Zayed Amro, Packer Laurence
Department of Biology, York University, 4700 Keele Street, Toronto, ON, Canada M3J 1P3.
Proc Natl Acad Sci U S A. 2005 Jul 26;102(30):10742-6. doi: 10.1073/pnas.0502271102. Epub 2005 Jul 14.
The role of genetic factors in extinction is firmly established for diploid organisms, but haplodiploids have been considered immune to genetic load impacts because deleterious alleles are readily purged in haploid males. However, we show that single-locus complementary sex determination ancestral to the haplodiploid Hymenoptera (ants, bees, and wasps) imposes a substantial genetic load through homozygosity at the sex locus that results in the production of inviable or sterile diploid males. Using stochastic modeling, we have discovered that diploid male production (DMP) can initiate a rapid and previously uncharacterized extinction vortex. The extinction rate in haplodiploid populations with DMP is an order of magnitude greater than in its absence under realistic but conservative demographic parameter values. Furthermore, DMP alone can elevate the base extinction risk in haplodiploids by over an order of magnitude higher than that caused by inbreeding depression in threatened diploids. Thus, contrary to previous expectations, haplodiploids are more, rather than less, prone to extinction for genetic reasons. Our findings necessitate a fundamental shift in approaches to the conservation and population biology of these ecologically and economically crucial insects.
对于二倍体生物而言，遗传因素在物种灭绝中的作用已得到确凿证实，但单倍二倍体生物一直被认为不受遗传负荷影响，因为有害等位基因在单倍体雄性中很容易被清除。然而，我们发现，单倍二倍体膜翅目昆虫（蚂蚁、蜜蜂和黄蜂）祖先的单基因座互补性别决定通过性位点的纯合性施加了相当大的遗传负荷，导致产生无活力或不育的二倍体雄性。通过随机建模，我们发现二倍体雄性产生（DMP）可以引发一个快速且此前未被描述的灭绝漩涡。在现实但保守的人口统计学参数值下，存在DMP的单倍二倍体种群的灭绝率比不存在DMP时高出一个数量级。此外，仅DMP就能使单倍二倍体的基础灭绝风险比受威胁二倍体中近亲繁殖衰退所导致的灭绝风险高出一个多数量级。因此，与之前的预期相反，单倍二倍体生物由于遗传原因更容易灭绝，而不是更不容易灭绝。我们的研究结果需要对这些在生态和经济方面至关重要的昆虫的保护及种群生物学研究方法进行根本性转变。
