Geographical variation in the bill-flower fit in a plant-pollinator interaction in western Mexico

Few studies have examined geographical variation in traits
involved in biotic interactions, although such variation is likely key in
the evolution of interactions. The fit between hummingbird bills and the
flowers they feed on suggests mutual selection pressures. We tested for
geographical variation in the pollinator – flower fit in the Mexican hermit
Phaethornis mexicanus and Heliconia spp. flowers by analyzing the
morphospaces of the interacting species and the ways they vary. To analyze
the geographical variation in the morphology of P. mexicanus and Heliconia
spp. flowers, we grouped samples into three operational geographic units
(OGUs). Within each OGU, we assessed pollinator-flower specificity by
analyzing floral resource preference, and morphological data using
correlations and principal component analysis. Our data on floral
preferences and morphology indicate geographical variation in the P.
mexicanus – Heliconia interaction in all of the OGUs. Heliconia was the
preferred flor...