Distinguishing habitat types and the relative influences of environmental factors on patch occupancy for a butterfly metapopulation

Abstract

The goals of this study were to examine whether subjective habitat types may be segregated based on environmental variables and whether the relative influences of environmental factors on patch occupancy differ among habitat types. We examined these questions using a metapopulation of the butterfly Speyeria nokomis carsonensis, surveying sites for environmental characteristics and butterfly presence/absence over a 2-year period. Discriminant function analyses correctly classified 84% of sites within habitat types based on environmental variables that explained 82 and 67% of the variance along two ordination axes. Occupancy models for each habitat type demonstrated that the relative influences of environmental factors differed among habitat types. This study broadens the current paradigm of metapopulation dynamics by demonstrating that systems exist in which distinct habitat types can be delineated and differential suites of environmental factors explain occupancy according to habitat type. These findings demonstrate that even for highly specialized species, all habitat areas cannot be assumed to contribute equally to occupancy status, and thus have comparable conservation value. Designing land-use plans and policies based, in part, on careful habitat assessments can have important implications for the conservation of species existing in patchy landscapes, and can help guide reserve design, management actions, and allocation of resources on multiple-use landscapes.