PS 7-86 - Metapopulations and disturbance: Effects of time since fire vary with neighboring habitat for a specialist beetle

Monday, August 8, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
Jessie Mutz, Nora Underwood and Brian D. Inouye, Biological Science, Florida State University, Tallahassee, FL

Metapopulations are characterized by extinction and colonization of interconnected patches.  Metapopulation models that include successional dynamics typically incorporate a time-lag in the recolonization of patches following disturbance, but do not account for differences in colonization rates due to variation among source habitats.  Differences between source patches may be expected especially in frequently-disturbed landscapes, such as fire-managed forests, where populations occur within a mosaic of habitat patches that vary in successional state and local extinctions are common.  We studied the effects of time since fire (TSF) on abundances of the specialist palmetto beetle Hemispherota cyanea both within and between individual burn units in Apalachicola National Forest, Florida.  We measured beetle densities at 3 distances from the edge in paired units, with sampled units ranging from 0-64 months since fire and the difference in burning time for a source-focal pair ranging from 3-58 months.  Sampling took place once every 4-5 weeks between May and August 2015.


Units with greater TSF generally hosted larger populations of beetles.  Within units, beetle abundance was highest at sites closer to the edge, but this effect diminished with increasing TSF.  Between units, focal unit abundance was positively related to the difference in TSF between source and focal units, and this relationship was strongest for recently-burned units.  These results suggest that both focal habitat history and type of source habitat can influence recolonization of recently-disturbed patches, and that these effects may be nonlinear and persist over long timescales.  Thus, when predicting metapopulation dynamics, habitat variability should be considered not only for patches receiving colonists, but for patches supplying colonists as well.