Area-sensitivity of reptiles and amphibians: Are there indicator species for habitat fragmentation?

Abstract

Indicator species should exhibit sensitivity to certain environmental conditions, for example, habitat fragmentation. Amphibian and reptile species were examined on three island archipelagos (Lake Erie, Georgian Bay and the St. Lawrence River) for sensitivity to insularization and hence, whether any might indicate effects of habitat fragmentation. Species that are most sensitive to habitat fragmentation are expected to be those that disappear first from assemblages as insularization increases (i.e., area decreases). The ranked order in which reptiles and amphibians disappeared from assemblages as island area decreased was positively correlated between two of the three archipelagos (p < 0.002 and p < 0.001). Species such as northern water snake (Nerodia s. sipedon [L.]), bullfrog (Rana catesbeinana Shaw), and American toad (Bufo americanus Holbrook) tended to be present on islands of all sizes; red-spotted newt (Notophthalmus v. viridescens Rafinesque), ringneck snake (Diadophis punctatus edwarsii Merrem) and gray treefrog (Hyla versicolor LeConte, 1825) tended to be absent from smaller islands and are, therefore, area-sensitive. However, variation in life history traits thought to correlate with area-sensitivity (body size, rarity and dispersal ability) could not account for the observed order of species’ disappearances with decreasing island area.