Effects of land use and climate change on functional and phylogenetic diversity of terrestrial vertebrates in a Himalayan biodiversity hotspot

Aim: Land use and climate change interact to impact functional and
phylogenetic diversity globally, but this pattern is largely unknown in
the eastern Himalayas. We aim to discern the response of community
diversity and structure of terrestrial mammals and birds to anthropogenic
land use and climate change in this hitherto understudied landscape.
Location: Himalayan biodiversity hotspot, Bhutan Methods: We used camera
trap and point-count transect data to estimate taxonomic, functional, and
phylogenetic diversity while accounting for detectability. We calculated
the abundance-weighted standardised effect sizes (ses) of mean pairwise
distance and mean nearest taxon distance. The ses metrics were regressed
against land use (agriculture and forest) and climate (temperature and
precipitation) variables using linear mixed effect models. Results:
Community diversity declined with agriculture in both groups. Mammal
diversity was higher farther from the settlement but birds remained
indifferent. Temperature and precipitation were positively associated with
mammal diversity, but birds displayed a mixed response: negative with
temperature and positive with precipitation. Agriculture had a strong
negative effect on the functional structure of birds but not mammals. The
functional and phylogenetic structure declined farther from the settlement
for mammals but increased for birds. Except for the functional structure,
all other metrics increased with temperature and precipitation for
mammals. Except for the positive relationship between functional structure
and temperature, other metrics showed a mixed response to climate in
birds.  Main conclusions: Our findings provide evidence that land
use rather than climate has an imminent effect in shaping local and
regional patterns of terrestrial vertebrate diversity in a Himalayan
biodiversity hotspot. Climate effects, although weak, may reduce
functional traits and consequently diminish functional roles. Species that
can persist in human-modified environments are clustered within a
phylogeny, suggesting possible loss of phylogenetic diversity.