Data from: Ecological drivers of avian community assembly along a tropical elevation gradient

Community assembly theory hypothesizes that two main niche-based processes
act to shape composition and organization of biological assemblages:
abiotic filtering and biological interactions. Here, we conducted repeated
surveys of bird abundance along an undisturbed elevational gradient in the
tropical Andes to investigate (1) signals of deterministic processes
driving community assembly and (2) potential mechanisms by which these
forces operate (temperature, habitat complexity, fruit and insect
availability), while correcting for imperfect detection and modeling
species abundances with N-mixture models. We observed strong signals of
abiotic filtering driving functionally and phylogenetically clustered
assemblages towards higher elevations, and a weaker signal of limiting
similarity resulting in few overdispersed assemblages at lower elevations.
Whereas the decay in species richness with increasing elevation was
explained by temperature, trait and phylogenetic dispersion were explained
by both temperature and vegetation structure, implying that an interplay
of abiotic and biotic mechanisms determines abundance-based community
structure in our montane assemblages. Interestingly, trait and
phylogenetic dispersion consistently decreased until ~3000 m but increased
above this elevation, highlighting a potential role of competition in
resource-scarce habitats. Combined, our findings suggest abiotic filters
are still the main process shaping montane biotas across elevations,
whereas resource availability might act locally upon assemblages further
modifying them. Our study challenges recent studies in tropical mountains
that suggest that biotic filters are a stronger force than abiotic filters
in shaping tropical montane assemblages, and exemplifies how accounting
for imperfect detection might overcome potential biases in detecting
environmental filtering signals in community assembly studies.