Density-dependent population dynamics and dispersal in heterogeneous metapopulations.

Area of Science:

• Ecology
• Population Dynamics
• Metapopulation Theory

Background:

• Habitat heterogeneity is a key factor influencing ecological processes.
• Metapopulation dynamics are crucial for understanding species persistence in fragmented landscapes.

Purpose of the Study:

• To investigate the effects of different habitat heterogeneity types on metapopulation dynamics and dispersal.
• To compare empirical data with mathematical models to understand population regulation and dispersal.

Main Methods:

• Construction of metapopulation microcosms using bruchid beetles (Callosobruchus maculatus).
• Recording long-term time series data under four heterogeneity treatments: homogeneity, spatial, temporal, and spatio-temporal.
• Fitting mathematical models with density-dependent and independent processes to empirical data using maximum likelihood.

Main Results:

• Local population sizes varied with habitat heterogeneity, with larger populations in resource-rich patches.
• Temporal heterogeneity increased population size variation within patches, while spatial heterogeneity increased variation between patches.
• Density-dependent regulation was strongest in homogeneous and temporally heterogeneous systems, best modeled by density-dependent mortality.
• Spatial and spatio-temporal heterogeneity were adequately described by density-independent processes.
• Dispersal was density-dependent, influenced by local population size and neighborhood density, except in homogeneous metapopulations.

Conclusions:

• Habitat heterogeneity significantly alters local population dynamics and inter-patch variation.
• The mechanisms regulating populations (density-dependent vs. independent) depend on the type of heterogeneity.
• Density-dependent dispersal is a critical component of metapopulation models, particularly in heterogeneous environments.