Implications of dominance hierarchy on hummingbird-plant interactions in a temperate forest in Northwestern Mexico

Abstract

The structuring of plant-hummingbird networks can be explained by multiple factors, including species abundance (i.e., the neutrality hypothesis), matching of bill and flower morphology, phenological overlap, phylogenetic constraints, and feeding behavior. The importance of complementary morphology and phenological overlap on the hummingbird-plant network has been extensively studied, while the importance of hummingbird behavior has received less attention. In this work, we evaluated the relative importance of species abundance, morphological matching, and floral energy content in predicting the frequency of hummingbird-plant interactions. Then, we determined whether the hummingbird species' dominance hierarchy is associated with modules within the network. Moreover, we evaluated whether hummingbird specialization (d') is related to bill morphology (bill length and curvature) and dominance hierarchy. Finally, we determined whether generalist core hummingbird species are lees dominant in the community. We recorded plant-hummingbird interactions and behavioral dominance of hummingbird species in a temperate forest in Northwestern Mexico (El Palmito, Mexico). We measured flowers' corolla length and nectar traits and hummingbirds' weight and bill traits. We recorded 2,272 interactions among 13 hummingbird and 10 plant species. The main driver of plant-hummingbird interactions was species abundance, consistent with the neutrality interaction theory. Hummingbird specialization was related to dominance and bill length, but not to bill curvature of hummingbird species. However, generalist core hummingbird species (species that interact with many plant species) were less dominant. The frequency of interactions between hummingbirds and plants was determined by the abundance of hummingbirds and their flowers, and the dominance of hummingbird species determined the separation of the different modules and specialization. Our study suggests that abundance and feeding behavior may play an important role in North America's hummingbird-plant networks.

Keywords: Aggressive dominance; David’s score; Ecological networks; Morphological traits.

Figure 1. Modules in the plant–hummingbird network from El Palmito during fall/winter.

The intensity of blue shading represents the interaction frequency. Hummingbird illustration credit: Marco Antonio Pineda Maldonado/Banco de Imágenes CONABIO.

Figure 2. Principal components analysis (PCA) for the hummingbird rankings and floral traits.

(A) David’s score (Ds) ranking, (B) Perc ranking, and (C) floral traits. The colors indicate the modules in the plant–hummingbird network.

Figure 3. Relationships of the species-level network specialization (d’) to dominance hierarchy (A) David’s score, and (B) Perc ranking, bill length (C), and bill curvature (D) of 13 hummingbird species.

We excluded Ruby-throated hummingbirds and broad-tailed hummingbirds from Perc ranking.