Context‐ and taxon‐dependent small‐scale taxonomic and phylogenetic nestedness of bryophytes on insular rocks in a karst natural reserve and its implication for their conservation

The distribution patterns of five categories and 183 species of bryophytes, and six physical attributes, on 92 insular rocks in three karst districts (Pangxiegou, the weather station in Shishangsenglin and Yaolancun) with different landscape properties in the Maolan National Nature Reserve, Guizhou, China, were recorded and analysed in terms of nestedness. By using matrix temperature, NODF metrics under four null models, treeNODF and permrows null model, we evaluated the taxonomic and phylogenetic nestedness at a small scale and explored possible underlying mechanisms. We found 1) a significant taxonomic and phylogenetic nestedness among the bryophytes and their main categories on these insular rocks, not only in the whole study region but also in each of the three districts; 2) higher taxonomic nestedness for mosses than for liverworts, and higher for acrocarpous mosses than for pleurocarpous mosses, indicating that nestedness of bryophytes on insular rocks in karst regions is taxon‐dependent; 3) rock area, habitat amount and height are the three main determinants of taxonomic and phylogenetic nestedness of bryophytes, while phylogenetic nestedness overall followed the same processes as taxonomic nestedness; 4) selective extinction and habitats nestedness were the two mechanisms accounting for the small‐scale nested pattern of bryophytes on insular rocks; 5) the determinants and mechanisms of taxonomic and phylogenetic nestedness varied among bryophytes in different landscapes and ecological habitats, thus being context‐dependent. Our results indicate that 1) large rocks with rich microhabitats should be given priority for the conservation of saxicolous bryophytes; 2) the conservation of different categories of saxicolous bryophytes that have a limited congruence will require a multiple criteria approach that incorporates phylogenetic diversity differences into reserve planning; 3) the conservation strategies for bryophyte diversities in different ecosystems should be adapted to local conditions and differences among bryophyte groups.