| Patch dynamics coexistence models often predict the regional coexistence of competitors, predators and prey, or parasites and hosts when populations are divided into many subpopulations, each inhabiting a fraction of available resource patches. A series of three field experiments used leaf packs in streams and laboratory-grown wild mushrooms as patchy ephemeral resources (PERs) for benthic and mycophagous insects. Each experiment included three patchiness treatments consisting of a constant mass of resource divided into one, four, or sixteen patches placed on the stream bed or forest floor for insect colonization and development. The first leaf pack experiment confirmed the predictions of increasing richness and diversity with increasing patchiness, but confounded surface-area and patchiness effects. The second leaf pack experiment controlled for species-area effects, and showed that generic richness and Margalef diversity, morpho-species richness, and species abundance were significantly higher in the most subdivided (sixteen-patch) treatment. Log-likelihood ratio goodness-of-fit G-tests showed that genera and morpho-species unique within their replicate and within the experiment as a whole (i.e. 'rare' and 'unique' taxa) were more likely to occupy the patchiest resource clusters. Unique taxa constituted 40% of the genera and 34% of the morpho-species, respectively. The mushroom experiment showed similar trends, but means were not significantly different due to high variance and low statistical power. G-tests showed that rare and unique morpho-species were significantly more likely to occupy the patchiest resource clusters. Of 228 taxa, 103 occurred only once in the entire experiment. These results suggest that spatial patchiness, apart from resource heterogeneity and species-area effects, may foster greater community richness on patchy ephemeral resources for a single generation or resource cycle. Results also suggest that rare and unique taxa are supported by patchiness and are very important components of the biodiversity in these habitats. Spatio-temporal discontinuity and duplication of resources may be an important factor in evolutionary diversification. Patch dynamics phenomena should be carefully investigated in a variety of systems and integrated into conservation planning with caution. |
