Local adaptation to hummingbirds and bees in Salvia stachydifolia : insights into pollinator shifts in a Southern Andean sage

IZQUIERDO, JULIANA V; COSTAS, SANTIAGO M; CASTILLO, SANTIAGO; BARANZELLI, MATÍIAS C; SAZATORNIL, FEDERICO; BENITEZ-VIEYRA, SANTIAGO

ANNALS OF BOTANY

OXFORD UNIV PRESS

Año: 2023

0305-7364

Background and Aims Differences among populations in pollinator assemblages can lead to local adaptationmosaics in which plants evolve different floral morphologies and attractive traits. Mountain habitats may promotelocal adaptation because of differences in environmental conditions with altitude, causing changes in pollinators,and because mountaintops can act as isolated habitats. We studied if the differences in floral shape, size andnectar traits in Salvia stachydifolia can be attributed to variations in the relative contribution of hummingbirdsand insects.• Methods We studied eight populations of S. stachydifolia in natural and under common garden conditions, toassess whether population differences have a genetic component. We recorded pollinators, their behaviour andvisitation rates, and characterized pollinator assemblages. In addition, we measured nectar volume and concentration, and collected flowers to describe floral shape and size variation using geometric morphometric methods.We then applied an unsupervised learning algorithm to identify ecotypes based on morphometric traits. Finally,we explored whether populations with different pollinator assemblages had different climatic and/or elevationpreferences.• Key Results We found that variation in the identity of the main pollinators was associated with differencesamong populations in all traits, as expected under a local adaptation scenario. These differences persisted in thecommon garden, suggesting that they were not due to phenotypic plasticity. We found S. stachydifolia populationswere pollinated either by bees, by hummingbirds or had mixed pollination. We identified two ecotypes that correspond to the identity of the main pollinator guilds, irrespective of climate or altitude.• Conclusions Variation in S. stachydifolia floral traits did not follow any evident association with bioclimaticfactors, suggesting that populations may have diverged as the product of historical isolation on mountaintops. Wesuggest that differences among populations point to incipient speciation and an ongoing pollinator shift.