Analysis of sexual phenotype and prezygotic fertility in natural populations of Fucus spiralis, F-vesiculosus (Fucaceae, Phaeophyceae) and their putative hybrids
Analysis of sexual phenotype and prezygotic fertility in natural populations of Fucus spiralis, F-vesiculosus (Fucaceae, Phaeophyceae) and their putative hybrids
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DOI：
10.1080/09670260500334354
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发表时间：
2005-11-01
影响因子：
2.4
通讯作者：
Valero, M
中科院分区：
文献类型：
--
作者：
Billard, E;Serrao, EA;Valero, M
在岩藻属中，雌雄异株的特征经历了多种状态的变化，具有不同交配系统的分类群之间可能进行杂交，例如雌雄异株的泡囊岩藻和两性的F。在交配系统进化的背景下，我们通过研究性别表型和受精率的变化来评估杂交的潜在后果。首先，由于两个性系统之间杂交的结果，性别差异可能会出现，这取决于具有大和小表型效应的基因的相对重要性。因此，我们定性地检查了个体杂交种内和个体间性别差异的程度，并与两个亲本物种进行了比较。其次，如果杂交打破了共适应的基因复合体，与两个亲本物种相比，杂交育性可能会降低。因此，我们还量化了亲本物种及其杂交后代中的雄性和雌性受精卵的可育性，以测试杂交适合度的降低。在两个地理位置较远的地区(法国和葡萄牙)采集了89只性成熟个体(20只旋毛虫、40只水泡蝇、10个两性杂交种和19个雌雄异株杂交种)，每个个体观察到6个胚胎。个体内部的变异在质量上和数量上都非常有限--只有一个杂交品种的受精卵具有与其他五个杂交品种不同的性别表型。这表明，性别决定有一个简单的遗传系统，涉及几个具有重大影响的基因。此外，分析表明，与亲本相比，杂交育性没有显著下降。此外，杂交种表现出所有的有性表型，表明杂交和回交经历了几代，因此，杂交种的繁殖是成功的。最后，雌性和两性个体的不育父本的出现被解释为雄性功能的遗迹，这表明，与高等植物一样，从两性到雌雄异株的进化可能是最节俭的途径。
In the genus Fucus, the character dioecy/hermaphroditism has undergone multiple state changes and hybridization is possible between taxa with contrasting mating systems, e. g. between the dioecious Fucus vesiculosus and the hermaphrodite F. spiralis. In the context of mating system evolution, we evaluated the potential consequences of hybridization by studying the variation in sexual phenotype and prezygotic fertility. Firstly, as a result of hybridization between the two sexual systems, gender variation may arise depending on the relative importance of genes with large versus small phenotypic effects. We thus qualitatively examined the extent of gender variation within and among individual hybrids in comparison with both parental species. Secondly, if hybridization breaks up co-adapted gene complexes, hybrid fertility may be reduced in comparison with both parental species. Therefore, we also quantified male and female prezygotic fertility in parental species and their hybrids in order to test for reduction in hybrid fitness. A total of 89 sexually mature individuals ( 20 F. spiralis, 40 F. vesiculosus, 10 hermaphrodite hybrids and 19 dioecious hybrids) were sampled in two geographically distant regions ( France and Portugal) and six conceptacles per individual were observed. Within-individual variation was very restricted qualitatively - only one hybrid carried a conceptacle with a different sexual phenotype from the five others - as well as quantitatively. This suggests a simple genetic system for sex determination involving a few genes with major effects. In addition, analyses showed no significant decrease in hybrid fertility compared with parental species. Moreover, hybrids exhibited all sexual phenotypes, suggesting several generations of hybridization and backcrossing and, therefore, that hybrids are reproductively successful. Finally, the occurrence of sterile paraphyses in female and hermaphrodite individuals was interpreted as a relic of male function and suggests that, as in higher plants, evolution from hermaphroditism to dioecy may be the most parsimonious pathway.