Greater pollination generalization is not associated with reduced constraints on corolla shape in Antillean plants

Abstract

Flowers show important structural variation as reproductive organs but the evolutionary forces underlying this diversity are still poorly understood. In animal-pollinated species, flower shape is strongly fashioned by selection imposed by pollinators, which is expected to vary according to guilds of effective pollinators. Using the Antillean subtribe Gesneriinae (Gesneriaceae), we tested the hypothesis that pollination specialists pollinated by one functional type of pollinator have maintained more similar corolla shapes through time due to more constant and stronger selection constraints compared to species with more generalist pollination strategies. Using geometric morphometrics and evolutionary models, we showed that the corolla of hummingbird specialists, bat specialists, and species with a mixed-pollination strategy (pollinated by hummingbirds and bats; thus a more generalist strategy) have distinct shapes and that these shapes have evolved under evolutionary constraints. However, we did not find support for greater disparity in corolla shape of more generalist species. This could be because the corolla shape of more generalist species in subtribe Gesneriinae, which has evolved multiple times, is finely adapted to be effectively pollinated by both bats and hummingbirds. These results suggest that ecological generalization is not necessarily associated with relaxed selection constraints.

Tracking temporal shifts in area, biomes, and pollinators in the radiation ofSalvia(sages) across continents: leveraging anchored hybrid enrichment and targeted sequence data

“…Plant groups that exhibit shifts between different pollinator guilds offer evolutionary insight into the role these shifts play in species diversification and influence convergent or parallel changes in floral color, shape, and structure (Schmidt‐Lebuhn et al., ; Tripp and Manos, ; Smith, ; Lagomarsino et al., ; Joly et al., ). Salvia is a unique model system to address these questions due to its large size, four identified shifts in species diversification (Figs.…”

“…Sclarea may allow for pollen deposition in a more isolated dorsal area of the pollinator's body, freeing species in this clade from competition for pollinators (Claßen‐Bockhoff et al., ). Moreover, these floral characters can be treated as continuous characters, are not susceptible to most of the problems discussed relative to categorical features, and can be analyzed with an innovative suite of emerging tools for phylogenetic comparative approaches (e.g., Chartier et al., ; Khabbazian et al., ; Rose et al., ; Kriebel et al., ; Joly et al., ).…”

Modularity and evolution of flower shape: the role of function, development, and spandrels inErica

“…In generalist flowers, three main hypotheses have been advanced to explain how pollinators affect floral shape (see Fig. b) (Aigner, ; Sahli & Conner, ; Joly et al , ), each of which implies a different floral modularity. (1) The ‘trade‐off’ hypothesis (Aigner, , ; Sahli & Conner, ) suggests that a trait change that increases the fitness contribution of one pollinator will decrease the fitness of another.…”

Divergent adaptations in resource‐use traits explain how pikas thrive on the roof of the world

“…See Figure S2 for a complete representation of the adaptive evolutionary hypotheses. To account for intraspecific variation, we include the sampling variance (the squared standard error) of species as measurement error in the model fitting following Joly et al (2018). For species represented by only one individual, we used the mean squared standard error.…”