Sunday, August 29, 2010

Field Photos: White-eyed Vireo in Nest

Vireo griseus the white-eyed vireo; nested in a forked branch of Myrica cerifera (wax myrtle).

Snapshot taken a couple months back in Manatee County, Florida – where vireos nest year around.

Saturday, August 28, 2010

Why EO Wilson’s Latest Eusociality Paper Fails

Martin Nowak, Corina Tarnita and E.O. Wilson made the cover of Nature this week with their article “The evolution of eusociality.” The argument presented in the paper is that inclusive fitness theory is an extraneous, unnecessary concept that has failed to provide insights into the evolution of eusociality.

Here are a few of the reasons why I think that their argument fails:

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

Field Photos: Jewel Beetle Vs Yellow-eyed Grass

A jewel beetle [Buprestis rufipes (?)] having a go at the wetland plant Xyris caroliniana.

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.

These photos were taken near Goethe State Forest back in April.

Thursday, August 19, 2010

Field Photos: An Endangered Fern

Below are a few snapshots of an endangered “hand fern” - Ophioglossum palmatum.

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

sporangial spikes

Here are a few more specimens – these ones guarded by Toxicodendron radicans (Poison Ivy)

Tuesday, August 17, 2010

A Motivating Herd of Squirrel Frogs

I’ve really neglected this blog the last few months… There’s really no excuse for the lack of posts; I’ve just been tied-up with work, extra work (thanks for nothing BP) and personal commitments. In an effort to get things rolling again, I thought that posting a couple of snapshots would be a good idea. Small steps…

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.

Squirrel frog in rafters of porch

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.