Macro-Climatic Distribution Limits Show Both Niche Expansion and Niche Specialization among C4 Panicoids

BENA J; ZULOAGA F; BIGANZOLI F; REINHEIMER R; AAGESEN L; GODOY BURKI AC

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2016

1932-6203

Grasses are ancestrally tropical understory species whose current dominance in warmopen habitats is linked to the evolution of C4 photosynthesis. C4 grasses maintain high ratesof photosynthesis in warm and water stressed environments, and the syndrome is consideredto induce niche shifts into these habitats while adaptation to cold ones may be compromised.Global biogeographic analyses of C4 grasses have, however, concentrated ondiversity patterns, while paying little attention to distributional limits. Using phylogenetic contrastanalyses, we compared macro-climatic distribution limits among ~1300 grasses fromthe subfamily Panicoideae, which includes 4/5 of the known photosynthetic transitions ingrasses. We explored whether evolution of C4 photosynthesis correlates with niche expansions,niche changes, or stasis at subfamily level and within the two tribes Paniceae andPaspaleae. We compared the climatic extremes of growing season temperatures, aridity,and mean temperatures of the coldest months. We found support for all the known biogeographicdistribution patterns of C4 species, these patterns were, however, formed both byniche expansion and niche changes. The only ubiquitous response to a change in the photosyntheticpathway within Panicoideae was a niche expansion of the C4 species intoregions with higher growing season temperatures, but without a withdrawal from the inheritedclimate niche. Other patterns varied among the tribes, as macro-climatic niche evolutionin the American tribe Paspaleae differed from the pattern supported in the globally distributedtribe Paniceae and at family level.