Metapopulation persistence and stability in red flour beetle: Roles of habitat fragmentation, connectivity and spatial configuration

Background/Question/Methods Metapopulation theory has emerged as a central paradigm to study the population dynamics of species living in fragmented landscapes and provide recommendations for conservation.  Unfortunately, empirical tests of theoretical predictions have lagged behind model development.  Here, we highlight the results from a lab study investigating the impact of habitat fragmentation, connectivity and configuration of patches on the metapopulation dynamics of red flour beetle, Tribolium castaneum, occupying a four patch micro-landscape.  We modified resource availability (constant and diminishing), patch connectivity (high and low) and spatial configuration of patches (fixed and alternating).  We designed a 3x2 factorial experiment, consisting of 8 metapopulations, each consisting of 3 replications.  For comparison, two control populations also were provided with resources at constant or diminishing levels, but lacked connectivity and alternation in patch configuration.  We report on the main and interaction effects of treatment factors affecting the persistence of T. castaneum metapopulations using ANOVA and linear mixed effects regression modeling on time series data collected for 22 generations or until extinction.  We also estimated fluctuation index, a measure of amplitude of population fluctuation over time to compare the stability of the metapopulations. 

Results/Conclusions Constant resource (P << 0.001) and alternate spatial configuration (P = 0.02) levels yielded significantly greater levels of adult beetle abundance.  Marginally more adults occurred on average in populations characterized by low connectivity (P = 0.08).  The mean adult mortality outside of patches was significantly affected by interactions between resource level and connectivity (P < 0.001) as well as resource level and configuration (P = 0.03).  The frequency of patch extinctions and colonization was significantly affected by the interaction of connectivity and spatial configuration (P >= 0.002).   Metapopulations residing in landscapes with constant resource, low connectivity and alternate spatial configuration had higher persistence and stability.