Meeting Abstract
P1.72 Tuesday, Jan. 4 Island Toads Mature at Smaller Sizes than Mainland Toads on Three Atlantic Coast Barrier Islands EVANCHO, B.J.*; GERARD, N.R.; HRANITZ, J.M.; KLINGER, T.S.; CORBIN, C.E.; Bloomsburg University PA jhranitz@bloomu.edu
Studies in 1988 and 1989 revealed island dwarfism in a population of Fowlers toads (Bufo woodhousii fowleri) inhabiting Assateague Island VA. The age structure of samples collected from summer ranges was also younger on Assateague Island than the nearby mainland. Within age classes, island toads were smaller than mainland toads. The age- and size-structure of these two populations suggests that body size evolution on Atlantic Coast barrier islands results in island dwarfism. Our objectives were to determine size at maturity in island and mainland populations of B. w. fowleri and to test if island dwarfism in this species is naturally replicated on Atlantic Coast barrier islands. We collected 180 breeding toads from three pairs of island (Assateague Island, Wallops Island, and Smith Island) and mainland sites in a north-south transect on the Eastern Shore of Virginia. We measured snout to vent length (SVL) and nine other metrics to the nearest 0.1 mm with calipers. We also compared male advertisement calls between two island-mainland pairs. In all island-mainland comparisons, island toads were smaller (SVL) than mainland toads. Toad populations were also distinguished by unique morphologies, head shape and limb proportions, among sites. Cluster analysis separated all sites into island and mainland groups, with the highest similarity occurring between the northern- and southern-most sites of each cluster. Male advertisement calls (beginning pulse duration, end pulse duration, and dominant frequency) varied among sites, possibly because of seasonal factors not controlled in this study. The small size at maturity of island toads and parallel pattern of island and mainland morphologies suggest that small body size originated independently in these barrier island toad populations.
