Dispersal of Karner blue butterflies among subpopulations within closed canopy forests of Michigan.
Dunn, James*,1, Shelagowski, Brett1, 1 Biology Department, Allendale, MI, USA
ABSTRACT- The Karner blue butterfly (KBB) (Lycaeides melissa samuelis Nabokov) is an endangered specie that occurs as subpopulations within patches of blue lupine (Lupinus perennis)embedded within a matrix of unsuitable oak forest in the Eastern USA. It is assumed that the butterfly behaves as a metapopulation with local extinctions occurring within patches (subpopulations), with subsequent re-colonization from adjacent patches by dispersal flights. It is also believed that dispersal is restricted to flights of less that 200 m (USFWS KBB recovery plan) and that mature forest acts as a barrier to dispersal. However, there is a paucity of critical dispersal data needed to determine the population dynamics of the KBB and to adequately manage this declining species. Using standard mark-recapture methods, we measured dispersal patterns and distances among ten isolated subpopulations of KBB within a 1.5 m square kilometer area of closed canopy oak and pine plantation. We documented 65 cases of inter-patch dispersal of KBB from patches with hard-edge of forest through a matrix of closed canopy forest. Fifty eight of 65 dispersal flights were greater than the 200 m suggested maximum. Mean dispersal of males (n = 49) being 440 m and females (n = 16) being 518 m. Maximum dispersal distance was 1.3 km, but was likely limited by the size of the experimental area. Median dispersal distance was 370 m for both male and female butterflies. Ten percent of marked butterflies (65/612) dispersed among subpopulations which supports the assumption that the KBB behaves as a true metapopulation. Also the recovery plan assumption that dispersal of KBB is limited to patches within 200 m and that flights are restricted by closed canopy forest is likely incorrect over most of the KBB range.
Key words: dispersal, metapopulations, butterfly, endangered species
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