A comparative study of phenotypic traits related to resource utilization in anuran communities

Larval anuran communities vary along a gradient of pond permanency. The families Hylidae, Ranidae, and Bufonidae have each diversified into multiple pond types. Species using ponds that dry seasonally (vernal ponds) must compete well to metamorphose before pond drying, while permanent ponds, which contain more predators, produce weaker selection for competitive ability. Quantifying phenotypic traits related to resource acquisition in 14 anuran species provides insight into the mechanistic underpinnings of adaptive radiation in anuran lineages. Under controlled laboratory conditions and at both early and late developmental stages, relative growth rate, relative consumption rate, assimilation efficiency and production efficiency varied significantly among species. As predicted, vernal pond species had high growth rates relative to species using more than one pond type. However, within a pond type, families frequently differed in phenotype. In species using permanent ponds with fish predators, hylids had high growth rates while ranids had low growth rates, and in species using vernal ponds, bufonids had higher assimilation efficiencies than hylids. Differences also occurred between stages; hylids and ranids in permanent, but fishless, ponds were similar at an early stage, but late stage hylids in the same pond type had lower growth and consumption rates, and higher assimilation efficiencies than ranids. Functional relationships between phenotypic traits also differed among species and developmental stage. Negative correlations between evolutionary change (independent contrast values) in both mass and growth rate (both stages), and mass and consumption rate (late stage), suggest the presence of trade-offs. These results indicate that different lineages have diversified in different ways into the same pond types.