PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 37 - Evolutionary ecology II: life history, speciation, and coevolution
L-14, Lobby Level, Cook Convention Center
Presiders: J Cavender-Bares
Should you save your sons or your daughters? Temperature-dependent sex determination offers a potential solution to this difficult choice.
Langkilde, Tracy*,1, 2, Shine, Richard2, 1 2
ABSTRACT- Temperature-dependent sex determination (TSD) has evolved independently in at least two lineages of viviparous Australian scincid lizards, but its adaptive significance remains unclear. We studied a viviparous (live-bearing) alpine lizard species (Eulamprus heatwolei) with TSD. Our data suggests that a mother's selection of thermal regimes during pregnancy modifies the body size of her offspring (mothers with higher and more stable temperatures produced smaller offspring), with sons and daughters affected in similar ways. However, a field mark-recapture study shows that optimal offspring size differs between the sexes: larger body size at birth enhanced the survival of sons but reduced the survival of daughters. Thus, a pregnant female may be faced with a difficult choice; she can optimize the fitness of either her sons or her daughters (via yolk allocation and thermoregulation), but cannot simultaneously optimize both. One evolutionary solution to this problem, and the associated fitness cost, is to modify the sex-determining mechanism so that a single litter consists entirely of either sons or daughters; TSD provides such a mechanism. Previous work has implicated a sex difference in optimal offspring size as a selective force for TSD in turtles. Hence, opposing fitness determinants of sons and daughters may have favored evolutionary transitions from genetic sex determination to TSD in both oviparous turtles and viviparous lizards.
Key words: life-history ecology, sex determination, reptile