Is variation in flower shape and length among native and non-native populations of Nicotiana glauca a product of pollina
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Is variation in flower shape and length among native and non-native populations of Nicotiana glauca a product of pollinator-mediated selection? Macarena García1 · Santiago Benítez‑Vieyra1 · Alicia Noemí Sérsic1 · Anton Pauw2 · Andrea Arístides Cocucci1 · Anna Traveset3 · Federico Sazatornil1 · Valeria Paiaro1 Received: 18 June 2020 / Revised: 14 September 2020 / Accepted: 23 September 2020 © Springer Nature Switzerland AG 2020
Abstract Due to drastic changes in pollinators between native and invaded habitats, we might expect that pollinator-mediated selection on floral traits of alien plants differ from that in their native ranges. Here, through geometric morphometric tools and phenotypic selection analyses, we examined whether adaptation in flower shape and length occurred in Nicotiana glauca as a response to pollinator selection in contrasting pollination environments. We assessed populations of this plant species in the native range (South America), where plants depend on hummingbird pollination, and in two invaded areas, one where sunbirds act as pollinators (South Africa), and another where nectar feeding birds are absent and reproduction is entirely by autonomous self-pollination (Mallorca, Spain). Corolla length and shape varied significantly among pollination environments. Non-native sites were less variable and their range of variation fell within the native range of variation. Flower length in native populations and in a South African population matched the bill length of their respective pollinators. In contrast with the straight floral tubes in the native range, both non-native areas had significantly curved tubes. Curvature may improve the fit with the curved bills of sunbirds in South Africa (versus straight beaks of hummingbirds) and may enhance self-pollination in Mallorca, but this similarity between invaded areas may equally be due to drift and a shared colonization route. We found spatial variation in selection acting on corolla length but not on corolla shape. Overall, selection patterns were not consistent with floral trait variation. Although some results are consistent with both drift and selection, our study suggests that population divergence in flower shape and length is more likely the result of long-term diversifying pollinator-driven selection, which is difficult to detect by studying a single selection event. Keywords Geometric morphometrics · Hummingbirds · Phenotypic selection · Selfpollination · Sunbirds
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1068 2-020-10082-w) contains supplementary material, which is available to authorized users. * Valeria Paiaro [email protected] Extended author information available on the last page of the article
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Evolutionary Ecology
Introduction Species introduction into new environments generally involves drastic changes in the selective regime, which can lead to adaptive evolution (Sakai et al. 2001; Murren et al. 2009; Molina-Montenegro et al. 2011; Westley 2011;
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