WHAT THE EVIDENCE SAYS
Surveys across five elevational bands in Mexico’s Sierra Madre del Sur compared hummingbird and nectar-plant alpha and beta diversity. Richness and diversity varied across elevation, with strong compositional turnover between the ends of the gradient. Plant richness and flower abundance were important correlates of hummingbird diversity, highlighting how the animal pattern was coupled to the distribution of floral resources rather than elevation alone.
WHY IT MATTERS / OUR READ
Mountain biodiversity planning benefits from tracking interaction resources as well as focal species. Protecting a continuous elevational gradient without maintaining the flowering community can preserve geography while losing part of the mechanism.
CAVEATS / UNCERTAINTY
This is an observational elevational study rather than an experiment; elevation covaries with climate, vegetation and land use. Survey timing and flowering phenology influence the observed network, and the results should not be converted into fixed elevational prescriptions for other mountains.
SOURCE
Biotropica — primary study
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