孤雌繁殖的白蟻：當雄性不再被需要

論文標題：Loss of males from mixed-sex societies in termites

期刊：BMC Biology

作者：Toshihisa Yashiro, Nathan LoView ORCID ID profile, Kazuya Kobayashi, Tomonari NozakiTaro FuchikawaView ORCID ID profile, Nobuaki MizumotoView ORCID ID profile, Yusuke Namba and Kenji MatsuuraView ORCID ID profile

發表時間：2018/09/25

數字識別碼：10.1186/s12915-018-0563-y

最近發表在BMC Biology上的研究表明，一種樹白蟻Glyptotermes nakajimai的群體可以在沒有雄性的情況下建立起成功的、可以繁衍的蟻窩。

這項由澳大利亞悉尼大學和日本京都大學合作的研究表明，在一些先進的動物社會的維繫中，雄性可能不是必需的，即便雄性之前在其中發揮過積極的作用。

研究的通訊作者矢代敏久說：「以前報道過的完全沒有雄性的現象只出現在螞蟻和蜜蜂中。白蟻的蟻窩一直都是雌雄數量均等且進行有性繁殖的。我們的論文第一次證明白蟻也可以完全脫離雄性生存，雌性們過得很好。」

作者們在日本偏遠沿海地區發現了沒有任何雄性的G. nakajimai種群。他們將這些地區37個蟻窩中個體的形態與日本其他地區發現的37個雌雄混合的蟻窩中的個體進行了比較。全雌蟻窩中的蟻后受精囊（一種雌性在交配後用來儲存精子的器官）是空的，而雌雄混合蟻窩中的蟻后都儲存了足夠多的精子。全雌蟻窩中的卵亦都為未受精卵。

矢代敏久說：「有趣的是，在雌雄混合種群中我們也偶爾會觀察到未受精卵的發育。這表明用未受精卵發育出後代的能力可能是從雌雄混合的祖先中來的，而這種能力為全雌蟻窩的演化提供了一種可能。我們還發現，全雌蟻窩中的兵蟻與雌雄混合蟻窩的相比，頭部大小更均勻，總數量上更少。這表明『全女兵』的陣容在防禦上更有效率，這可能有助於全雌蟻窩的維繫和傳播。」

我們還需要進一步的研究來確認其他白蟻物種中是否存在全雌蟻窩的現象。

摘要：

Background

Sexual reproduction is the norm in almost all animal species, and in many advanced animal societies, both males and females participate in social activities. To date, the complete loss of males from advanced social animal lineages has been reported only in ants and honey bees (Hymenoptera), whose workers are always female and whose males display no helping behaviors even in normal sexual species. Asexuality has not previously been observed in colonies of another major group of social insects, the termites, where the ubiquitous presence of both male and female workers and soldiers indicate that males play a critical role beyond that of reproduction.

Results

Here, we report asexual societies in a lineage of the termite Glyptotermes nakajimai. We investigated the composition of mature colonies from ten distinct populations in Japan, finding six asexual populations characterized by a lack of any males in the reproductive, soldier, and worker castes of their colonies, an absence of sperm in the spermathecae of their queens, and the development of unfertilized eggs at a level comparable to that for the development of fertilized eggs in sexual populations of this species. Phylogenetic analyses indicated a single evolutionary origin of the asexual populations, with divergence from sampled sexual populations occurring about 14 million years ago. Asexual colonies differ from sexual colonies in having a more uniform head size in their all-female soldier caste, and fewer soldiers in proportion to other individuals, suggesting increased defensive efficiencies arising from uniform soldier morphology. Such efficiencies may have contributed to the persistence and spread of the asexual lineage. Cooperative colony foundation by multiple queens, the single-site nesting life history common to both the asexual and sexual lineages, and the occasional development of eggs without fertilization even in the sexual lineage are traits likely to have been present in the ancestors of the asexual lineage that may have facilitated the transition to asexuality.

Conclusions

Our findings demonstrate that completely asexual social lineages can evolve from mixed-sex termite societies, providing evidence that males are dispensable for the maintenance of advanced animal societies in which they previously played an active social role.

期刊介紹：BMC Biology(https://bmcbiol.biomedcentral.com/) is an open access journal publishing outstanding research in all areas of biology, with a publication policy that combines selection for broad interest and importance with a commitment to serving authors well.

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Citation Impact

5.770 - 2-year Impact Factor

7.556 - 5-year Impact Factor

1.377 - Source Normalized Impact per Paper (SNIP)

3.425 - SCImago Journal Rank (SJR)

來源：BMC Biology

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