Snapshots taken this past summer near Bradenton, Florida.
Tuesday, December 21, 2010
Snapshots taken this past summer near Bradenton, Florida.
Friday, November 12, 2010
Transgenic organisms are critters that have been genetically engineered to express characteristics unique to their species. By snipping, swapping and splicing DNA between different species, organisms can be designed to provide specific benefits to people. For example, bacteria can be engineered to synthesis human insulin for treating diabetes, tomatoes can be manipulated to have an improved shelf-life, and pigs can be designed to more efficiently digest phosphorus, thus easing both their own cost of feeding and the amount of phosphorus pollution discharged into the surrounding environment. But, despite the potential benefits to people, what trouble could ensue if a transgenic organism were to evade human controls and escape its confinement? Would the transgenic organism out-compete the wild type and push it to extinction?
Cucurbita pepo is a species of squash cultivated around the world as a popular food; common varieties of the species include the zucchini, yellow squash and gourd. In addition to being commonplace at dinner tables, Cucurbita also maintains fame as a widely utilized transgenic plant – a transgenic plant that has managed to pass its transplanted genes to wild populations.
Prior to their escape, the genes of the Cucurbita plant had been engineered to have resistance to a leaf-wilting virus transmitted by aphids. The reasoning behind the genetic transplant was simple, by reducing susceptibility to the aphid borne disease, the agricultural yield of squash could be increased and more humans could be fed; but, having escaped, would the disease-resistant plants replace their naturally more disease-susceptible counterparts?
According to a case study just published in the November issue of the International Journal of Plant Sciences, when mixed populations of transgenic and wild type squash were naturally exposed to the aphid borne disease, the transgenic members did indeed exhibit better health – at least at first. After initially showing better health, the condition and reproductive success of the transgenic squash later equalized and balanced to that of the non-transgenic type. The reason for the equalization was that the robust appearance of the transgenic plants attracted the attention of leaf-munching, and bacteria-transporting, beetles. The beetles’ preference for the healthy looking plants affectively buffered any benefit the plants received from their introduced viral resistance.
Sasu, M., Ferrari, M., & Stephenson, A. (2010). Interrelationships among a Virus-Resistance Transgene. International Journal of Plant Sciences, 171 (9), 1048-1058 DOI: 10.1086/656531
Monday, October 11, 2010
Sunday, September 12, 2010
…The female, being responsible for a greater investment in the rearing of offspring, acts as chooser during courtship displays…
…The male of the species entices the female by inflating his chest and lifting his shoulders. The illusion of a larger size is even further accentuated by posturing and strutting…
…Having failed to impress the female the male abandons his territory; but, his departure leaves open an opportunity for rivals who are also competing for access…
…Intrasexual competition is also evident with the females… The subordinate attempts to manipulate the behavior of the dominant female through use of ethanol…
Check it out:
Monday, September 6, 2010
Thursday, September 2, 2010
Charles Darwin writes a letter to Stephen Hawking
Dr. Stephen Hawking,
I am sending this correspondence out of admiration of your recently published book, The Grand Design. Although I am not a physicist by trade, in my assessment I found the text of your explanations to be written with a clarity, thoroughness and prose rarely encountered in popular works of the sciences; undeniably the book was both informative and inspiring. However, dear sir, at the risk of confusing my professional appraisal of your theories with my own personal motivations, I must be completely honest as to the true reason for holding your publication in such regards, and indeed the real purpose behind this current letter.
Since publication of my abominable theory of natural selection in the Origin of Species, I have been bombarded with continuous assault, and insult, from the pious in our shared world community. My publications have been banned, burned, intentionally misconstrued and even cited as the works of the devil. Despite having paid little time or mind to harebrained allegations of being a pointy-tailed marauder, I must confess that I have found religion’s interference with science, and the pursuit of knowledge in general, to be the most disheartening of experiences. In short, dear sir, thank you for deflecting the gaze of the religious eye from me and my field of interest - the biological sciences.
Not since publication of the Origin of Species in 1859 have I been so at ease; and remember dear sir, I have been dead since April of 1882! Now finally, after all of this time, religious zealots of every ilk, sect and creed can take a break from their incessant efforts to ban the teaching of evolution. Now, thanks to you sir, these fools can focus on other issues they deem to be of importance - unfortunately the issues they deem important will likely include banning instruction in chemistry, physics and astronomy…
With the most sincere of gratitude,
PS: If I may be so bold as to offer a parting word of advice, you may wish to inquire into the availability of fire retardant book covers for your publication.
The Bowie-Wallace-caterpillar connection became apparent to me yesterday morning as I was heading off to work. While stepping outside in route to the car, I noticed a rather strange looking creature attached to the exterior of the door frame (no, it wasn’t David Bowie!). In trying to figure-out what the creature was, my brain struggled to match its distinctive shape, color and pattern to familiar morphological templates filed away in the dark recesses of my memory. Then it hit me! Although the overall proportions of the beastie seemed diminutive in comparison to the model held in my head, its overall appearance reminded me of something from my adolescence back in the late 1980s – it reminded me of a mullet!
For those with a functional fashion sense (or a selective memory), Wikipedia defines a “mullet” as a “hairstyle that is short at the front and sides, and long in the back. Often ridiculed as a lowbrow and unappealing hairstyle, the mullet began to appear in popular media in the 1960s and 1970s but did not become generally well-known until the early 1980s.”
The tiny creature (which fortunately turned-out to be a caterpillar, not an outdated and free-living hairstyle) looked exactly like a mouse-sized mullet! In fact, it looked like a miniaturized version of the very mullet sported by David Bowie just a few decades ago.
Check it out:
As evidenced by the images shown above, both Bowie and the caterpillar exhibited a conspicuous, yet strangely similar, appearance. It’s this conspicuous appearance that brings us to Alfred Wallace; because, Wallace knew a thing or two about conspicuous caterpillars.
In 1889 Alfred Wallace published a book titled, “Darwinism: an Exposition of the Theory of Natural Selection with Some of its Applications.” In this work, Wallace expanded on one of his theories - a theory that he had previously presented to Charles Darwin and to members of the Entomological Society of London - the evolutionary phenomena now known as ‘aposematism.’
Aposematism refers to signaling adaptations exhibited by prey species that serve to dissuade would be predators from attacking. In other words, aposematic species are those organisms that intimidate, scare, or warn predators of their ‘unprofitability’ as potential prey items. Aposematic species are considered ‘unprofitable’ because in addition to the signaling adaptation, they also bear an underlying secondary defensive mechanism. For example, a coral snake could be considered an aposematic species because in addition to its secondary defense mechanism (a venomous bite), it also warns predators of this lethal capacity through the use of visual cues; in this case, warning coloration via strongly contrasting yellow, red and black colored bands along the length of its body.
Speaking to warning displays, Wallace wrote, “…instead of serving to conceal the animals that posses them or as recognition marks to their associates, they are developed for the express purpose of rendering the species conspicuous. The reason of this is that the animals in question are either possessors of some deadly weapons, as stings or poison fangs, or they are uneatable, and are thus so disagreeable to the usual enemies of their kind that they are never attacked when their peculiar powers or properties are known.” (Chapter IX of Alfred Wallace’s 1889 book; my emphasis added)
As an alternative to Wallace’s quoted learned avoidance of prey due to ‘known’ risks (learned through prior bad/unprofitable encounters), predators could also facilitate the evolution of conspicuous prey by practicing dietary conservatism. By simply avoiding prey items that look weird or unusual, predators could thin populations of normal looking individuals, thereby contributing to a reproductive boom for the remaining strange-looking conspecifics. In the case of a predator of caterpillars, for example, by eating ‘normal’ hairless caterpillars a predator could open the door for a surge in ‘strange-looking’ caterpillars - like those caterpillars that flaunt mullets.
In fact, Wallace frequently used conspicuous caterpillars as examples in explaining the phenomena of warning signaling - caterpillars not dissimilar to the venomous Megalopyge opercularis found on the frame of my door yesterday morning.
Looking strange can sometimes be advantageous - just ask David Bowie!
Wallace, A. R. 1889. Darwinism: an Exposition of the Theory of Natural Selection with Some of its Applications. London: MacMillan.
Lee, et al. (2010). Can dietary conservatism explain the primary evolution of aposematism? Animal Behaviour, 79 (1), 63-74 DOI: 10.1016/j.anbehav.2009.10.004
Sunday, August 29, 2010
Saturday, August 28, 2010
Failure 1: In the first couple of paragraphs, the paper guides unwary readers into accepting two false premises; the first is that kin selection and inclusive fitness are alternatives to “standard natural selection theory,” and the second false premise is that altruism is synonymous with eusociality.
Explanation: The authors confuse altruism (one type of cooperative behavior) with eusociality. Eusociality is a type of social organization seen in bees, ants, termites, naked mole rats, and a variety of other critters. The sophisticated level of cooperation exhibited by these groups can be achieved through a host of mechanisms; including mutualisms, rewarding, active enforcement, policing, reciprocity and a number of other phenotypes. Altruism is just one mechanism for cooperation; explaining altruism isn’t the same as thing as explaining all of eusociality, and explaining eusociality doesn’t explain all altruism. Despite the authors’ intended objective of detailing the evolution of eusociality (a long term process), they continuously revert to explaining only short term altruistic behavior – these are not the same thing.
The distinctions between kin selection, inclusive fitness, and “standard natural selection theory” are discussed in Failure 2 below.
Failure 2: Under the heading “Rise and fall of inclusive fitness theory” on page one of the paper the authors incorrectly/narrowly define both kin selection and inclusive fitness.
Explanation: The authors write, “The defining feature of kin selection theory is the concept of inclusive fitness…”
No it isn’t. The idea of inclusive fitness is central to modern biology and refers to the combination of both direct fitness (i.e. the reproductive success of the individual) AND indirect fitness (e.g. an individual controlling or manipulating other reproducers in proximity). Kin selection represents only a limited portion of inclusive fitness; more specifically, it’s a subset of indirect fitness.
Kin selection is the sort of cooperative behavior in which an organism works to enhance the reproductive success of a relative. (By helping relatives, organisms can increase the percentage of their family’s genes in the larger population.) In contrast to kin selection, inclusive fitness is the measure of an individual’s total ability to affect the passing of its genes to the larger gene pool. Inclusive fitness exists even in the complete absence of relatives and kin selection. More broadly, inclusive fitness can even be viewed as the modern interpretation of Darwin’s original linkage between adaptation and differential survival and can thus be seen as wholly coinciding with natural selection.
Failure 3: The authors make the “Selfish gene assumption”
Explanation: Immediately following Failure 2 described above, the authors enter into a discussion as to the validity of Hamilton’s rule (Relatedness >cost/benefit). The gist of their argument here is that because there are in existence eusocial animals with a low degree of familial relationship (e.g. those with diplodiploid sex determination) Hamilton’s rule is not valid. I call this failure the “Selfish gene assumption” because I’ve heard the same erroneous interpretation made during critiques of Richard Dawkins’ book the “Selfish Gene.”
Some folks incorrectly assume that Richard Dawkins forwards a view in which a single copy of a gene – a single gene in a specific individual – unintentionally works to be passed on to future generations. This isn’t the case. The book the “Selfish Gene” describes a perspective in which all genes for a specific phenotype – all copies present in the entire population - unintentionally work to increase in frequency. This may seem like a subtle difference, but it isn’t. It isn’t a subtle difference because like Dawkins in the Selfish Gene, Hamilton expressed relatedness in terms of genetic frequency, not in terms of genealogical proximity. Therefore, if E.O. Wilson and the other authors of the currently evaluated paper want to 'disprove' Hamilton, they shouldn’t be so concerned with the degree of familial relatedness shared between two INDIVIDUALS; rather, they should be concerned with the frequency of one individual’s genes as compared to the population’s gene pool as a whole. It doesn’t matter if individuals in a group are sisters, brother and sister, or third cousins twice removed – what does matter is genetic similarity. Members of a group can hold a huge compliment of genes in common without having the same parents.
Getting a bit lengthy, so I’ll stop here for now; the three “failures” listed above can be found on the first two pages of the paper. Rather than moving on to page three, I’ll wrap-up by saying that in the paper’s conclusion the authors summarize the stages of natural selection they believe to be required for the evolution of eusociality. This may not come as a surprise, but all of the listed stages could be explained in terms of inclusive fitness...
In summary, the paper doesn’t offer anything novel and in my opinion represents merely the latest pitch for group selection view - a pitch that fails on page one due to lack of a shared vocabulary.
Nowak, M., Tarnita, C., & Wilson, E. (2010). The evolution of eusociality Nature, 466 (7310), 1057-1062 DOI: 10.1038/nature09205
Saturday, August 21, 2010
Xyris caroliniana is a species of “yellow-eyed grass” belonging to the Xyridaceae Family of monocots. It’s an herbaceous perennial common to Florida’s marshes, hydric pine flatwoods, and wetland ecotones. They display a compact erect stem and ascending leaves. Its flowers are short lived with three yellow petals.
The iridescence shown by Buprestis rufipes isn’t due to pigmentation in the exoskeleton, but rather microscopic textures in its cuticle which reflect and scatter particular frequencies of light.
Thursday, August 19, 2010
Members of the Ophioglossum palmatum are epiphytic ferns that take root in the humus that collects between the fronds and the trunks of palm trees.
These snapshots were taken last month during fieldwork near the Fakahatchee Preserve in south Florida.
Although, they’re listed by the State of Florida as an endangered species, the hand fern can also be found in Southeast Asia, South America and Madagascar.
A close-up showing the spore-bearing
Tuesday, August 17, 2010
Despite a recent malaise brought about by incidents in the Gulf of Mexico, I was briefly inspired this weekend when I discovered a couple hundred juvenile frogs in my backyard. Yeah, a COUPLE HUNDRED!
Though, I’m not exactly certain where the deed went down (no ponds or puddles around), my best guess is that about 45-days ago (tadpole-to-froglet growth time) a couple (perhaps a few) of the squirrel frogs that reside in the rafters of my porch got “frisky” (i.e. mated). The result: hundreds of these guys in my yard:
Squirrel frogs (Hyla squirella) are common throughout the Southeastern United States. They’re terrestrial tree frogs that breed and undergo early development in water (puddles, ponds, ditches, etc…). Once sufficiently mature to undertake travel, they move to forested areas (or the exteriors of human dwellings) to live as adults. Eventually, the upland dwelling adult frogs return to water to reproduce and the cycle starts anew.
As another quick natural history note, Hyla squirella are at least bimodel when it comes to sexual selection. Like many frog species, the females home-in on distant males by converging on the sound of the male’s song; but, in addition to sound, female squirrel frogs also select mates based on appearance.
Males with low-frequency and energetic calls are preferred by the females, but the females also consider the size of the yellow stripe that runs down the male’s side. The male’s yellow stripe may give some indication as to his overall health.
Sunday, July 25, 2010
Like the adaptation of flight, eyes too have independently evolved in a number of different animal taxa. From the photoreceptive eyespots of a flatworm to the sharply focusing lenses of a great horned owl, eyes have arisen at least forty different times during the Earth’s biological history. ‘Convergent evolution’ is the phrase science uses to describe the common adaptations shared between different lineages of animals. For example, a case for convergent evolution could be made for the possum’s opposable thumb, which may very well represent an adaptation for improved grip; but, this enhanced grasping ability is hardly an indicator of a hereditary tie to primates. Rather than having been passed through genetic transmission from parent to offspring, the opposable thumb simply has an analogous structure and function for both possums and primates. So, just as flight isn’t unique to birds, the opposable thumb isn’t unique to primates.
If not opposable thumbs, is there a trait that is unique to primates? More to the point, is there a trait that is unique to the variety of apes called Homo sapiens? Perhaps intelligence is unique?
Maybe not as unique as we’d like to think:
de Waal, F., & Ferrari, P. (2010). Towards a bottom-up perspective on animal and human cognition Trends in Cognitive Sciences, 14 (5), 201-207 DOI: 10.1016/j.tics.2010.03.003
Monday, July 19, 2010
From Florida Department of Environmental Protection:
“Tsunamis are unlikely to occur as a result of the Deepwater Horizon incident. These rumors involve the naturally occurring methane beneath the seafloor in the Macondo Discovery, which is the petroleum reservoir into which the Deepwater Horizon production well was drilled. Scientists and engineers are aware of the physical and chemical behavior of methane in the earth and ocean, as well as during production of petroleum.
Science does not support the notion of a methane-induced tsunami resulting from Deepwater Horizon activities. However, while the possibility of an induced tsunami is extremely remote, DEP continues to take all concerns seriously and is consulting with experts in all related scientific fields.
View the following DEP fact sheet with more information about methane gas and the Deepwater Horizon incident: http://www.dep.state.fl.us/deepwaterhorizon/files/methane_fact_sheet.pdf
Saturday, July 17, 2010
The poll (PDF available here) asked respondents in Britain, Canada and the United States to choose which of the following statements came closest to their own point of view regarding the origin and development of human beings on planet earth?
A. Human beings evolved from less advanced life forms over millions of years
B. God created human beings in their present form within the last 10,000 years
C. Not sure
68% of participating Brits selected evolution as the best explanation for human existence, as did a 61% majority of the Canadian respondents. In the United States however, only 35% of those polled accepted that humans came to be via a process of graduated change.
From the regional perspective, residents of Southern United States showed the greatest alignment with a creationist view of human origins; 51% indicated that they believed humans to have only been around for 10,000 years or less. Respondents from the Northeastern U.S. demonstrated more inkling towards accepting evolution with 41% endorsing change over millions of years and 38% opting for more divine explanations.
Yankees and their highfalutin ideas…
Photo: Australopithecus afarensis from Wikipedia
Sunday, May 23, 2010
Your announcement on May 20th that your lab had created the first synthetic cell has left me absolutely terrified. Because of your work, I fear that the human race is now teetering on the edge of self-destruction. Although I assume that you had good intentions when you embarked on such a foolhardy line of experimentation, you have obviously failed to fully consider the possible consequences of your actions. Like many scientists and inventors in times past you seem to take pride in your ability to arrogantly tinker with nature – Dr. Venter, consider the consequences!
Like you, the inventor of the wheel probably intended only to help humanity by providing a new technology for improved transportation, but that near sidedness ultimately resulted in despair and anguish for the rest of us. By not thinking about the consequences of the vile wheel, its inventor didn’t plan for the possibility of wheeled-trailers used to move mobile nuclear missiles, wheeled-vehicles pumping noxious fumes into the atmosphere or even the potential for road killed kittens. No, the inventor of the wheel selfishly left those concerns for future generations to resolve – Dr. Venter, think about future generations!
I’m not a geneticist, but I know enough about science to understand that by meddling around with DNA you run the risk of creating super-viruses, flesh eating bacteria and possibly even tyrannosaurs. The perfection seen in nature is the result of thousands of years of evolution, and that evolution has brought everything into harmony. By creating synthetic cells you run the risk of altering the course of evolution; you could inadvertently upset the natural harmonies that exists between things like parasitoid wasps and their host caterpillars, you could unintentionally change petroleum’s natural adhesion to the Gulf of Mexico, or you could even disrupt the natural balance that exists between humans and the HIV virus – Dr. Venter don’t upset the natural balance!
Life isn’t just chemistry. Life is an invisible force driven by a magical spirit-energy that flows through all of us. You must understand that only God can create life, and because of that only he can understand how life works. Your ego has obviously overridden your ability to reason; you have no idea how DNA, cells or biology really function – Dr. Venter, stop playing God!
P.S. On second thought, the above pleading is probably unnecessary… After all, your so called ‘synthetic cell’ is really no big deal at all. So what, you can turn a few million digits on a computer screen into a living and reproducing organism. Big whoop! You scientists should be focusing on more important issues.
Wednesday, April 14, 2010
In recent posts I have written about Marco Rubio (the current front runner in Florida’s U.S. Senate race) being a closeted creationist, Rick Santorum’s fight against the teaching of evolution, Utah State Representative Mike Noel idiotic work opposing climate change policy, and a host of other proud science deniers - all republican!
Can you imagine living in a place where people lacking knowledge, rationality or even the ability to reason opted to seek education or guidance in lieu of running for a political office? If you are able to imagine such a utopia, it’s probably safe to wager that it doesn’t look anything like the State’s of Tennessee or Illinois - the leading candidates for governor in both states are creationists! More specifically, they’re republican creationists (I know - shocking!!!).
In Tennessee gubernatorial poll-leader Ron Ramsey - the State’s current Lieutenant Governor - wants to include Intelligent Design as part of the public schools’ science curriculum. In considering the teaching of evolution and the possibility of instructing creationism, Ramsey stated that to “choose one or the other would ignore the beliefs of large numbers of Tennesseans. Our young people are smart enough to come to their own conclusions if both sides are presented fairly.” That’s right; his position on education is that the personal beliefs held by the majority override and supersede science.
Illinois’ leading Republican Candidate, current State Senator Bill Brady, is towing a similar party-line; but in addition to teaching creationism, he also supports inclusion of prayer in public schools…
There’s nothing special about the republicans in Florida, Utah, Illinois, Pennsylvania, or Tennessee; a philosophy of anti-science is ubiquitous to the Republican Party. Now, it very well may be possible - though it’s a stretch - that not all republicans deny science; but, the emerging pattern seems to overwhelmingly demonstrate that all science deniers are republican!
If not yet convinced of this phenomenon just consider the leading republican presidential candidates for 2012; Mitt Romney, Mike Huckabee, and of course Sarah Palin - all fundamental creationists and all climate change deniers.
I fully realize that when selecting a politician to lead us there are many things to consider - more than just their views on science and science policy - but for goodness sake, how has science denial become a desired attribute for an entire political party?
Sources (Linked News Artcles):
Bill Brady Info
Ron Ramsey Info
Tuesday, April 13, 2010
Last Thursday, while doing some fieldwork in Levy County, I came across this Florida cottonmouth as it was sunning itself after an early morning swim:
The warning behavior being demonstrated in the last photo is how the ‘cottonmouth’ earned its common name; trespassers and would be predators can be caught off-guard and intimidated when the snake curtly flashes the white interior of its mouth. The warning was certainly well received by me – I’ll take being startled over enduring a venomous bite any day of the week!
The Florida cottonmouth Agkistrodon piscivorus conanti is one of three subspecies of water moccasin native to the United States; the other two varieties include the Eastern cottonmouth (Agkistrodon piscivorus piscivorus) and the Western cottonmouth (Agkistrodon piscivorus leucostoma). These three subspecies of semi-aquatic pit vipers are renowned for their exceptional swimming ability and their associated preference for habitats in and around the freshwater lakes, streams and swamps of the Southeast U.S. They have adapted to be masters of wetlands; well, masters of freshwater wetlands anyway…
Even though their preferred range places them in proximity to the Atlantic Ocean and the Gulf of Mexico, the conquest of marine ecosystems by the cottonmouths has been - as it has with most aquatically inclined reptiles - blockaded. The physiological demands of maintaining adequate hydration in a high-saline environment has constrained the Agkistrodon genus to a landward life. But things could change.
Could cottonmouths evolve to live in the sea, like kraits or sea snakes?
As mentioned previously, the above images show a cottonmouth from Levy County, Florida. Levy County is located in West Central Florida and boasts an impressive coastline along the Gulf of Mexico. The coastline even has barrier islands. In fact, one such barrier island, called Seahorse Key, has its very own population of cottonmouths - cottonmouths that have found a niche in the intertidal zone.
Generally considered opportunistic carnivores, the bulk of the average cottonmouth’s diet is derived through consumption of its wetland neighbors - frogs and fish - however, they have been known to occasionally snack on insects, lizards, birds, rats, or even other moccasins. The cottonmouths of Seahorse Key have taken their tastes for fish from the freshwater to the saltwater; there they eat marine fish scavenged from the intertidal zone or haphazardly dropped from the Key’s bird rookeries. In addition to marine fish, the cottonmouths of Seahorse Key will even eat SEAWEED if it has the odor of fish on its leaves.
So, the cottonmouths of Seahorse Key have a proven ability to eat, digest and process marine food resources. They posses elongate lungs to provide buoyancy and streamlined bodies capable of eel-like swimming locomotion. As with other pit vipers they have venom to aid in capture of fast moving fish. And, in regards to reproduction, cottonmouths give birth to live young, so there’s no need to go to shore to lay eggs…
It seems that the only other major factor restricting the cottonmouths’ sea-ward invasion is a limited tolerance for high-salinity…
If only there was a selective pressure for improved salt water tolerance; for instance, a selective pressure something like being stuck on an island that is subject to rising sea levels. What are the chances of that happening?
The behavioral and physiological adaptations required in order for a land animal to successfully undertake a conquest of the sea are undoubtedly both varied and numerous; but, with sufficient selection pressure, ample time, and an incremental, step-wise process it can and has happened.
For example, consider all of the behavioral and physiological changes that must have occurred in order for a few Devonian lobe-finned fish to find their way to shore as fully terrestrial tetrapods! Or, viewing the scenario in reverse, imagine the adaptations that permitted Eocene land mammals to re-enter the sea as a line of cetaceans!
Subtle cumulative changes over time can alter a lineage’s dietary preferences, reproductive rituals and even bodily mechanics.
Lillywhite, H., Sheehy, C., & Zaidan, F. (2008). Pitviper Scavenging at the Intertidal Zone: An Evolutionary Scenario for Invasion of the Sea BioScience, 58 (10) DOI: 10.1641/B581008
Sunday, April 11, 2010
Tuesday, April 6, 2010
The email (from a reliable source) advises that the photo was recently taken during a fly-over of the Picayune Strand near Naples in South Florida.
Looks like three wild Florida panthers - cool!
Also pictured are what looks like a recently cleared road and stands of noxious Melaleuca – could be better! (As a matter of fact it is getting better - click here for info).
In addition to dealing with us ecosystem-altering and land-lusting apes, Florida panthers must also cope with other parasites – including highly specialized trematodes that have evolved a fancy for fare of the feline sort...
Trematodes are flukes of nature (sorry, couldn’t resist) in that they've evolved an astonishing, almost incomprehensible level of developmental plasticity. Most have evolved the ability to subtly manipulate their growth rates and sexual maturation to track the resources available in their environment. For parasitic nematodes, their environment is manifested by the internal chemistry of their victims. Id est, the digestive enzymes, hormones and antibodies expressed through the physiology of their hosts help the trematodes gauge the probability of reproductive success and to tune their own developmental process accordingly. This fantastic capacity for flexibility is of survival benefit because should a trematode happen to find itself immersed in the body of an unsuitable host, it can induce a state of arrested development and shift its metabolism to complete dormancy while awaiting transmission to a more favorable chemical climate. As a natural corollary, if the trematode succeeds in locating its target host (aka, its 'definitive host') it can quickly push development into overdrive and achieve reproductive adulthood in short order, thereby maximizing the opportunity to its individual advantage. Being unrestrained by the ticking-clock of reproductive efficacy, trematodes can migrate from host-to-host and even between species with relative ease. As a case study, consider the misadventures undertaken by the trematode species named Alaria marcianae.
Alaria marcianae is a fascinating organism known to target, as definitive hosts, the kittens of the Florida Panther (Puma concolor couguar). The Florida Panther holds a critically endangered status and, as the common name strongly suggests, resides in the state of Florida. The tawny colored Florida Panther is one variety of a widely recognized group of felids that are also known by the names cougar, mountain lion and puma. The panther-intersecting life cycle of Alaria marcianae is complex with several possible vectors of transmission, but in choosing an arbitrary starting point for the purpose of description, we can assume that its convoluted journey begins within the intestines of an adult panther.
Having recently been deposited in the intestinal tract of an adult feline, members of Alaria marcianae start their lifecycle as eggs. The eggs, unembryonated germ cells, intermix with the partially digested remnants of raccoons, armadillos and other common delicacies found in the panther's system, and are then excreted with the animal's feces. On being submerged in the inundated wetlands for which south Florida – and the Picayune Strand - is renowned, water stimulates the eggs to internally develop embryos. Once these embryos have achieved sufficient maturation, sunlight triggers the eggs to hatch free swimming, cilia-driven, paramecium-looking critters called miracidia.
The miracidia are not adult Alaria marcianae, rather they represent a sexually immature stage of development that is specialized for seeking out a very specific (obligate) intermediate host. To ultimately succeed in stalking a panther, the miracidia of Alaria marcianae must first locate and infect a ram's horn snail of the genus Helisoma.
On locating a ram's horn, the miracidium attaches itself to the soft exposed flesh of the snail, and by excreting tissue-degrading enzymes, it parts ways with its cilia-bearing outer layer. It then penetrates into the snail's body cavity. Shedding its ciliated epithelium, the miracidium becomes an immature sporocyst. Although sporocysts still lack the ability to reproduce sexually, by embedding in the snail's nutrient rich organs they acquire the power to produce additional replicates of themselves - clones called 'daughter sporocysts.'
Further advancing on the panther, the new daughters promptly leave their mother's side and venture to the snail's gonads. Mollusk hormones produced by the gonads fuel special cells within the daughters as they morph into tailed, tadpole-looking larval forms called cercariae. The cercariae swim to, and exit from, the snail's shell-producing mantle. From there, they return once again to the open water as free-swimmers.
Leaving the snail behind, the cercariae swim to the water's surface and hunt down the true tadpoles of the leopard frog (Rana pipiens) - their second intermediate host. Hijacking the leopard frog's tadpoles for transport, the cercariae drop their own tail and burrow into the tadpole's skin. There's no need for self-propulsion when riding inside a tadpole. Once inside the developing frog, Alaria marcianae, then at a stage where they're referred to as mesocercaria, cease further development and undergo another round of asexual cloning. As numbers continue to multiply, they patiently rest, waiting for the tadpoles to carry them landward as adult leopard frogs.
In time, the mesocercaria-bearing tadpoles grow into leopard frogs and move their parasitic cargo to land. On terra firma the leopard frogs are hunted by a wide range of predators; occasionally falling prey to yet another preferred host (aka, a 'paratenic host') of Alaria marcianae, the raccoon. After catching an infested frog, the raccoon's digestive enzymes make short work of the frog's flesh - in the process releasing the mesocercaria. As with its previous host, the mesocercaria multiply in the raccoon, but continue to maintain a state of arrested development - they are not yet adults.
Did I mention that raccoons in south Florida happen to be a favorite prey item of the endangered panther?
Utilizing methods similar to those during the frog-to-raccoon transmission, Alaria marcianae find their way into adult panthers by contaminating raccoons - panther prey. During the process of raccoon digestion, mesocercaria are liberated from tissue and enter the bloodstream by penetrating the intestinal wall.
Now, if the panther they find themselves parasitizing, by chance, turns out to be a lactating female, her hormones will stir the mesocercaria into migrating to her mammary glands where they will transmit (trans-mammary) to the digestive system of her kittens'. The term used to describe the situation in which a mother acts as a paratenic host to her own offspring is called 'amphiparatenesis.'
Here, amphiparatenesis results in the imbibing of mesocercaria-laden milk by the kittens. As with the mesocercaria residing within their mother, the parasites in the kittens will penetrate the intestinal wall and enter the blood stream. They'll surf the blood stream until reaching the lungs where they become metacercaria; as metacercaria they harden the surrounding lung tissue forming protective cysts. Having profitably acquired housing in their definitive host, the cysts in the lungs will eventually be coughed-up the trachea and then promptly swallowed into the esophagus. Once back in the intestines, Alaria marcianae accelerates its developmental process, achieves sexually reproductive adulthood (as sequential hermaphrodites), and deposits the next generation of eggs in the intestine.
Thus the cycle comes full circle.
Foster, G., Kinsella, J., Sheppard, B., & Cunningham, M. (2009). Transmammary Infection of Free-Ranging Florida Panther Neonates by Alaria marcianae (Trematoda: Diplostomatidae) Journal of Parasitology, 95 (1), 238-239 DOI: 10.1645/GE-1749.1
Saturday, April 3, 2010
It's From back in 2001.
Douglas Adams' close encounters with these rare and unusual animals reveal that evolution, ever ingenious, can be fickle too -- in a University of California talk that sparkles with his trademark satiric wit.
Wednesday, March 31, 2010
At least according to a paper in Arizona, which proclaims that “Research by UA assistant anthropology professor David Raichlen and his colleagues provide evidence suggesting that 3.6 billion years ago, hominins walked with the same upright gait that humans do today...”
Link: Arizona Daily Wildcat
Really, upright hominins 3.6 BILLION years ago??? Bipedal locomotion is one thing, but upright walking during the Archean that’s impressive - especially considering the lack of oxygen.
Incidentally, the mentioned research actually makes an argument for hominin bipedalism first occurring around 3.6 MILLION years ago. And the research is not a challenge to evolution; in fact, it fully endorses it.
The research is available at PloS; here’s the abstract:
Debates over the evolution of hominin bipedalism, a defining human characteristic, revolve around whether early bipeds walked more like humans, with energetically efficient extended hind limbs, or more like apes with flexed hind limbs. The 3.6 million year old hominin footprints at Laetoli, Tanzania represent the earliest direct evidence of hominin bipedalism. Determining the kinematics of Laetoli hominins will allow us to understand whether selection acted to decrease energy costs of bipedalism by 3.6 Ma.
Using an experimental design, we show that the Laetoli hominins walked with weight transfer most similar to the economical extended limb bipedalism of humans. Humans walked through a sand trackway using both extended limb bipedalism, and more flexed limb bipedalism. Footprint morphology from extended limb trials matches weight distribution patterns found in the Laetoli footprints.
These results provide us with the earliest direct evidence of kinematically human-like bipedalism currently known, and show that extended limb bipedalism evolved long before the appearance of the genus Homo. Since extended-limb bipedalism is more energetically economical than ape-like bipedalism, energy expenditure was likely an important selection pressure on hominin bipeds by 3.6 Ma.
Raichlen, D., Gordon, A., Harcourt-Smith, W., Foster, A., & Haas, W. (2010). Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009769
Tuesday, March 30, 2010
The survey’s data was derived from the responses of 353 Florida biology teachers; 28% of which taught biology in kindergarten through the fifth grade, 24% instructed biology in grades six through eight and 48% taught biology at the high school level (grades 9–12).
A Few of the Findings:
20% of Florida’s biology teachers are NOT COMFORTABLE with even INCLUDING evolution as a required science standard
17% of the teachers felt that biology COULD be taught and understood WITHOUT teaching evolution
17% DISAGREED that the earth is at least 4 billion years old (34% of those that disagreed believed that the earth is only between 4,000 and 40,000 years old)
34% felt that believing in God MEANS rejecting evolution
72% of the respondents reported that they HAD NEVER BEEN criticized by other teachers or school administrators in regards to HOW they taught evolution
44% of the teachers indicated that their teaching of evolution HAS BEEN criticized by students or parents
If the above numbers seem frightening consider this: The study’s respondents were solicited from the Building a Presence in Science (BaP) program of the National Science Teachers Association. Therefore, the numbers could be biased towards the "pro" science education end of the spectrum!!!
FOWLER and MEISELS (2010). Florida Teachers’ Attitudes about
Teaching Evolution The American Biology Teacher, 72 (2), 96-99 : 10.1525/abt.2010.72.2.8
Sunday, March 28, 2010
Although it is often considered politically incorrect to ‘out’ someone without their permission, in Rubio’s case I doubt that revealing his irrational ideologies will be much of a shock to anyone. In fact - now that I think about it - referring to Rubio as a creationist probably only serves to reinforce the devotion of his flock… After all, religious fundamentalism has been his political platform throughout his career.
For example, prior to 2008 the word ‘evolution’ wasn’t even included in Florida’s science education standards. In 2007, when a much needed revision of the State’s education standards began to lift the veil from the eyes of Florida’s students, Rubio was there as Speaker of the House pleading for inclusion of intelligent design as part of the science curriculum. Rubio fought against the teaching of evolution claiming that it infringed on Academic Freedom. Rubio argued for Academic Freedom in the same sense that it is propped by the Discovery Institute; the version of teaching that allows creationism to be placed on equal ground with biology, astrology on common footing with astronomy, and the version that grants alchemy the scientific relevancy of chemistry.
When interviewed about the teaching of evolution, Cuban-American Rubio compared the teaching of evolution to the tactics used by Fidel Castro’s communist party to undermine families and the church - a means of controlling the masses.
Rubio also said that "…whether what a parent teaches their children at home should be mocked and derided and undone at the public school level. It goes to the fundamental core of who is ultimately, primarily responsible for the upbringing of children. Is it your public education system or is it your parents?" He continued, "And for me, personally, I don't want a school system that teaches kids that what they're learning at home is wrong."
Indeed Mr. Rubio, the purpose of education should be to reinforce already held beliefs!
In addition to his battles against the Florida Board of Education, Rubio’s website also boasts that he would oppose any legislation that would allow Federal dollars to be spent on stem cell research.
Article:Rubio: Florida House open to legislative fix on evolution
Sunday, March 21, 2010
In addition to normal variations encountered at the regional level, or within individual populations, the colors and shapes exhibited by tadpole tails can differ from one location to another; this is because tail characteristics can be changed in response to cues in the environment. In waters lacking abundant predators, Hyla femoralis tadpole tails are generally colorless, or are of a dull brownish-red color. In contrast to relatively safer waters, the tadpoles hosted by puddles with abundant predators (predators like dragon fly larvae, for example) are often found bearing tails with distinct red-spot markings and an enhanced, taller shape and muscular robustness. Increased tail muscle provides greater propulsion, allowing the tadpoles to employ accelerated speeds as part of their predator evasion tactics. Though, it’s still an area for inquiry, changes in the pattern and coloration of tails may provide a crypsis function by either providing improved camouflage, or by directing predatory attacks tail-ward, away from the tadpoles’ main body mass – improved survival through either concealing or revealing.
The chemical signals that switch tail enhancement into overdrive include those compounds released by other tadpoles as warning pheromones during predatory attack and those molecules discharged by the predator while digesting prey-tadpole tissues. So, in other words, a predator’s attack and digestion of a conspecific tad liberates chemicals into the water that are received by other tadpoles during development; as a result, resources are directed away from ‘normal’ growth processes and are directed to tail augmentation.
Pinewoods tree frogs display distinct orange or yellow spots on their inner side of their thighs, while in the field these spots help distinguish Hyla femoralis from other species with similar body color patterns. Though not pictured here, the leg spots were observed during the frogs’ recent attempts at evading a certain species of primate paparazzi. Their tadpole stage lasts for about two months, and the breeding season begins in March and runs through the summer months.
Although cypress swamps and pine flatwoods are distinct natural community types, they are both occupied by the pinewoods tree frog. The first snapshot above shows one Hyla femoralis precariously perched on the stem of a saw palmetto plant just a few inches off the ground in a well-drained upland flatwoods area. The second shows another individual leisurely laying on a tree branch about five feet above the surface waters of a swamp. In Florida, these communities are often directly adjacent to each other:
LaFiandra, E., & Babbitt, K. (2004). Predator induced phenotypic plasticity in the pinewoods tree frog, Hyla femoralis : necessary cues and the cost of development Oecologia, 138 (3), 350-359 DOI: 10.1007/s00442-003-1412-3
Saturday, March 13, 2010
Reproduction is an expensive endeavor. Tremendous time and resources are invested in seeking-out healthy partners, in consummating relationships, and in rearing the resultant offspring. Luckily, evolution has resulted in life being programmed to strive for resource efficiency; to work towards maximum reproductive benefit at minimum personal expense. In regards to pair-bonding between the sexes, this biological imperative for reproductive economy has made promiscuity the rule and monogamy the exception. However, despite the fact that promiscuous mating systems are the prevailing strategy in nature, environmental factors can push typically promiscuous species towards monogamy.
As a case in point, a report published in the April issue of The American Naturalist details how the ‘mimic poison dart frog’ (Ranitomeya imitator) parted ways with promiscuity to adapt a lifestyle as the first scientifically recognized genetically monogamous amphibian.
Like other frog species, poison dart frogs incur a certain amount of risk by laying their eggs in water. Although water is a biological prerequisite for frog survival, ponds, lakes and puddles also house predatory fish and other animals that prey on vulnerable eggs and tadpoles. During its evolutionary past, the menace of predation pushed the mimic poison dart frogs away from larger, riskier ponds to the considerably smaller, but safer, pools held by leaves of large bromeliad plants. Unfortunately, although the tree-top bromeliads decreased the rate of frog young predation, the movement from the big ponds raised a separate issue – nutrient limitation.
The big ponds definitely had more predators; but, they also had substantially more food. In fact, the ponds had so much food that a single frog-parent (in this case the male) was able to handle the tadpoles all by himself – a single parent family arrangement was all that was necessary to raise the next generation. In contrast, the waters held by the bromeliads averaged only about 24 milliliters in volume, far too little to hold ample provisions for a startup tadpole. In order to maintain their newly acquired safe housing, the mimic dart frogs had to adapt a new tactic.
Male mimic dart frogs had previously evolved the capacity to both transport and guard young tadpoles, but having moved to the suburbs, the females needed to help-out with feeding; rearing had become too difficult a task for the males to handle on their own. If they were to ensure the survival of their young, the days of leaving dad to care for the kids were over – monogamy was the best option. Unlike males, female mimic darts have the ability to produce eggs. To do their part, mom frogs adopted a strategy called trophic egg feeding, a practice in which they lay unfertilized eggs in the bromeliad pools for the tadpoles to eat.
An absolutely amazing video of this monogamous behavior was recorded by the BBC during the dissertation work of Jason Brown. Jason was the lead author of the cited paper, and the mimic dart footage was included in the David Attenborough narrated documentary “Life in Cold Blood.”
This is awesome footage:
Brown, J., Morales, V., & Summers, K. (2010). A Key Ecological Trait Drove the Evolution of Biparental Care and Monogamy in an Amphibian The American Naturalist, 175 (4), 436-446 DOI: 10.1086/650727
Saturday, March 6, 2010
I just received an email from Research Blogging requesting my votes for 2010’s best blog awards…
Working through the nominees, I was surprised to discover that Ecographica was selected as a finalist in the Conservation and Geosciences category – I had no idea!
My thanks to the readers and judges for supporting this blog!!!!
Since January of 2009, Ecographica has contributed 109 research related posts to Research Blogging. Vertebrate Proxies of Climate Change has been the most popular of the research postings; it reviews/summarizes some of the ways in which vertebrates can be used to study shifting climates.
Saturday, February 20, 2010
By undermining the normal life-processes of the host’s cells, viruses are detriments to health; however, more than just illness can remain in the wake of a virus’s biological sabotage. Sometimes included with the observable symptoms of an ailment are other characteristics of viral infection that serve to promote the spread of disease. The genes that viruses splice into a host cell’s mainframe can code for phenotypes that manipulate unwitting vectors into exposing themselves – purely for the benefit of the virus.
For example, recent work out of Penn State University has shown that a virus common to the squash group of plants does more than just hack a virus-building program into the cells of its vegetative victims - it also includes a program that attracts insects. The cucumber mosaic virus (CMV) infects plants with a gene that causes the plant to synthesize and release chemicals that draw-in hungry aphids. Normally, aphids use their capacity to chemically sense plants as a way to zero-in on healthy and nutritious foodstuffs essential to their survival. By manipulating the aphids’ chemo-sense, the virus’s genes trick the insects into locating and then taking a bite from the diseased leaves of an infected plant. Even though the plant may emit a ‘delicious smell,’ because it has been subjected to disease, it lacks the nutrients needed by the aphids. Luckily for the aphids, after just one bite their tasting-sense overrides their smelling-sense and they’ll bugger-off in search of better food. Unfortunately for other squash plants, the aphids now have a mouthful of CMV virus! Thus, the virus spreads.
The genes of the cucumber mosaic virus can integrate into the DNA of a plant, causing it to produce a chemical compound that manipulates aphids into volunteering their time and services as vectors of disease. This scenario isn’t unique to viruses, plants and insects. Other studies have shown that a similar pathogen to chemo-attractant dynamic exists between sandflies and hamsters; the parasitic protozoa Leishmania causes infected hamsters to produce chemicals that attract sandflies as vectors. And in humans, there is some evidence that Plasmodium falciparum causes more than just malaria, it also hijacks human bodies to produce chemicals that attract more mosquitoes.
Mauck, K., De Moraes, C., & Mescher, M. (2010). Deceptive chemical signals induced by a plant virus attract insect vectors to inferior hosts Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0907191107
Friday, February 19, 2010
Great conversation - Listen to the Audio!
Go to the NPR webpage and click on Communicating Science in the Recent Episodes column: Here
From NPR's Science Friday
Saturday, February 13, 2010
Daniel poses great questions, because, recognizing that we live in a world of mass travel and shifting climates, the study of invasive dynamics is of critical importance to the conservation of biodiversity – protecting natural habitats and native species. In addition to conservation, by researching the interplay of native and non-native species during the establishment of ecosystems we will undoubtedly gain a wealth of knowledge in regards to the feedbacks between evolution and ecology (i.e. how do those species lacking a shared co-evolutionary history come to achieve a stable strategy for survival?).
So, with that in mind, here’s my answer to Daniel’s question: Both!
Cause’ in a nutshell: Although invasive species will exhibit some life-history strategies comparable to those of plants from the newly invaded habitat (growth pattern, time to reproductive maturity, etc…) they will also be subject to environmental factors of a temporal nature that do not influence the natives (at least to the same extent).
Said differently, because the growth, reproductive habits and resource needs of an invasive likely mirror those of at least one native plant, the invasive could theoretically replace the native with little ill effect to the ecosystem; the invasive could fill the niche left void by the out-competed native plant without disrupting the energetics of the plant community as a whole. BUT, at the same time, a newly arrived invasive species may have a distinct advantage over a native transient because it is completely foreign to the ecosystem. For example, being unrecognized by its new environment the invasive may, for a period of time, be buffered against attack by herbivores, parasites and other stressors that may be actively reducing the fitness of the locals.
Similar to the above potential advantages, the invasive could also be subject to the detrimental affects of being an outsider - brought about by a lack of co-evolved pollinators, ect…
I would also argue that the above temporal effects associated with being a novel addition to an ecosystem, though only short-lived, can be magnified greatly by stochastic events. I would suggest this because – generally – variability in initial survival rates contributes greatly to ultimate establishment; often more so than reproductive strategy, which is subject to greater phylogenetic constraint (i.e. initial survival is more important than in choosing to produce many low-quality seeds when young, or to conserve energy and produce fewer higher-quality seeds when older).
Daniel’s essay is a great read and offers plenty of real-world case studies to emphasize his points; definitely check it out!
Simberloff, D. (2010). Invasions of Plant Communities – More of the Same, Something Very Different, or Both? The American Midland Naturalist, 163 (1), 220-233 DOI: 10.1674/0003-0031-163.1.220
Thursday, February 11, 2010
Linked below are a few videos, a website and a paper that I plan to enjoy today in celebration of the greatest scientist to have ever lived!
A biographical sketch of Darwin by John van Wyhe (Darwin Online)
E.O. Wilson on ‘Darwin’s Four Great Books’ (FSU Mediasite)
Richard Dawkins on 'There is grandeur in this view of life' (YouTube)
Sean Carroll on ‘Endless Forms Most Beautiful’ (Google Video)
Paper (Free, PDF)
Spencer C. H. Barrett. Darwin's legacy: the forms, function and sexual diversity of flowers. Phil. Trans. R. Soc. B February 12, 2010 365:351-368; doi:10.1098/rstb.2009.0212