Study group
Merianieae (Melastomataceae) are a Neotropical plant tribe of ca. 300 species, which has radiated recently in the tropical Andes (Dellinger et al. 2021). Bee pollination is ancestral and common both among lowland rainforest and cloud forest Merianieae, while shifts to vertebrate pollination (3 x passerine, 3 x mixed assemblages of vertebrates) are restricted to cloud forest species (for detailed empirical pollinator obsevations, see Dellinger et al. 2014, 2019b, 2021). For this study, we chose six species: lowland rainforest bee-pollinated Adelobotrys adscendens (Sw.) Triana, cloud forest bee-pollinated Meriania maxima Markgr., passerine-pollinated Axinaea costaricensisCogn., and three species pollinated by different combinations of vertebrates (M. phlomoides (Triana) Almeda and M. tomentosa (Cogn.) Wurdack, pollinated by hummingbirds and bats;M. sanguinea Wurdack, pollinated by hummingbirds, bats and rodents, Dellinger et al. 2019b). Our sampling covers three independent pollinator shifts from bee to vertebrate pollination (1: M. sanguinea , 2: M. tomentosa and M. phlomoides (part of the same subclade of Merianieae), 3. A. costaricensis ; Dellinger et al. 2019b). The six species differ in distribution ranges and ecosystems colonized (i.e. lowland rainforests, cloud forests, Fig. 1). Our approach of directly addressing these differences through landscape genetics and (historic) niche modelling allows us to objectively evaluate the multifarious factors potentially structuring population genetic diversity across multiple related species. Since all six species have similarly small, dry, wind-dispersed seeds, gene flow attributable to seed dispersal is comparable (and potentially limited to short distances given the dense structure of tropical forests, Kartzinel et al. 2013, Nazareno et al. 2020).