Abstract
Weedy species provide excellent opportunities to examine the process of successful colonization of novel environments. Despite the influence of the sexual system on a variety of processes from reproduction to genetic structure, how the sexual system of species influences weediness has received only limited consideration. We examined the hypothesis that weedy plants have an increased likelihood of being self‐compatible compared with nonweedy plants; this hypothesis is derived from Baker's law, which states that species that can reproduce uniparentally are more likely to successfully establish in a new habitat where mates are lacking. We combined a database of the weed (weedy/nonweedy) and introduction status (introduced/native) of plant species found in the USA with a database of plant sexual systems and determined whether native and introduced weeds varied in their sexual systems compared with native and introduced nonweeds. We found that introduced weeds are overrepresented by species with both male and female functions present within a single flower (hermaphrodites) whereas weeds native to the USA are overrepresented by species with male and female flowers present on a single plant (monoecious species). Overall, our results show that Baker's law is supported at the level of the sexual system, thus providing further evidence that uniparental reproduction is an important component of being either a native or introduced weed.
Highlights
| MATERIALS AND METHODSThe Sex Systems Database (Tree of Sex Consortium, 2014) was concatenated with a database of North American plant species that included introduction status (native/introduced) and weed status (weedy/nonweedy) (Kuester et al, 2014), in which weeds were defined as troublesome plants in agriculture, horticulture, ornamental, and natural areas
Introduced species are accidentally or purposefully moved across great distances, and those that establish in new areas may or may not eventually become weedy or invasive (Richardson, Pyšek et al, 2000; Williamson, 1996). Those that do become weedy are hypothesized to exhibit preexisting traits that allow for uniparental reproduction in mate-limited areas (Pannell, 2015) and may show a strong pattern of enrichment for hermaphroditism
In support of Baker’s law, we found that introduced weeds are more likely to be hermaphroditic than introduced nonweeds (p < .0001; Figures 1 and 3); 78% of introduced weeds are hermaphroditic compared with 40% of introduced nonweeds
Summary
The Sex Systems Database (Tree of Sex Consortium, 2014) was concatenated with a database of North American plant species that included introduction status (native/introduced) and weed status (weedy/nonweedy) (Kuester et al, 2014), in which weeds were defined as troublesome plants in agriculture, horticulture, ornamental, and natural areas. To determine the effect of sexual systems (see Table 1) on weed status, we performed binomial regressions separately for each sexual system and weed status comparison. While we found that sexual systems were highly conserved within genera (Figure 2), the phylogenetic logistic regression provides support for the above taxonomic comparisons (Table 2), suggesting the patterns we uncovered are not due solely to phylogenetic relatedness. Native and introduced weeds exhibited different sexual systems: native weeds were enriched for monoecious species whereas introduced weeds were enriched for hermaphrodites. These results support Baker’s law and the idea that certain sexual systems underlie the likelihood that a particular species will be identified as a weed
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