Multiple traits and multifarious environments: integrated divergence of morphology and life history

Understanding complex responses of multiple character suites (e.g.,
behaviour, life history, morphology) to multifarious environments is a
challenging task. Here we use a multivariate approach (partial least
squares structural equation modelling) to disentangle drivers (i.e.,
predation, resource availability, and population demographics) of
phenotypic divergence among populations of Bahamas mosquitofish (Gambusia
hubbsi) inhabiting blue holes. We further employ a two-block partial least
squares analysis in a novel approach to uncovering integrated and
independent aspects of divergence in correlated character suites. Results
suggest that phenotypic divergence mainly resulted from
differences in predation regimes, with population demography and resource
availability also influencing particular aspects of divergence. We
uncovered statistically significant covariation of life histories
and morphologies, and revealed that phenotypic divergence between
predation regimes involved both integrated and independent responses. For
instance, female life histories diverged mostly independently of
morphology, although some morphological shifts (abdominal distension)
resulted from changes in fecundity. In contrast, males showed strong
morphological divergence independent of life history, but much of their
life-history shifts reflected joint morphological changes (lean weight and
body shape). Our study illustrates the utility of gathering disparate data
types from multiple populations/species to understand the causes and
nature of phenotypic divergence in the wild.