Species diversity of aquatic macroinvertebrates in playa lakes: island biogeographic and landscape influences

Patterns of species diversity have long intrigued ecologists. This fascination has resulted in numerous theories explaining differences among sites in species diversity. Two such theories are those pertaining to island biogeography and landscape ecology. They differ in the import placed on patch versus matrix characteristics. Island biogeographic theory suggests that patch characteristics are the foremost influences on diversity. Conversely, landscape ecology proposes that attributes of the surrounding matrix are of primary significance.

Playas of the Southern High Plains are an excellent environment in which to study the relative influence of patch versus matrix characteristics. They are numerous and surrounded by a mosaic of landuse practices. These ephemeral lakes differ greatly in size and contain an abundance of aquatic macroinvertebrates.

Macroinvertebrates were sampled three times over a two month period and were categorized as resident or transient species based on life history characteristics. Species richness and diversity were analyzed for the effects of landuse practices, basin size, and surface area via analysis of covariance. In addition, G-tests of independence were used to analyze the influence of landuse practices and surface area on species composition. Surrounding landuse practices were found to influence resident species richness and species composition; total species richness was sensitive to basin size. Surface area affected total, resident, and transient species richness, resident species diversity, and species composition. However, all relationships were contingent on sampling period.

Regression analyses revealed that resident species richness and diversity were influenced more by island biogeographic characteristics than by landscape attributes. However, the converse was true for transient species richness and diversity. Neither resident nor transient species richness and diversity were related strongly to differences in water quality.

Both island biogeographic and landscape characteristics affect the diversity of macroinvertebrates in playa lakes. However, the extent of the influence of these two factors is dependent on life history strategy of the biota and time since inundation. The idiosyncratic pattern of species diversity is a reflection of the stochastic nature of playa inundation overlain by the effects of island biogeographic and landscape processes.