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I had thirty minutes to spare before our movie started tonight, and instead of reading colorful but dull lobby cards for films I'll never see, I donated blood. Given the sheer number of times that I've been involved in a life-mangling accident, I figure it is only fair (and about time) I gave a little back. There are plenty of injured people in the world who need blood, and you've got more than enough...
"The lack of molecular-only and molecular and morphology support for monophyly of the S. dorsalis complex suggests that this 'species' may actually be comprised of several morphologically indistinguishable species which can only be separated using molecular analyses..."
- Hoddle et al 2008b
As discussed earlier, I suggest (as do authors Inoue and Sakurai in the paper described) that in order to better resolve the phylogenetic relationships between the assorted genera of family Thripidae, someone would first have to expand the analysis of genus Scirtothrips by sequencing and comparing several unambiguously defined species for that genus at the always-popular COI allele. Now, the Hoddle lab at UC: Riverside has done precisely that.
They sequenced eighteen different species of genus Scirtothrips against a two-member outgroup at two alleles and twenty-one morphological character states. More importantly, based on prior work conducted in their lab by Rugman-Jones et al., they chose to analyze members collected from geographically disparate areas. They chose to look into this geographic variation, for while most species carry some genetic variation between individuals and populations, one species of Scirtothrips was unusually (but not conclusively) variable at the first two alleles tested, ITS1 and ITS2 - and this variation appeared to be related to the geographic region from which they were collected.
One of the results that this expanded experiment uncovered is that populations of S. dorsalis sampled from geographically disparate regions showed significant molecular divergence in spite of an identical external morphology. This is interesting, because the alleles examined are not prone to mutation over the short term, which implies that the regional populations have been isolated and not breeding with one another for long enough that the small variations found inside of some individuals to have become representative of their regional population. This is akin to having two cars with the same external body moulding, but different engines running on the inside, depending on the factory where they were built.
Perhaps these findings should not be considered terribly surprising, as S. dorsalis has a very broad geographic range, and each regional infestation was probably begun by a few parthenogenetic individuals, resulting in a genetic bottleneck. All of the descendants of the initial colonists would have a very limited gene pool to operate with, and it would reflect the limited variation of the initial founding population.
Of more interest to me is to note that the external morphology for this group of critters is generally presumed to be subject to greater variation than the proteins which make up the internal metabolism of the organism. These findings suggest either that there has been strong selection maintaining the form of the organism (possibly because it is good to have this body shape to live in flower buds before they open, or because these thrips carry ancestral cues that trigger them to only choose mates who fall within certain resemblance parameters), or that these thrips are very small and there may well be may external morphological differences between regional populations that the thrips are aware of, but which these researchers' studies did not detect.
All of this suggests that S. dorsalis may represent another example of a cryptic species complex, wherein members resemble one another, but are either incapable of or unwilling to reproduce with one another. This might actually help to explain S. dorsalis' broad host range, and some of the variation and conflict present in the literature describing the beast's habitus. No one really knows what these molecular differences portend for the whole phenotype and behavior of each regional population.
It is possible that each regional group of S. dorsalis might possess slightly different but overlapping host-preferences, ranges, pesticide resistance, and developmental profiles. The different chemical environments that each regional population must adapt to in order to feed upon prominent local plants might encourage variation in the metabolism required to survive on those plants without also necessitating a change in the shape of the gross physical machinery required to obtain it.
The good news is that these small internal differences might be important to the overall management of the pest, and this makes my current research all the more relevant. Recording the way my population of S. dorsalis behaves when confronted with different environmental conditions and hosts, and then comparing it to the results observed by other researchers looking at different regional populations might reveal slightly different food preferences or heat tolerances. As a result, the pest-management response to a population from Vietnam might be very different than the one appropriate to a population from India or Kenya.
Furthermore, now that the work has finally been done, someone still needs to complete the question that Inoue and Sakurai initially asked, and use this published information to resolve the evolutionary relationships for the family.
References
"For science to work, clear questions, hypotheses, and testable predictions are an absolute must. Without them, research is blind and typically ineffective."
- Zachary Blount
Sometimes I wonder if I am just not working hard enough.
Certain parties have suggested that my head resembles certain varieties of tropical fruit. I disagree, but leave it to my public to decide such things for themselves:
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Since it seems to be a theme, I might as well introduce my latest pair of shoes:
After slightly more than a year here, I can suggest that the constant moisture and humidity of South Florida really does a number on footwear. My previous pair lasted considerably less than a year before rotting away until my toes started to poke out the distal end, and the tread of the soles had worn down to an almost unrecognizable veneer of rubber. It was desperately past time to replace them, and I decided to go back to my roots.
For those who are not in the know, my roots are mired in the thick soil of high-quality hiking boots. Of course, I have been told that it was "not very fashionable to stomp around polite society in such things", and I eventually made certain concessions to style, comfort, and my fencing coach by surrendering to running shoes.
Running shoes can be a great joy, as a good pair feels like putting on a fresh set of socks in the morning - but they do not appear durable enough to survive the heady subtropical jungle of Southern Florida. I decided to compromise, and turned instead to the North Face and their waterproof line of trailrunners. Trailrunners are an odd hybrid of both running shoe and hiking boot, with a stiffer sole, slightly more ankle support, and built of a tougher fabric. I used to have a pair of Nikes that I was exceptionally fond of, but these new guys are growing increasingly comfortable.
We'll see if I still wear them on my feet in another year.