Sunday, September 12, 2010

Human Sexual Selection and Beer!

I can almost here David Attenborough’s voiceover:

…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

Field Photos: Fishing Spider in Nyssa Swamp

The fishing spider Dolomedes tenebrosus as found in a Nyssa swamp near Tallahassee, Florida.

Snapshots taken about a month ago.

Thursday, September 2, 2010

Charles Darwin writes a letter to Stephen Hawking

World renowned physicist Stephen Hawking has just published a new book titled The Grand Design. According to Hawking, the aim of the book is to answer questions like, why are the laws of nature what they are, why do we exist and did the universe need a designer and creator? The Grand Design, which is scheduled to be released on September 7th, is drawing harsh criticism from the religious community because its conclusions specifically state that there is no need to invoke God as an explanation for existence.

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,

Charles Darwin

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.

Alfred Russel Wallace, a Conspicuous Caterpillar and David Bowie

Prior to yesterday morning I had never contemplated the linkages between rock’n roller David Bowie and the co-founder of Natural Selection Alfred Russel Wallace. It turns-out that these famous Brits hold at least two things in common; the first and most obvious of which is the already mentioned fact that both Wallace and Bowie were born in the U.K. The second linkage between the two, as strange as this may sound, is caterpillars!

Yes, caterpillars!

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.
Megalopyge opercularis, the asp caterpillar, is the larval form of the southern flannel mouth. Its range extends from the southern United States through tropical South America. Though its retro hairstyle may look cute and harmless, it packs a painful punch. The ‘hairs’ of the asp moth aren’t really even hairs at all; they’re actually bundles of venom injecting spikes! The spikes are the caterpillar’s secondary defensive mechanism, and its conspicuousness serves as its primary defense – it sends a warning signal to predators.

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