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Fitosociologia numero 48 (2) S1

pag. 31-39: Habitat transitions and patterns of diversification of the genus Aquilegia in the Mediterranean context

*J. Mª Bastida Alamillo1, R. J. Bueno2, J. M. Alcántara Gámez2 & P. J. Rey Zamora2

1Posdoc Lab. Ecología y evolución de polinización y sistemas reproductivos en plantas. CIEco, UNAM Antigua Carretera a Pátzcuaro # 8701. Col. Ex-Hacienda de San José de La Huerta. C.P. 58190. Morelia, Michoacán, MÉXICO, e-mail: jbastida@oikos.unam.mx

2Departamento de Biología Animal, Biología Vegetal y Ecología. Universidad de Jaén, E-23071, Jaén. Spain, e-mail: rjaime@ujaen.es, jmalcan@ujaen.es, prey@ujaen.es

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abstract

Genus Aquilegia in North America has become a recurrent example of adaptive radiation driven by pollinator specialization and floral syndromes differentiation. However, Eurasian columbines show similar taxonomic diversity despite to be mainly pollinated by bumblebees. This situation makes Eurasian columbines an ideal counterpoint to explore diversification process under low pollinator diversity but high environmental heterogeneity scenarios. In this paper we explore diversification rates and patterns of habitat (habitat and altitudinal range) transitions underlying the European columbines evolution. A density-dependent lineal model of diversification best fitted our data, which implies a lineal decrease of diversification rate through radiation. Our results point to an important role of habitat (14.3-15.8 habitat transitions) in driving European columbines diversification. Habitat and altitudinal range reconstruction showed a pattern from wide altitudinal range (encompassing 1000-1200 m) and generalist ancestors to narrow altitudinal ranges (≈ 800 m) and open-rocky habitats in more recent taxa (i.e. those species inhabiting mountains regions of South Europe). Ecological opportunity has been the preferred explanation for density-dependence diversification during a radiation. Glacial impacts on European flora and the coincidence of the initiation of the radiation with the onset of Mediterranean climate probably did generate ecological opportunities for niche expansion and habitat specialization and evolution. However, we suggest that some biological features of Aquilegia (low seed dispersal, small population sizes and frequent inbreeding depression) unrelated to ecological opportunity together with the orography might also be involved in density-dependent speciation and habitat evolution in this genus. Specifically, we propose that high geographical isolation between and within distinct South European peninsulas, restricted geographical range size and specialization on open-rocky habitats combined with low seed dispersal might have contributed to the density-dependence mode of diversification in European columbines.

keywords

Aquilegia, altitudinal range, density-dependent diversification, European columbines, glaciations, habitat specialization, South European peninsulas