Tuesday, June 08, 2010

Splitters

Because I will likely never call Aster azureus by its new name, Symphiotrichium oolentangiense. I think the natural world has much bigger problems to contend with than dealing with new nomenclature. We know A. azureus is dependent on a high quality ecosystem for sustainability. Let's focus our efforts on making sure that ecosystems are healthy enough to support such plants rather than wasting our time renaming them with fake Latin and Greek names.

Here's an article pertaining to taxonomic changes in warblers and how we really can't depend on DNA to tell us much:

Molecular methods are not sufficient in systematics and evolution
A lesson from flashy Central American warblers
Modern evolutionary systematists often use molecular methods, such like mitochondrial DNA analysis, to differentiate between species and subspecies. However, current research indicates that the picture painted by these methods may be incomplete, and only a creative combination of classical field-based ecology, museum-based systematics and DNA-based phylogenetics, can lead to right conclusions. In the last issue of the internationally acclaimed “Ornithological Monographs” (pages: 90-102), a team of biologists from the Universidad Central de Venezuela, Allegheny College in USA, Seoul National University in South Korea and Centre for Ecological Studies in Poland demonstrate how modern evolutionary biology needs the “old-style” biology in order to explain evolution and systematics of birds.

The team composed of Jorge Perez-Eman, Ronald Mumme, and Piotr Jablonski studied mitochondrial DNA, plumage coloration and behavior of 10 subspecies of a Central and South American warbler the Slate-throated redstart, an inhabitant of montane forests. Mitochondrial DNA analyses indicated that evolution of these birds started in northern and central areas of modern Mexico. From there, the birds rapidly expanded southwards to South America diversifying into several genetically and morphologically different subspecies. About 40-70 million years ago, when today’s montane forest types existed at lower elevations, a rapid expansion started producing several morphologically distinct subspecies that differ in the coloration of their bellies from yellow, orange, through red, and in the tail pattern from small to large white patches, but do not differ in the mitochondrial DNA. The researchers believe that during this rapid expansion of the populations, the genes responsible for these morphological traits have evolved rapidly due to adaptation to local habitats, while the mitochondrial genes often used in the phylogenetic research, remained unaffected by the evolutionary change.

Why would local conditions lead to rapid changes in the plumage pattern? The answer to this question can be found in the role of tail pattern in foraging of these warblers. The Slate-throated redstarts, as well as their relatives, the Painted Redstarts, use “flush-pursue foraging”. The foraging birds look like butterflies when they spread their tails and wings in order to be conspicuously visible by the insects. Insects, such like treehoppers or flies, are scared by the sudden visual displays and are flushed away from their resting sites on leaves and branches. The birds only wait for this to happen, and in elegant pursuits they catch the escaping insects in the air. Field experiments conducted by the research team with birds of the Costa Rican subspecies Myioborus miniatus comptus (see photo) and their key prey indicated that a contrasting black-and-white tail is critical to flush-pursuit foraging success, and that subspecific variation in the extent of white in the tail reflects evolutionary adaptation to regional prey or habitat characteristics that maximizes flush-pursuit foraging performance. Thus, even though the subspecies of the Central American clade are genetically homogeneous with respect to the mitochondrial genes, analysis of tail pattern and its effect on foraging performance suggests a recent adaptive evolutionary divergence, warranting the status of separate subspecies.

The researchers conclude: “Our findings serve as a reminder that mitochondrial DNA (mtDNA) gene trees will not always succeed in capturing all evolutionarily significant genetic change, and that manipulative field experiments can provide crucial information on the selective factors that lead to evolution of subspecies-specific morphological traits even in the absence of mtDNA diversification”

5 comments:

James C. Trager said...

Well, a lot more than mt-DNA went into the coining of the genus name Symphiotrichum, and the naming of the new genus does make sense if one reads the whole argument. One could also note the oolentangiense, or rather the masculine form oolentangiensis, is in fact the old species name for this aster.

But your are so right, however the systematists decide whatever one must call it in Botanish, we need more concern about succesful habitat conservation measures for the sky-blue aster and the wonderful host of species associated with it.

Allison Vaughn said...

I guess it also wrangles me because the taxonomists have done a great job at alienating native plant enthusiasts who would like to learn scientific names but won't take the time to do it since "they'll just go changing the name on me...hrmph."
Similarly, I sometimes can't recall the last last part of FimCar and a host of other plants that show up in my quadrats. Caroliniana? Carolinensis? Carolina? FimCar, a 7 or 8 on the CC list, know it when I see it, don't know the common name, a staple on good quality glades. I think it's caroliniana, but all I need is the "car" for the database.

Justin Thomas said...

Though inconvenient, some name changes are based on solid science and must therefore be adopted. I personally find the argument separating Aster and Symphiotrichum to be very unconvincing. In situations like this, Arthur Cronquist argued that the utility of taxonomy must supersede ambivalent data.

The beauty of it is that any name attributable to a given taxon is a synonym (much of the time) and thereby a valid name to be use to one's heart's contentment; no different that saying "soda" instead of "pop" or "aqua" instead of "water".

Allison Vaughn said...

You're right, of course, and as usual, but the asters splitting seemed really superfluous. I don't buy it. There's also the case of taxonomists spending way too much time looking at a certain plant on igneous versus dolomite --same plant, but different growth pattern-- and then totally blowing hours and days and weeks trying to convince someone with power that indeed, it's a different species when it's really just different genetics. By the way, added Cx frankii to my yard list...

James C. Trager said...

Or maybe not even genetics -- just phenotypic plasticity.