Journal Article
Regressive evolution in the Mexican cave tetra, Astyanax mexicanus
Protas, M., Conrad, M., Gross, J.B., Tabin, C. and Borowsky, R.L.
Record Number:
1864
Year:
2007
Journal:
Current Biology
Pages:
452-454
Volume:
17
Abstract:
The evolutionary forces driving the reduction of eyes
and pigmentation in cave-adapted animals are unknown;
Darwin famously questioned the role of natural
selection in eye loss in cave fishes: ‘‘As it is difficult
to imagine that eyes, although useless, could be in any
way injurious to animals living in darkness, I attribute
their loss wholly to disuse’’ [1]. We studied the genetics
of eye and pigmentation regression in the Mexican
cave tetra, Astyanax mexicanus, by mapping and
quantitative trait loci (QTL) analysis. We also mapped
QTL for the putatively constructive traits of jaw size,
tooth number, and numbers of taste buds. The data
suggest that eyes and pigmentation regressed
through different mechanisms. Cave alleles at every
eye or lens QTL we detected caused size reductions,
consistent with evolution by natural selection but not
with drift. QTL polarities for melanophore number
were mixed, however, consistent with genetic drift.
Arguments against a role for selection in the regression
of cave-fish eyes cited the insignificant cost of
their development [2, 3], but we argue that the energetic
cost of their maintenance is sufficiently high
for eyes to be detrimental in the cave environment.
Regression can be caused either by selection or drift.
Times Cited:
1
Relevent Species: