Landscape structure plays a key role in mediating a variety of
ecological processes affecting biodiversity patterns, however its
precise effects and the mechanisms underpinning them remain unclear.
While the effects of landscape structure have been extensively
investigated both empirically, and theoretically from a metapopulation
perspective, the effects of spatial structure at the landscape scale
remain poorly explored from a metacommunity perspective. Here, we
attempt to address this gap using a spatially explicit, individual-based
metacommunity model to explore the effects of landscape compositional
heterogeneity and per se spatial configuration on diversity at the
landscape and patch level via their influence on long term community
assembly processes. Our model simulates communities composed of lineages
of annual, asexual organisms living, reproducing, dispersing, and
competing within grid-based, fractal landscapes which vary in their
magnitude of spatial environmental heterogeneity and in their degree of
spatial environmental autocorrelation. Communities are additionally
subject to temporal environmental fluctuation and external immigration,
allowing for turnover in community composition. We found that
compositional heterogeneity and spatial autocorrelation had differing
effects on richness and diversity and the landscape and patch scales. We
also note a slight negative effect of compositional heterogeneity on
median total landscape population size. Landscape level diversity was
driven by community dissimilarity at the patch level and increased with
greater heterogeneity, while landscape richness was largely the result
of short-term accumulation of immigrants and decreased with greater
compositional heterogeneity. Both richness and diversity decreased in
variance with greater compositional heterogeneity, indicating a
reduction in community turnover over time. Patch-level richness and
diversity patterns appeared to be driven by overall landscape richness
and local mass effects, resulting in maximum patch level richness and
diversity at moderate levels of compositional heterogeneity and high
spatial autocorrelation.