Laboratory of Genetics, Wageningen University and Research Center, , Droevendaalsesteeg 1, Radix West, Building 107, 6708 PB Wageningen, The Netherlands.
Proc Biol Sci. 2010 Feb 7;277(1680):359-65. doi: 10.1098/rspb.2009.1373. Epub 2009 Oct 14.
The mutualism between fungus-growing termites (Macrotermitinae) and their mutualistic fungi (Termitomyces) began in Africa. The fungus-growing termites have secondarily colonized Madagascar and only a subset of the genera found in Africa is found on this isolated island. Successful long-distance colonization may have been severely constrained by the obligate interaction of the termites with fungal symbionts and the need to acquire these symbionts secondarily from the environment for most species (horizontal symbiont transmission). Consistent with this hypothesis, we show that all extant species of fungus-growing termites of Madagascar are the result of a single colonization event of termites belonging to one of the only two groups with vertical symbiont transmission, and we date this event at approximately 13 Mya (Middle/Upper Miocene). Vertical symbiont transmission may therefore have facilitated long-distance dispersal since both partners disperse together. In contrast to their termite hosts, the fungal symbionts have colonized Madagascar multiple times, suggesting that the presence of fungus-growing termites may have facilitated secondary colonizations of the symbiont. Our findings indicate that the absence of the right symbionts in a new environment can prevent long-distance dispersal of symbioses relying on horizontal symbiont acquisition.
共生白蚁（Macrotermitinae）与其共生真菌（Termitomyces）之间的共生关系始于非洲。白蚁已在马达加斯加进行了二次殖民，而在这个孤立的岛屿上只发现了非洲共生真菌中的一小部分。成功的长途殖民可能受到白蚁与其真菌共生体之间的强制性相互作用以及大多数物种（水平共生体传播）从环境中获得这些共生体的需求的严重限制。与这一假设一致，我们表明，马达加斯加现存的所有共生白蚁物种都是属于仅具有垂直共生体传播的两个组之一的白蚁的单一殖民事件的结果，我们将这一事件追溯到大约 1300 万年前（中/上新世）。因此，垂直共生体传播可能促进了长途扩散，因为两个伙伴一起扩散。与它们的白蚁宿主不同，真菌共生体已经多次殖民马达加斯加，这表明共生白蚁的存在可能促进了共生体的二次殖民。我们的研究结果表明，在新环境中缺乏合适的共生体可能会阻止依赖水平共生体获取的共生关系的长途扩散。
