R<scp>eproductive allocation and the fitness consequences of selfing in two sympatric species of</scp><i>E<scp>pilobium</scp></i>(O<scp>nagraceae</scp>)<scp>with contrasting mating systems</scp>

Parker, Ingrid M.; Nakamura, Robert R.; Schemske, Douglas W.

doi:10.1002/j.1537-2197.1995.tb11565.x

Cited by 53 publications

(55 citation statements)

References 86 publications

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“…Given that limited dispersal is common in Macrocystis (Anderson and North 1966, Reed et al 1988, 2004b, the opportunity for self-fertilization should be great. However, while studies on flowering plants show that the costs of selfing frequently decrease with incidence of self-fertilization (Barrett and Charlesworth 1991, Parker et al 1995, Husband and Schemske 1996, they rarely vanish. Moreover, it has been suggested that if the potential for self-fertilization is high and costs are chronically very severe some sort of selfincompatibility will evolve.…”

Section: Discussionmentioning

confidence: 99%

Effects of Self-Fertilization in the Giant Kelp, Macrocystis Pyrifera

Raimondi

Reed

Gaylord

et al. 2004

Ecology

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The costs of self-fertilization were evaluated for the giant kelp, Macrocystis pyrifera. Macrocystis, like other kelps, has a biphasic life history in which the dispersal stage is the 1N spore generation. Once spores settle, they grow into sedentary and microscopic male or female gametophytes, which produce sperm and eggs. Fertilization ensues, and the resultant 2N sporophyte, the spore-producing form, grows rapidly to a height of up to 25 m. Based on previous empirical studies and modeling field surveys, the potential for self-fertilization is expected to be high, largely due to the shape and extent of spore dispersal distributions. The costs of self-fertilization were assessed with laboratory and field experiments over the entire life history of the sporophyte stage. There was no evidence for self-incompatibility, and fitness was dramatically lower in selfed compared to outcrossed individuals. In addition, there was evidence that costs were more severe under intraspecific competition with outcrossed individuals. The demonstrated severity of the consequences of self-fertilization suggests a species that typically outcrosses (at least under the assumption that costs result from rare recessive deleterious alleles). However, costs were more pronounced in later life history phases, suggesting routine self-fertilization. One implication of significant levels of self-fertilization in Macrocystis is a sort of inbreeding-mediated localized population senescence, leading to striking oscillations in populations, a pattern seen in many Californian kelp beds.

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Section: Discussionmentioning

confidence: 99%

Effects of Self-Fertilization in the Giant Kelp, Macrocystis Pyrifera

Raimondi

Reed

Gaylord

et al. 2004

Ecology

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“…This novel finding supports field genetic data, which indicate extremely localized breeding and strong heterozygote deficiencies in these beds (Rhode, 2002). Chesapeake Bay eelgrass seems to be an exception to this generality, but it resembles other plant populations with limited life spans or restricted windows of reproduction (Parker et al, 1995;Eckert and Schaefer, 1998). Most studies of plants with mixed mating systems have demonstrated that self-fertilization produces fewer seeds and offspring of lower fitness than outbreeding (reviewed in Waser [1993b]).…”

Section: Discussionmentioning

confidence: 99%

Seed production from the mixed mating system of Chesapeake Bay (USA) eelgrass (Zostera marina; Zosteraceae)

Rhode

Duffy

2004

American J of Botany

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In monoecious plants, gametes can be exchanged in three ways: among unrelated genets (outbreeding), with close relatives (inbreeding), or within individuals (geitonogamous selfing). These different mating systems may have consequences for population demography and fitness. The experiment presented herein used artificial crosses to examine the mating system of Chesapeake Bay, Virginia, USA eelgrass (Zostera marina L; Zosteraceae), a bisexual submerged aquatic plant that can outbreed, inbreed, and self. Genetic data indicate severe heterozygosity deficiencies and patchy genotype distribution in these beds, suggesting that plants therein reproduce primarily by vegetative propagation, autogamy, or geitonogamy. To clarify eelgrass reproductive strategies, flowers from three genetically and geographically distinct beds were hand-pollinated in outbred, inbred, and selfed matings. Fertilization success and seed production, life history stages which contribute greatly to the numeric maintenance of populations, were monitored. We found no evidence that inbreeding had negative consequences for seed production. On the contrary, selfed matings produced seeds significantly more frequently than outcrossed matings and produced significantly larger numbers of seeds than either inbred or outbred matings. These results contrast with patterns for eelgrass in other regions but might be expected for similar populations in which pollen limitation or a short reproductive season renders selfing advantageous.

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“…For example, 11 of 24 maternal parents in the 1987 diallel cross produced both 10-m and 100-m progeny that survived to flower, thus yielding estimates of for both crossing distance treatments applied to each parent. Based on this measure the variation among maternal sibships is impressive, ranging from outbreeding depression of 40% to Ϫ14% (calculated as {[ 10m Ϫ 100m ]/ max [ 10m , 100m ]}, which yields a symmetrical measure bounded by ϩ1 and Ϫ1, with negative values indicating heterosis at the longer relative to the shorter distance; see Parker et al 1995;Dudash et al 1997). In 1990 we used 36 plants as parents, but each was used in fewer matings, and we obtained comparable information for only seven maternal parents; here the range in outbreeding depression was 31% to Ϫ57%.…”

Section: Discussionmentioning

confidence: 99%

“…Their table 2 indicates substantial variation in germination of seeds resulting from crosses among blueberry varieties, ranging from outbreeding depression of 68% to Ϫ38%. Turning to the level of individual plants, Parker et al (1995) applied pollination treatments of selfing and ''outcrossing'' (i.e., nonself crosses within populations) in two species of Epilobium and assessed the short-term performance of progeny in the greenhouse. Performance varied among maternal sibships, with outbreeding depression ranging in E. ciliatum from 40% to Ϫ20% and in E. angustifolium from 80% to Ϫ100%.…”

Section: Discussionmentioning

confidence: 99%

Outbreeding Depression Varies Among Cohorts of Ipomopsis Aggregata Planted in Nature

2000

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Outbreeding depression in progeny fitness may arise from disruption of local adaptation, disruption of allelic coadaptation, or a combination of these "environmental" and "physiological" mechanisms. Thus the minimum spatial scale over which outbreeding depression arises should depend on the spatial scale of gene dispersal and (with an environmental mechanism) of change in selection regimes. We previously reported substantial outbreeding depression in lifetime fitness of progeny resulting from crosses among parents separated by 100 m in natural populations of the herbaceous plant Ipomopsis aggregata. In this paper we explore the effect of crossing distance on fitness in two additional experiments begun in 1987 and 1990. We planted seed progeny derived from partial diallel crossing designs in randomized blocks in maternal environments and scored emergence of seedlings, survival, and eventual flowering of individuals over the subsequent six to eight years. Nested within each diallel design were crossing distances of 1 m, 10 m, and 100 m. Compared to 1-m and 10-m progeny, 100-m progeny of the 1987 diallel suffered a significant reduction in seedling emergence, and both 1-m and 100-m progeny that survived to flower achieved lower lambda-values on average than 10-m progeny. Total outbreeding depression suffered by 100-m relative to 10-m progeny was approximately 10%, compared to approximately 30% in our earlier study of I. aggregata. Progeny of 10-m crosses also outperformed 1-m and 100-m progeny of the 1990 diallel by approximately 5%, but no difference among crossing distance treatments was significant. Thus, the magnitude of outbreeding depression in 100-m crosses varied among experiments. This is not surprising given likely spatial and temporal variation in gene flow and selection regimes, different population histories, and different parental and progeny environments. Characterizing outbreeding depression on the shortest spatial scales over which it is expressed, as well as its variation and causes, is worthwhile because it promises to shed light on the earliest stages of angiosperm speciation.

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Reproductive allocation and the fitness consequences of selfing in two sympatric species ofEpilobium(Onagraceae)with contrasting mating systems

Cited by 53 publications

References 86 publications

Effects of Self-Fertilization in the Giant Kelp, Macrocystis Pyrifera

Effects of Self-Fertilization in the Giant Kelp, Macrocystis Pyrifera

Seed production from the mixed mating system of Chesapeake Bay (USA) eelgrass (Zostera marina; Zosteraceae)

Outbreeding Depression Varies Among Cohorts of Ipomopsis Aggregata Planted in Nature

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