Competition for pollination influences selection on floral traits of Ipomopsis aggregata
Competition for pollination influences selection on floral traits of Ipomopsis aggregata
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DOI：
10.1111/j.0014-3820.2000.tb00700.x
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发表时间：
2000-10-01
期刊：
影响因子：
3.3
通讯作者：
Caruso, CM
中科院分区：
文献类型：
--
作者：
Caruso, CM
尽管很少被检验，但人们经常认为，种间竞争导致了与资源利用相关的性状的差异。以植物-传粉者系统为模型，我检验了预测。授粉竞争者的存在会影响传粉者对花性状的选择的强度和/或方向。通过雌体适合度对7个居群的五个花卉性状进行表型选择。其中4株只含有同种异物(I)，3株还含有竞争对手亚麻黄(C+I)。在C+I群体中，花冠长度上通过果实/植株和同种花粉沉积/花朵进行的定向选择是积极的，且显著增强。这种选择上的差异显然是由种群间的差异驱动的，在多大程度上，聚合草的繁殖受到花粉的限制。与种间竞争的预期一致，C+I群体中的聚合体植株每花接受的同种花粉较少，每果和每株果实的种子数也比仅有I群体的少。在C+I种群中，Ipomopsis Aggregata的花冠也明显较长，这表明在过去的几代人中，也曾对类似的选择机制做出过反应。花冠长度和花冠宽度之间的表型相关性在C+I群体中显著较弱，这两个表型相关决定了聚合草花形的变异。这些数据表明，对授粉的竞争可以影响对聚合花性状的选择强度和相关模式。如果有和没有竞争授粉的聚合花种群通过基因流联系在一起，那么在竞争和非竞争环境中测量选择可能是准确预测花卉性状进化的必要手段。
Although rarely tested, it is often assumed that interspecific competition results in the divergence of traits related to resource use. Using a plant-pollinator system as a model, I tested the prediction the presence of a competitor for pollination influences the strength and/or direction of pollinator-mediated selection on floral traits. I measured phenotypic selection via female fitness on five floral traits of Ipomopsis aggregata in seven populations. Four contained only conspecifics (I only) and three also contained the competitor Castilleja linariaefolia (C + I). Directional selection via fruits/plant and conspecific pollen deposited/flower on corolla length was positive and significantly stronger in C + I populations. This difference in selection was apparently driven by interpopulation variation in the degree to which reproduction of I. aggregata was pollen limited. Consistent with expectations of interspecific competition, I. aggregata plants in C + I populations received less conspecific pollen per flower and set fewer seeds per fruit and fruits per plant than those in I only populations. Ipomopsis aggregata's corollas were also significantly longer in C + I populations, suggesting that there had been a response to a similar selective regime in past generations. Phenotypic correlations between corolla length and width, which determine the variation in I. aggregata's flower shape, were significantly weaker in C + I populations. These data suggest that competition for pollination can influence the strength of selection on and patterns of correlations among floral traits of I. aggregata. If I. aggregata populations with and without competitors for pollination are linked by gene flow, then measuring selection in competitive and noncompetitive environments maybe necessary to accurately predict how floral traits will evolve.