Using superparasitism by a stem borer parasitoid to infer a host refuge
Using superparasitism by a stem borer parasitoid to infer a host refuge
复制标题
DOI：
10.1046/j.1365-2311.1999.00165.x
复制
发表时间：
1999-02-01
影响因子：
2.2
通讯作者：
Hopper, KR
中科院分区：
文献类型：
--
作者：
Edwards, OR;Hopper, KR
1. Macrocentrus cingulum Reinhard（膜翅目：茧蜂科），是欧洲玉米螟 Ostrinia nubilalis 和亚洲玉米螟 O.furnacalis（鳞翅目：螟科）的寄生蜂，具有高繁殖力，但据报道寄生的寄主幼虫比例较低。这一点在野外采集中得到了证实：在中国河北和美国特拉华州，M. cingulum 分别仅寄生了所采集宿主的 15% 和 25%。2．由于M. cingulum 雌性无法通过植物组织产卵，因此它们必须在钻入茎之前或在靠近入口孔时寄生宿主，因此在任何时候，许多Ostrinia 幼虫都可能无法被M. cingulum 获取。这种庇护所，加上觅食的M. cingulum 雌性丰度的波动，可以解释为什么M. cingulum 寄生相对较少的Ostrinia 幼虫。3。为了验证这一假设，在现场测量了超级寄生水平。寄主幼虫避难所导致的低寄生率会导致避难所外寄主的高寄生率。4．由于M. cingulum 是多胚的，每个寄主的寄生蜂数量并不表明超寄生水平。随机扩增的多态性 DNA 标记用于确定每个宿主出现的不同基因型的数量。将所得的频率分布与随机产卵下预期的频率分布进行拟合，以估计 M. cingulum 无法获得的玉米螟幼虫的比例。5。在河北和特拉华州的样本中，如果所有宿主都可用，超级寄生水平远高于偶然预期。将每个宿主的基因型频率拟合为泊松分布，作者估计这些集合中分别有 74-82% 和 69-74% 的宿主幼虫无法被 M. cingulum 捕获。这意味着 M. cingulum 分别寄生了这些集合中 60-84% 和 82-95% 的可用宿主。这些寄生水平与假定所有宿主均可产卵时发现的 15-25% 形成鲜明对比。6。宿主内部和宿主之间的 M. cingulum 遗传距离没有差异，从而否定了高水平的超级寄生是由雌性在同一宿主中产下多个卵造成的假设。7。由于许多幼虫都在避难所中，M. cingulum 寄生了很少的玉米螟幼虫，这一假设比其他提出的假设更好地解释了这些数据和之前发布的信息。
1. Macrocentrus cingulum Reinhard (Hymenoptera: Braconidae), a parasitoid of the European corn borer, Ostrinia nubilalis, and the Asian corn borer, O. furnacalis (Lepidoptera: Pyralidae), has high fecundity but has been reported to parasitize a low proportion of host larvae. This was corroborated in field collections: in Hebei (China) and Delaware (U.S.A.), M. cingulum parasitized only 15 and 25%, respectively, of hosts collected.2. Because M. cingulum females cannot oviposit through plant tissue, they must parasitize hosts either before they have bored into stalks or while they are near entrance holes, so that at any one time, many Ostrinia larvae may be unavailable to M. cingulum. This refuge, together with fluctuations in abundance of foraging M. cingulum females, may explain why M. cingulum parasitizes relatively few Ostrinia larvae.3. To test this hypothesis, levels of superparasitism were measured in the field. Low parasitism resulting from a refuge for host larvae should cause high rates of superparasitism in hosts outside the refuge.4. Because M. cingulum is polyembryonic, the number of parasitoids per host does not indicate the level of superparasitism. Random amplified polymorphic DNA markers were used to determine the number of different genotypes emerging from each host. The resulting frequency distributions were fitted to those expected under random oviposition to estimate the proportion of Ostrinia larvae unavailable to M. cingulum.5. In the samples from Hebei and Delaware, the level of superparasitism was much higher than expected by chance if all hosts were available. Fitting the frequencies of genotypes per host to a Poisson distribution, the authors estimated that 74-82% and 69-74% of host larvae were unavailable to M. cingulum in these collections, respectively. This means that M. cingulum parasitized 60-84% and 82-95% of available hosts in these collections, respectively. These levels of parasitism contrast strongly with the 15-25% found when all hosts were assumed available for oviposition.6. Genetic distances of M. cingulum within and between hosts did not differ, allowing rejection of the hypothesis that high levels of superparasitism resulted from a female laying several eggs in the same host.7. The hypothesis that M. cingulum parasitizes few Ostrinia larvae because many larvae are in a refuge explains these data and previously published information better than other hypotheses that have been suggested.