Fox Charles W, Waddell Kim J, Mousseau Timothy A
Department of Biological Sciences, University of South Carolina, 29208, Columbia, SC, USA.
Oecologia. 1994 Sep;99(3-4):329-336. doi: 10.1007/BF00627746.
The geographic distributions of many generalist herbivores differ from those of their host plants, such that they experience coarse-grained spatial variation in natural selection on characters influencing adaptation to host plants. Thus, populations differing in host use are expected to differ in their ability to survive and grow on these host plants. We examine host-associated variation in larval performance (survivorship, development time, and adult body weight) and oviposition preference, within and between two populations ofStator limbatus (Coleoptera: Bruchidae) that differ in the hosts available to them in nature. In one population,Acacia greggii (Fabaceae: Mimosoideae) andCercidium microphyllum (Fabaceae: Caesalpininoideae) are each abundant, while in the second population onlyC. floridum andC. microphyllum are present. In both populations, egg-to-adult survivorship was less than 50% onC. floridum, while survivorship was greater than 90% onA. greggii. Most of the mortality onC. floridum occurred as larvae were burrowing through the seed coat; very low mortality occurred during penetration of the seed coat ofA. greggii. Significant variation was present between populations, and among families (within populations), in survivorship and egg-to-adult development time onC. floridum; beetles restricted toCercidium in nature, without access toC. floridum, survived better and developed faster onC. floridum than beetles that had access toA. greggii. Large host effects on body size were detected for female offspring: females reared onA. greggii were larger than those reared onC. floridum, whereas male offspring wee approximately the same size regardless of rearing host. Trade-offs between performance onC. floridum andC. floridum were not detected in this experiment. Instead, our data indicate that development time and survivorship onC. floridum may be largely independent of development time and survivorship onA. greggii. Patterns of oviposition preference corresponded to the observed patterns of host suitability: in laboratory preference tests, beetles with access toA. greggii in nature tended to prefer this host more than beetles without access to this host in nature.
许多广食性食草动物的地理分布与其寄主植物不同，因此它们在影响对寄主植物适应性的性状上经历自然选择的粗粒度空间变异。因此，在寄主利用上存在差异的种群，其在这些寄主植物上生存和生长的能力也有望存在差异。我们研究了自然条件下寄主可利用性不同的两个豆象种群（鞘翅目：豆象科）内部和之间幼虫性能（存活率、发育时间和成虫体重）以及产卵偏好与寄主相关的变异。在一个种群中，格雷格金合欢（豆科：含羞草亚科）和小叶扁轴木（豆科：云实亚科）都很丰富，而在第二个种群中，只有佛罗里达扁轴木和小叶扁轴木存在。在两个种群中，在佛罗里达扁轴木上从卵到成虫的存活率都低于50%，而在格雷格金合欢上存活率大于90%。在佛罗里达扁轴木上的大部分死亡发生在幼虫钻穿种皮时；在穿透格雷格金合欢种皮时死亡率非常低。在佛罗里达扁轴木上，种群之间以及家系之间（种群内部）在存活率和从卵到成虫的发育时间上存在显著变异；自然条件下局限于扁轴木属、无法接触佛罗里达扁轴木的甲虫，在佛罗里达扁轴木上比可以接触格雷格金合欢的甲虫存活得更好且发育得更快。检测到寄主对雌性后代体型有很大影响：在格雷格金合欢上饲养的雌性比在佛罗里达扁轴木上饲养的雌性更大，而雄性后代无论饲养寄主如何，体型大致相同。在本实验中未检测到在佛罗里达扁轴木上的性能与在佛罗里达扁轴木上的性能之间的权衡。相反，我们的数据表明，在佛罗里达扁轴木上的发育时间和存活率可能在很大程度上独立于在格雷格金合欢上的发育时间和存活率。产卵偏好模式与观察到的寄主适宜性模式相对应：在实验室偏好测试中，自然条件下可以接触格雷格金合欢的甲虫比自然条件下无法接触该寄主的甲虫更倾向于选择这种寄主。
