Absence of conspecific pollen advantage in the dynamics of an Ipomopsis (Polemoniaceae) hybrid zone

被引:23
作者
Alarcón, R
Campbell, DR [1 ]
机构
[1] Univ Calif Irvine, Dept Ecol & Evolut Biol, Irvine, CA 92697 USA
[2] Rocky Mt Biol Labs, Crested Butte, CO 81224 USA
关键词
gene flow; hybridization; hybrid zone; interspecific pollen competition; Ipomopsis; male fitness; Polemoniaceae; pollen interactions; reproductive isolation;
D O I
10.2307/2656889
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
The frequency of hybrid formation in angiosperms depends on how often heterospecific pollen is transferred to the stigma and on the success of that heterospecific pollen at fertilizing ovules. Even if heterospecific pollen is capable of effecting fertilization it may perform poorly when conspecific pollen is also available on the stigma. We applied pollen mixtures to stigmas to determine how pollen interactions affect airing success and the frequency of hybrid formation between two species of Ipomopsis (Polemoniaceae) in Colorado. plants of both parental species and natural hybrids were pollinated with I. aggregata and I. tenuituba pollen in ratios of 100:0, 80:20, 50:50, 20:80, and 0:100 by mass. Plants were homozygous for different alleles at an isozyme marker, allowing us to distinguish the type of pollen parent for 2166 viable seeds from 273 fruits. In contrast to studies of many other hybridizing taxa, there was no evidence of an advantage to conspecific pollen, nor did composition of the stigmatic pollen load affect seed set. Instead, the frequency of seeds sired by a given species was proportional to its representation in the pollen load. In this hybrid zone, both the frequency of first-generation hybrid formation and the relative male fitness of the two parental species should be predictable from the rates of pollen transfer to stigmas.
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页码:819 / 824
页数:6
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