PARENT SESSION
Oral Session # 43: A. Insect Ecology I; B. Traditional Ecological Knowledge.
Presiding: E Borer and SP Yanoviak
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.
Temporal variability in source-sink dynamics.
Johnson, Derek*,1, 2, 1 University of Miami, Coral Gables, FL, USA2 Penn State University, State College, PA, USA
ABSTRACT- Source-sink models are used to address spatial questions about organisms living in heterogeneous environments. In traditional source-sink models, vital rates and movement probabilities are assumed to be temporally homogeneous. Numerous studies, however, have demonstrated that temporal heterogeneity in many forms is the rule rather than the exception in natural systems. In this study, I present a temporally-variable source-sink dynamic of a neotropical beetle, Cephaloleia fenestrata, driven by flooding disturbance. A flood completely inundated a subset of C. fenestrata host plants, Pleiostachya pruinosa during the study. Survival and movement probabilities of C. fenestrata were estimated from data on approximately 1,200 individually-marked beetles. I demonstrate that a stochastic flood event caused a 6-fold increase in mortality in the flood zone compared to the upland habitat. In non-flood periods survival probability did not differ between habitats. Thus, the flood zone acts as a sink only during flood periods. Movement among the habitats was low (1-5%) during non-flood periods, but during a flood event increased over 10-fold (69%). Despite this, the net movement of beetles was from the upland to the flood zone. Given the estimated flood frequency of once per year, the overall population growth rate in the flood zone was determined to be < 1. Given estimates of flood probability, these results are consistent with the flood zone acting as a sink habitat for C. fenestrata. Ultimately, whether or not the flood zone is a sink or pseudo-sink habitat, and how strong a sink it is, depends on the flooding frequency and density-dependent effects.
Key words: source-sink, temporal variability, beetles, flood disturbance