The influence of incubation temperature on offspring traits varies
across northern and southern populations of the American alligator
Maternal provisioning and the developmental environment are fundamental
determinants of offspring traits, particularly in oviparous species.
However, the extent to which embryonic responses to these factors differ
across populations to drive phenotypic variation is not well understood.
Here, we examine the contributions of maternal provisioning and
incubation temperature to variation in hatchling morphological and
metabolic traits across four populations of the American alligator
(Alligator mississippiensis), encompassing a large portion of the
species’ latitudinal range. Our results show that whereas the influence
of egg mass is generally consistent across populations, responses to
incubation temperature show extensive population-level variation in
several fitness-related traits, including mass, head length, head width
and residual yolk mass. Additionally, the influence of incubation
temperature on developmental rate is greater at northern populations,
while the allocation of maternal resources towards fat body mass is
greater at southern populations. Overall, our results suggest that
responses to incubation temperature, relative to maternal provisioning,
are a larger source of interpopulation phenotypic variation and may
contribute to the local adaptation of populations.