Paper: Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabs
Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabsSebastian Klaus1,2, José C. E. Mendoza1, Jia Huan Liew1, Martin Plath2, Rudolf Meier1 and Darren C. J. Yeo11Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore2Department of Ecology and Evolution, J.W. Goethe-Universität, Max-von-Laue-Straße 13, Frankfurt am Main 60438, Germanye-mail: klaus@...-frankfurt.de
This study asked whether reductive traits in cave organisms evolve at a slower pace (suggesting neutral evolution under relaxed selection) than constructive changes, which are likely to evolve under directional selection. We investigated 11 subterranean and seven surface populations of Sundathelphusa freshwater crabs on Bohol Island, Philippines, and examined constructive traits associated with improved food finding in darkness (increased leg and setae length) and reductive traits (reduced cornea size and eyestalk length). All changes occurred rapidly, given that the age of the most recent common ancestor was estimated to be 722271 ka based on three mitochondrial markers. In order to quantify the speed of character change, we correlated the degree of morphological change with genetic distances between surface and subterranean individuals. The temporal pattern of character change following the transition to subterranean life was indistinguishable for constructive and reductive traits, characterized by an immediate onset and rapid evolutionary change. We propose that the evolution of these reductive traitsjust like constructive traitsis most likely driven by strong directional selection.
Source: The Royal Society [Open access Paper]
Robert Karl Stonjek