How do altitude and soil properties influence the taxonomic and phylogenetic structure and diversity of Brazilian páramo vegetation?

Altitude and environmental variables such as edaphic properties are considered determinants of species distribution and community composition in mountain ecosystems.Here,we aimed to outline the effects of distinct mountain peaks,altitude and soil properties on community composition,species density,phylogenetic structure and diversity of angiosperm páramo communities from the Serra do Brigadeiro State Park,Minas Gerais,southeastern Brazil.For that,we identified all angiosperm species found in 300 plots(1 m×1 m)from three mountain peaks,measured soil depth and analyzed soil fertility and texture in each plot.To reduce the number of soil variables and species composition,we computed principal coordinates based on soil properties and principal coordinates based on species-plot matrix for each plot.Furthermore,we computed the standard effect sizes of the mean phylogenetic pairwise distance and the mean nearest phylogenetic taxon distance for each plot to investigate differences in the degree of relatedness among coexisting species.We compared differences in response variables between peaks and modelled them in function of altitude and principle components of soil properties using mixed effect models.Species density and phylogenetic diversity differed between peaks,but,contrary to the previous findings,no relationships between species richness or phylogenetic diversity and altitude or soil properties were found,indicating that further investigations are necessary to understand the altitude-biodiversity relationship in Brazilian páramo vegetation.Community composition differed between peaks and depended on altitude,soil properties and interactions between them,indicating that upward shifting of bioclimatic conditions due to climate changes may alter communities of this ecosystem.Phylogenetic structure differed between peaks and was influenced by altitude and soil properties.As phylogenetic clustering increased with altitude,eventual upward movements of species in Brazilian páramo vegetation due to climate change may alter community composition and the degree of relatedness among coexisting species,increasing the risk of species from higher altitudes to disappear.Therefore,conservation priorities arise for higher landscape portions,where these high altitude species may find refuges.

Using resistance distance from circuit theory to model dispersal through habitat corridors

Aims Resistance distance(RD),based on circuit theory,is a promising metric for modelling effects of landscape configuration on dispersal of organ-isms and the resulting population and community patterns.The values of RD reflect the likelihood of a random walker to reach from a source to a certain destination in the landscape.Although it has successfully been used to model genetic structures of animal populations,where it most often outperforms other isolation metrics,there are hardly any applications to plants and,in particular,to plant community data.Our aims were to test if RD was a suitable metric for studying dispersal processes of plants in narrow habitat corridors(linear landscape ele-ments[LLE]).This would be the case,if dispersal processes(seed dis-persal and migration)resembled random walks.Further,we compared the model performance of RD against least-cost distance(LCD)and Euclidean distance(ED).Finally,we tested the suitability of different cost surfaces for calculations of LCD and RD.Methods We used data from 50 vegetation plots located on semi-natural LLE(field margins,ditches,road verges)in eight agricultural landscapes of Northwest Germany.We mapped LLE,including hedges and tree rows,from aerial images in a Geographic Information System,con-verted the maps into raster layers,and assigned resistance values to the raster cells,where all cells outside of LLE received infinite resist-ance and,thus,represented barriers to dispersal.For all pairs of plots within study areas,we calculated Jaccard similarity assuming that it was a proxy(or correlate)of dispersal events between plots.Further,we calculated RD and LCD of the network of LLE and ED between the plots.We modelled the effects of distance metrics on community similarity using binomial generalized linear mixed models.Important Findings ED was clearly the least suitable isolation metrics.Further,we found that RD performed better than LCD at modelling Jaccard similar-ity.Predictions varied markedly between the two distance metrics suggesting that RD comprises additional information about the landscape beyond spatial distance,such as the possible presence of multiple pathways between plots.Cost surfaces with equal cell-level resistances for all types of LLE performed better than more complex ones with habitat-specific resistances.We conclude that RD is a highly suitable measure of isolation or,inversely,connec-tivity for studying dispersal processes of plants within habitat cor-ridors.It is likely also suitable for assessing landscape permeability in other landscape types with areal habitats instead of narrow cor-ridors.RD holds the potential to improve assessments of isolation(or connectivity)for models of regional population and meta-com-munity dynamics.