Bat-flower trait matching: Extreme phenotypic specialization affects diet preferences but not diet breadth

Nectarivorous bats have evolved various adaptations to feeding from flowers, such as long, extensible tongues and the ability to hover. The champion of tongue length, Anoura fistulata, can extend its tongue 150% of its body length, yet little is known about its interactions with flowers in the wild. Here we analyzed the diet of A. fistulata and co-occurring nectar bats in eight sites across Ecuador. Results demonstrate that, despite its phenotypic specialization, A. fistulata is no more ecologically specialized in its dietary breadth than co-occurring nectar bats. However, it prefers deeper flowers and is the sole visitor to two species (Centropogon nigricans and Marcgravia williamsii) whose extremely deep flowers make their nectar inaccessible to other bats. Furthermore, A. fistulata only occurred in sites with at least one flower deeper than the tongue length of other nectar bats, suggesting it needs such a guaranteed nectar source to maintain a population. Finally, we found strong covariation across sites between the local tongue length of A. fistulata and the depth of the deepest flowers it visits. This suggests that the coevolutionary race that selected for the exceptional tongue length of this bat over time is also playing out in a geographic mosaic across space.