Hasegawa Eisuke, Yamaguchi Takeshi
Department of Biology, Faculty of Science, Tokyo Metropolitan University, Minamiohsawa 1-1, Hachioji-si, Tokyo 192-03, Japan.
Department of Ecological Sciences, Natural History Museum and Institute, Chiba, Aoba-cho 955-2, Chuou-ku, Chiba 260, Japan.
Evolution. 1995 Apr;49(2):260-265. doi: 10.1111/j.1558-5646.1995.tb02238.x.
Population-genetic structure and sex-allocation ratios were investigated for the ant Messor aciculatus, a species that conducts mass nuptial flights. An electrophoretic survey on two polymorphic loci revealed excessive homozygosities in two populations. Because inbreeding inside nests does not occur, the heterozygote deficiency may result from population subdivision rather than assortative inbreeding during nuptial flights. Assuming no inbreeding, a simulation based on the observed genotype distribution in the study site suggested that, on average, a breeding swarm consists of alates from only 1.7 colonies. This population genetic structure seems to cause local mate competition (LMC), a factor that can shift population sex ratio toward females. The sex-allocation ratio to males in the population (0.166 ± 0.030; mean ± SE) was significantly female biased and lower than the expected optima for queens (0.5) and for workers (0.25) without LMC. Sex-ratio variability among colonies was explained by a pattern of constant male investment, which is predictable assuming LMC. Thus, the study provides the first evidence of LMC in ants with mass nuptial flights and contradicts previous assumptions about breeding structure in swarming ants. The results suggest that LMC can affect sex-allocation patterns for ant colonies and populations.
对进行大规模婚飞的针毛收获蚁的种群遗传结构和性别分配比例进行了研究。对两个多态位点的电泳调查显示，两个种群中存在过多的纯合子。由于蚁巢内不存在近亲繁殖，杂合子缺乏可能是由于种群细分，而非婚飞期间的选型近亲繁殖所致。假设不存在近亲繁殖，基于研究地点观察到的基因型分布进行的模拟表明，平均而言，一个繁殖群体仅由1.7个蚁群的有翅蚁组成。这种种群遗传结构似乎会导致局部配偶竞争（LMC），这是一个可使种群性别比例偏向雌性的因素。该种群中雄性的性别分配比例（0.166±0.030；平均值±标准误）显著偏向雌性，且低于不存在LMC时蚁后（0.5）和工蚁（0.25）的预期最优比例。蚁群间性别比例的变异性可通过恒定的雄性投资模式来解释，假设存在LMC，这是可预测的。因此，该研究首次提供了大规模婚飞蚂蚁中存在LMC的证据，并与之前关于群居蚂蚁繁殖结构的假设相矛盾。结果表明，LMC会影响蚁群和种群的性别分配模式。
