Neo-Allopatry and Rapid Reproductive Isolation

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. abstract: Over the past 3 centuries, many species have been dispersed beyond their natural geographic limits by humans, but to our knowledge, reproductive isolation has not been demonstrated for such neo-allopatric species. We grew seeds from three species of Centaurea (Centaurea solstitialis, Centaurea calcitrapa, and Centaurea sulphurea) that are native to Spain and have been introduced into California, and we tested to what extent seed production was affected by pollen source. Compared with within-population crosses, seed production decreased by 52% and 44%, respectively, when C. solstitialis and C. sulphurea from California were pollinated with conspecific pollen from native populations in Spain. This implies rapid evolution of reproductive isolation between populations in their native and nonnative ranges. Whether reproductive isolation has evolved following the introduction of other species is unknown, but additional cases are likely, considering the large number of neoallopatric species.

Traits correlate with invasive success more than plasticity: A comparison of three Centaurea congeners

“…This is consistent with the perspective that local adaptation is a more common mechanism than phenotypic plasticity allowing plants to deal with environmental variability (Palacio‐López et al., 2015). Several studies have reported different sets of local adaptations to different non‐native ranges for several traits of the same Centaurea species studied here (García, Callaway, Diaconu, & Montesinos, 2013; Graebner, Callaway, & Montesinos, 2012; Montesinos et al., 2012). Together with our results, this suggests that local adaptation may be more important than plasticity for dealing with the new environments of the non‐native ranges for these three Centaurea species.…”

“…These species are related enough to hybridize when artificially crossed (Montesinos, Santiago, & Callaway, 2012). The three species have overlapping distributions and appear to have similar environmental requirements in both their native (Eurasia) and non‐native (North America) and thus share aspects of their evolutionary histories.…”

Admixture between native and invasive populations may increase invasiveness of Mimulus guttatus

“…For a native Swiss provenance of Silene alba, heterosis was observed for progeny from crosses with three other European provenances, but outbreeding depression was observed for progeny from a cross with a non-native North American provenance [38]. In two Centaurea species, there was even evidence that reproductive barriers may have arisen between invasive and native populations, as between-continent crosses resulted in fewer seeds per inflorescence than within-continent crosses [36]. In our study, we did not systematically score seed set of the crosses that we made, but as most of the crosses resulted in sufficient numbers of seeds and the offspring had increased performance, we have no reason to believe that reproductive barriers have arisen yet between native and invasive M. guttatus plants, nor that between-continent outcrossing will result in outbreeding depression.…”

“…The heterosis effects of such between-range outcrossing might even be larger than the effects of outcrossing between plants from different populations within a range, particularly when there is limited genetic variation between populations, as one may expect in the invasive range. On the other hand, when native and invasive populations have been separated for a considerable time, genetic incompatibilities may have arisen that could result in strong outbreeding depression [36].…”

Rapid acceleration of plant speciation during the Anthropocene

“…Here, I consider the role of humans in bringing new species into existence. I concentrate on hybridisation because of the speed with which this process can generate new species, while recognising that speciation through ecological separation can also be rapid ( [17,18]; see [9] for a wider framework). In addition, I focus on new species as opposed to other levels of genetic variation because researchers use species as the primary currency to estimate biodiversity losses, and species often represent the focus of conservation efforts.…”