Elle E, Hare J D
Department of Entomology, University of California, Riverside, CA 92521, USA e-mail:
Oecologia. 2000 Apr;123(1):57-65. doi: 10.1007/s004420050989.
Populations of Datura wrightii vary in the frequency of plants that produce glandular trichomes, a resistance trait under the control of a single gene. Such variation may be maintained if the production of glandular trichomes is costly in the absence of herbivory, and if selection imposed by herbivore communities varies spatially or temporally. Here, we document costs in the presence of herbivory for established glandular plants relative to established non-glandular plants growing in natural populations from coastal mountain, Riversidian sage scrub, and Mojave desert habitats in southern California. Damage caused by the herbivore community varied spatially, with significant differences in herbivore-specific damage between plants of the two trichome types and among populations within habitats, although not generally among habitats. Plants with greater canopy size and canopy persistence had higher viable seed production than smaller or more damaged plants, but this relationship was statistically significant only for non-glandular plants. However, the relationship between viable seed production and canopy persistence became significant for glandular plants when damage caused by sap suckers, which do not remove leaf area, was pooled with undamaged leaf area. The high cost exhibited by glandular plants leads us to predict that in the absence of any additional, unknown benefits of producing glandular trichomes, the frequency of these plants should decline in all natural populations of D. wrightii.
曼陀罗种群中，产生腺毛的植株频率存在差异，腺毛是一种受单基因控制的抗性性状。如果在没有食草动物的情况下产生腺毛成本高昂，并且如果食草动物群落施加的选择在空间或时间上有所不同，那么这种变异可能会持续存在。在这里，我们记录了相对于生长在加利福尼亚州南部沿海山区、里弗赛德鼠尾草灌丛和莫哈韦沙漠栖息地自然种群中的已建立的非腺毛植物，已建立的腺毛植物在有食草动物存在时的成本。食草动物群落造成的损害在空间上有所不同，两种腺毛类型的植物之间以及栖息地内的种群之间，在食草动物特异性损害方面存在显著差异，尽管一般在不同栖息地之间没有差异。树冠大小和树冠持久性较大的植物比树冠较小或受损更严重的植物具有更高的可存活种子产量，但这种关系仅在非腺毛植物中具有统计学意义。然而，当由不去除叶面积的吸汁昆虫造成的损害与未受损叶面积合并时，对于腺毛植物而言，可存活种子产量与树冠持久性之间的关系变得显著。腺毛植物表现出的高成本使我们预测，在没有产生腺毛的任何额外未知益处的情况下，这些植物的频率在曼陀罗的所有自然种群中都应该下降。
