Rasekh Arash, Osawa Naoya
Department of Plant Protection College of Agriculture Shahid Chamran University of Ahvaz Ahvaz Iran.
Laboratory of Forest Ecology Graduate School of Agriculture Kyoto University Kyoto Japan.
Ecol Evol. 2020 Jun 9;10(12):5899-5912. doi: 10.1002/ece3.6326. eCollection 2020 Jun.
In this study, we focused on the direct (i.e., predation) and indirect (i.e., potential threat from coexisting with a larger individual) effects of cannibalism and intraguild predation (IGP) during larval stages of two sibling ladybird beetles. These effects play an important role in the coexistence of the generalist-common and specialist-rare (Coleoptera: Coccinellidae). Direct predation effect of cannibalism and IGP was asymmetric in the two sibling ladybird beetles; the fourth instar larvae of . were better intraguild predators than cannibals, while the reverse was true in the larvae of . Neither cannibalism nor IGP significantly affected female body weight in either species. Larval . surviving exposure to cannibalism or IGP had a reduced number of ovarioles as adults, whereas adult ovarioles were not affected. For the indirect effects, longer developmental times in males and females and a lower total number of ovarioles in females were detected in . . In , shorter developmental time of males, lighter adult weight and fewer total ovarioles in females were observed. Olfactometer choice experiments clarified that the fourth instar larvae of . avoided the first instar conspecific larvae, while those of were attracted to the odors from . and conspecifics. Thus, . has an avoidance mechanism only for cannibalism but not for IGP whereas does not have any avoidance mechanism. These different behaviors in the direct and indirect effects of cannibalism and IGP observed in the laboratory may play important roles in the coexistence of generalist-common . and specialist-rare in natural conditions, compensating for the large handicap of at reproductive interference from . .
在本研究中，我们聚焦于两种近缘瓢虫幼虫阶段同类相食和种内互食（IGP）的直接影响（即捕食）和间接影响（即与较大个体共存的潜在威胁）。这些影响在多食性常见种和寡食性稀有种（鞘翅目：瓢虫科）的共存中起着重要作用。同类相食和种内互食的直接捕食影响在这两种近缘瓢虫中是不对称的；[物种名称1]的四龄幼虫作为种内捕食者比同类相食者更具优势，而在[物种名称2]的幼虫中情况则相反。同类相食和种内互食对这两个物种的雌虫体重均无显著影响。经历过同类相食或种内互食的[物种名称1]幼虫成虫期的卵巢小管数量减少，而[物种名称2]成虫的卵巢小管则未受影响。对于间接影响，在[物种名称1]中检测到雄性和雌性发育时间延长以及雌性卵巢小管总数减少。在[物种名称2]中，观察到雄性发育时间缩短、成虫体重较轻以及雌性卵巢小管总数较少。嗅觉仪选择实验表明，[物种名称1]的四龄幼虫会避开一龄同种幼虫，而[物种名称2]的四龄幼虫则会被[物种名称1]和同种个体的气味所吸引。因此，[物种名称1]仅对同类相食有回避机制，而对种内互食没有回避机制，而[物种名称2]则没有任何回避机制。在实验室中观察到的同类相食和种内互食的直接和间接影响中的这些不同行为，可能在自然条件下多食性常见种[物种名称1]和寡食性稀有种[物种名称2]的共存中发挥重要作用，弥补了[物种名称2]在来自[物种名称1]的生殖干扰方面的巨大劣势。
