The influence of incubation temperature on offspring traits varies across northern and southern populations of the American alligator (Alligator mississippiensis)

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 in northern populations, while the
allocation of maternal resources towards fat body mass is greater in
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.