Friberg Magne, Wiklund Christer
Department of Zoology, Stockholm University, 106 91, Stockholm, Sweden.
Oecologia. 2009 Feb;159(1):127-37. doi: 10.1007/s00442-008-1206-8. Epub 2008 Nov 11.
A large proportion of phytophagous insect species are specialised on one or a few host plants, and female host plant preference is predicted to be tightly linked to high larval survival and performance on the preferred plant(s). Specialisation is likely favoured by selection under stable circumstances, since different host plant species are likely to differ in suitability-a pattern usually explained by the "trade-off hypothesis", which posits that increased performance on a given plant comes at a cost of decreased performance on other plants. Host plant specialisation is also ascribed an important role in host shift speciation, where different incipient species specialise on different host plants. Hence, it is important to determine the role of host plants when studying species divergence and niche partitioning between closely related species, such as the butterfly species pair Leptidea sinapis and Leptidea reali. In Sweden, Leptidea sinapis is a habitat generalist, appearing in both forests and meadows, whereas Leptidea reali is specialised on meadows. Here, we study the female preference and larval survival and performance in terms of growth rate, pupal weight and development time on the seven most-utilised host plants. Both species showed similar host plant rank orders, and larvae survived and performed equally well on most plants with the exceptions of two rarely utilised forest plants. We therefore conclude that differences in preference or performance on plants from the two habitats do not drive, or maintain, niche separation, and we argue that the results of this study do not support the trade-off hypothesis for host plant specialisation, since the host plant generalist Leptidea sinapis survived and performed as well on the most preferred meadow host plant Lathyrus pratensis as did Leptidea reali although the generalist species also includes other plants in its host range.
很大一部分植食性昆虫物种都专食一种或几种寄主植物，预计雌虫对寄主植物的偏好与幼虫在偏好植物上的高存活率和良好生长表现紧密相关。在稳定环境下，选择可能有利于物种的专一化，因为不同的寄主植物物种在适宜性上可能存在差异——这种模式通常由“权衡假说”来解释，该假说认为在某一特定植物上生长表现的提高是以在其他植物上生长表现的降低为代价的。寄主植物专一化在寄主转移物种形成中也被认为起着重要作用，不同的初始物种专食不同的寄主植物。因此，在研究近缘物种之间的物种分化和生态位划分时，比如蝴蝶物种对中华褐蛱蝶（Leptidea sinapis）和瑞氏褐蛱蝶（Leptidea reali），确定寄主植物的作用就很重要。在瑞典，中华褐蛱蝶是一种栖息地泛化种，在森林和草地中都有出现，而瑞氏褐蛱蝶则专食草地。在这里，我们研究了这两种蝴蝶在七种最常利用的寄主植物上，雌虫的偏好以及幼虫的存活率和生长表现，包括生长速率、蛹重和发育时间。两个物种对寄主植物的排序相似，除了两种很少被利用的森林植物外，幼虫在大多数植物上的存活和生长表现都一样好。因此，我们得出结论，两种栖息地的植物在偏好或生长表现上的差异并不会驱动或维持生态位分离，并且我们认为本研究结果并不支持寄主植物专一化的权衡假说，因为寄主植物泛化种中华褐蛱蝶在最偏好的草地寄主植物草地香豌豆（Lathyrus pratensis）上的存活和生长表现与瑞氏褐蛱蝶一样好，尽管泛化种的寄主范围还包括其他植物。
