Elbaz M, Lahav N, Morin S
Department of Entomology, Faculty of Agriculture, the Hebrew University of Jerusalem, Rehovot 76100, Israel.
Bull Entomol Res. 2010 Oct;100(5):581-90. doi: 10.1017/S0007485309990630. Epub 2010 Feb 17.
The degree of reproductive isolation between the B and Q biotypes of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is currently not clear. Laboratory experiments have shown that the two biotypes are capable of producing viable F1 hybrids but that these females are sterile as their F2 generation failed to develop, indicating, most likely, a post-zygotic reproductive barrier. Here, we confirm, by molecular and ecological tools, that the B and Q biotypes of Israel are genetically isolated and provide two independent lines of evidence that support the existence of a pre-zygotic reproductive barrier between them. Firstly, monitoring of mating behaviors in homogeneous and heterogeneous couples indicated no copulation events in heterogeneous couples compared to approximately 50% in homogeneous B and Q couples. Secondly, we could not detect the presence of sperm in the spermathecae of females from heterogeneous couples, compared to 50% detection in intra-B biotype crosses and 15% detection in intra-Q biotype crosses. The existence of pre-zygotic reproductive barriers in Israeli B and Q colonies may indicate a reinforcement process in which mating discrimination is strengthened between sympatric taxa that were formerly allopatric, to avoid maladaptive hybridization. As the two biotypes continued to perform all courtship stages prior to copulation, we also conducted mixed cultures experiments in order to test the reproductive consequences of inter-biotype courtship attempts. In mixed cultures, a significant reduction in female fecundity was observed for the Q biotype but not for the B biotype, suggesting an asymmetric reproductive interference effect in favour of the B biotype. The long-term outcome of this effect is yet to be determined since additional environmental forces may reduce the probability of demographic displacement of one biotype by the other in overlapping niches.
烟粉虱（半翅目：粉虱科）的B型和Q型生物型之间的生殖隔离程度目前尚不清楚。实验室实验表明，这两种生物型能够产生可育的F1代杂种，但这些雌性是不育的，因为它们的F2代无法发育，这很可能表明存在合子后生殖障碍。在这里，我们通过分子和生态学工具证实，以色列的B型和Q型生物型在基因上是隔离的，并提供了两条独立的证据支持它们之间存在合子前生殖障碍。首先，对同型和异型配对中的交配行为进行监测表明，异型配对中没有交配事件发生，而同型的B型和Q型配对中的交配率约为50%。其次，我们在异型配对雌性的受精囊中未检测到精子，相比之下，B型生物型内杂交的检测率为50%，Q型生物型内杂交的检测率为15%。以色列B型和Q型种群中合子前生殖障碍的存在可能表明了一种强化过程，即以前异域分布的同域分类群之间的交配歧视得到加强，以避免不适应的杂交。由于这两种生物型在交配前仍会经历所有求偶阶段，我们还进行了混合培养实验，以测试生物型间求偶尝试的生殖后果。在混合培养中，观察到Q型生物型的雌性繁殖力显著降低，而B型生物型则没有，这表明存在有利于B型生物型的不对称生殖干扰效应。由于其他环境因素可能会降低一个生物型在重叠生态位中被另一个生物型取代的概率，这种效应的长期结果还有待确定。
