The functional integrity of northern leopard frog (Rana pipiens) and green frog (Rana clamitans) populations in orchard wetlands. I. Genetics, physiology, and biochemistry of breeding adults and young‐of‐the‐year

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Abstract
Northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at eight wetland sites, four of which were within apple orchards, to determine if environmental changes associated with orchard management affected measured biological parameters. Size, age, genetic variation, condition indices, levels of circulating steroid hormones, 7‐ethoxyresorufin‐O‐deethylase activity (EROD), and organochlorine and organophosphorus residues in breeding males sampled at pond sites in orchards were compared to the same parameters measured in breeding males from reference sites. Also, the size and physiological condition of young‐of‐the‐year captured in orchard and reference ponds were compared. No evidence of a reduction in genetic variation was found in populations of either species at any sites, but unexpectedly high average heterozygosity values (0.191–0.282) in concert with low overall fixation indices (0.012–0.059) in adults of both species did suggest that pond populations were interacting with neighboring populations in nonorchard habitats. Few significant differences in levels of circulating steroid hormones or condition indices of breeding males were found among sites. Significant EROD induction in male green frogs collected from one orchard site during one sampling event was the only indication that a metabolic challenge due to presence of cytochrome P450‐inducing toxicants may have existed, whereas elevated concentrations of organochlorines (dichlorodiphenyltrichloroethane [DDT]‐ or endosulfan‐related) in green frog tissues suggested that frogs at three orchard sites were taking up pesticides. Significant differences in size of equivalent‐age male and juvenile leopard frogs and green frogs occupying different study sites suggested that suboptimal habitat characteristics existed at one or two of the four orchard sites. However, site‐specific habitat deficiencies could not be related to orchard study sites in general, and, thus, wetlands in apple orchards appeared to provide viable breeding habitat for both northern leopard frogs and green frogs.