PARENT SESSION
Oral Session #59: Conservation Ecology: Terrestrial Biodiversity. Presiding: K. Schulz.
Thursday, August 9, 2001. 8:00 AM to 12:15 PM. Madison Ballroom D.

Measuring interpatch movement in a closed metapopulation of an imperiled insect.

OMLAND, KRISTIAN¹, ¹

ABSTRACT- Metapopulation dynamics and movement among patches are central to the viability of insect populations, particularly those that occupy early successional habitats. The Puritan tiger beetle is a Threatened species that occurs on open sand beaches along the Connecticut River. I used the method of marking and resighting beetles to measure the frequency of movement among beaches. I was able to conduct the work simultaneously on all beaches where the species is found within a 125 km reach of the river, thus I viewed the metapopulation as closed. I conducted the study in 1998 and 1999 marking 595 and 660 beetles respectively. Despite resighting 44% and 24% of marked beetles, I observed few instances of movement (~5% of resightings). Fitting a full multi-strata model to such sparse data proved inappropriate. However, since a number of simplifying assumptions (e.g., uniform survival rates and detection probabilities among beaches, symmetrical exchange probabilities) appeared to hold, I was able to calculate maximum likelihood estimates of the exchange probabilities between pairs of beaches. I verified the goodness of fit of that model using a parametric bootstrap procedure. I concluded that the probability of movement among beaches separated by as little as 200 m is no greater than 3% per day; the probability of moving 2 km or more is vanishingly small.

KEY WORDS: movement, mark-recapture, metapopulation, threatened species