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.