Tallgrass prairie remnants as 'living museums': Landscape context, metacommunity dynamics, and private management practices of native prairie hay meadows

Metacommunity theory is currently the dominant framework for understanding processes of species assembly. It predicts that local communities are linked in a network by dispersal of species, the establishment of which is filtered through local environmental conditions. In a fragmented landscape, such as native tallgrass prairie remnants within eastern Kansas, smaller patch area, greater isolation, and poorer matrix quality are predicted to result in (1) decreased species richness, (2) decreased site 'quality' (measured with a Floristic Quality Index), and (3) decreased presence of specialist species. Within five counties in eastern Kansas, 301 native tallgrass remnants were surveyed and mapped. Sites were grouped by cluster analysis to test these hypotheses of metacommunity theory. The total area of a site, as well as habitat heterogeneity of sites, contributed to richness and quality of sites, but isolation and matrix quality did not. In fact, isolation and matrix quality appeared to contribute to decreasing richness and quality of sites. The relationship of isolation with richness and quality can be explained by regional environmental variation having a greater influence on community composition than habitat connectivity in this system. The relationship of landscape matrix quality with richness and floristic quality may be explained by the historic nonrandom process of human landscape changes at the time of settlement, with soil quality rather than connectivity affecting composition. These results suggest that the hypothesis that dispersal plays a role in the community assembly of tallgrass prairie remnants is probably false. Although species-rich communities may persist for decades and possibly centuries after fragmentation, in the long term the effects of random local extinction and the burden of "extinction debt" have been underestimated for native tallgrass prairies, and the forecast for long-term persistence of these communities is grim.;KEY WORDS: fragmentation, island biogeography, coexistence, competition-colonization trade-off, dispersal, extinction...