreted if humans could see ultraviolet light through the eyes of a bee, smell pheromones from six-miles’ distance like a moth, or interpret chemical stimuli through soil like a plant… Far from serene, if viewed through time, adaptive maneuvers, survival strategies and arms races would be manifest in every action undertaken by the immense diversity of organisms on Earth. If these actions could be viewed more directly, the landscape would appear saturated with war. Even the plant community boundaries which demarcate prairie from savanna from hammock in the above described landscape are maintained by way of fierce battles waged over evolutionary time. These ecosystems, which appear stable and so pleasingly haphazardly scattered, are in fact tightly ordered armies of competing plants struggling for resources and existence. In these recurrent ecotonal conflicts one species has honed a new weapon – it has adapted to exploit the power of fire.

Naturally existing plant communities exist in a continuum of ecosystems which through evolution have adapted to almost every available habitat on the planet; from “box thorns” (Lycium pallidum) in Death Valley to fully aquatic hyacinths (Eichhornia paniculata) floating around the lakes of Brazil, genetic plasticity in plants is the product of natural selection. Although diverse habitats represent a surmountable challenge, a multitude of both biotic and abiotic factors determine the overall abundance (density), composition (diversity) and ultimate success of plant communities at any given location.

For example, looking across the landscape of the Big Cypress, densely concentrated hardwood trees form hammocks which, due to the broad area of their collective canopies, limit the amount of sunlight available to underlying herbaceous groundcover. This is a straight forward relationship - no sun reaching the ground means fewer plants on the ground. Following this rationale, if the tree canopy should be opened (by a storm, hurricane or by the death of older trees) and sunlight is able to temporarily penetrate to the floor, a rapid emergence of both herbaceous plants and new saplings would be predicted. This is precisely what happens; sunlight is the limiting resource, once made available, those plants best able to take advantage of the situation (through rapid growth) will be able to literally overshadow their competitors; plants with genetic compliments favoring a period of “initial rapid growth” are at an advantage and will be positively selected.

Extrapolating this scenario to the prairies of Big Cypress begs the question – why aren’t there any trees in the prairie?

Prairies, typically found on relatively low topographical gradients in Florida, have an abundance of soil nutrients and water; at least enough to support the enormous quantity of grasses and herbaceous plants currently found there. Additionally, from the perspective of a tree, grasses present little competition for sunlight. So, what is it that prevents trees from invading the prairie?

One often suggested possibility is that because prairies are occupied by dense populations of grasses - some of which more than six feet in height - young trees are prevented from taking hold; sort of like a reverse hammock scenario in which the grasses overshadow the young trees thereby starving them of sunlight instead of vice versa… This is plausible, but why wouldn’t trees take hold after wildfires? Wildfires have been historically inevitable in Florida and have the effect of clearing grasses long enough for those trees possessing an “initial rapid growth gene” in their arsenals to stake a claim.

Slash Pine (Pinus elliotti), for example, has just such an initial rapid growth gene. This permits the tree to take advantage of any opportunity to seize real estate, whether it is in a forest or a prairie. Slash Pine is even capable of expressing secondary needles in less than six month’s time – seedlings grow rapidly. Once present, this conifer could easily out-compete grasses for sunlight.

A quick word about wildfires: Florida’s climate cycle is punctuated by alternating dry and wet periods. November to February is the dry season, with relatively little precipitation, and is followed by heavy rains and thunderstorms (particularly near the coasts) during the months of June, July and August. The spring season, February through May, represents a transition from dry to wet, but during this period lightening strikes often cause wildfires due to the parched conditions of plants – parched, having just come out of the dry season. Regularity of climate has resulted in a cyclic “fire season” arriving during the early spring.

Speaking of wildfires… Being a regular occurrence, they are often offered as another explanation for limiting the advance of trees into prairies. Although this suggestion is partially correct, it isn’t the whole story - in some instances trees have even wielded fire as a weapon to destroy its grass competitors.


4-19-09 UPDATE: The Second Half of this Post can be Viewed HERE.

Beckage, B., Gross, L., & Platt, W. (2006). Modelling responses of pine savannas to climate change and large-scale disturbance Applied Vegetation Science, 9 (1) DOI: 10.1658/1402-2001(2006)9[75:MROPST]2.0.CO;2

Nordlund, D., & Lewis, W. (1976). Terminology of chemical releasing stimuli in intraspecific and interspecific interactions Journal of Chemical Ecology, 2 (2), 211-220 DOI: 10.1007/BF00987744

Morse, A., Peterson, D., Islam-Faridi, M., Smith, K., Magbanua, Z., Garcia, S., Kubisiak, T., Amerson, H., Carlson, J., Nelson, C., & Davis, J. (2009). Evolution of Genome Size and Complexity in Pinus PLoS ONE, 4 (2) DOI: 10.1371/journal.pone.0004332

Platt, W. J., J. M. Huffman, M. G. Slocum, and B. Beckage. In press. Fire regimes and trees in Florida dry prairie landscapes. In: Noss, R. & Singh, S. (eds.) Land of fire and water: The Florida dry prairie ecosystem. Avon Park Air Force Range and Department of Defense, Avon Park, FL,

US.Kabrick, John M.; Dey, Daniel C.; Gwaze, David, eds. Shortleaf pine restoration and ecology in the Ozarks: proceedings of a symposium; 2006 November 7-9; Springfield, MO. Gen. Tech. Rep. NRS-P-15. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 28-32.

Night Vision and DNA

Science Friday at NPR -

Why do some animals have much better night vision than others? We'll talk about new research tracing the root of improved night vision to the architecture of the DNA inside the photoreceptor rod cells of the animals' eyes. Writing in the journal Cell, researchers say that an unusual way of packing the DNA within the rod cell nuclei turns the nuclei themselves into into tiny light-collecting lenses. The structure prevents light from excessive scattering within the eyes, improving their light collecting efficiency.

Guests:
Jochen Guck Lecturer, Physics DepartmentUniversity of Cambridge

Click here to hear the broadcast.

Beautiful Data

Demonstration of the “AlloSphere,” an entirely new way to see and interpret scientific data - in full color and surround sound inside a massive metal sphere.

A 3D immersive theater that maps complex data in time and space.

Dive into the brain, feel electron spin, hear the music of the elements...

New Study Merges Genetics, Demography and Paleoanthropology

Mitochondrial DNA from twelve Neanderthal fossil assemblages was sequenced, compared and correlated with morphological data from fossil skulls, limbs and dentary remains to render evidence for multiple demes of Neanderthals from across Asia and Europe.

According to the authors, this “…approach to Neanderthal variability, based on nucleotide sequences analysis, confirms from a genetic point of view the morphological variations between western and eastern Neanderthals and the existence of a southern group…”

The mtDNA portion of the study therefore supports prior determinations based on morphological analysis that at least three separate Neanderthal sub-groups (and possibly a fourth group from western Asia) emerged from an ancestral population approximately 130,000 years ago. Furthermore, there is evidence that these populations existed in a dynamic state of migration.

Figure 2. Neanderthal Group Distribution

Abstract:
The Neanderthals are a well-distinguished Middle Pleistocene population which inhabited a vast geographical area extending from Europe to western Asia and the Middle East. Since the 1950s paleoanthropological studies have suggested variability in this group. Different sub-groups have been identified in Western Europe, in southern Europe and in the Middle East. On the other hand, since 1997, research has been published in paleogenetics, carried out on 15 mtDNA sequences from 12 Neanderthals. In this paper we used a new methodology derived from different bioinformatic models based on data from genetics, demography and paleoanthropology. The adequacy of each model was measured by comparisons between simulated results (obtained by BayesianSSC software) and those estimated from nucleotide sequences (obtained by DNAsp4 software). The conclusions of this study are consistent with existing paleoanthropological research and show that Neanderthals can be divided into at least three groups: one in western Europe, a second in the Southern area and a third in western Asia. Moreover, it seems from our results that the size of the Neanderthal population was not constant and that some migration occurred among the demes.


In case you were wondering about genetic links to modern Homo sapiens, the study was limited to “…what occurred previous to the arrival of modern humans in the Neanderthal landscape and we therefore do not consider the potential phylogenetic relationship between Neanderthals and modern Humans.”

The article, in its entirety, is available at the below referenced link.

Fabre, V., Condemi, S., & Degioanni, A. (2009). Genetic Evidence of Geographical Groups among Neanderthals PLoS ONE, 4 (4) DOI: 10.1371/journal.pone.0005151

Anti-Science and Ignorance Prevail – No on Stem Cell Research

State funding for embryonic stem cell research falls to the wayside at the State’s Capital today as Reps put politics and ignorance before science, ethics and public health during a debate at the Florida State University…

Rep. Eric Eisnaugle oppossed the research because his mommy said so…

“As much of a stake she has in this, she is absolutely against using public money to fund embryonic stem cell research,” said Eisnaugle.

And Miami Representative Anitere Flores decided to make a “definitive statement” in hopes of promoting misinformation and avoiding ethical challenges. Read her letter to Science and Ethics Chair Claire Thuning-Roberson - here.


Their arguments are as baseless and ignorant as the positions themselves.

Absolutely shameful, welcome to the south ya’ll !

Wetland Plant of the Week #13

Pistia stratiotes

"Water lettuce"

In Florida, this Obligate species is a non-native invasive.

Glazier (1996) describes P. stratiotes as a free-floating perennial of quiet ponds. It is stoloniferous, forms colonies, and has rosettes up to 15cms across. It has long, feathery, hanging roots. Its leaves are obovate to spathulate-oblong, truncate to emarginate at the apex, and long-cuneate at the base. Leaves are light green and velvety-hairy with many prominent longitudinal veins. Inflorescences are inconspicuous and up to 1.5cms long. Flowers are few, unisexual, and enclosed in a leaflike spathe.


Juvenile gator Concealed in the P. stratiotes

Emergence of a Predator

While checking out a floodplain along the Ochlocknee River yesterday, I ran into an emerging predator – a dragonfly.

Fresh from the naiad, this Darner (Family Aeschnidae) represents one of the largest and fastest dragonflies found anywhere in the world. After hatching from an egg, they immediately begin to feed on minnows, tadpoles, aquatic insects, and other small prey - including conspecifics (like siblings). Once reaching adulthood, they quickly become the scourge of mosquitoes and flies.

Naiad

Newly Emerged

Almost Ready to Hunt!

Reference:

Density-Dependent Cannibalism in Larval Dragonflies
Josh Van Buskirk
Ecology, Vol. 70, No. 5 (Oct., 1989), pp. 1442-1449
Published by: Ecological Society of America
Stable URL: http://www.jstor.org/stable/1938203

“Extreme” Imperfection?

I just happened across a nifty little article from the Journal of Evolution: Education and Outreach. It discusses the fossil record, Darwin and other concepts such as “missing links” and transitional forms.

It’s jargon free and would be a good resource for teachers, or anyone interested in explaining to lay persons how fossils provide evidence for evolution.

It can be downloaded as a PDF - HERE.

Cretaceous Multituberculata from Australia

Thomas H. Rich (et. al.), Curator of Vertebrate Paleontology at the Museum of Victoria in Melbourne, Australia, recently published a description of dentary fragments from a member of the Multituberculata in the Journal Acta Palaeolontologica Polonica.

Several mammalian families have previously been identified from the Aptian formation (where the current fossil was found), most of these are believed to represent species endemic to Australia; however one family – the Ornithorhynchidae – have also been found in Argentina. Ornithorhynchidae, a group of monotremes, have been used to provide evidence for mammalian dispersal between South America and Australia during the Mesozoic.

According to the authors, these prehistoric platypuses provide biogeographical clues because “[g]iven the relative geographic positions of Australia and South America during the Mesozoic, it is reasonable to expect that were it then possible to do so, at least one of these terrestrial mammals would have traversed the Antarctic landmasses, in one direction or the other…”


Abstract:
A dentary fragment containing a tiny left plagiaulacoid fourth lower premolar from the Early Cretaceous (Aptian) of Victoria provides the first evidence of the Multituberculata from Australia. This unique specimen represents a new genus and species, Corriebaatar marywaltersae, and is placed in a new family, Corriebaataridae. The Australian fossil, together with meagre records of multituberculates from South America, Africa, and Madagascar, reinforces the view that Multituberculata had a cosmopolitan distribution during the Mesozoic, with dispersal into eastern Gondwana probably occurring prior to enforcement of climatic barriers (indicated by marked differentiation in regional floras) in the Early Cretaceous.

Holotype of multituberculate mammal Corriebaatar marywaltersae gen. et sp. nov. from Flat Rocks, Wonthaggi Formation (Aptian), Australia (NMV P216655), a left dentary fragment with p4 and anterior root of m1 in labial (A), lingual (B), and occlusal (C) views. Artwork by P. Trusler.

THOMAS H. RICH,et al. (2009). An Australian multituberculate and its palaeobiogeographic implications Acta Palaeolontologica Polonica

The article is available as a PDF HERE.

Beck, R., Godthelp, H., Weisbecker, V., Archer, M., & Hand, S. (2008). Australia's Oldest Marsupial Fossils and their Biogeographical Implications PLoS ONE, 3 (3) DOI: 10.1371/journal.pone.0001858

Phylogenomics and Metazoan Evolution

During the course of constructing a “Tree of Life” based on more than 120 gene sequences and fifty-five different species, a group of scientists led by Gert Wörheide of Munich have reached two conclusions; one, all Porifera (sponges) share a common sponge-like ancestor, and two, that ancestor did not give rise to the Bilateria.

According to Wörheide, “If the ancestral animal would have had a sponge-like organization or body, as some earlier molecular studies repeatedly claimed, then we would all be descendents of such sponge-like organisms. This proposition generated a lot of attention in the past. But our results clearly disagree with it."

Abstract:

The origin of many of the defining features of animal body plans, such as symmetry, nervous system, and the mesoderm, remains shrouded in mystery because of major uncertainty regarding the emergence order of the early branching taxa: the sponge groups, ctenophores, placozoans, cnidarians, and bilaterians. The ‘‘phylogenomic’’ approach has recently provided a robust picture for intrabilaterian relationships but not yet for more early branching metazoan clades. We have assembled a comprehensive 128 gene data set including newly generated sequence data from ctenophores, cnidarians, and all four main sponge groups. The resulting phylogeny yields two significant conclusions reviving old views that have been challenged in the molecular era: (1) that the sponges (Porifera) are monophyletic and not paraphyletic as repeatedly proposed, thus undermining the idea that ancestral metazoans had a sponge-like body plan; (2) that the most likely position for the ctenophores is together with the cnidarians in a ‘‘coelenterate’’ clade. The Porifera and the Placozoa branch basally with respect to a moderately supported ‘‘eumetazoan’’ clade containing the three taxa with nervous system and muscle cells (Cnidaria, Ctenophora, and Bilateria). This new phylogeny provides a stimulating framework for exploring the important changes that shaped the body plans of the early diverging phyla.

Phylogenomics is the science of comparing genetic compliments, such as genes, nucleotides or entire genomes from different species, and through the application of statistics determining the “best fit” in terms of any evolutionary history (phylogeny) that the organisms share. Frequently these studies result in multiple “possible fits” and determining the most parsimonious model isn’t always a simple task, but in the case of this current study, it appears that the bar has been raised.

(A) Schematic section of an adult sponge (bottom) and SEM picture showing a choanocyte, the sponge collar cell (top, choanocyte from Chelonaplysilla noevus, Demospongiae). The arrows indicate the direction of circulation of water in the aquiferous system of the sponge. Abbreviations: atr, atrial cavity; cb, cell body; cc, choanocyte chamber; col, collar of microvilli; ex, exhalant canal; fl, flagellum; in, inhalant canal; mes, mesohyl; osc, osculum (or exhalant orifice); ost, ostium (or inhalant orifice); pin, pinacoderm (thin epithelial layer, limiting the sponge body on its external surface and within the canals); sp, spicule.

(B) Most parsimonious scenario for the evolution of sponge body plan characters, imposed on a scheme of sponge paraphyly.


(C) Most parsimonious scenario assuming sponge monophyly.

In (B) and (C), the gray branches indicate the presence of sponge body plan characters (aquiferous system, internalized choanocyte chambers, pinacoderm) and the black branches indicate the absence of these characters. The gray horizontal line indicates character acquisition; the hollow horizontal line indicates character loss. ‘‘Sponges 1, 2, and 3’’ correspond to the major lineages (silicisponges, homoscleromorphs, and calcisponges), of which exact branching order varies among published studies recovering sponge paraphyly.

Incidentally, if your interested in the search for the urbilaterian (common ancestor of Bilateria), I’d recommend a look at a recent paper by Neil Shubin, Cliff Tabin and Sean Carroll titled Deep homology and the origins of evolutionary novelty. This article was published this past February in Nature.

Philippe, H., Derelle, R., Lopez, P., Pick, K., Borchiellini, C., Boury-Esnault, N., Vacelet, J., Renard, E., Houliston, E., & Quéinnec, E. (2009). Phylogenomics Revives Traditional Views on Deep Animal Relationships Current Biology DOI: 10.1016/j.cub.2009.02.052

Shubin, N., Tabin, C., & Carroll, S. (2009). Deep homology and the origins of evolutionary novelty Nature, 457 (7231), 818-823 DOI: 10.1038/nature07891

Eugenie Scott on Texas Schools

Today on NPR's Science Friday, Eugenie Scott talks about the Texas School Board and its endorsement of ignorance. Audio HERE.

Recorded Today.

People don’t understand science

I missed this post earlier in the week - good stuff!

Science IS Imagination

Does Protein-coding Occur at a Steady-state?

Interesting Article;

Abstract:

The evolutionary rates of protein-coding genes in an organism
span, approximately, 3 orders of magnitude and show a universal,
approximately log-normal distribution in a broad variety of species
from prokaryotes to mammals. This universal distribution implies
a steady-state process, with identical distributions of evolutionary
rates among genes that are gained and genes that are lost. A
mathematical model of such process is developed under the single
assumption of the constancy of the distributions of the propensities
for gene loss (PGL). This model predicts that genes of different
ages, that is, genes with homologs detectable at different phylogenetic
depths, substantially differ in those variables that correlate
with PGL. We computationally partition protein-coding genes from
humans, flies, and Aspergillus fungus into age classes, and show
that genes of different ages retain the universal log-normal distribution
of evolutionary rates, with a shift toward higher rates in
‘‘younger’’ classes but also with a substantial overlap. The only
exception involves human primate-specific genes that show a
heavy tail of rapidly evolving genes, probably owing to gene
annotation artifacts. As predicted, the gene age classes differ in
characteristics correlated with PGL. Compared with ‘‘young’’ genes
(e.g., mammal-specific human ones), ‘‘old’’ genes (e.g., eukaryotespecific),
on average, are longer, are expressed at a higher level,
possess a higher intron density, evolve slower on the short time
scale, and are subject to stronger purifying selection. Thus, genome
evolution fits a simple model with approximately uniform rates of
gene gain and loss, without major bursts of genomic innovation.

Read the rest here;
The universal distribution of evolutionary rates of genes and distinct characteristics of eukaryotic genes of different apparent ages

Street Smart Birds

Omnivorous Pleistocene Bears Give Clues to Adaptation

By comparing the morphological features of Pleistocene bear fossils (Arctodus simus and Ursus spelaeus) with that of modern bears, scientists report that analogous cranio-mandibular structures indicate that even the prehistoric hyper carnivores had omnivorous tendencies.

These and other findings provide clues as to the niche plasticity and the ability of mammals to adapt to fluctuating climates.



'Knowing what the extinct bears ate is of utmost relevance to finding out about the evolution of carnivore niches in the Pleistocene when climatic conditions were changing', explains Borja Figueirido, lead author of the study and researcher for the Ecology and Geology Department of the Faculty of Sciences at the University of Málaga.



Figure Above: Landmarks used for describing cranial and mandibular shape. Cranium: (1) most postero-dorsal border of the canine alveolus, (2) most antero-dorsal border of the canine alveolus, (3) most antero-dorsal border of the I3, (4) most anterior edge of the nasal bones, (5) dorsal outline directly superior to post-orbital process, (6) dorsal outline directly superior to the end of the zygomatic arch, (7) most postero-ventral point of the occipital crest, (8) intersection between the occipital condyle and the occiput, (9) intersection between the occipital condyle and the paraoccipital process, (10) ventral tip of postglenoid process, (11) posterior edge of the upper tooth row, (12) point between the upper carnassial and the first upper molar, (13) anterior edge of the upper tooth row, (14) postero-dorsal border of the zygomatic arch, (15) dorsal tip of the frontal process of the zygomatic arch, (16) orbit midheigth, (17) ventral tip of the post-orbital process, (18) ventral intersection between the zygomatic arch and the axilla.Mandible: (1) antero-dorsal border of the incisive alveolus, (2) postero-dorsal border of the canine alveolus, (3) intersection between the trigonid/talonid notch of the lower carnassial and the dorsal border of the alveolus of this tooth, (4) posterior edge of the lower tooth row, (5) posterior edge of the coronoid process, (6) most posterior edge of the articular surface condyle, (7) tip of angular process, (8) ventral outline below the mesial end of the tooth row, (9) ventral outline below the trigonid/talonid notch of the lower carnassial, (10) most ventral point of the symphyseal region. Scale bar equals 5 cm. Deviations of the specimens analyzed from the consensus configuration of landmarks are shown.



Read the research article published in the Journal of Zoology - HERE.



Figueirido, B., Palmqvist, P., & Pérez-Claros, J. (2009). Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics Journal of Zoology, 277 (1), 70-80 DOI: 10.1111/j.1469-7998.2008.00511.x

Wetland Plant of the Week #12

Sphagnum spp.

“Sphagnum Moss”

Small (1-10cm), obligate, non-vascular plant with tightly arranged clusters of branch fascicles, usually found growing as a dense mat (Picture 2).

Neither flowers nor seeds are present in this Bryophyte with reproduction occurring by fragmentation.

Sphagnum mat, between grasses

Photographed last week in Volusia County, Florida

Copulating for Carrion

Found this personal ad on Craigslist:

The ad reads:

Copulating for Carrion,
Currently unattached chimp with a passion for Tarzan swings and coprophagia seeks mutually compatible primate for reciprocal grooming, marking territory with urine and hanging around with the troop. Must have own carrion and be willing to share. No weirdoes need respond!

Unprofessional - I know – but couldn’t resist…

But in all seriousnessness (or at least in relative seriousness), check out this article on PLoS One;

Wild Chimpanzees Exchange Meat for Sex on a Long-Term Basis

From the Abstract

"Humans and chimpanzees are unusual among primates in that they frequently perform group hunts of mammalian prey and share meat with conspecifics. Especially interesting are cases in which males give meat to unrelated females. The meat-for-sex hypothesis aims at explaining these cases by proposing that males and females exchange meat for sex, which would result in males increasing their mating success and females increasing their caloric intake without suffering the energetic costs and potential risk of injury related to hunting. Although chimpanzees have been shown to share meat extensively with females, there has not been much direct evidence in this species to support the meat-for-sex hypothesis. Here we show that female wild chimpanzees copulate more frequently with those males who, over a period of 22 months, share meat with them. We excluded other alternative hypotheses to exchanging meat for sex, by statistically controlling for rank of the male, age, rank and gregariousness of the female, association patterns of each male-female dyad and meat begging frequency of each female. Although males were more likely to share meat with estrous than anestrous females given their proportional representation in hunting parties, the relationship between mating success and sharing meat remained significant after excluding from the analysis sharing episodes with estrous females. These results strongly suggest that wild chimpanzees exchange meat for sex, and do so on a long-term basis. Similar studies on humans will determine if the direct nutritional benefits that women receive from hunters in foraging societies could also be driving the relationship between reproductive success and good hunting skills."

The Hand of God Photographed!

Or, a nebula...


From Cosmic Hand Reaches for the Light:





In a new image from NASA's Chandra X-ray Observatory, high-energy X-rays emanating from the nebula around PSR B1509-58 have been colored blue to reveal a structure resembling a hand reaching for some eternal red cosmic light.

Classic Attenborough Video - 1979

"Invasion of the Land"

FROM: Life on Earth: A Natural History by David Attenborough (1979)

Holotomography of a Carboniferous Chimaeroid

Impressive brain imagery of a 300 million year old fish…


“This application of holotomography confirms the rapidly growing possibilities of X-ray synchrotron phase imaging techniques in palaeontology, especially when dealing with the exceptional soft-tissue preservations. It imposes synchrotron radiation as a powerful tool for nondestructive imaging of fossils.”

From Abstract: “Living cartilaginous fishes, or chondrichthyans, include numerous elasmobranch (sharks and rays) species but only few chimaeroid (ratfish) species. The early history of chimaeroids, or holocephalans, and the modalities of their divergence from elasmobranches are much debated. During Carboniferous times, 358–300 million years (Myr) ago, they underwent a remarkable evolutionary radiation, with some odd and poorly understood forms, including the enigmatic iniopterygians that were known until now from poorly informative flattened impressions. Here, we report iniopterygian skulls found preserved in 3 dimensions in _300-Myr-old concretions from Oklahoma and Kansas…”

[Click Link Below to Continue]

Figure 1

Fig. 1. The anatomy of iniopterygians. (A) Reconstruction of Sibyrhynchus denisoni (based on ref. 5, not to scale). (B and C) Part (B) and counterpart (C) of a phosphatic nodule from the Pennsylvanian of Oklahoma (AMNH OKM38) containing the braincase and shoulder girdle of Sibyrhynchus sp. (D–F) Threedimensional reconstruction of the same specimen, obtained from conventional X-ray _CT images, showing the braincase in dorsal (D), ventral (E), and lateral (F) view, with associated teeth. (G–I) Three-dimensional reconstruction of the braincase, shoulder girdle, and pectoral fin elements of a sibyrhynchid iniopterygian from the Pennsylvanian of Kansas (KUNHM 21894), based on SR-_CT images. Braincase in dorsal (G), posterior (H), and ventral views, with articulated shoulder girdles and pectoral fin radials (I). Scale bar, 5 mm; f.IX and f.X, foramina for glossopharyngeus and vagus nerves).

Figure 2

Fig. 2. Braincase anatomy and exceptional brain preservation in a sibyrhynchid iniopterygian from the Pennsylvanian of Kansas. (A and B) articulated skull preserved in a nodule (KUNHM 22060) (see also Fig. S1) in dorsal (A) and anterior (B) view (arrow points forward). (C–Q), three-dimensional reconstructions and putative preserved brain structures of the same specimen, obtained from SR-_CT images (and holotomography for brain details). (C–H), Braincase, teeth, and lower jaw in lateral (C), anterior (D), ventral (E), posterior (F), and dorsal (G) view, showing by transparency the outline of the endocranial cavity and labyrinth (H). (I–K), Selected transverse (I and J), and horizontal (K) SR-_CT (holotomography) slices through the calcite-filled endocranial cavity, showing the probably phosphatized brain at the level of the rhombencephalon (I), hypophysis (J), and roof of the optic tectum and cerebellum (K). (L–N) Reconstruction of the endocranial cavity and otic capsule in dorsal (L andM) and lateral (N) view, showing the putative brain by transparency (Mand N). (O–Q), reconstruction of the putative phosphatized brain in dorsal (O), ventral (P), and lateral (Q) view. (Scale bar, 5mmfor A–N and 1mmfor I—K and O–Q. Asc, anterior semicircular canal; Cer, cerebellum; Ed, endolymphatic duct; Hsc, horizontal semicircular canal; Hyp, hypophysis; Olftr, canals for olfactory tracts; Opch, optic chiasm; Optec, optic tectum; Psc, posterior semicircular canal; II, optic nerve; III?, oculomotorius nerve?; IV?, trochlear nerve?; X?, roots of vagus nerve?).


Check out the article HERE.


Pradel, A., Langer, M., Maisey, J., Geffard-Kuriyama, D., Cloetens, P., Janvier, P., & Tafforeau, P. (2009). Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography Proceedings of the National Academy of Sciences, 106 (13), 5224-5228 DOI: 10.1073/pnas.0807047106

Astrobiology and the Origins of Life

Recorded April 3, 2009 @ NPR Science Friday
Is the appearance of life on Earth a fluke, or is the universe teeming with alien life? In a special broadcast from the Origins Symposium at Arizona State University, leading astrobiologists debate the origin of life on this planet and talk about the best places to look for other life in the universe.

Guests:
Ariel Anbar, principal investigator, NASA Astrobiology Institute team, professor, Arizona State University, Tempe , Ariz.

Barry Blumberg, M.D., winner, 1976 Nobel Prize in Physiology or Medicine, founding director, NASA Astrobiology Institute, senior advisor to the President, Fox Chase Cancer Center, Philadelphia, Penn.

Paul Davies, cosmologist, physicist, astrobiologist, director, The Beyond Center, Arizona State University, Tempe, Ariz.

Peter Ward, professor, department of biology, The Astrobiology Program, The University of Washington, Seattle, Wash.

CLICK HERE TO LISTEN TO THE PODCAST

Caution: Wide Turns - Shell in Tow

If one were to draw a line depicting the rate of average global speciation or evolutionary novelty produced over the last billion years, this linear representation would certainly have a spike near the geologic time of the Cambrian Explosion. By about 500 million years ago, all present day phyla (i.e. body-plans, or animal “designs”) had representative species on the planet (with the exception of Bryozoa), including that of the most abundant animal and second-most abundant organism overall found on earth today (following only bacteria) - the arthropods. The challenges these arthropods overcame in their journey from the sea to a terrestrial existence were both immense and varied. In a recent article published in Geology, James W. Hagadorn and Adolf Seilacher find clues to one arthropod’s strategy to overcome the obstacles of dehydration and desiccation as it makes the transition landward. Within the Orthoquartzites of the Elk Mound Group in central Wisconsin, a type of ichnofossils called Protichnites tell a tale of behavioral adaptation and evolution.

Protichnites are trace fossils that display two parallel lines of tracks with a linear depression at the center. The parallel lines are essentially rows of footprints aligned towards the animal’s direction of travel. Carefully examined, these lines can be used to translate and interpret gait. In the case of the currently examined Elk Mound fossils, “the deeper impressions made by the rear pair of walking legs (i.e., the “pushers”) repeat symmetrically, in the same rhythm as the shell marks. This suggests synchronous movement of leg pairs, similar to modern Limulus and eurypterids, rather than the alternating gait reflected in tracks of crustaceans, scorpions, and insects.”

Photos from Referenced Article

The linear depression at the center of the Protichnites fossils is thought to be remnant drag marks from a tail. When turning, the arthropod’s tail swings outward from the direction of the turn, like a pendulum; these “wide turns” can provide biomechanical clues describing the gait of the animal.

One set of fossils studied by the authors, later named Protichnites eremite (eremite = Hermit), displayed a medial depression with irregular characteristics. “Instead of following the midline, its markings consist of oblique impressions that are always offset and shingled to the left side. It is unlikely that this represents an individual or population of individuals characterized by a malformed tail, because similar trackways of different widths occur on the same bedding plane and because such trackways occur on more than one horizon. Because there are no pushback hills on the rear sides of the oblique ‘tail’ impressions, it is also unlikely that this asymmetry reflects a behavioral strategy, in which the tail was bent sideways in order to assist in locomotion.”

If the irregular tail marks don’t represent a morphological malformation or provide evidence for locomotion, then what do they indicate, what’s the diagnosis? According to Hagadorn and Seilacher, “the impressions resemble the touch marks of a high-spired, dextrally coiled shell” similar to that carried by modern day hermit crabs.

The conclusion reached by the researchers is that the arthropods, while in transition to a terrestrial existence, probably “still left the water only for short durations, crawling around on the wet sand flats during low tides.” These intertidal sand flats proved ideal for promoting the growth of thin microbial films on which the light-footed arthropods left tracks and trails that later fossilized.

Using modern hermit crabs as an analog, the authors surmised that, “with their cuticular exoskeletons and stiff appendages, arthropods were particularly well preconditioned for terrestrialization. Nevertheless their early pioneers still required special adaptations, such as large body sizes and the use of foreign shells, to minimize water loss.” Transporting a shell on their back buffered the arthropods from arid conditions, but at the same time altered their gait to such an extent that we can read it in the fossils today.

Hagadorn, J., & Seilacher, A. (2009). Hermit arthropods 500 million years ago? Geology, 37 (4), 295-298 DOI: 10.1130/G25181A.1

Capturing the Superorganism or Reviving a Monster?

"The beauty of the dream vanished, and breathless horror and disgust filled my heart," so said Victor, a well established scientist from the upper east side of Transylvania Switzerland as he witnessed life cross the threshold of the lifeless and into his newly created monster – Frankenstein!

Well, OK – maybe quoting from Mary Shelly’s Frankenstein is a bit over-the-top, but a recent article published in the Journal of Evolutionary Biology has made me question whether or not Andy Gardner and Alan Grafen have created a monster of their own – one that they may eventually come to regret.

In a recent article (available as a PDF Here) titled “Capturing the superorganism: a formal theory of group adaptation,” Gardner, a Royal Society University Research Fellow, and Grafen, a Professor at Oxford University widely known for his work in statistics (most memorable to me for his mathematical modeling of Zahavian Handicaps), define, describe and quantify group adaptation and group selection as functional modes of natural selection.

On one hand the article is innovative in that it takes steps to cleanly differentiate between often befuddled concepts, like “kin selection” versus “group selection” and various interpretations of “fitness;” it also empirically formalizes (and limits) the group adaptation theory - indeed it lifts the theory to new heights. However, on the other side of the coin, the article (antagonistically in my mind) compounds any preexisting misunderstanding of these concepts by arguing for even greater expansion of analogy.

For example, the article tediously - though accurately - makes distinctions between various measures of fitness, including inclusive fitness, relative fitness, within-group fitness, personal fitness, between-group fitness, individual fitness and indirect fitness; but then, rather than provide simplicity and clarity to this dizzying collection of measurement methodologies, the article uses them as a foundation in support of further artificial constructs – namely groups as individual units or actors in natural selection.

The superorganism enters… [As a side note, there is a good E.O. Wilson interview (audio file) at NPR’s Science Friday website from last December in which he discusses the superorganism concept and his book of the same title – HERE]

Through their delineations, Capturing the Superorganism’s authors intentionally reveal that both the individual organism and the “group” as focal points of adaptation are only ‘maximizing agent’ analogies and that both are only intermediaries to ever fluctuating gene frequencies. Unfortunately, rather than arguing for a more reductive measure of selection, an all encompassing fitness-model or perhaps even a gene-centered perspective, they instead suggest viewing the process at a greater scale and wider focus.

Ironically, the article opens with a quote from Richard Dawkins’ Extended Phenotype;

“I have characterized inclusive fitness as ‘that property of an individual organism which will appear to be maximized when what is really being maximized is gene survival’... One might generalize this principle to other ‘vehicles’. A group selectionist might define his own version of inclusive fitness as ‘that property of a group which will appear to be maximized when what is really being maximized is gene survival’!

This excerpt, and the context in which it is constructed, clearly makes an argument against viewing the individual organism as a unit of selection and implies that any unit above that of the gene is so artificial as to be considered arbitrary. Key to this idea is the phrase “will appear to be maximized,” which means that it is not truly being maximized, but rather it is a merely an extension of the gene – a vehicle. A “vehicle” is precisely what a “group” represents, a vehicle composed of multiple smaller vehicles – all of which have a gene behind the wheel.

From the abstract: “Adaptation is conventionally regarded as occurring at the level of the individual organism.”

Perhaps individual organisms are ‘conventionally regarded,’ but not accurately so… Individual organisms may be units of reproduction, but they are not replicators. Genes lay at the core of all phenotypes; morphological, behavioral, social or otherwise - is it really convenient to think of natural selection as occurring at the level of the individual organism? Most successful organisms aren’t replicated in their entirety; rather it’s the successful, or surviving, genes contained within their DNA that are passed on with an increased probability of contributing to the genome of future generations. Genes are passed on, not whole organisms; if the analogy is not “true” for individuals, why up the ante and recommend adopting a level of biological organization that is even higher than an individual?

The authors admit that the Group Maximization Analogy (GMA) does have limitations;

“we find that there is a strong mathematical correspondence between the ynamics of gene frequency change and the GMA analogy in scenarios where groups comprise genetically identical individuals or where within-group competition is repressed. This correspondence reveals that, in such scenarios, natural selection acts to optimize group phenotypes for the purpose of group fitness maximization –i.e. group adaptation.”

According to the authors, group adaptation seems a best fit in those situations in which individual members have identical genomes (i.e. are “cloned”) or in those scenarios where competition is repressed (i.e. is “policed,” or controlled by an external agent). Wouldn’t these situations, one in which like-vehicles “strive” to move like-genes, and one in which a dominant phenotype exhibits some level of control (policing or chemical control via pheromones) over a less-dominant phenotype, also represent strong cases for a gene-centered, or an Individual Maximization Analogy?

Considering that within-group selection (i.e. genes by way of individual organisms) is inevitable, are there any cases, or models for group-selection that take this into account?

“We have found no formal justification for group adaptationism in any scenario in which within-group selection is permitted. Obviously, no real-world species will perfectly embody the ideal of zero within-group selection.”

OK, doesn’t such a finding impair the group model as an inclusive theory?

“…we emphasize that this is not sufficient grounds for abandoning the notion of group adaptation in evolutionary biology.”

Why not?

“The theory of individual-level adaptation is similarly based upon limiting assumptions, such as unbiased genetic transmission, which are not expected to be perfectly realized in any species; yet, it enjoys huge experimental and empirical success.”

True, however the individual-level adaptation model is also a “maximization analogy,” used as a tool, artificially constructed to demonstrate, measure and communicate what in actuality is occurring at a lower level - the level of the gene. Is that the purpose of the GMA, simply an additional tool to be used in exhibiting the effects of genetic frequency, and if so what is the benefit of up-scaling from the level of the organism to that of the group, or extending the phenotype to greater distances, bearing in mind that at the very least the individual is the unit of reproduction and any expansion of analogy is likely to cause even greater confusion?

“Our emphasis has been on formality and not generality – there is much work to be carried out to establish whether other scenarios will admit a group adaptationist view of social evolution. In the meantime, we suggest that it is safer to view social adaptations as occurring at the level of the individual organism, where they function to maximize inclusive fitness.”

Gardner et al. (2009). Capturing the superorganism: a formal theory of group adaptation. Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2008.01681.x