An elevational gradient in floral traits and pollinator assemblages in the Neotropical species Costus guanaiensis var. tarmicus in Peru

Abstract

Different populations of plant species can adapt to their local pollinators and diverge in floral traits accordingly. Floral traits are subject to pollinator‐driven natural selection to enhance plant reproductive success. Studies on temperate plant systems have shown pollinator‐driven selection results in floral trait variation along elevational gradients, but studies in tropical systems are lacking. We analyzed floral traits and pollinator assemblages in the Neotropical bee‐pollinated taxon Costus guanaiensis var. tarmicus across four sites along a steep elevational gradient in Peru. We found variations in floral traits of size, color, and reward, and in the pollinator assemblage along the elevational gradient. We examined our results considering two hypotheses, (1) local adaptation to different bee assemblages, and (2) the early stages of an evolutionary shift to a new pollinator functional group (hummingbirds). We found some evidence consistent with the adaptation of C. guanaiensis var. tarmicus to the local bee fauna along the studied elevational gradient. Corolla width across sites was associated with bee thorax width of the local most frequent pollinator. However, we could not rule out the possibility of the beginning of a bee‐to‐hummingbird pollination shift in the highest‐studied site. Our study is one of the few geographic‐scale analyses of floral trait and pollinator assemblage variation in tropical plant species. Our results broaden our understanding of plant‐pollinator interactions beyond temperate systems by showing substantial intraspecific divergence in both floral traits and pollinator assemblages across geographic space in a tropical plant species.

Contradistinctive floral attributes, pollination guilds and their consequence on the outcrossing rate in two elevational morphs of Rhododendron arboreum Sm.

“…Additionally, floral traits also shape interactions with effective pollinators and gene-flow patterns ( Junker et al., 2013 ). Studies conducted in multiple mountain ranges have provided evidence regarding floral polymorphism and associated pollinators across elevational gradients, both at the community and species levels ( Adedoja et al., 2018 ; Maguiña-Conde et al., 2023 ). However, a limited number of studies have investigated how floral traits, pollinator pools, and mating outcomes may vary with elevation within a species, especially in the Himalayan region ( Gurung et al., 2018 ).…”

“…tarmicus (Loes.) Maas (Costaceae), differences in floral traits and pollinator assemblages indicated a transition to pollination by hummingbirds from bees ( Maguiña-Conde et al., 2023 ). In Trollius ranunculoides Hemsl.…”