Diversity and interactions of the epiphyte community associated with ant‐gardens are not influenced by elevational and environmental gradients

Abstract

AbstractQuestionThe distribution and interactions of terrestrial biodiversity are influenced by environmental gradients. In general, tropical species present a hump‐shaped altitudinal species richness pattern related to gradients of temperature and precipitation. However, the effects of the elevational and environmental gradients on the co‐occurrence of species that form specialized mutualisms in the lowland tropical forest canopy and the relative importance of these species in interaction networks are unknown. We studied ant‐gardens, which are constituted by vascular epiphytes that inhabit ant nests exclusively. Our main question was: do the vegetation type, elevation, temperature, and precipitation alter the diversity and interactions of the associated species in ant‐gardens?LocationSoutheastern Mexico.MethodsWe recorded epiphytes and ants associated with ant‐gardens in 21 sites in southeastern Mexico (elevational range of 23–643 m a.s.l.), which is located on the northern limit of the distribution of Neotropical ant‐gardens. We tested whether the vegetation type and gradients of elevation, temperature and precipitation influence the diversity (richness and composition) and interactions (centrality, i.e., relative importance of each species in epiphyte–epiphyte interaction networks) of the ant‐gardens.ResultsWe found a total of 126 ant‐gardens formed by 15 epiphyte species and two ant species. Seven epiphytes and only one ant (Azteca gnava) are specialists of ant‐gardens (true ant‐garden epiphyte and ant species respectively). Neither vegetation type nor elevational and environmental gradients influenced the richness, composition and centrality of the epiphytes, although some species only occurred in sites with greater precipitation. The true ant‐garden epiphytes were more central than the non‐true ant‐garden epiphytes, with the orchid Epidendrum flexuosum being the most frequent and central epiphytic species in Mexican ant‐gardens.ConclusionsUnlike guilds of epiphytes and ants considered individually, the ant‐gardens represent a mutualism that maintains their patterns of diversity and interspecific interactions along gradients of elevation, temperature and precipitation.