Campbell Lesley G, Husband Brian C
Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Present address: Department of Evolution, Ecology and Organismal Biology, Ohio State University, 318 W 12th Avenue, Columbus, OH 43210, USA.
New Phytol. 2007;174(4):915-925. doi: 10.1111/j.1469-8137.2007.02045.x.
If pollinators or compatible mates are scarce, plants in small populations may be pollen-limited and consequently produce fewer offspring. However, determining the relative importance of the genetic vs ecological mechanisms limiting successful pollination is challenging. We explored the relationships among population size, population connectivity, pollinator visitation, allozyme diversity, mate availability (measured as percent compatible crosses among plants within a population), and pollen limitation in 12 populations (N = 39-885,274) of the self-incompatible plant Hymenoxys herbacea in Ontario, Canada. Unexpectedly, small populations had more insect flower visitors per capitulum than large populations. Consistent with the effects of genetic drift, both allozyme polymorphism and mate availability decreased with decreasing population size. Pollen limitation was low and significant in only one population and could not be predicted based on knowledge of population size, connectivity, compatible mate availability, or pollinator visitation. Population size had detectable effects on both pollinator activity and mate availability. However, because the effect of population size was complementary on these two potentially limiting mechanisms, this threatened plant was rarely pollen-limited.
如果传粉者或合适的配偶稀少，小种群中的植物可能会受到花粉限制，从而产生较少的后代。然而，确定限制成功授粉的遗传机制与生态机制的相对重要性具有挑战性。我们在加拿大安大略省对自交不亲和植物草本膜苞菊的12个种群（N = 39 - 885,274），研究了种群大小、种群连通性、传粉者访花情况、等位酶多样性、配偶可利用性（以种群内植物间可育杂交的百分比衡量）和花粉限制之间的关系。出乎意料的是，小种群每头状花序的昆虫访花者比大种群更多。与遗传漂变的影响一致，等位酶多态性和配偶可利用性都随着种群大小的减小而降低。仅在一个种群中花粉限制较低且显著，并且无法根据种群大小、连通性、可育配偶可利用性或传粉者访花情况来预测。种群大小对传粉者活动和配偶可利用性都有可检测到的影响。然而，由于种群大小对这两种潜在限制机制的影响是互补的，这种受威胁植物很少受到花粉限制。
