What Can Bryophyte Diversity On Cangas (Ironstone Outcrops) Teach Us?

Questions Bryophytes are a common plant component of the mining-threatened ironstone outcrops called Cangas, although quite neglected. Aiming to improve conservation strategies for this Brazilian landscape, here we ask: (a) are there differences in species composition, richness and abundance and the role of reproduction (i.e., sexual and asexual expression, and reproductive success) among bryophyte communities of Cangas; and (b) do abiotic and geographic factors influence species composition on these outcrops? Location Eight Canga sites in the Quadrilatero Ferrifero (QF) of the state of Minas Gerais, southeast Brazil. Methods We sampled eight Canga sites for bryophyte species composition, richness, abundance, and reproduction (i.e., sexual and asexual expression, reproductive success) using 18 4-m(2) plots per site. Similarities in species composition among sites were assessed by cluster analysis; differences in richness, abundance, and reproduction parameters were tested by ANOVA; and the correlations between species composition and climatic variables, altitude, and geographical distance were tested by the Mantel test. Results The Canga sites had unique species compositions of bryophytes, with only liverwort richness and abundance differing significantly among sites. Nonetheless, there were floristic similarities among certain geographically close sites, and bryophyte composition was not completely explained by either environmental variables or geographical distance. Additionally, sexual, and asexual reproduction did not differ among Cangas. Conclusions Cangas of the Brazilian QF have unique bryophyte communities (i.e., high beta diversity), especially for liverworts. Liverwort composition was found to be strongly affected by threats to Cangas, especially in areas disturbed by intensive fire. We hypothesize that the local landscape and microclimate have a greater influence on bryophyte diversity than regional aspects. Therefore, future conservation efforts on Cangas must emphasize local diversity and the functionality of liverworts and mosses in different habitats, combined with enhanced protection of Conservation Units.