Parrish J A D, Bazzaz F A
Department of Botany, University of Illinois, 61801, Urbana, IL, USA.
Oecologia. 1978 Jan;35(2):133-140. doi: 10.1007/BF00344726.
Differences in major selective forces important in early and late successional communities should influence niche breadth and degree of overlap. Early successional species may not experience consistent, strong selection against competition and can be expected to have broader niches with more overlap than later successional species. This paper presents data from 2 early successional winter annuals that show clear niche separation under conditions in which coevolution is unlikely. Lactuca scariola L. and Erigeron annuus (L.) Pers. flower in mid-summer and attract the same insect visitors. Erigeron, the more common species, begins to flower in mid-morning when insect visitors are quite active. Lactuca flowers open earlier in the morning and close just before Erigeron flowers open. The early morning hours are not optimum for Lactuca visitation, as most of the visits occur just before floral closing. Both species can selffertilize without a vector, and Lactuca was introduced from Europe. It is, therefore, not possible that niche separation inflowering time and subsequent time of visit in Erigeron and Lactuca is a result of coevolutionary niche differentiation between the two species. This separation is likely to be a preadaptation resulting from coevolution with other species.
在早期和晚期演替群落中起重要作用的主要选择压力的差异，应该会影响生态位宽度和重叠程度。早期演替物种可能不会经历针对竞争的一致、强烈的选择，因此可以预期它们比晚期演替物种具有更宽的生态位和更多的重叠。本文展示了两种早期演替冬季一年生植物的数据，这些数据表明在不太可能发生共同进化的条件下存在明显的生态位分离。刺莴苣和一年蓬在仲夏开花，并吸引相同的昆虫访客。一年蓬是更常见的物种，在上午中旬昆虫访客相当活跃时开始开花。刺莴苣的花在早晨更早开放，并在一年蓬的花开放前关闭。清晨时段对刺莴苣的访花来说并非最佳时间，因为大多数访花发生在花期即将结束时。两种植物都可以在没有传粉媒介的情况下自花受精，并且刺莴苣是从欧洲引入的。因此，一年蓬和刺莴苣在开花时间以及随后的访花时间上的生态位分离，不太可能是这两个物种之间共同进化的生态位分化的结果。这种分离可能是与其他物种共同进化产生的一种预适应。
