Environmental influences on egg and clutch sizes in lentic- and lotic-breeding salamanders

Abstract

Recent research indicates that social and environmental factors influenceegg and clutch sizes in amphibians. However, most of this work is based on the reproductively diverse order Anura (frogs and toads), whereas less research has been conducted on Caudata (salamanders) and Gymnophiona (caecilians). Researchers have suggested that a relationship exists between social and environmental factors and egg and clutch sizes in salamanders, but studies controlling for phylogenetic context are lacking. We could not identify a sufficient number of comparisons for social influences on egg and clutch sizes; therefore, we focused on environmental influences for this study. Data on eggsize, clutch size, environmental factors, and phylogenies for salamanders were assembledfrom the scientific literature. We used independent, pair-wise comparisons to investigatethe association of larval salamander habitat and egg size and the association of larvalsalamander habitat with clutch sizes within a phylogenetic framework. There is a significant association between larval habitat and egg size; specifically, stream-breeding species produce larger eggs. There is no significant association between larval habitat and clutch size. Our study confirms earlier reports that salamander egg size is associated with larval environments, but is the first to use phylogenetically independent contrasts to account forthe lack of phylogenetic independence of the traits measured (egg size and clutch size) associated with many of the diverse lineages. Our study shows that environmental selection pressure can be quite strong on one aspect of salamander reproduction-egg size.