Geographic variation in nesting behavior and reproductive biology of an insular iguana (Cyclura cychlura)

Abstract

Intraspecific comparisons among geographically separated populations of wide-ranging species are particularly useful in elucidating variation in behavioral and reproductive life histories resulting from proximate and ultimate causes. From 2001 to 2004, we investigated geographic variation in nesting behavior and reproductive biology of a large-bodied Bahamian iguana ( Cyclura cychlura Cuvier, 1829) inhabiting two distinct island systems varying in area, topography, and rainfall. Studies of C. cychlura cychlura were conducted on Andros Island (approx. 6000 km2; annual rainfall 1100 to 1300 mm) and the results were compared with those for C. cychlura inornata Barbour and Noble, 1916 inhabiting two cays (each <4 ha; annual rainfall <600 mm) in the northern Exuma Island chain (approx. 140 km distant). Female iguanas from Andros Island initiated oviposition 5 to 6 weeks earlier than females from the Exumas. The Andros Island population deposited eggs primarily in termitaria, whereas the lizards in the Exumas deposited eggs in subterranean sand chambers. Female iguanas from Andros deposited significantly more eggs per clutch, heavier total clutches, and wider eggs than conspecifics from the Exumas. Despite egg size differences, hatchling snout–vent length and body mass per clutch did not differ significantly between the Andros and Exuma populations. Our results support the hypothesis that proximate environmental factors play an important role in determining geographic variation associated with not only reproductive output but also reproductive behavior.