Selfing ability and dispersal are positively related, but not affected by range position: a multispecies study on southernAfricanAsteraceae

Abstract

Dispersal and breeding system traits are thought to affect colonization success. As species have attained their present distribution ranges through colonization, these traits may vary geographically. Although several theories predict associations between dispersal ability, selfing ability and the relative position of a population within its geographic range, there is little theoretical or empirical consensus on exactly how these three variables are related. We investigated relationships between dispersal ability, selfing ability and range position across 28 populations of 13 annual, wind-dispersed Asteraceae species from the Namaqualand region of South Africa. Controlling for phylogeny, relative dispersal ability--assessed from vertical fall time of fruits--was positively related to an index of autofertility--determined from hand-pollination experiments. These findings support the existence of two discrete syndromes: high selfing ability associated with good dispersal and obligate outcrossing associated with lower dispersal ability. This is consistent with the hypothesis that selection for colonization success drives the evolution of an association between these traits. However, no general effect of range position on dispersal or breeding system traits was evident. This suggests selection on both breeding system and dispersal traits acts consistently across distribution ranges.

The link between selfing and greater dispersibility in a heterocarpic Asteraceae

“…Thus, the percentage of beaked fruits (BF ratio) is a good estimate of the potential capacity for long‐distance dispersal of a plant. Our study also demonstrates that fruit‐drop velocity is negatively correlated with dispersal distance, and thus dropping velocity is a useful trait as a surrogate of dispersal distance for wind‐dispersed species (Cody and Overton, ; Fresnillo and Ehlers, ; de Waal et al., ).…”

“…with similar protandry and head phenology , higher outcrossing levels were found in outer flowers, giving rise to the link between outcrossing and nondispersibility (Cheptou et al., ). The association between selfing and greater dispersibility was also found in a multi‐species study of Asteraceae from South Africa (de Waal et al., ).…”

“…Breeding system and dispersibility are anatomically and ontogenetically linked; thus, selective pressures on breeding systems can generate consequences for dispersal and vice versa (Primack, ; Rubio de Casas et al., ; Auld and Rubio de Casas, ). Both reproductive traits impact gene flow, genetic diversity, and the colonization ability of flowering plants and thus may affect the adaptation potential of their populations; therefore, an evolutionary association between both reproductive traits could be expected (de Waal et al., ). However, the association between breeding systems and dispersal does not show a clear pattern, and opposing links (low or high dispersal and selfing) are predicted (Auld and Rubio de Casas, ; de Waal et al., ).…”

“…Both reproductive traits impact gene flow, genetic diversity, and the colonization ability of flowering plants and thus may affect the adaptation potential of their populations; therefore, an evolutionary association between both reproductive traits could be expected (de Waal et al., ). However, the association between breeding systems and dispersal does not show a clear pattern, and opposing links (low or high dispersal and selfing) are predicted (Auld and Rubio de Casas, ; de Waal et al., ).…”

Climate structures genetic variation across a species' elevation range: a test of range limits hypotheses

“…de Waal et al . ). Increased plant density towards both climate limits found here remains unexplained, but could be related to the availability of suitable open‐canopy environments in the lower and upper elevations of the Sierra Nevada (i.e.…”