At last, a geoscientific April Fool joke?

Maybe it was a coincidence, but the April issue of Geology contain a paper whose title looked suspiciously unreal (White, K. et al. 2009. Hydrologic evolution of the Edwards Aquifer recharge zone (Balcones fault zone) as recorded in the DNA of eyeless Cicurina cave spiders, south-central Texas. Geology, v. 37, p. 339-342). Seemingly, the Cretaceous Edwards Aquifer now flows through cavern systems at the base of a fault-controlled escarpment. At higher levels in the unit are air-filled caves, that are relics of previous karstic events. It is in these dark, dry caves that the arachnid troglobites dwell. Troglobitic animals (those that inhabit totally dark caves and have no eyes) originate as normal surface dwellers, which through successive generations lose functioning eyes and coloration. Conversely, they evolve improved senses of smell, taste and vibration detection. The species that emerge are among the rarest of creatures, for they often occur in only a single cave: a special case of allopatric speciation that may happen when small populations are cut off from one another. Technically, then, this study is no joke, for analysis of mtDNA from the spiders in different caves ought to show evidence of microcosmic evolution, and possible provide a molecular ‘clock’ to chart the times of cave colonisation. And this is what the authors from the University of Mississippi and the endangered invertebrate group of a Texan consulting company have tried to do. The spiders in the higher caves are more evolved than those at progressively lower levels. Moreover, since the karst evolution has developed in a structurally active setting, the spider data correlates with tectonic history…

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