Brady Seán G, Sipes Sedonia, Pearson Adam, Danforth Bryan N
Department of Entomology and Laboratories of Analytical Biology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA.
Proc Biol Sci. 2006 Jul 7;273(1594):1643-9. doi: 10.1098/rspb.2006.3496.
Eusocial organisms are characterized by cooperative brood care, generation overlap and reproductive division of labour. Traits associated with eusociality are most developed in ants, termites, paper wasps and corbiculate bees; the fossil record indicates that each of these advanced eusocial taxa evolved in the Late Cretaceous or earlier (greater than 65 Myr ago). Halictid bees also include a large and diverse number of eusocial members, but, in contrast to advanced eusocial taxa, they are characterized by substantial intra- and inter-specific variation in social behaviour, which may be indicative of more recent eusocial evolution. To test this hypothesis, we used over 2400 bp of DNA sequence data gathered from three protein-coding nuclear genes (opsin, wingless and EF-1a) to infer the phylogeny of eusocial halictid lineages and their relatives. Results from relaxed molecular clock dating techniques that utilize a combination of molecular and fossil data indicate that the three independent origins of eusociality in halictid bees occurred within a narrow time frame between approximately 20 and 22 Myr ago. This relatively recent evolution helps to explain the pronounced levels of social variation observed within these bees. The three origins of eusociality appear to be temporally correlated with a period of global warming, suggesting that climate may have had an important role in the evolution and maintenance of eusociality in these bees.
真社会性生物的特征是合作育幼、世代重叠和生殖分工。与真社会性相关的特征在蚂蚁、白蚁、胡蜂和无刺蜂中最为发达；化石记录表明，这些高等真社会性类群中的每一个都是在白垩纪晚期或更早（超过6500万年前）进化而来的。隧蜂科蜜蜂也包括大量不同的真社会性成员，但与高等真社会性类群不同的是，它们的特点是社会行为在种内和种间存在很大差异，这可能表明真社会性进化的时间更近。为了验证这一假设，我们使用了从三个蛋白质编码核基因（视蛋白、无翅基因和EF-1a）收集的超过2400个碱基对的DNA序列数据，来推断真社会性隧蜂科谱系及其亲属的系统发育。利用分子和化石数据相结合的宽松分子钟定年技术得出的结果表明，隧蜂科蜜蜂真社会性的三个独立起源发生在大约2000万至2200万年前的一个狭窄时间范围内。这种相对较新的进化有助于解释在这些蜜蜂中观察到的明显的社会差异水平。真社会性的三个起源似乎在时间上与全球变暖时期相关，这表明气候可能在这些蜜蜂真社会性的进化和维持中起到了重要作用。
