Rapid development of increased competitive ability and mechanisms of reproductive isolation of Centaurea species
Coordinator - Daniel Montesinos
Programme - FCT
Execution dates - 2013-05-01 - 2015-10-31 (30 Months)
Funding Entity - FCT
Funding for Grupo - 57 028.00 €
Total Funding - 57 028 €
Proponent Institution - Centro de Ecologia Funcional - Universidade de Coimbra
Participating Institutions
The University of Montana (USA)
Universidad Nacional de La Pampa (Argentina)
York University (Canada)

Humans have dispersed many species far beyond their original native ranges, resulting in new non-native ranges that are geographically isolated from the original range. After populations are isolated, gene flow between them ceases and genetic drift and adaptation to different environments leads to genetic divergence [1]. There is circumstantial evidence for selection in non-native ranges for ecological traits such as growth, herbivore defense, and competitive ability [2-4]. Theory predicts that divergent selection of ecological traits can drive reproductive isolation, and eventually, speciation [5]. Comparing plants from native and non-native ranges has provided insight into the role of competition in invasions [6], and separate comparisons of native and exotic congeners have shed light on the traits and mechanisms involved in invasions [7]. Centaurea solstitialis and C. sulphurea are closely related annual plants [15]; the former has become an aggressive invader in several areas of the world while the later was naturalized without becoming a noxious weed [7]. These species thus provide with a good comparative system to test for competitive ability, phenotypic plasticity and reproductive isolation among closely related species with different invasive success and between native and non-native ranges.
Previous works from our research group showed clear evidence for morphological divergence between native (Europe) and non-native (North America) ranges of the invasive C. solstitialis and also for the non-invasive C. sulphurea. Quite unexpectedly, additional preliminary data revealed effective reproductive barriers between the non-native and native ranges of the species, suggesting that rapid reproductive isolation (less than 200 years) might be occurring for this neo-allopatric species (see Fig. 1). As far as we know this is the first record of rapid acquisition of reproductive barriers between native and non-native ranges of a weed. Within this context, the present study aims to (1) assess for differences in phenotypical changes, phenotypic plasticity and competitive ability among geographically isolated populations (native vs. non-native); (2) assess reproductive isolation across a broad geographical range of native and non-native regions and considering the colonization history of the species; and (3) assess the genetic consequences of allopatry and reproductive isolation. The study will include ten populations from each of the native (Southern Europe) and non-native (North America) ranges of C. sulphurea; and four critical regions for C. solstitialis distribution: (1) Eastern Europe, the origin of diversification for C. solstitialis, from where it spread to (2) Southern Europe, the native range from where seeds were exported and the species naturalized into (3) South America, from where seeds were exported again to (4) North America, where it became a highly aggressive and damaging invader. We will assess not only the morphological divergences among populations from each of these four regions, but also the different levels of phenotypic plasticity and, most importantly, the levels of reproductive isolation among them. Understanding where and when reproductive barriers arise after recent geographical expansions will have broad implications for biogeography and speciation studies. Correlating the presence of these reproductive barriers with other morphological divergences across a broad geographical range, and taking into consideration colonization history, might be fundamental to understand how invasive species adapt and successfully invade newly colonized habitats.

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