Influences of wetland and landscape characteristics on the distribution of carpenter frogs

Abstract

The distribution of wetland breeding amphibians may be influenced by multiple habitat variables interacting at various scales. We applied a multi-scaled modeling approach to relate the presence and absence of carpenter frogs (Lithobates virgatipes), a species of conservation concern in Maryland, to several wetland and landscape characteristics. We also investigated relationships between wetland habitat quality and adjacent landscape composition using correlation analysis and summarized those relationships in a hierarchical path model. Breeding call surveys were conducted at 40 wetland sites to determine the presence of calling male carpenter frogs. We collected data on aquatic and terrestrial habitat using both on-site measurements and geographic information system analyses. Logistic regression modeling revealed that wetlands occupied by carpenter frogs were significantly more acidic, exhibited intermediate hydroperiods, and had higher proportions of surrounding forest cover than did sites unoccupied by carpenter frogs. Path analysis revealed forest cover exhibited a negative correlation with wetland pH and hydroperiod. Our study corroborates a growing body of research that suggests the distributions of many amphibians are related to forest cover adjacent to wetland habitat and provides evidence on the importance of forest cover for maintaining wetland habitat quality.