ARTICLE Origin, elevation, and evolutionary success of hybrids and polyploids in British Columbia, Canada Jana C. Vamosi and Jamie R. McEwen Abstract: Although it is well established that many clades have polyploidization in their evolutionary history, the question of whether polyploidization is actually adaptive is far from resolved. It has been hypothesized that the evolutionary advantages of polyploidy are context-dependent, although we have yet to clearly identify the geographical or ecological contexts in which polyploids are more common. One reason why polyploidy may be displaying idiosyncratic ecological patterns is that previous comparative studies have often not separated polyploids into allopolyploids and autopolyploids, and we posit that there may be important differences in the origin and evolutionary success between the two types. Here, we examine the distribution of allopolyploid, autopolyploid, and diploid hybrid species along an elevation gradient from sea level to 4500 m within British Columbia, Canada, and find that polyploids (especially those of hybrid origin) are disproportionately present at high elevations. These processes of hybridization and polyploidization may contribute to species richness patterns observed in British Columbia. We discuss whether the associations are more likely to be the result of differential ecological tolerance or differential origination rates of allopolyploids at higher elevations. These findings highlight the importance of studying both hybridization and polyploidy when considering the diversification process in plants. Key words: polyploidization, elevation gradients, allopolyploidy, autopolyploidy, hybridization. Résumé : Bien qu'il soit bien établi que plusieurs clades possèdent de la polyploïdisation dans leur histoire évolutive, la question a ` savoir si la polyploïdisation est réellement adaptative demeure entière. On a formé l'hypothèse que les avantages évolutifs de la polyploïdie dépendent du contexte dans lequel les polyploïdes sont les plus communs. Une raison pour laquelle la polyploïdie montrerait des patrons écologiques idiosyncrasiques est que les études comparatives antérieures n'ont souvent pas séparé les polyploïdes en allopolyploïdes et autopolyploïdes; les auteurs soumettent qu'il pourrait y avoir des différences importantes dans l'origine et le succès évolutif entre les deux types. Ils examinent ici la distribution des allopolyploïdes, autopolyploïdes et diploïdes par espèce, le long d'un gradient d'élévation allant du niveau de la mer jusqu'a ` 4500 m en Colombie Canadienne, au Canada, et constatent que les polyploïdes (surtout d'origine hybride) montrent une présence disproportionnée aux hautes altitudes. Ces processus d'hybridation et de polyploïdisation pourraient contribuer aux patrons de richesse observés en Colom- bie Canadienne. Les auteurs discutent a ` savoir si les associations sont plus susceptibles de résulter de tolérances écologiques différentielles ou de taux d'origine différentiels des alloplolyploïdes aux hautes altitudes. Ces constatations soulignent l'importance d'étudier a ` la fois l'hybridation et la polpyploïdie lorsque l'on considère le processus de diversification chez les végétaux. Mots-clés : polyploïdisation, gradients d'élévation, allopolyploïdie, autopolyploïdie, hybridation. Introduction Polyploidy and interspecific hybridization occur frequently in plants and can affect genetic diversity, adaptation, and diversifi- cation . For instance, polyploid speciation is recently estimated to have been involved in at least 15% of angiosperm speciation events and 31% of fern speciation events (Wood et al. 2009), and may be higher (Soltis et al. 2007). Thus, the phylogenetic (and geographi- cal) distribution of polyploidization has the potential to affect variation in species richness among clades and regions (Vamosi and Vamosi 2010), as well as altering genetic diversity at a given site (Ohsawa and Ide 2008). The idea that polyploid species may be more prevalent at high latitudes and high altitudes was originally spurred by the finding that experimental manipulations of tem- perature resulted in the de novo formation of polyploids (Manton 1937; Ramsey and Schemske 1998). Since then, examinations of the geographical distribution of polyploids have not revealed ex- cessively strong patterns. Some studies have found high incidence of polyploid species at colder temperatures (Brochmann et al. 2004; Hijmans et al. 2007), while other comparative studies have found moderate to no evidence to suggest wider temperature tolerances or latitudinal patterns amongst polyploid lineages (Martin and Husband 2009; McIntyre 2012). The effect of polyp- loidy on altitude range is equally enigmatic with studies finding polyploids more prevalent at high (Love and Love 1943; Otto et al. 2007) and low elevations (Liu et al. 2004). Yet few studies thus far have attempted to tease apart the factors that may affect polyp- loid formation from the potential differential success of incipient polyploids in extreme environments. The genomic consequences of polyploidization could poten- tially increase the ecological breadth of a species (Rieseberg et al. 1996; Soltis and Soltis 1999) by affecting pollination and breeding system as well as physiological and environmental tolerances (Husband and Sabara 2003; Maherali et al. 2009; Otto and Whitton 2000). Despite the potential importance of polyploidy to adaptive differentiation and speciation (Mayrose et al. 2012; Vamosi and Dickinson 2006), long standing questions about how the genetics Received 12 July 2012. Accepted 1 December 2012. J.C. Vamosi and J.R. McEwen. Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada. Corresponding author: Jana C. Vamosi (e-mail: jvamosi@ucalgary.ca). 182 Botany 91: 182–188 (2013) dx.doi.org/10.1139/cjb-2012-0177 Published at www.nrcresearchpress.com/cjb on 11 December 2012. Botany Downloaded from www.nrcresearchpress.com by UNIV CALGARY on 03/16/13 For personal use only.