Host-associated fitness trade-offs do not limit the evolution of diet breadth in the small milkweed bug Lygaeus kalmii (Hemiptera: Lygaeidae)
Host-associated fitness trade-offs do not limit the evolution of diet breadth in the small milkweed bug Lygaeus kalmii (Hemiptera: Lygaeidae)
复制标题
与宿主相关的适应性权衡并不限制小马利筋虫Lygaeus kalmii（半翅目：Lygaeidae）饮食宽度的进化
作者：
C. Fox;R. Caldwell
在一个随时间变化的环境中进化的理论模型预测，基因型在各代之间的适应性差异小，将受到青睐。当主机使用随时间变化和健身权衡主机之间存在，这样一个主机上的性能增加的结果在另一个相关的下降，选择低方差的健身跨代将有利于基因型是通才。然而，在这样的预测可以扩展到自然的食草动物种群之前，有必要了解性能权衡限制同时适应多个主机的程度。这里报道的实验比较了两个种群的常见马利筋错误，Lygaeus kalmii（半翅目：Lygaeidae）不同的主机使用模式。一个种群主要限于马利筋（Asclepias spp.）当乳草种子可用时，但当乳草种子不可用时，它就成为大量可用种子的清道夫。第二个种群主要限于蒲公英（Taraxacum officinale），无法获得乳草。我们检查这些群体，以测试宿主相关的遗传权衡之间的专业化对蒲公英（蒲公英）和两种马利筋，Asclepias fascicularis，这是低的强心苷含量，和A。美洲红毛菊，其强心苷含量高。尽管两种L. kalmii种群中，种群在它们对任何宿主植物的表现上没有差异。在每个种群中，臭虫在每个宿主上的表现几乎一样好，除了臭虫在杂草上的存活率显著低于任何一种马利筋。权衡主机之间的性能不存在于任何人口：估计的遗传相关性在主机之间是强烈的积极。本研究无法检测与宿主相关的健身权衡，这与有关该主题的大多数已发表数据一致。
Theoretical models of evolution in a temporally variable environment predict that genotypes with low variance in fitness across generations will be favored. When host use varies temporally and fitness trade-offs exist among hosts, such that an increase in performance on one host results in a correlated decrease on the other, selection for low variance in fitness across generations will favor genotypes which are generalists. Before predictions such as this can be extended to natural herbivore populations, however, it is necessary to understand the extent to which performance trade-offs limit simultaneous adaptation to multiple hosts. The experiment reported here compares two populations of the common milkweed bug, Lygaeus kalmii (Hemiptera: Lygaeidae) which differ in patterns of host usage. One population is largely restricted to milkweed (Asclepias spp.) when milkweed seeds are available, but becomes a scavenger on a large assortment of available seeds when milkweed seeds are unavailable. The second population is restricted largely to dandelion (Taraxacum officinale), without access to milkweed. We examine these populations to test for host-associated genetic trade-offs between specialization on dandelion (Taraxacum) and two species of milkweed, Asclepias fascicularis, which is low in cardiac glycoside content, and A. speciosa, which is high in cardiac glycoside content. Despite the difference in patterns of host use of the two L. kalmii populations, the populations did not differ in their performance on any of the host plants. Within each population, bugs performed nearly as well on each host, except that bugs had significantly lower survivorship on dandelion than on either milkweed species. Trade-offs in performance among hosts were not present in either population: estimated genetic correlations across hosts were strongly positive. The inability of this study to detect host-associated fitness trade-offs is consistent with most published data on this topic.