Data from: Plasticity matches phenotype to local conditions despite genetic homogeneity across 13 snake populations

In a widespread species, a matching of phenotypic traits to local
environmental optima is generally attributed to site-specific adaptation.
However, the same matching can occur via adaptive plasticity, without
requiring genetic differences among populations. Adult sea kraits
(Laticauda saintgironsi) are highly philopatric to small islands, but the
entire population within the Neo-Caledonian lagoon is genetically
homogenous because females migrate to the mainland to lay their eggs at
communal sites; recruits disperse before settling, mixing up alleles.
Consequently, any adaptive matching between local environments (e.g., prey
sizes) and snake phenotypes (e.g., body sizes and relative jaw sizes) must
be achieved via phenotypic plasticity rather than spatial heterogeneity in
gene frequencies. We sampled 13 snake colonies spread along a ~200km
northwest-southeast gradient (N>4,500 individuals) to measure two
morphological features that affect maximum ingestible prey size in
gape-limited predators: body size and relative jaw size. As proxies of
habitat quality, we used protection status, fishing pressure and lagoon
characteristics (lagoon width and distance of islands to the barrier
reef). In both sexes, spatial variation in body sizes and relative jaw
sizes was linked to habitat quality; albeit in different ways, consistent
with sex-based divergences in foraging ecology. Strong spatial divergence
in morphology among snake colonies, despite genetic homogeneity, supports
the idea that phenotypic plasticity can facilitate speciation by creating
multiple phenotypically distinct sub-populations shaped by their
environment.