Macroclimatic and maternal effects on the evolution of reproductive traits in lizards

Much of life-history theory rests on fundamental assumptions about
constraints on the acquisition and allocation of energy to growth and
reproduction. In general, the allocation of energy to reproduction depends
on maternal size, which in turn depends on environmental factors
experienced throughout the life of the mother. Here, we used phylogenetic
path analyses to evaluate competing hypotheses about the environmental and
maternal drivers of reproductive traits in lizards. In doing so, we
discovered that precipitation, rather than temperature, has shaped the
evolution of the life history. Specifically, environments with greater
rainfall have enabled the evolution of larger maternal size. In turn,
these larger mothers produce larger clutches of larger offspring. However,
annual precipitation has a negative direct effect on offspring size,
despite the positive indirect effect mediated by maternal size. Possibly,
the evolution of offspring size was driven by the need to conserve water
in dry environments, because small organisms are particularly sensitive to
water loss. Since we found that body size variation among lizards is
related to a combination of climatic factors, mainly precipitation and
perhaps primary production, our study challenges previous generalizations
(e.g., temperature-size rule and Bergmann's rule) and suggests
alternative mechanisms underlying the evolution of body size.