Coupled Patterns of Hummingbird and Nectar‐Plant α‐ and β‐Diversity Along a Mexican Montane Elevational Gradient

ABSTRACT

Elevational gradients promote ecological filters in species distributions. Along these gradients, ecological factors such as vegetation structure and the availability of food resources vary markedly and play a crucial role in structuring both alpha and beta hummingbird diversity. In this study, we examined patterns of alpha and beta diversity of hummingbirds and their nectar‐producing plants along an elevational gradient in the Sierra Madre del Sur, spanning five elevational bands (1200, 1500, 1800, 2200, and 2500 m). At each elevation, we characterized hummingbird species composition and the plant species they visited and identified indicator species for both groups along the gradient based on relative abundance and frequency. We applied generalized linear models to assess the effects of floral resource availability on hummingbird richness and abundance. We found a correspondence between the distribution and turnover of hummingbirds and plants across the elevational gradient. Species richness and diversity of both groups peaked at the highest elevations, whereas species turnover was greatest among sites located at the extremes of the gradient. We also found elevation‐specific associations between particular hummingbird and plant species that contributed to these turnover patterns. Plant species richness and flower abundance significantly influenced hummingbird richness and abundance across elevations. Together, these findings clarify the mechanisms structuring hummingbird‐plant assemblages and highlight the need to conserve environmental heterogeneity in tropical and temperate habitats, which supports unique species combinations, maintains hummingbird diversity, and promotes spatial turnover.