Michaud J P, Grant Angela K
Kansas State University, Agricultural Research Center--Hays, Hays, KS 67601, USA.
J Insect Sci. 2005 Oct 21;5:25. doi: 10.1093/jis/5.1.25.
The biology and behavior of the longhorned beetle Dectes texanus LeConte (Coleoptera: Cerambycidae) was studied on two host plants that suffer economic losses from this pest; sunflower, Helianthus annuus, and soybean, Glycines max. Reciprocal crosses of D. texanus collected from the two plants all produced viable progeny, indicating that conspecific insects attack both crops. Pupae from soybean stalks weighed about 40% less than those from sunflower, and adults fed on soybean lived a mean of 23 days, compared to a mean of 53 days (males) and 76 days (females) for those fed sunflower. A female's larval host plant had no effect on her tendency to ovipuncture plants of either type in a greenhouse trial. A field-tested population collected exclusively from sunflower contained three types of females in similar proportions: those that laid eggs only on sunflower, those that laid only on soybean, and those that laid equally on both host plants. Females in field trials fed more on the plant they had fed on in the laboratory, but soybean-fed females fed more on soybean than did sunflower-fed females. Females fed soybean also made more ovipunctures on soybean plants in field trials than sunflower-fed females, but their responses to sunflower plants were similar. Females displayed higher total ovipositional activity when they encountered sunflower first in the field, and lower total activity when they encountered soybean first. Feeding scores were significantly correlated with ovipunctures and eggs on both plant types. We conclude that sunflower is the preferred host plant, although females will accept soybean when it is the only available food. The results suggest that D. texanus is still in the initial stages of a host range expansion with female host selection behavior demonstrating both genetic influences and phenotypic flexibility. Sunflower represents a nutritionally superior, ancestral host plant and relatively high fitness costs are still associated with utilization of the novel host plant, soybean, costs that may be offset by benefits such as reduced intraspecific competition. These potential benefits and their consequent implications for D. texanus host range evolution are hypothesized and discussed.
对德克萨斯长角天牛（Dectes texanus LeConte，鞘翅目：天牛科）在两种因这种害虫而遭受经济损失的寄主植物上的生物学特性和行为进行了研究，这两种寄主植物分别是向日葵（Helianthus annuus）和大豆（Glycine max）。从这两种植物上采集的德克萨斯长角天牛进行正反交，均产生了可存活的后代，这表明同种昆虫会侵害这两种作物。来自大豆茎杆的蛹比来自向日葵的蛹重量轻约40%，以大豆为食的成虫平均存活23天，而以向日葵为食的成虫平均存活时间为雄性53天、雌性76天。在温室试验中，雌性幼虫的寄主植物对其在两种类型植物上产卵穿刺的倾向没有影响。一个仅从向日葵上采集并经过田间测试的种群包含三种比例相近的雌性：只在向日葵上产卵的、只在大豆上产卵的以及在两种寄主植物上产卵量相同的。在田间试验中，雌性成虫取食它们在实验室中取食过的植物更多，但取食大豆的雌性成虫比取食向日葵的雌性成虫在大豆上取食更多。在田间试验中，取食大豆的雌性成虫在大豆植株上的产卵穿刺也比取食向日葵的雌性成虫多，但它们对向日葵植株的反应相似。当雌性成虫在田间首先遇到向日葵时，其总产卵活动更高，而首先遇到大豆时，总活动更低。取食得分与两种植物类型上的产卵穿刺和卵显著相关。我们得出结论，向日葵是首选寄主植物，不过当大豆是唯一可用食物时，雌性成虫也会接受。结果表明，德克萨斯长角天牛仍处于寄主范围扩展的初始阶段，雌性寄主选择行为既显示出遗传影响，也表现出表型灵活性。向日葵代表营养更优的原始寄主植物，利用新寄主植物大豆仍会带来相对较高的适合度成本，这些成本可能会被诸如种内竞争减少等益处所抵消。对这些潜在益处及其对德克萨斯长角天牛寄主范围进化的后续影响进行了假设和讨论。
