Phylogenetic and functional structure

The phylogenetic structure of Caatinga further from roads differed from randomness at the 10-m x 10-m scale (Table 2), with NRI significantly overdispersed for woody species (p=0.027) as well as for non-woody species (p=0.002). Those woody and non-woody species were phylogenetically overdispersed in plots further from roads for NRI (Table 2). Woody and non-woody species were phylogenetically clustered in plots near roads for NTI (Table 2). At the scale of 10-m x 10-m, the samples near roads presented NTI significantly clustered (Table 2) for woody species (p=0.037) and for non-woody species (p=0.031). Woody and non-woody species presented different phylogenetic structure at the 20-m x 50-m scale as well as at the 10-m x 10-m scale depending on the distance from roads. Further from roads, NRI shows phylogenetic overdispersion at both scales (Table 2, Table S3, Figure S2), whereas NTI shows phylogenetic clustering for plots near roads at both scales (Table 2).
Calculating phylogenetic structure only with plants possessing traits related to herbivory (resprouters, urticants or toxic, succulents with spines), the traitNTI was significantly higher than zero in plots near roads, indicating functional clustering and closer relatedness among individuals than by chance (Table 3). Calculating phylogenetic structure with plants with all traits, the traitNRI of plots near roads was significantly greater than zero, indicating phylogenetic clustering, that is, closer relatedness than by chance (Table 3). These results show that environmental filtering near roads filters in species resilient/resistant to herbivory throughout the entire phylogenetic tree, but especially towards the tips of the phylogenetic branches.