PARENT SESSION
Poster Session 30: Invertebrate Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Butterfly movements among isolated prairie patches: distance, habitat edge, and forest-matrix effects.
Stasek, David*,1, Crist, Thomas1, 1 Miami University, Oxford, OH, USA
ABSTRACT- Multiple factors are known to affect animal movement patterns and spatial structure of populations. The size and isolation of suitable habitats, the edge characteristics of patches, and the composition of the surrounding matrix influence the rates of within- and among-patch movements. Using mark-recapture and abundance counts, we assessed within- and among-patch movements and population sizes of two species of butterfly (Lepidoptera: Nymphalidae) in a set of remnant prairie patches isolated by forest matrix. The Lynx prairie system in Adams County, OH consists of nine remnant tall-grass prairie patches with an average patch size of 0.22 ha, separated by an average distance of 50 m. The great-spangled fritillary (Speyeria cybele) is a highly vagile species with a wingspan of 76-100 mm, while the pearl crescent (Phyciodes tharos) is a low vagility species with a wingspan of 31-41 mm. Recaptures of the great-spangled fritillary showed significantly more between-patch movements than those of the pearl crescent (X2 = 5.382, df =1, p= 0.02) with 66% of recaptures of the great-spangled fritillary occurring in a different patch than where they were first marked. Only 30% of recaptured pearl crescent butterflies showed between-patch movements. Although the two species had similar abundances, the great-spangled fritillary had higher relative abundances along the prairie-forest edge than did the pearl crescent, which was more commonly found in the patch interior (X2 =10.08, df =1, p= 0.0015). The probability of movement between patches decreased exponentially from 14% to 6% at distances ranging from 12 to 300 m (inverse power function, z =.26, R2 =.30). These results suggest that both butterfly populations exhibit the characteristics of a patchy population rather than a classic metapopulation, although the pearl crescent showed a tendency to be more spatially structured than the great-spangled fritillary.
Key words: landscape ecology, Lepidoptera, habitat matrix, habitat fragmentation