Meeting Abstract
Intraspecific variation in the elemental phenotype, i.e., the elemental signature of biological processes such as growth, metabolism, and excretion, can form a foundation for linking evolution to ecosystem ecology. While intraspecific elemental variation is quite high in many species, the drivers of this variation are still poorly understood. Here we investigated developmental temperature as a source of intraspecific variation in the elemental phenotype of the poeciliid fish Gambusia marshi, which inhabit thermal springs in the Cuatro Cienegas basin in Coahuila, Mexico. Developmental temperature can affect growth rate, metabolic rate, and size at maturity, which are all linked to the elemental phenotype under the theory of biological stoichiometry. Among adult females sampled from eight springs, we found that body %C and excretion N:P were lower and body %P was higher in fish at a given size from warmer springs. We then reared F1 fish from two populations on a single diet at both cool (25 C) and warm (33 C) temperatures and found that excretion N:P ratio was still higher in fish reared at the cooler temperature. We used growth data from laboratory-reared fish to apply bioenergetics models to each developmental temperature regime, which suggested that higher respiration and consumption rates of fish at warmer temperatures could explain our results. In the context of stoichiometric theory, these results suggest that fish at warmer temperatures have a lower gross growth efficiency for C and a lower maximum accumulation efficiency for N and/or P. Linking the environmental and genetic controls on metabolism through stoichiometry provides a tangible bridge between evolutionary and ecosystem processes.
