Effects of plant sex on range distributions and allocation to reproduction

Abstract

Summary• Despite an abundance of theory, few empirical studies have explored the ecological and evolutionary consequences of sex. We used a comparative phylogenetic approach to examine whether transitions between sexual and asexual reproduction are associated with changes in the size and distribution of species' geographical ranges, and their investment in reproduction.• Here, we reconstructed the phylogeny of the genus Oenothera sections Oenothera and Calylophus (Onagraceae), which contain 35 sexual and 30 functionally asexual species. From each species, we collected data on the geographical distribution and variation in plant traits related to reproduction.• Functionally asexual species occurred at higher latitudes, but did not differ in range size, compared with sexual species. Transitions to asexuality were associated with decreased investment in floral structures, including the length of petals, floral tubes and styles. Decreased anther size and increased seed size within asexual species also suggest altered allocation to male and female fitness.• The observed range shifts are consistent with superior colonization of environments by asexual species following glaciation, and the observed changes in reproductive allocation support predictions made by models relating to the evolution of selfing. Our results suggest that the evolutionary consequences of asexual reproduction might be less restrictive than previously thought.

Molecular Phylogenetics and Reproductive Biology of <I>Oenothera</I> section <I>Kneiffia</I> (Onagraceae)

“…We also show that the self-compatible, relatively smallflowered O. perennis, previously described as autogamous (Straley 1977), actually has a pollination system involving small and medium bees of the family Halictidae and the genus Bombus. This is a surprising result because O. perennis is well known for having a permanent translocation heterozygote (PTH) genetic system (Johnson et al 2009;Johnson et al 2010). Typically, PTH species selfpollinate prior to the flowers opening, and therefore, any visitors are not important or effective pollinators (Johnson et al 2009;Johnson et al 2010;Brown and Levin 2011).…”

“…This is a surprising result because O. perennis is well known for having a permanent translocation heterozygote (PTH) genetic system (Johnson et al 2009;Johnson et al 2010). Typically, PTH species selfpollinate prior to the flowers opening, and therefore, any visitors are not important or effective pollinators (Johnson et al 2009;Johnson et al 2010;Brown and Levin 2011). However, for the populations of O. perennis included in this study, we observed that the receptive stigmas, without pollen on their surface, were exserted out of the opening buds of the flowers.…”

“…For group two, the Cross-pollen treatment, when the flower opened the bag was removed and all stamens were removed. Some Oenothera species, especially those with permanent translocation heterozygote (PTH) chromosome patterns (Johnson et al 2009;Johnson et al 2010) have anthers that generally dehisce prior to the flower opening. The anthers of O. perennis, which is a PTH species, did not dehisce prior to opening.…”

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“…3, 4). These differences mimic the large distribution ranges and/or poleward expansions in self-fertilizing and asexual plants (Johnson et al 2010). The extended distribution of parthenogenetic lineages toward the poles could stem from enhanced colonization abilities in these lineages, for example because parthenogenesis confers reproductive assurance ["Baker's law"; (reviewed by Pannell et al 2015)] and/or because parthenogens have an advantage over sexual relatives in colder climates.…”

A phylogenetic comparative study of preadaptation for invasiveness in the genus Silene (Caryophyllaceae)

“…The idea behind this use of path analysis is to explore the influence that life history traits have on predicting invasiveness, either directly through a causal relationship, and/or indirectly through a correlation with native range size. Such an approach is well suited to reveal novel insights into predicting invasiveness, since previous studies give us the a priori expectation that strong correlations exist between life history and geographic range size (Brown et al 1996;Johnson et al 2010), life history and invasiveness (Pyšek and Richardson 2007), and geographic range size and invasiveness (Goodwin et al 1999;Kolar and Lodge 2001;Pysek et al 2009). Based on this expectation, we predicted that life history traits and native range size would be strong determinants of invasiveness in Silene, but that the effect of individual life history traits would involve both direct and/or indirect correlations, mediated by the enormous variation in geographic range size in this diverse genus.…”