A note on the relationship between outcrossing rate and gene flow in plants

Govindaraju, Diddahally R.

doi:10.1038/hdy.1988.130

Cited by 33 publications

(32 citation statements)

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“…Furthermore, habitat fragmentation may reduce pollen migration and thus increase levels of selfing in populations of self-compatible species, suggesting another possible link between selfing and pollen migration (e.g., Cruzan 2001). There is circumstantial evidence supporting the idea of lower pollen migration rates in inbreeding plant species (Govindaradju 1988;Fenster and Ritland 1992), although the data supporting this notion comes from studies that estimate gene flow from levels of genetic differentiation (F ST ). This is problematic, because the method relies on very strict assumptions regarding the underlying population structure (Whitlock and McCauley 1999).…”

Section: Discussionmentioning

confidence: 85%

“…For instance, selfing species often have reduced allocation to male function, such as pollen production and floral display in plants (Charlesworth and Pannell 2001). Genetic differentiation among populations is also generally higher in inbreeding species due to lower levels of gene flow between populations (Govindaradju 1988;Jarne 1995). Low pollen migration rates could explain why selfing species often have low levels of genetic variation within populations but still maintain fairly high levels of genetic diversity at the metapopulation level, because the lower migration rate would result in higher levels of genetic differentiation among populations (Pannell and Charlesworth 2000).…”

Section: Ismentioning

confidence: 99%

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A Metapopulation Perspective on Genetic Diversity and Differentiation in Partially Self-Fertilizing Plants

Ingvarsson¹

2002

Evolution

139

134

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Abstract. Partial self-fertilization is common in higher plants. Mating system variation is known to have important consequences for how genetic variation is distributed within and among populations. Selfing is known to reduce effective population size, and inbreeding species are therefore expected to have lower levels of genetic variation than comparable outcrossing taxa. However, several recent empirical studies have shown that reductions in genetic diversity within populations of inbreeding species are far greater than the expected reductions based on the reduced effective population size. Two different processes have been argued to cause these patterns, selective sweeps (or hitchhiking) and background selection. Both are expected to be most effective in reducing genetic variation in regions of low recombination rates. Selfing is known to reduce the effective recombination rate, and inbreeding taxa are thus thought to be particularly vulnerable to the effects of hitchhiking or background selection. Here I propose a third explanation for the lower-than-expected levels of genetic diversity within populations of selfing species; recurrent extinctions and recolonizations of local populations, also known as metapopulation dynamics. I show that selfing in a metapopulation setting can result in large reductions in genetic diversity within populations, far greater than expected based the lower effective population size inbreeding species is expected to have. The reason for this depends on an interaction between selfing and pollen migration. Self-fertilization is a common mode of reproduction in plants and has important consequences for how genetic variation is distributed within and among populations. Selfing is known to have several effects on both genetic diversity and differentiation, but two general observations have been made. First, data on allozyme variation in both plants (Hamrick andGodt 1990, 1996) and animals (Jarne 1995) have shown that inbreeding species have lower neutral genetic diversity within populations than more outcrossing taxa. Recent studies, using molecular data have verified this observation and also shown that neutral genetic diversity at the species level is often lower in inbreeding species, compared to closely related, more outcrossing species, although this effect is far less pronounced than within-population diversity

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Section: Discussionmentioning

confidence: 85%

Section: Ismentioning

confidence: 99%

A Metapopulation Perspective on Genetic Diversity and Differentiation in Partially Self-Fertilizing Plants

Ingvarsson¹

2002

Evolution

139

134

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“…The most representative parameter of the genetic structure in plants is the rate of outcrossing, estimated as the proportion of seed produced through self-fertilization with respect to those produced through cross-fertilization (Govindaraju 1988). Mating system has consequences on inbreeding levels and through that on the different factors that produce inbreeding depression.…”

Section: Microsatellites: Comparative Approachesmentioning

confidence: 99%

“…The first one refers to the inverse relationship between outcrossing rates and genetic differentiation (Govindaraju 1988), so that species of tropical trees or trees in general show an outcrossing rate close to one and genetic differentiation estimates (usually estimated through allelic frequencies variance or F ST ) very close to zero (e.g., Furnier & Adams 1986, Eguiarte et al 1993, Ledig 1998.…”

Section: Introductionmentioning

confidence: 99%

Comparative genetic structure in pines: evolutionary and conservation consequences

Delgado

Cuenca

Escalante

et al. 2002

Rev. chil. hist. nat.

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Pines have been the focus of several studies that estimate population genetic parameters using both allozymes and chloroplast single sequence repeats (SSRs). Also, the genus has also been recently studied using molecular systematics so that we now have a more clear understanding of their evolutionary history. With this background we studied comparatively the genetic structure in pines. Expected heterozygosity is particularly constant with a 99 % confidence interval between 0.19 and 0.23 in species that have been studied until now using allozymes. There is a significant proportion of species (9/41) that show high population differentiation estimates (F ST = or larger than 0.15) and five of these have large and wingless seeds probably associated with low densities, bird dispersal mechanisms and resistance to water stress. These species include the North American pinyon pines. Outcrossing rates are also constant among species from both subgenus Pinus and subgenus Strobus, which probably reflects a selective limit to the amount of deleterious alleles that can be maintained in pine species and this also affects inbreeding levels. We also explored the data published using microsatellites in pines and conclude that these markers uncover a higher proportion of variation and genetic differentiation as expected and that the evolutionary models that are used to derive the population genetic structure estimators should take into account other sources of mutation (point mutations, larger insertions and or deletions and duplications) to better understand the comparative applications of these molecular markers.

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“…High rates of gene flow can increase effective population size (N e ) and reduce population differentiation by natural selection or genetic drift (Slatkin 1985). Variation among plant species in estimates of gene flow (Nm) and genetic differentiation often reflect differences in their pollination and mating systems (Govindaraju 1988). For example, average values of Nm range from 0.06 in selfing species to 5.4 for outcrossing wind-pollinated species (Hamrick 1987) demonstrating that mating patterns and gene flow are inextricably linked.…”

Section: Introductionmentioning

confidence: 99%

Mating strategies in flowering plants: the outcrossing–selfing paradigm and beyond

Barrett

2003

Phil. Trans. R. Soc. Lond. B

420

356

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Comparisons of the causes and consequences of cross-and self-fertilization have dominated research on plant mating since Darwin's seminal work on plant reproduction. Here, I provide examples of these accomplishments, but also illustrate new approaches that emphasize the role of floral design and display in pollen dispersal and fitness gain through male function. Wide variation in outcrossing rate characterizes animal-pollinated plants. In species with large floral displays, part of the selfing component of mixed mating can arise from geitonogamy and be maladaptive because of strong inbreeding depression and pollen discounting. Floral strategies that separate the benefits of floral display from the mating costs associated with geitonogamy can resolve these conflicts by reducing lost mating opportunities through male function. The results from experiments with marker genes and floral manipulations provide evidence for the function of herkogamy and dichogamy in reducing self-pollination and promoting pollen dispersal. Evidence is also presented indicating that increased selfing resulting from changes to floral design, or geitonogamy in large clones, can act as a stimulus for the evolution of dioecy. The scope of future research on mating strategies needs to be broadened to include investigations of functional links among flowers, inflorescences and plant architecture within the framework of life-history evolution.

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A note on the relationship between outcrossing rate and gene flow in plants

Cited by 33 publications

References 38 publications

A Metapopulation Perspective on Genetic Diversity and Differentiation in Partially Self-Fertilizing Plants

A Metapopulation Perspective on Genetic Diversity and Differentiation in Partially Self-Fertilizing Plants

Comparative genetic structure in pines: evolutionary and conservation consequences

Mating strategies in flowering plants: the outcrossing–selfing paradigm and beyond

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