A Cool Science Project...

I found this nifty new video on YouTube. The info on the page indicates that it was made for a biology class. The video overviews info on pine flatwoods ecology.

I'd give it an A+

Have a look:

The Tactics of an Egg Tending Lynx

While stomping through a northwest Florida flatwoods community earlier this week, I took pause to admire a couple of swamp sunflowers (Helianthus angustifolius). The sunflowers’ brilliant yellow display glared brightly through the otherwise dark and rainy Tuesday afternoon and beckoned for a closer look. On turning-over one of the composite flower heads to better examine its calyx, I discovered a green lynx spider (Peucetia viridans). The spider was standing guard on top of its egg sac, which it had tethered securely to the optimistic sunflower’s underside with hard-wearing silk.

The green lynx spider is a member of the Oxyopidae Family and accordingly displays several traits characteristic for the group. In terms of identifying morphology, members of the group show a hexagon-like pattern of eye arrangement, and legs that bear large spines. Behaviorally, members of the Oxyopidae are aggressive daytime hunters which, as opposed to constructing webs, stalk their prey over the leaves and stems of the herbaceous groundcover. In regards to Peucetia viridans specifically, the spider’s body is translucent and exhibits a bright green coloration with red spots on the cephalothorax and black spots on its spiny legs.


Considering the presence of an egg sac and the sentinel-like bearing demonstrated by the spider appended to the sunflower, it was very likely a female. As a strategy, females of the species uncompromisingly guard their reproductive investment using a variety of tactics. These protective measures are necessitated by the low-to-the-ground habitat they share with a number of other voracious predators. Here in Florida, some of the most abundant and hostile species encountered by lynx spiders are fire ants (Solenopsis spp.)

The specific tactic used to defend an egg sac from fire ant onslaught is dependent on the intensity of the ant attack. Intensity is here a measure of ant quantity and the frequency of assault. Generally, female lynx spiders will utilize a mode of defensive escalation in which infrequent or isolated attacks from a single ant will be dealt with through deployment of a rapid and violent head-on confrontation. As the ant approaches the female, she’ll pounce forward and use her mass to knock the assailant from the plant, or, if failing to physically remove the ant, she’ll alternatively utilize her fangs to pierce the exoskeleton of her antagonist, ultimately slaying the provoker. The spider will almost always prevail during one-on-one combat with an ant, however if the ant attack is undertaken in number, evasion becomes the best option for the lynx.

If the incidences of attack become too frequent, or if the ants attack in larger quantities, mother Peucetia viridans will attempt to dissuade the egg-seeking aggressors by removing the prize for which they hunger – she’ll move the eggs out of reach. Once again depending on the seriousness and intensity of the ants’ offensive maneuvers, she’ll execute one of two evasive actions. One option is to cut all but a couple of the silk cables holding the egg sac in place, causing it drop from its anchor point and remain suspended in air; the second option to completely untie the sac and relocate to an entirely new host plant. The suspension method removes the eggs from hostility and forces any persistent attackers to travel down individual threads to continue pursuit – where they’ll undoubtedly meet an agitated mother face-to-face. Relocating the egg sac to a new host is a sure-fire way to end the current dispute however it is a risky option, because increased visibility during transport may leave both the mother and her eggs vulnerable to other hungry predators.


Eubanks, M. (2001). Estimates of the Direct and Indirect Effects of Red Imported Fire Ants on Biological Control in Field Crops Biological Control, 21 (1), 35-43 DOI: 10.1006/bcon.2001.0923

Linda S. Fink (1987). Green Lynx Spider Egg Sacs: Sources of Mortality and the Function of Female Guarding (Araneae, Oxyopidae Journal of Arachnology, 15 (2), 231-239

Adapting to Climate Change, the Uphill Pursuit of the Shifting Niche

This post represents the final in a three part series discussing Joseph Grinnell, climate change and ecological niches. The initial post can be found here: Joseph Grinnell, Climate Change and the Legacy of the California Thrasher, and the second here: Tracking the Niche, a Project of Grinnellian Proportions.



Having adopted Joseph Grinnell’s vision as their own, the current Director of the Museum of Vertebrate Zoology at Berkeley and his colleagues have taken on the challenge of following in Grinnell’s footsteps – quite literally. The group, headed by current Director Craig Moritz, has begun the process of resurveying the 700-plus localities that were originally surveyed by Grinnell in the early 20th Century. Their goal is to compare the newly collected data to that inherited from Grinnell in aspirations of gaining insight into how a century of environmental change has impacted California’s avian, mammalian and herpetological faunas. Through application of carefully recalibrated Grinnellian field-methods, and the employment of modern techniques, the group is expanding biology’s understanding of the ecological niche.

As discussed during the first post on this topic (available HERE), the effects of average changes in global climate can be dramatically amplified at local levels. As a case in point, consider the region of California that was originally surveyed by Grinnell between the years 1914 and 1920. Over the past 100 years an approximate one-degree rise in global temperatures has resulted in a 3.7°C increase in minimum monthly temperature! A four-degree change in temperature has undoubtedly altered the ecology of this region - Yosemite National Park – in substantial and quantifiable ways. Such quantification has been precise goal of Grinnell’s successor.

Pulling data from Grinnell’s field-notes and DNA from his collected specimens, Craig Moritz has used climate models, modern genetics and biodiversity informatics to decipher and compare the demographies of mammals, birds, reptiles and amphibians of past and present. The analysis rendered from this research clearly indicates that the link between environment-and-species has remained true since its inception in Grinnell’s 'The Niche-Relationships of the California Thrasher'. More specifically, as the 3.7°C increase in minimum monthly temperature pushed Yosemite’s available habitats towards new equilibriums its fauna followed suit.

Yosemite’s geologic and geographic setting entails a range of elevations that extend from about 50 meters to well over 3000 meters above sea level. As is typical for diverging elevations, as altitude increases average temperatures decrease. So, if moving towards the top of a mountain one could anticipate encountering bands of cooler micro-climates. The relationship that exists between a specific temperature range and its corresponding physical components allow for identification of specific ‘life zones’. For example, the hydrology found on a mountain’s glacial peaks will differ in type and quantity to that located near the base of the mountain. In considering this natural phenomenon of elevational transition with specific regard to an overall increase in temperature across the mountainous region as a whole, an upward shift in ‘life zones’ could be predicted. In other words, as a temperature increase reaches a certain threshold, the glaciers capping a mountain will recede as to reduce the total area occupied by ice, and to increase the availability of liquid water. With increased access to water, life zones that had been previously locked in a frozen state will become biologically available to plants formerly bounded to lower glacier-free altitudes.

Moritz’s comparison of the life zones documented by Joseph Grinnell to those surveyed by his research group demonstrated that as Yosemite’s temperature increased over the past century, its life zones moved upwards. Significantly, the research showed that the uphill advance of life zones induced pursuit by those avian and mammalian faunas found below. The general pattern discovered by Moritz was that as temperatures increased in the park, the majority of wildlife populations found at high elevations contacted upwards, abandoning previously occupied portions of their lower habitat range. Correspondingly, those animals occupying lower altitudes shifted their habitats uphill.

The ability of Yosemite’s wildlife to confront ever-shifting environmental attributes with resilience and flexibility is critical to maintaining lineages with the capacity to undergo the morphological and behavioral modifications required for their continued survival. The study of the processes driving this evolution, provides more than just a greater understanding of natural history, it also imparts the tools to ensure species conservation as global climate change accelerates environmental fluctuation. Luckily, field scientists such as Joseph Grinnell have, and will continue, to provide insight into the plasticity of adaptation.


See: The Grinnell Project's website.



Moritz, C., Patton, J., Conroy, C., Parra, J., White, G., & Beissinger, S. (2008). Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA Science, 322 (5899), 261-264 DOI: 10.1126/science.1163428

Tingley, M., Monahan, W., Beissinger, S., & Moritz, C. (2009). Colloquium Papers: Birds track their Grinnellian niche through a century of climate change Proceedings of the National Academy of Sciences, 106 (Supplement_2), 19637-19643 DOI: 10.1073/pnas.0901562106

Joseph Grinnell (1917). The Niche-Relationships of the California Thrasher The Auk, 34 (4), 427-433

Joseph Grinnell (1924). Geography and Evolution Ecology, 5 (3), 225-229

Tracking the Niche, A Project of Grinnellian Proportions

This post is the second in a mini-series discussing Joseph Grinnell, climate change and ecological niches. The previous post is available here: Joseph Grinnell, Climate Change and the Legacy of the California Thrasher



Joseph Grinnell was THE quintessential field biologist. From the time of his birth in 1877 (or, roughly thereabouts), until his to death in 1939 he marveled at the natural world. He reveled in nature’s aesthetic splendor, and he contemplated its immense mystery. He dedicated his entire life to the field of biology; birds, reptiles, mammals and amphibians – he studied them all, and he did so with great detail.

Grinnell’s philosophy of scientific inquiry focused intently on the task of accumulating as much raw data as possible. For example, during the biological survey he carried out in Yosemite National Park between the years 1914 and 1920, Grinnell and his field crews collected 817 photographs, nearly 3000 animal specimens and more than 2000 pages of notes! Being organized and detail oriented is one thing, but Grinnell’s drive for thoroughness approached the obsessive.

As testimony to Grinnell’s view on taking accurate field notes, consider the following precept that he was known for continuously repeating as a mantra for meticulousness;

“Put it all down. You might not think it’s important, but somebody else may.” (1)

It may very well have been the sheer bulk of his available data that guided Joseph Grinnell to develop the concept of the ‘ecological niche’ discussed during the last post in this series (Available HERE). After all, he collected information on everything from the individual behavioral characteristics and morphology of observed animals to the daily weather patterns of Yosemite; all of these informational axes have been incorporated into the ecological niche concept. Even if the ‘niche’ wasn’t born of the data directly, the huge quantity of collected information would certainly have been useful during the writing of Grinnell’s numerous research papers and species descriptions, which are more than 500 in number.

Yet greater evidence to Grinnell’s tenacity can be found in the fact that despite his time spent collecting, he still managed to teach and perform administrative duties as the first Director of the Museum of Vertebrate Zoology at Berkeley. An absolutely astonishing scientist!

In considering Grinnell’s knack for field work, another of his now famous quotes comes to mind. This one (from 1910) relates to the long-term value of the data that he and his colleagues were collecting.

“This value will not, however, be realized until the lapse of many years, possibly a century, assuming that our material is safely preserved. And this is that the student of the future will have access to the original record of faunal conditions in California and the West, wherever we now work.”

This quote would turn out to be very prophetic…

What possible value could be reaped in modern times for century-old data collected during Grinnell’s survey of the ‘Yosemite Tract’? What would comprehensive and weather-correlated descriptions of wildlife niches tell us about contemporary linkages of climate-and-niche?

A few steps are required in order to assess the above questions. As an initial step, there would be a need to quantify the climate-to-niche relationships of current systems. Once such modern data was in-hand, comparisons could be made between the ‘old’ and the ‘new’ to identify any patterns or inconsistencies. In other words, to gauge change compare Grinnell’s data with what is exhibited by Yosemite’s ecosystems today.



This is precisely what the present Director of the Museum of Vertebrate Zoology at Berkeley has done. He and his colleagues went to field, and using Grinnell’s notes and methods collected new data for the purpose of comparison. Their resurvey - The Grinnell Project - and findings will be discussed during the next post...


UPDATE: The 3rd and final installment of this series is available HERE.


1-As told to Ward Russell during a field survey; an audio recording of Ward’s 1992 interview can be found at the MVZ @ Berkeley website – HERE



Joseph Grinnell (1917). The Niche-Relationships of the California Thrasher The Auk, 34 (4), 427-433

Joseph Grinnell (1924). Geography and Evolution Ecology, 5 (3), 225-229

Moritz, C., Patton, J., Conroy, C., Parra, J., White, G., & Beissinger, S. (2008). Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA Science, 322 (5899), 261-264 DOI: 10.1126/science.1163428

A Gopher Tortoise in my Email...

Below are a couple of pictures emailed to me today by Lisa, a wildlife enthusiast and fellow Floridian. She took them this morning on her farm in central Florida.

I guess her horse had invited a neighbor over for breakfast..?






-Thanks Lisa, great shots!



Description:
The gopher tortoise, Gopherus polyphemus, is a large terrestrial turtle having forefeet well adapted for burrowing, and elephantine hind feet. The front legs have scales to protect the tortoise while burrowing. Body length averages approximately 25 cm (10 inches), with the shell ranging in height from 15 – 37 cm (6 – 15 inches). Body mass averages approximately 4 kg (9 pounds). Color is a dark brown to gray-black, with a yellow plastron (bottom shell). A gular projection is evident on the anterior...

You can find additional gopher tortoise info on the August 10th post - The Threatened Gopher Tortoise

Joseph Grinnell, Climate Change and the Legacy of the California Thrasher

Adaptive plasticity is a predictor of future reproductive fitness. The ability of an organism to confront ever-shifting environmental attributes with resilience and flexibility is critical to maintaining lineages with the capacity to undergo the morphological and behavioral modifications required for continued survival. Regardless if such elastic traits are realized through major swings in ontogenic development, or through the advent of novel life-history strategies, the ability of an organism to accommodate ecological variability is essential. This biological tenet is certainly true today as anthropogenically incited climate change is forcing accelerated rates of ecological alteration.

The Intergovernmental Panel on Climate Change has reported that mean global temperatures could increase by more than six-degrees over the course of the next century. Six degrees of global change translates to extremely dramatic transformations of biotic and abiotic conditions at the local level. Even if the ‘worse case scenario’ of six-degrees doesn’t come to pass changes in hydrology, periodic weather, seasonal patterns, emigration, extinction and in the availability of resources at regional and local levels are almost certainly inevitable during the next century. To cope with these changes it will be necessary for organisms to adjust their tolerances to environmental variability, they may need to more-efficiently utilize the resources on-hand, or they may need to physically relocate to habitats for which they are better suited. To better understand how these impending organism-to-environment adjustments will occur, it's important to seek understanding as to how organisms fit into their ecosystem. It is the relative position of an organism in its environment and the way in which it behaviorally responds to its surroundings that is referred to as the organism’s ‘niche’.

With respect to etymology, the word ‘niche’ is derived from the French word ‘nicher’ which literally means ‘to nest,’ as in a bird going to nest. In regards to the word’s use in biology – broadly defined above - this literal translation is very appropriate, because the term was first introduced by an ornithologist in a publication describing the distribution of a bird - the California thrasher (Toxostoma redivivum).

The California thrasher is the largest member of the Mimidae Family and can grow to be uupwards of 30 cm in length and weigh as much as 85 grams. The bird’s coloration is fairly non-descript; its body is brown and it has a tan or buff-colored ventral side. There are however a couple of characteristics that make T. redivivum especially unique. One is the bird's restriction to a very narrow geographic range in California, and another is its habitat preference for densely vegetated brushlands. It was the thrasher’s limited distribution and fondness for the concealment offered by shrubs that first attracted the interest of the celebrated naturalist and scientist Joseph Grinnell.

In the October 1917 issue of The Auk, Joseph Grinnell published his work 'The Niche-Relationships of the California Thrasher'. In that enduring contribution Grinnell explained that the reason for the thrasher’s

“…restricted distribution is probably to be found in the close adjustment of the bird in various physiological and psychological respects to a narrow range of environmental condition.”

In other words, Grinnell clearly recognized that the bird’s morphological and behavioral traits linked it to the specific ecosystem that it inhabited. Furthermore, Grinnell identified that

“[t]hese various circumstances, which emphasize dependence upon cover, and adaptation in physical structure and temperament thereto, go to demonstrate the nature of the ultimate associational niche occupied by the California Thrasher.”

In Grinnell’s mind, the relative position of the thrasher in its environment, as well as its distinctive behaviors, established a general rule that could be extrapolated and used as a tool for detailing and predicting the spatial and temporal relationships held between organisms and their environments. The ‘niche’ would quickly become a tool for not only itemizing individual life-history traits, but also for interpreting the evolutionary and adaptive implications of the organism-to-environment dynamic.

Building on his idea of an ecological niche, in July of 1924 Grinnell went on to publish ‘Geography and Evolution,’ a work in which he fathered what are contemporarily known as the competitive exclusion principle and the concept of ‘vacant niches.’

“Some of us have concluded that we can usefully recognize, as measures of distributional behavior, the realm, the region, the life-zone, the fauna, the subfauna, the association, and the ecologic or environmental niche. The latter, ultimate unit, is occupied by just one species or subspecies; if a new ecologic niche arises, or if a niche is vacated, nature hastens to supply an occupant, from whatever material may be available. Nature abhors a vacuum in the animate world as well as in the inanimate world.”

The competitive exclusion principle is the idea that two species occupying the same habitat and fighting for the same resources will not obtain equilibrium until one species overcomes, or out-competes, the other. These ideas are front-and-center to modern biology and are both credited to Grinnell.

Serving as the founding father of the ‘niche’ was but one of Joseph Grinnell’s numerous contributions to science. Over the next couple of days I hope to post more of Grinnell’s work, as well as that of his modern counterparts that are – literally – following in Grinnell’s footsteps in hopes of gaining insight into how the observations of an early 20th Century scientist can be used to decode the effects of climate change in a 21st Century world.


UPDATE: The second part of this post available HERE.

Joseph Grinnell (1917). The Niche-Relationships of the California Thrasher The Auk, 34 (4), 427-433

Joseph Grinnell (1924). Geography and Evolution Ecology, 5 (3), 225-229

Jack Horner on Dino-Chickens

Another short clip from a Jack Horner interview that appeared on CBS's 60-minutes last night. This one touches on the possibility of reverse-engineering chickens to create a dinosaur (or, dinosaur-like critter).

The Evo-devo clip with Sean Carroll (previous post) is from the same broadcast.



Watch CBS News Videos Online

Prime Time Evo Devo with Sean Carroll

Sean Carrol Talking Evo Devo on 60-Minutes


Watch CBS News Videos Online

Dead Zones, Conservation and Commercial Fishing

I’ve just read in the local news that Kevin Craig from the Florida State University’s Coastal and Marine Laboratory will be heading-up a collaborative four-year project funded by NOAA's Northern Gulf of Mexico Ecosystem and Hypoxia Assessment Program. The project’s goal is to assess the impact of the Gulf of Mexico’s ‘dead zone’ on marine ecosystems with a particular focus on shrimp and the shrimping industry.

It has long been known that agricultural run-off carrying excesses of fertilizer from the ‘bread basket’ of the United States are finding their way into the tributaries of the Mississippi River, and in turn, into the Gulf of Mexico. Once in the Gulf they consequently spawn explosions of algae growth resulting in hypoxic conditions and the conception of massive Dead Zones. Surges in the growth of algae and other noxious plants as a product of fertilizer facilitated Nitrogen and Phosphorous loading is called eutrophication. Eutrophication leads to de-oxygenated environments, and the resultant death of those organisms that require oxygen - of which there are many. The loss of oxygen-dependent organisms leaves vacant important positions in long established food-webs, potentially leading to the total breakdown of ecosystem function. To make matters worse, far from being stationary the dead zones move or “creep” from their epicenters corrupting ecosystems both far and wide. For Florida, the Gulf of Mexico Dead Zone may contribute to “Red Tide” and the death of everything from phytoplankton to manatees in the State’s coastal waters.

Kevin Craig is certainly the person for the job; back in 2005 he wrapped-up a research project that examined the effects of hypoxia on the abundance and distribution of Farfantepenaeus aztecus - the Gulf of Mexico’s ‘brown shrimp’. In that study, Craig, Larry Crowder, and Tyrrell Henwood used shrimp trawl surveys to compare the distributions of shrimp between hypoxic and non-hypoxic areas. What the team found was that the spatial distribution of shrimp in hypoxic regions was substantially different that those associated with non-hypoxic areas. The researchers also concluded that the effects of hypoxia contributed to as much as a 25% loss in F. aztecus’s available habitat.

The new NOAA funded project will undoubtedly have implications for both the science of ecology and in that of conservation. Shrimping is a major industry in the United States, and as such the participating fishermen and other commercial industries hold considerable economic and political clout. I'm eerily reminded of the warnings from biologists that were left unheeded and initially overthrown by rule-makers during the collapse of the Northern Cod Fishery…


Craig, J., Crowder, L., & Henwood, T. (2005). Spatial distribution of brown shrimp (Farfantepenaeus aztecus) on the northwestern Gulf of Mexico shelf: effects of abundance and hypoxia Canadian Journal of Fisheries and Aquatic Sciences, 62 (6), 1295-1308 DOI: 10.1139/f05-036

Wetland Plant of the Week #32

Aster carolinianus

Climbing Aster

Climbing aster, unlike the majority of the other varieties in the genus (which are herbaceous), presents as a many branched shrub with a woody stem base and often even woody branches. The Obligate plant displays numerous leaves that range from elliptic to lanceolate in shape. The flowers are typically about an inch in diameter and generally have a light-blue or light-purple color.

Aster carolinianus is native to the coastal plain of the southeastern United States and is often found residing in marshes, along stream banks and - as pictured above - in freshwater swamps.

As a characteristic trait, the climbing aster has the habit of entangling itself in the branches of surrounding plants, or even tying itself in large tousled masses.

Asterales, the order to which the Asteraceae family belongs, has origins in the Cretaceous period about 100 million years ago and probably experienced diversification during the Oligocene and Miocene. In regards to their evolutionary past, recent research by Tom Viaene (et al) examined the variability of stamen and petal morphologies within the basal asterid families. Through comparisons of the genes that coded for these floral structures, he determined that the early members of the asterid group likely duplicated the petal and stamen genes as a strategy for moving into a wider range of niches.

The above images were taken last week near St. Marks National Wildlife Refuge in northern Florida.

Viaene, T., Vekemans, D., Irish, V., Geeraerts, A., Huysmans, S., Janssens, S., Smets, E., & Geuten, K. (2009). Pistillata--Duplications as a Mode for Floral Diversification in (Basal) Asterids Molecular Biology and Evolution, 26 (11), 2627-2645 DOI: 10.1093/molbev/msp181

Fire Ecology Marathon; Nature Red in Tooth and Flame Part-4

The savannas of the southeastern United States are inimitable natural communities that have undergone ecological assembly in the presence of seasonal fire cycles and, as discussed during the first three installments on this topic (available here; Part-1, Part-2, Part-3), are rich in organisms capable of manipulating the regularity, movement and intensity of these wildfires. During the preceding post (Part-3) the phenotypes of two such fire-born species, the longleaf and slash pines, were detailed as exemplars of organisms with traits that not only aid in defending against heat and flame, but also as species that exhibit specific physical structures, chemicals and behaviors that could intrinsically promote fire. In closing that previous discussion, consideration was given to the possible motives behind the longleaf and slash pine’s ability to deliberately provoke fire.

Though it may initially seem to be counterproductive or even a hindrance to survival, through promoting fires the savanna pines obtain benefits that directly enhance their inclusive fitness. Because of the processes that drove the organismal evolution of the longleaf and southern slash pines in geological time, and the processes that propelled community assembly in savannas, the presence of wildfires effectively created a duality in the character of potential pine competitors and that of would-be savanna inhabitants - either they can tolerate fire, or they can’t tolerate fire.

In the absence of wildfires over extended periods of time (i.e. fire suppression) several ecological changes can occur in savannas. Most profoundly, without regular wildfires not only would the already present fire-tolerant plant species survive, but in addition, fire-intolerant species would experience greater fecundity. Without the deterrence provided by fire, resource-rich savannas can quickly become the envy of plants from surrounding hammocks and mixed hardwood forests, thus encouraging invasion and recruitment from these neighboring communities. Such movement of new species into the savannas would contribute to substantial ecological alteration of the natural processes that maintain the system’s predictable boundaries, ecotones and makeup.

Recall from Part-1 of this post that the plants found in hammocks have undergone selection for initial rapid growth and direct competition for sunlight. Just as the natural history of the pines has been shaped by fire, the history of dense-canopy species have evolved to fight for radiance. If unobstructed access to the abundant savanna sun is tantalizingly flaunted, these species would quickly invade, rapidly recruit and hurriedly regenerate to overtake all biologically available space. What was initially a patchwork of invasive species would spread to encompass and overcrowd the savanna, in the process reducing the diversity of appropriate groundcover plants, and adversely impacting the reproductive success of the native inhabitants – slash and longleaf fitness would decline.

In addition to increasing interspecific competition in the savannas, invasive species also create positive feedbacks in the wildfire cycle - magnifying fire suppression. The presence of abundant shrubs and woody species in a normally open savanna formulate densely vegetated landscapes that reduce fine fuel loads on the ground and decrease the likelihood of fire propagation. The lack of fire - in turn - facilitates further invasions, which increases vegetative densities even more, which reduces fire even more, which allows for yet greater invasive proliferation, etcetera…

With continued fire suppression, what was once a savanna, characterized by thinly distributed trees, would transition towards a densely canopied hammock with an impenetrable thicket understory. Growing populations of invasive species would amplify competition for resources, thus pushing the fitness experienced by the longleaf and southern slash pines to dangerously low values. This is precisely why the ‘fire gene’ is so critically important to the pine’s genotype. As crowding increases in this scenario, and essential resources dwindle, hormonal stress responses within the pines intensify. The hormones drive physiological changes in the trees causing leaves to drop and internal hydrocarbon chemistry to move toward increased combustibility. The probability for fire is increased. And, when fire does return, the stems, branches, leaves and roots from newly arrived invasives will serve as kindling for augmented wildfire intensity - to such extremes that only the hardiest of the fire-tolerant will be able to survive.

For clarification, conceptual genes (like the ‘fire gene’) aren’t confirmed as actual chromosomal localities for which variable alleles compete. Rather, conceptual genes are offered as thought-tools for understanding the premise that natural selection operates on phenotypical traits that are the products of genotypical coding. In regards to the ‘fire gene’ specifically, it is a hypothetical genetic compliment that is expressed in such a manner that the physical presence of fire improves the likelihood of that genotype being passed on to future generations. In other words, if a population of trees exist in which some members have a genotype that provides increased fitness in the presence of fire, AND that population is then exposed to fire - ultimately killing a certain percentage of the population - those trees with fire gene advantage will experience higher survivability and greater measures of fecundity compared to those not possessing a fire gene.

Returning to the savanna pines expressly, irregardless or not if there is literally a single gene that provides for all of the phenotypical adaptations to fire described throughout this post, or if these traits are the result of a cooperative epistasis, or if the characters are disparate and independent, it remains likely that their occurrence and continued propagation through evolutionary time has provided a significant advantage.

Through 300 million years of natural selection, wildfires have propelled the savanna defending pines to levels of adaptation in which they are capable of wielding fire. ‘Nature, red in tooth and flame’ has fashioned a true ecosystem engineer, one that is capable of establishing and defending the ecotonal boundaries between natural communities.


Beckage, B., Platt, W., & Gross, L. (2009). Vegetation, Fire, and Feedbacks: A Disturbance‐Mediated Model of Savannas The American Naturalist, 174 (6), 805-818 DOI: 10.1086/648458

Stevens, J., & Beckage, B. (2009). Fire feedbacks facilitate invasion of pine savannas by Brazilian pepper New Phytologist, 184 (2), 365-375 DOI: 10.1111/j.1469-8137.2009.02965.x

Ecosytem Engineering and Fire Ecology, Part 3

The closing paragraph of ‘Nature, Red in Tooth and Flame Part-2’ mentioned how extrinsic factors in the environment, such as the presence of increased atmospheric oxygen and an abundance of herbaceous plants to serve as fuel, collectively worked to generate frequent and intense wildfires during the Pennsylvanian Period approximately 300 million years ago. It was the presence of these Carboniferous wildfires that positively selected fire-tolerant gymnosperm species for continued development, and initiated their adaptive radiation towards the representative pine trees that occupy the modern-day savannas in the southeastern United States. It is within contemporary savannas that the longleaf pine (Pinus palustris) and the southern slash pine (Pinus elliottii var. densa) express their fiery ancestry; however, the fire ecology observable in these natural communities isn’t limited to wildfires born of purely extrinsic factors. Through, evolution the longleaf and slash pines have developed the ability to intrinsically influence the movement of fire, and they have learned to use this powerful tool as an instrument for customized ecosystem engineering.

During the description of savanna communities in Part-2, it was detailed that the canopies of these systems exist in an open condition that allows for ample access to sunlight by a diverse range of groundcover plants. Ample sunlight, water and soil nutrients can all be found in savannas. So, considering the occurrence of these botanical prerequisites, compounded with the highly competitive, almost war-like, tendencies of nature (as elaborately described in Part-1), one might wonder why trees from the hammocks don’t advance to occupy the promising and resource-rich savannas… The reason for the limited progress of hammock trees in moving to the savannas is that invasions are tightly controlled by the few trees already inhabiting the systems – the few trees usually being longleaf and slash pine.

An open canopy is a characteristic physiognomy of savannas precisely because the ground gaining charge of closed-canopy trees is impeded by the heirs of the Carboniferous gymnosperms. Said differently, the trials-by-fire endured by the antecedents of the modern-day conifers have shaped the phenotypes of the savanna-defending longleaf and southern slash pines. Furthermore, the phenotypes shown by the longleaf and slash pine reach outward to encompass the savanna as a whole, where these phenotypes serve as catalysts for engineering ecosystem towards one purpose – making more pine trees.

The longleaf and southern slash pine exhibit a host of morphological features that facilitate their continued manipulation of fire. For instance, both of these trees have thickly armored plates of bark on the exterior of their trunks; like fire-retardant shields, the plates guard the tree's interrior tissues against excessive heat and all but the most intense of wildfires. Similarly, the undifferentiated cells (meristematic cells) found within the trees, the ones that make-up the growth tissue found in meristems, are safeguard by a casing of heat resistant scales. And, as opposed to a pattern of wide lateral spreading, the roots of the slash and longleaf trees penetrate perpendicularly downward, where they are sheltered from harsh surficial temperatures. These are but a small number of the morphological – anatomical – traits displayed by the fire-scaping pines; their reproduction and growth habits give additional clues as to their natural history.



The reproductive cycle of the longleaf and southern slash pine include strategies that take into account the recurring spring fires described in Post-2; by germinating in the fall and occasionally producing periodic mast crops, young pines are afforded several months of growth before the first ravages of wildfire arrive. In spite of the head start gained through fall germination, the longleaf and slash pine don’t approach growth from a mere lackadaisical standpoint, quite the contrary, both trees posses the ability to quickly establish themselves. Just as the most successful plants of a closed canopy hammock battling for access to solar radiation (see the ‘competition for sunlight’ example provided in Part-1), the savanna pine trees – in addition to a ‘fire gene’ – also hold in their genetic arsenal a ‘rapid growth gene.’ Slash pine, for instance, has a genetic compliment that permits the tree to take advantage of every opportunity to seize real estate; once germinated, it rapidly shoots upward expressing secondary needles in less than six month’s time, and by the time it is two-years old, it is able to survive a wildfire of ‘average' intensity.

The above characteristics depict but a few of the intrinsic phenotypes that improve the survivability and reproduction of the savanna dwelling pines in the presence of fire; but what is truly remarkable is the trees’ ability to channel fire directly – the trees’ ability to shape their ecosystem through offensive tactics.

In addition to the defensive phenotypes of the savanna pines, the chemistry of their leaves (i.e. pine needles) have undergone adaptation such that while on the tree, the leaves produce flame resistant chemicals, but when the leaves are shed, their chemical consistency changes to achieve an altogether different effect - they become flammable and easily ignited. As the leaves are shed from branches, they fall to the ground where they accumulate around the circumference of the trees. The piled pine needles are composed of cellulose-laden fibers, which unlike the fire-resistant lignin that evolved during the Paleozoic, serve as excellent fuel for fires. So when on the tree, the pine needles are similar to the armored plates found on the trunks, they help defend against tissue damage when exposed to wildfire; but, in the absence of recurrent fire, the leaves are quickly dropped and their chemistry changes to promote fire. Moreover, pine leaves aren’t the only fire stoking property of the savanna pines. The very structure of the pine’s thin and supra-numerous branches can facilitate the spreading of fire (horizontally and vertically) through increasing the surface area of exposed tissues to flame. And, the flammable hydrocarbons produced in the plant’s resins can incite wildfires or encourage lightening strikes to take hold (for example, the terpenes produced by the conifers in question; think ‘turpentine’).

Though it may initially seem to be counterproductive, or a hindrance to survival, through promoting fires the savanna pines obtain benefits that actually enhance inclusive fitness….

[Continue HERE, PART-4.]


Beckage, B., Platt, W., & Gross, L. (2009). Vegetation, Fire, and Feedbacks: A Disturbance‐Mediated Model of Savannas The American Naturalist, 174 (6), 805-818 DOI: 10.1086/648458


Stevens, J., & Beckage, B. (2009). Fire feedbacks facilitate invasion of pine savannas by Brazilian pepper New Phytologist, 184 (2), 365-375 DOI: 10.1111/j.1469-8137.2009.02965.x