DOI: 10.5061/dryad.rr4xgxd7n
title: The influence of biogeographical and evolutionary histories on morphological trait-matching and resource specialization in mutualistic hummingbird-plant networks

description: Functional traits can determine pairwise species interactions, such as
 those between plants and pollinators. However, the effects of biogeography
 and evolutionary history on trait-matching and trait-mediated resource
 specialization remain poorly understood. We compiled a database of 93
 mutualistic hummingbird-plant networks (including 181 hummingbird and
 1,256 plant species), complemented by morphological measures of
 hummingbird bill and floral corolla length. We divided the hummingbirds
 into their principal clades and used knowledge on hummingbird biogeography
 to divide the networks into four biogeographical regions: Lowland South
 America, Andes, North & Central America, and the Caribbean
 islands. We then tested: (i) whether hummingbird clades and
 biogeographical regions differ in hummingbird bill length, corolla length
 of visited flowers and resource specialization, and (ii) whether
 hummingbirds’ bill length correlates with the corolla length of their food
 plants and with their level of resource specialization. Hummingbird clades
 dominated by long-billed species generally visited longer flowers and were
 the most exclusive in their resource use. Bill and corolla length and the
 degree of resource specialization were similar across mainland regions,
 but the Caribbean islands had shorter flowers and hummingbirds with more
 generalized interaction niches. Bill and corolla length correlated in all
 regions and most clades, i.e. trait-matching was a recurrent phenomenon in
 hummingbird-plant associations. In contrast, bill length did not generally
 mediate resource specialization, as bill length was only weakly correlated
 with resource specialization within one hummingbird clade (Brilliants) and
 in the regions of Lowland South America and the Andes in which plants and
 hummingbirds have a long co-evolutionary history. Supplementary analyses
 including bill curvature confirmed that bill morphology (length and
 curvature) does not in general predict resource specialization. These
 results demonstrate how biogeographical and evolutionary histories can
 modulate the effects of functional traits on species interactions, and
 that traits better predict functional groups of interaction partners (i.e.
 trait-matching) than resource specialization. These findings reveal that
 functional traits have great potential, but also key limitations, as a
 tool for developing more mechanistic approaches in community ecology.
description: We compiled a dataset of 93 quantitative hummingbird-plant
 interaction networks from localities distributed widely across the
 Americas. Each of the 93 networks describes interaction frequencies within
 assemblages of hummingbirds and their food plants in a specific location.
 We only included mutualistic interactions in which a given hummingbird was
 observed drinking nectar and touching the stigma / anthers of the given
 flower, thereby potentially acting as a pollinator. The networks were
 sampled to represent all hummingbird clades and hummingbird-visited plant
 families without any taxonomic bias. Species names of the hummingbirds
 follow the International Ornithological Committee World List (IOC version
 9.2; www.worldbirdnames.org). Hummingbirds were divided into nine clades following McGuire et al. (2014). Species names and families of the plants follow ‘The Plant List’ (TPL version 1.1; www.theplantlist.org), with a few exceptions where species names of recorded plants were not found in TPL.