title: The role of edaphic environment and climate in structuring phylogenetic pattern in seasonally dry tropical plant communities.
abstract: Seasonally dry tropical plant formations (SDTF) are likely to exhibit phylogenetic clustering owing to niche conservatism driven by a strong environmental filter (water stress), but heterogeneous edaphic environments and life histories may result in heterogeneity in degree of phylogenetic clustering. We investigated phylogenetic patterns across ecological gradients related to water availability (edaphic environment and climate) in the Caatinga, a SDTF in Brazil. Caatinga is characterized by semiarid climate and three distinct edaphic environments - sedimentary, crystalline, and inselberg -representing a decreasing gradient in soil water availability. We used two measures of phylogenetic diversity: Net Relatedness Index based on the entire phylogeny among species present in a site, reflecting long-term diversification; and Nearest Taxon Index based on the tips of the phylogeny, reflecting more recent diversification. We also evaluated woody species in contrast to herbaceous species. The main climatic variable influencing phylogenetic pattern was precipitation in the driest quarter, particularly for herbaceous species, suggesting that environmental filtering related to minimal periods of precipitation is an important driver of Caatinga biodiversity, as one might expect for a SDTF. Woody species tended to show phylogenetic clustering whereas herbaceous species tended towards phylogenetic overdispersion. We also found phylogenetic clustering in two edaphic environments (sedimentary and crystalline) in contrast to phylogenetic overdispersion in the third (inselberg). We conclude that while niche conservatism is evident in phylogenetic clustering in the Caatinga, this is not a universal pattern likely due to heterogeneity in the degree of realized environmental filtering across edaphic environments. Thus, SDTF, in spite of a strong shared environmental filter, are potentially heterogeneous in phylogenetic structuring. Our results support the need for scientifically informed conservation strategies in the Caatinga and other SDTF regions that have not previously been prioritized for conservation in order to take into account this heterogeneity.
authors: State University of Campinas-UNICAMP, Departamento de Biologia Vegetal, Bloco M, CEP 13.083-970, Campinas, São Paulo, Brazil.
authors: Marcelo Freire
authors: MF
authors: Moro
authors: State University of Campinas-UNICAMP, Departamento de Biologia Vegetal, Bloco M, CEP 13.083-970, Campinas, São Paulo, Brazil.
authors: Igor Aurélio
authors: IA
authors: Silva
authors: Federal University of Ceará-UFC, Departamento de Biologia, Centro de Ciências, Universidade Federal do Ceará, Campus do Pici, Bloco 906, CEP 60455-760, Fortaleza, CE, Brazil.
authors: Francisca Soares
authors: FS
authors: de Araújo
authors: Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, United Kingdom.
authors: Eimear
authors: E
authors: Nic Lughadha
authors: School of Biology, University of St Andrews, St Andrews, Fife, KY16 9TH, United Kingdom.
authors: Thomas R
authors: TR
authors: Meagher
authors: State University of Campinas-UNICAMP, Departamento de Biologia Vegetal, Bloco M, CEP 13.083-970, Campinas, São Paulo, Brazil.
authors: Fernando Roberto
authors: FR
authors: Martins
mesh_terms: D044822:Biodiversity; D010802:Phylogeny; D010944:Plants / Q000145:classification*; D012621:Seasons; D012987:Soil; D062211:Spatio-Temporal Analysis; D014329:Tropical Climate; D014934:Wood / Q000145:classification
chemical_list: D012987:Soil