Interspecific Pollen Competition as a Reproductive Barrier Between Sympatric Species of Helianthus (Asteraceae)

Rieseberg, Loren H.; Desrochers, Andrée M.; Youn, Sue J.

doi:10.2307/2445699

Cited by 94 publications

(81 citation statements)

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“…Heterospecific pollen tubes grew more slowly than conspecific pollen tubes in all of the pairs of crosses, with one species pair failing to produce 50% hybrids after 100 min, the maximum pollination interval used in the study. In contrast with the results for Iris described here and those of Smith (1968Smith ( , 1970, Rieseberg et al (1995) did not find an increase (from 0%) in hybrid seed formation when Helianthus annuus pollen was given a 15 or 30 min temporal advantage over H. petiolaris pollen on H. petiolaris flowers. However, pollinations with only heterospecific pollen led to achene set that was not significantly different from that following conspecific pollinations (Rieseberg et al 1995), and therefore, longer pollination intervals than those used in their experiment may be needed to provide H. annuus pollen tubes with a growth advantage over H. petiolaris tubes.…”

Section: Discussioncontrasting

confidence: 99%

“…However, of the three studies that used pollination intervals to assess pollentube growth as a barrier to hybridization, interspecific pollen competition has been shown to be important among two groups and is equivocal in the third (Smith 1968(Smith , 1970Rieseberg et al 1995;this study). In fact, Darwin suggested such an isolating mechanism:…”

Section: Discussionmentioning

confidence: 96%

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Effects of Differential Pollen‐tube Growth on Hybridization in the Louisiana Irises

1996

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Abstract.-To elucidate the importance of hybridization in evolution, it is necessary to understand the processes that affect hybridization frequency in nature. Here we focus on postpollination, prefertilization isolating mechanisms using two hybridizing species of Louisiana iris as a study system. We compared the effects of differential pollen-tube growth on the frequency of F, hybrid formation in experimental crosses between Iris fulva and Iris hexagona. Analyses of seed production in fruits from pure conspecific and heterospecific pollinations revealed that more seeds were produced in the top half than the bottom half of fruits for all four crosses. Heterospecific pollen was applied to flowers of each species at zero to 24 h prior to conspecific pollen, thereby giving a head start to the foreign pollen. Using diagnostic isozyme markers, the frequency of hybrid progeny was examined at the level of the whole fruit and separately for the top and bottom halves of fruits. In both species, the proportion of hybrid seeds per fruit increased significantly with increasing head starts, suggesting that differences in pollen-tube growth rates affect the frequency of hybridization.In I. julva fruits, the increase in hybrid seeds occurred in both halves of the fruits, but in I. hexagona an increase was only detected in the top half of fruits. These findings are consistent with a model that assumes attrition of pollen tubes due to the greater length of I. hexagona styles. While pollen-tube growth rate appears to be the most important factor affecting hybridization frequency in I. fulva, both pollen-tube growth rate and pollen-tube attrition appear to be important in I. hexagona.Key words.-Hybridization, Iris, pollen competition, pollen-tube attrition, reproductive isolation.Received August 10, 1995. Accepted March 19, 1996 Hybridization is an important mechanism in the evolution of both plants and animals

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 96%

Effects of Differential Pollen‐tube Growth on Hybridization in the Louisiana Irises

1996

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“…We were, however, surprised at the complete hybrid compatibility at the gametic level-especially in a situation of sperm competition with another species. Unlike our results, previous studies have shown a conspecific sire advantage (Bella et al, 1992;Rieseberg et al, 1995;Geyer and Palumbi, 2005). Previous work on amphibian cross-fertilization has also shown wide among-species compatibility at the fertilization level.…”

Section: Trial Number Proportion Offspring Siredcontrasting

confidence: 89%

“…show similar results with poorer motility of heterospecific sperm stored in the spermathecae of females, resulting in lower fertilization success compared with conspecific males (Gregory and Howard, 1994). Work by and shows very similar conspecific dominance in siring success in Tribolium beetles, as do marine organisms (for example, sea urchins Geyer and Palumbi, 2005) and some plants (for example, Rieseberg et al, 1995), although the underlying mechanisms differ (reviewed in Arnold, 1997Arnold, , 2006.…”

Section: Introductionmentioning

confidence: 79%

Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri

2009

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Hybridization between closely related species often leads to reduced viability or fertility of offspring. Complete failure of hybrid offspring (post-zygotic hybrid incompatibilities) may have an important role in maintaining the integrity of reproductive barriers between closely related species. We show elsewhere that in Peron's tree frog, Litoria peronii, males more closely related to a female sire more offspring in sperm competition with a less related rival male. Observations of rare 'phenotypic intermediate' males between L. peronii and the closely related L. tyleri made us suggest that these relatedness effects on siring success may be because of selection arising from risks of costly hybridization between the two species. Here, we test this hypothesis in an extensive sperm competition experiment, which shows that there is no effect of species identity on probability of fertilization in sperm competition trials controlling for sperm concentration and sperm viability. Instead, there was a close agreement between a male's siring success in isolation with a female and his siring success with the same female in competition with a rival male regardless of species identity. Offspring viability and survival, however, were strongly influenced by species identity. Over a 14-day period, hybrid offspring suffered increasing mortality and developed more malformations and an obvious inability to swim and right themselves, leading to compromised probability of survival. Thus, hybridization in these sympatric tree frogs does not compromise fertilization but has a strong impact on offspring viability and opportunity for reinforcement selection on mate choice for conspecific partners.

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“…It is well established that natural populations of many species exhibit variation in the rate of pollen tube growth (Walsh & Charlesworth, 1992), but few studies have examined the extent to which differential pollen tube growth rates contribute to reproductive isolation between naturally sympatric species (Rieseberg et al, 1995 ;Carney et al, 1996). The major advantage of fast pollen tube growth rates is assumed to be gametophytic competition in mixed pollen loads (Haldane, 1932 ;Stephenson & Bertin, 1983).…”

Section: mentioning

confidence: 99%

Pollen tube competition as a mechanism of prezygotic reproductive isolation between Mimulus nasutus and its presumed progenitor M. guttatus

1999

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This paper considers the extent to which differences in pollen tube growth rates can provide prezygotic reproductive isolation between Mimulus nasutus and its presumed progenitor, Mimulus guttatus. Mimulus nasutus is partially cleistogamous, but its larger chasmogamous flowers offer appreciable opportunity for outcrossing. Mimulus nasutus was found to have smaller pollen grains and shorter styles than M. guttatus. No differences were observed in pollen grain germination on conspecific and heterospecific stigmas. However, pollen tube growth rates of M. nasutus were found to be much slower than those of M. guttatus in the styles of that species. Consequently, any M. nasutus pollen transferred to an M. guttatus stigma was found to be competitively disadvantaged in an M. gutattus style. By contrast, no difference in pollen tube growth rate was detected between the species when growing in M. nasutus styles, possibly because M. nasutus styles are unable to support fast pollen tube growth. We tested the prediction from the pollen tube studies that a 50 : 50 mix of M. guttatus and M. nasutus pollen would produce 50% hybrid seeds when M. nasutus was the maternal parent, and near to 0% hybrid seed when M. guttatus was the maternal parent. The results were found to support this prediction. We conclude that pollen-pistil interactions can effect strong reproductive isolation between these species, as M. guttatus pollen tubes have a competitive advantage over those of M. nasutus in an M. guttatus style, but not in an M. nasutus style.

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Interspecific Pollen Competition as a Reproductive Barrier Between Sympatric Species of Helianthus (Asteraceae)

Cited by 94 publications

References 0 publications

Effects of Differential Pollen‐tube Growth on Hybridization in the Louisiana Irises

Effects of Differential Pollen‐tube Growth on Hybridization in the Louisiana Irises

Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri

Pollen tube competition as a mechanism of prezygotic reproductive isolation between Mimulus nasutus and its presumed progenitor M. guttatus

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