Differential temperature preferences of vertebral phenotypes in Gasterosteus

Across a broad diversity of freshwater and marine fish that have a wide latitudinal distribution, intraspecific variability in vertebral number shows a robust trend for higher vertebral counts in colder latitudes (Jordan's Rule). Variability in this meristic trait is determined during early larval development by a combination of heritable and temperature-mediated influences. We experimentally evaluate for the first time whether different vertebral phenotypes from a population actively segregate across a temperature gradient and if so, whether the segregation is consistent with broad geographical trends across taxa of greater vertebral counts associating with cooler waters. Using threespine stickleback (Gasterosteus aculeatus L., 1758) from two populations, we conducted 22 trials with ~50 fish per trial and a temperature gradient ranging from 2 to 150C degrees among trials. Results show that 6 trials yielded statistically significant or near-significant results of which 5 trials were in the predicted direction of more vertebrae in cooler waters. The effects were more expressed in small body-size classes (35-55 mm) than in larger fish (60-85 mm) and in longer duration trials. We feel these data are novel and consistent with recent studies on swimming efficacy among vertebral phenotypes but also hint at much great ecological functionality than currently assumed to intrapopulation variation in this meristic trait.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author