Crozier R H, Dobric N, Imai H T, Graur D, Cornuet J M, Taylor R W
Department of Genetics and Human Variation, La Trobe University, Bundoora, Victoria, Australia.
Mol Phylogenet Evol. 1995 Mar;4(1):20-30. doi: 10.1006/mpev.1995.1003.
Australian ants of the Myrmecia pilosula species complex include some individuals (in M. croslandi) with the lowest possible metazoan chromosome number of 2n = 2. Others in this cluster of sibling species have much higher numbers, the known maximum being 2n = 32. Two species (M. pilosula and M. 'banksi') are believed on cytogenetic and morphological grounds to have hybridized over a long period. To investigate the phylogeny and age of this group relative to the congeneric outgroup species M. gulosa, we sequenced part of the cytochrome b gene and the intergenic sequence between it and a primer anchored on the nearby tRNA(UCNSer) gene and analyzed the coding region using bootstrapped parsimony and neighbor-joining trees using the numbers of synonymous and nonsynonymous codons per site. The intergenic space demonstrated a profusion of repeated sequences, and only very closely related sequences (as judged by that for cytochrome b) showed detectable similarity at this almost 100% A+T region. In agreement with predictions from karyotype studies, the phylogenetic analyses showed that M. croslandi is the sister group to the other siblings; the time of separation of M. croslandi from the rest of the pilosula group is unexpectedly ancient. Other relationships were poorly resolved, but the results suggest that M. 'banski' and M. pilosula cluster together, as expected on cytogenetic grounds, and the tentative suggestion of close affinity of the M. pilosula samples and two "PB" samples supports derivation of PB from female M. pilosula and male M. 'banksi.'
澳大利亚毛蚁属（Myrmecia pilosula）物种复合体中的蚂蚁，包括一些个体（克罗斯兰毛蚁，M. croslandi），其后生动物染色体数目低至2n = 2，为已知最低。该姐妹物种群中的其他个体染色体数目则高得多，已知最高为2n = 32。基于细胞遗传学和形态学依据，人们认为两个物种（毛蚁，M. pilosula和“班克斯毛蚁”，M. “banksi”）长期以来发生了杂交。为了研究该类群相对于同属外群物种古氏毛蚁（M. gulosa）的系统发育和演化年龄，我们对细胞色素b基因的部分序列以及它与锚定在附近tRNA(UCNSer)基因上的引物之间的基因间序列进行了测序，并使用每个位点的同义密码子和非同义密码子数量，通过自展简约法和邻接法分析了编码区。基因间区域显示出大量重复序列，只有非常密切相关的序列（根据细胞色素b判断）在这个几乎100%为A+T的区域表现出可检测到的相似性。与核型研究的预测一致，系统发育分析表明，克罗斯兰毛蚁是其他姐妹物种的姐妹群；克罗斯兰毛蚁与毛蚁属其他物种的分离时间出人意料地古老。其他关系解析得很差，但结果表明，“班克斯毛蚁”和毛蚁聚集在一起，这在细胞遗传学上是预期的，并且毛蚁样本和两个“PB”样本密切相关的初步推测支持了PB是由雌性毛蚁和雄性“班克斯毛蚁”衍生而来的观点。
