Montalvo Arlee M
Department of Biology, University of California, Riverside, CA, 92521, USA.
Evolution. 1992 Aug;46(4):1181-1198. doi: 10.1111/j.1558-5646.1992.tb00627.x.
Flowers frequently receive both self (S) and outcross (OC) pollen, but S pollen often sires proportionally fewer seeds. Failure of S pollen can reflect evolved mechanisms that promote outcrossing and/or inbreeding depression expressed during seed development. The relative importance of these two processes was investigated in Aquilegia caerulea, a self-compatible perennial herb. In the field I performed single-donor (S or OC) and mixed-donor (S plus OC) pollinations to compare the relative success of both pollen types at various stages from pollen germination to seed maturity. Single-donor S pollinations produced significantly fewer and lighter seeds (x decrease = 12% and 3%, respectively) than OC pollinations. Abortion rates differed by an average of 38% whereas fertilization rates differed by only 5%, indicating that most differences in seed number arose postzygotically. This suggests that inbreeding depression was responsible for most failure of S pollen. One prezygotic effect measured was that 10% fewer S than OC pollen tubes reached ovaries after 42 hr, suggesting S pollen might fertilize proportionately fewer ovules after mixed pollination. Using allozyme markers, I found mixed-donor pollinations produced significantly more and heavier outcrossed than selfed seeds. However, the proportion of selfed seed, fertilized ovules, and aborted seeds for mixed-donor fruits were each predictable from pollen performance in single-donor fruits, suggesting that differential paternity is best explained by inbreeding depression during seed development. Even given these similarities between mixed- and single-donor fruits in the relative performance of S and OC pollen, both individual seed weight and seed set were significantly higher in multiply-sired fruits.
花朵常常会同时接受自花（S）和异花（OC）花粉，但S花粉产生的种子数量往往相对较少。S花粉的败育可能反映了促进异交和/或种子发育过程中表达的近亲繁殖衰退的进化机制。在自交亲和的多年生草本植物蓝花耧斗菜中，研究了这两个过程的相对重要性。在田间，我进行了单供体（S或OC）和混合供体（S加OC）授粉，以比较两种花粉类型在从花粉萌发到种子成熟的各个阶段的相对成功率。单供体S授粉产生的种子数量和重量明显少于OC授粉（分别减少了12%和3%）。败育率平均相差38%，而受精率仅相差5%，这表明种子数量的大多数差异发生在合子形成之后。这表明近亲繁殖衰退是S花粉大多数败育的原因。所测量的一个合子前效应是，42小时后到达子房的S花粉管比OC花粉管少10%，这表明混合授粉后S花粉可能使更少的胚珠受精。使用等位酶标记，我发现混合供体授粉产生的异交种子明显比自交种子更多、更重。然而，混合供体果实的自交种子、受精胚珠和败育种子的比例都可以根据单供体果实中的花粉表现来预测，这表明种子发育过程中的近亲繁殖衰退最能解释父本差异。即使考虑到混合供体和单供体果实在S和OC花粉相对表现上的这些相似性，多父本果实中的单个种子重量和结实率都显著更高。
