Selection on floral traits through male fertility in a natural plant population

Abstract

Most studies on selection in plants estimate female fitness components and neglect male mating success, although the latter might also be fundamental to understand adaptive evolution. Information from molecular genetic markers can be used to assess determinants of male mating success through parentage analyses. We estimated paternal selection gradients on floral traits in a large natural population of the herb Mimulus guttatus using a paternity probability model and maximum likelihood methods. This analysis revealed more significant selection gradients than a previous analysis based on regression of estimated male fertilities on floral traits. There were differences between results of univariate and multivariate analyses most likely due to the underlying covariance structure of the traits. Multivariate analysis, which corrects for the covariance structure of the traits, indicated that male mating success declined with distance from and depended on the direction to the mother plants. Moreover, there was directional selection for plants with fewer open flowers which have smaller corollas, a smaller anther-stigma separation, more red dots on the corolla and a larger fluctuating asymmetry therein. For most of these traits, however, there was also stabilizing selection indicating that there are intermediate optima for these traits. The large number of significant selection gradients in this study shows that even in relatively large natural populations where not all males can be sampled, it is possible to detect significant paternal selection gradients, and that such studies can give us valuable information required to better understand adaptive plant evolution.

Mating patterns and pollen dispersal in four contrasting wild cherry populations (Prunus avium L.)

“…Furthermore, there is high evidence that neighbouring pollen donors exhibit higher reproductive success (Burczyk 1996;Dow and Ashley 1998;Kaufman et al 1998;van Kleunen and Burczyk 2008). Although we observed marginally significant differences among families showing equal and unequal paternity contributions in pollination distances, this still does not explain why some families were strongly pollinated by a few pollen donors.…”

Viability selection prior to trait expression is an essential component of natural selection

“…Also, we admit that our study did not include one critical component of fitness: outcross siring success. Few studies have considered this variable, but the available data suggest that differential siring success may generate selection on flower size (Bell 1985;Stanton et al 1986;van Kleunen & Burczyk 2008). Also, because M. guttatus is a self-compatible hermaphrodite, female fecundity may include both outcrossed and self-fertilized seed.…”

TOWARD THE EVOLUTIONARY GENOMICS OF GAMETOPHYTIC DIVERGENCE: PATTERNS OF TRANSMISSION RATIO DISTORTION IN MONKEYFLOWER (MIMULUS) HYBRIDS REVEAL A COMPLEX GENETIC BASIS FOR CONSPECIFIC POLLEN PRECEDENCE

“…(3) Competition between diploid sporophytes (sexual selection ). Although there are relatively few studies of paternity patterns in plants, multiple paternity of individual fruits appears common in outcrossing, animal‐pollinated taxa (Bernasconi 2004; Mitchell et al 2005; Schierup et al 2006; Llaurens et al 2008), including a population of perennial M. guttatus (Van Kleunen and Burczyk 2008). In a screen using a single highly polymorphic SSR locus, four of five fruits assayed ( N = 5 seeds each) from the Iron Mountain M. guttatus population showed evidence of multiple paternity (>2 different paternal alleles; L. Fishman and J. Willis, unpubl.…”