The macroecology of phylogenetically structured hummingbird–plant networks

Abstract

Aim To investigate the association between hummingbird–plant network structure and species richness, phylogenetic signal on species' interaction pattern, insularity and historical and current climate. Location Fifty‐four communities along a c. 10,000 km latitudinal gradient across the Americas (39° N–32° S), ranging from sea level to c. 3700 m a.s.l., located on the mainland and on islands and covering a wide range of climate regimes. Methods We measured the level of specialization and modularity in mutualistic plant–hummingbird interaction networks. Using an ordinary least squares multimodel approach, we examined the influence of species richness, phylogenetic signal, insularity and current and historical climate conditions on network structure (null‐model‐corrected specialization and modularity). Results Phylogenetically related species, especially plants, showed a tendency to interact with a similar array of mutualistic partners. The spatial variation in network structure exhibited a constant association with species phylogeny (R2 = 0.18–0.19); however, network structure showed the strongest association with species richness and environmental factors (R2 = 0.20–0.44 and R2 = 0.32–0.45, respectively). Specifically, higher levels of specialization and modularity were associated with species‐rich communities and communities in which closely related hummingbirds visited distinct sets of flowering species. On the mainland, specialization was also associated with warmer temperatures and greater historical temperature stability. Main conclusions Our results confirm the results of previous macroecological studies of interaction networks which have highlighted the importance of species richness and the environment in determining network structure. Additionally, for the first time, we report an association between network structure and species phylogenetic signal at a macroecological scale, indicating that high specialization and modularity are associated with high interspecific competition among closely related hummingbirds, subdividing the floral niche. This suggests a tighter co‐evolutionary association between hummingbirds and their plants than in previously studied plant–bird mutualistic systems.

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

“…Thus, ecological and historical factors may both shape geographical patterns of specialization. This has been found for hummingbird-plant networks, which have higher community-wide specialization in areas with higher precipitation and temperature, lower seasonality, and more stable climate conditions since the last glacial maximum [6,20].…”

Opposed latitudinal patterns of network‐derived and dietary specialization in avian plant–frugivore interaction systems

“…Networkderived specialization is here characterized by two metrics that quantify niche partitioning among species ('niche-based metrics', sensu Blüthgen 2010). Modularity can be interpreted as a measure of niche-based specialization, as the division of networks into modules reflects the specialization of species on specific groups of interaction partners (Olesen et al 2007), such as phylogenetically or phenotypically related groups of species (Maruyama et al 2014, Schleuning et al 2014, Martín González et al 2015). The biological assumption here is that if species have preferences for specific interaction partners, these preferences would be captured as deviation from random encounters given by partner availability (Blüthgen et al 2006).…”

Spatial distance and climate determine modularity in a cross‐biomes plant–hummingbird interaction network in Brazil

“…Indeed, modularity appears as a common feature across a wide variety of ecological and biogeographical networks, i.e. networks based on species occurrence across large areas (Dalsgaard et al., ; Kougioumoutzis, Simaiakis, & Tiniakou, ; Martín González et al., ; Olesen, Bascompte, Dupont, & Jordano, ). In modular networks species tend to interact intensively within subsets of species (modules), so that species in a given module interact more frequently with species in the same module than with species outside of it (Olesen et al., ).…”

“…Several factors such as current and historical climate, species’ distributional ranges, morphological traits and phylogenetic relationships may show associations with the level of modularity and module composition, and hence, with the specialization of plant–hummingbird interactions (Dalsgaard et al., ; Martín González, Allesina, Rodrigo, & Bosch, ; Martín González et al., ). However, the importance of these factors seems to vary according to network type and scale of the study (Allen, ; Gilarranz, Hastings, & Bascompte, ; Martín González et al., ; Schleuning et al., ).…”