Graduate Degree Program in Ecology and Department of Bioagricultural Sciences and Pest Management, Colorado State University, 1177 Campus Delivery, Fort Collins, CO, 80523-1177, USA.
Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands.
Oecologia. 2019 Oct;191(2):261-270. doi: 10.1007/s00442-019-04470-5. Epub 2019 Jul 24.
Interspecific competition for limited resources can drive ecological specialization and trait expression. Organisms released from intense competition may exploit a broader range of resources, but if reunited with stronger competitors, survivorship may depend on foraging behaviors that reduce competition. We compared the host selection behavior of the parasitoid Cotesia glomerata from two North American populations that differ in their association with Cotesia rubecula, a superior competitor. Both parasitoids originate from Europe and attack the imported cabbageworm (a.k.a. small cabbage white) Pieris rapae, but C. glomerata was introduced into North America almost a century before C. rubecula. After re-association in North America, C. rubecula has displaced C. glomerata in several regions, but not in other regions. Host selection was measured in female C. glomerata from Maryland (MD) where it coexists with C. rubecula, and in conspecifics from Colorado (CO) where C. rubecula is absent. Unparasitized and C. rubecula-parasitized P. rapae hosts were used in choice tests to examine whether C. glomerata host selection behavior differed based on the population's association history with C. rubecula. We found that C. glomerata from MD had a higher likelihood of avoiding hosts parasitized by C. rubecula (and thus avoiding competition) than did wasps from CO. The ability of C. glomerata to avoid hosts parasitized by C. rubecula may facilitate coexistence in MD; whereas, the lack of discrimination in CO populations of C. glomerata naïve to C. rubecula could contribute to the displacement of C. glomerata were C. rubecula to enter the same habitat.
种间竞争会对有限资源产生影响，从而导致生态特化和特征表达。从激烈竞争中释放出来的生物可能会利用更广泛的资源，但如果与更强的竞争者重新结合，生存可能取决于减少竞争的觅食行为。我们比较了来自两个北美的北美种群的寄生蜂 Cotesia glomerata 的宿主选择行为，这两个种群与 Cotesia rubecula 的联系不同，后者是一种更具竞争力的竞争者。这两种寄生蜂都起源于欧洲，攻击被引入的白菜蠕虫（又名小菜蛾）Pieris rapae，但 C. glomerata 被引入北美的时间比 C. rubecula 早近一个世纪。在北美重新结合后，C. rubecula 在几个地区取代了 C. glomerata，但在其他地区没有。宿主选择是在马里兰州（MD）的 C. glomerata 雌蜂中测量的，那里与 C. rubecula 共存，以及在科罗拉多州（CO）的同种中测量的，那里没有 C. rubecula。在选择测试中使用未寄生和被 C. rubecula 寄生的 P. rapae 宿主，以检查 C. glomerata 的宿主选择行为是否因种群与 C. rubecula 的联系历史而有所不同。我们发现，来自 MD 的 C. glomerata 比来自 CO 的蜂更有可能避免被 C. rubecula 寄生的宿主（从而避免竞争）。C. glomerata 避免被 C. rubecula 寄生的宿主的能力可能有助于在 MD 共存；然而，CO 种群中对 C. rubecula 没有辨别力的 C. glomerata 可能会导致 C. glomerata 被取代，如果 C. rubecula 进入同一栖息地。
