Selfing rate variation within species is unrelated to life‐history traits or geographic range position

Abstract

Premise In plants, populations and species vary widely along the continuum from outcrossing to selfing. Life‐history traits and ecological circumstances influence among‐species variation in selfing rates, but their general role in explaining intraspecific variation is unknown. Using a database of plant species, we test whether life‐history traits, geographic range position, or abundance predict selfing rate variation among populations. Methods We identified species where selfing rates were estimated in at least three populations at known locations. Two key life‐history traits (generation time and growth form) were used to predict within‐species selfing rate variation. Populations sampled within a species’ native range were assessed for proximity to the nearest edge and abundance. Finally, we conducted linear and segmented regressions to determine functional relationships between selfing rate and geographic range position within species. Results Selfing rates for woody species varied less than for herbs, which is explained by the lower average selfing rate of woody species. Relationships between selfing and peripherality or abundance significantly varied among species in their direction and magnitude. However, there was no general pattern of increased selfing toward range edges. A power analysis shows that tests of this hypothesis require studying many (i.e., 40+) populations. Conclusions Intraspecific variation in plant mating systems is often substantial yet remains difficult to explain. Beyond sampling more populations, future tests of biogeographic hypotheses will benefit from phylogeographic information concerning specific range edges, the study of traits influencing mating system (e.g., herkogamy), and measures of abundance at local scales (e.g., population density).

The evolutionary dynamics of plant mating systems: how bias for studying ′interesting′ plant reproductive systems could backfire

“…Species with multiple conflicting designations (i.e., studies indicating both SC and SI for the same species) were excluded. This decision was based on similar practices in other mating system studies (Moeller et al 2017, Prior and Busch 2021). These species with conflicting designations comprised 7.5% of the dataset.…”

“…In keeping with previous studies (Goodwille et al 2005, Moeller et al 2017, papers which reported a sexual system (i.e., apomixis) but not a selfing designation were excluded. Sexual relatives of apomictic species are generally selfing, and apomixis has been hypothesized to be correlated with selfing (Hörandl 2009, Prior andBusch 2021), so this was unlikely to impact the inclusion of outcrossing species in the dataset. Additionally, crop species were excluded, as breeding efforts and crop domestication often directly select on the ability to self (Solís Montero et al 2021).…”

“…Papers which address the interplay of selfing at a multi-family level with other various topics in ecology and evolution have been especially prolific. For example, selfing has been explored in conjunction with geographic range dynamics (Grossenbacher et al 2015(Grossenbacher et al , 2016, invasive status and naturalization (Rananjatovo et al 2016), island biogeography (Grossenbacher 2017), within-population selfing rate variation (Whitehead et al 2018), life history and range size (Prior and Busch 2021), and seed size (Tateyama et al 2021). Additionally, studies focused on estimating rates of transitions to and from selfing using phylogenetic comparative methods (PCMs) have contributed significantly to knowledge about the tempo and mode of selfing evolution.…”

Coexistence of self-compatible and self-incompatible alleles in a plant metapopulation via spatial rock-paper-scissors dynamics

“…Recent work has revealed that there is no general trend of selfing rate across populations of species when going from the central to the peripheral zones[26]. However, they did reveal that there was significant heterogeneity between species on this metric.…”

Recent speciation associated with range expansion and a shift to self-fertilization in North American Arabidopsis

“…Similarly, a shift in mating system towards self-compatibility and self-fertilization was described in the context of postglacial range expansion in Campanula americana 43 . Many hermaphroditic species may show such a trend, but detection is hampered by a lack of range-wide investigations on mating system variation 44 . Range expansions by serial bottlenecks were typical after Pleistocene glaciation cycles and may have often helped speciation.…”