Phylogenetic Systematics of South American Akodontine Rodents (Muridae: Sigmodontinae)

南美鼠形啮齿动物辐射的大鼠和小鼠 (the主要是地方性亚科Sigmodontinae）代表了一个非常 大量的生物体， 从亚洞穴动物到水生动物再到树栖动物， 亚马逊河流域的热带雨林， 安第斯山脉的最高处。 这种适应性辐射 包括大约70个属，其中大部分通常分为 五大血统之一。 在这些动物中， 其中最多样和最古老的，与现代形式的化石 可以追溯到六百万年前的阿根廷 尽管 这一谱系的多样性得到广泛承认，大多数分类群是 既知之甚少，定义，和系统发育，生态， 它们生物学的生活史方面要么完全未知 或者只是勉强如此。 这对阿肯丁人来说尤其如此 组，辐射约15属，约50种，主要是 局限于从北方安第斯山脉到 巴塔哥尼亚大草原。 目前的研究将利用DNA 序列，从线粒体内的几个基因获得， 通过聚合酶链反应技术， 实现以下一组总体目标：（1）建立一个 所有属之间的系统发育关系假说， 复杂的大多数物种;（2）执行文本的模型， 物种的形成是由于在强生境中的分歧 梯度，使用选定的物种栖息在陡峭的东部 以安第斯山脉的坡度为例;以及（3）确定是否 特殊的颅骨构造， 在这个组合内的分类群共享一个接近的共同祖先或 这种类型的颅骨结构是否在 不同的血统 这项研究令人兴奋的方面是， 由于DNA可以从干燥的皮肤中提取并扩增， 已经保存在自然历史收藏中的标本， 现已灭绝或极其稀有的分类群可以用 以前从未有过。 五是关注的对象， 例如，每一个已知的形式非常少的标本，其中大多数 只在偏远地区采集过一次 因此， 这是第一次对群体内部关系的研究， 以比较的方式研究现存的分类群。

Rats and mice of the South American murid rodent radiation (the largely endemic subfamily Sigmodontinae) represent a very large array of organisms that range in morphologic adaptations from subfossorial to aquatic to arborel and in habitat from tropical rainforest of the Amazon Basin to puna grassland in the highest elevations of the Andes. This adaptive radiation comprises some 70 genera, most of which are commonly divided into one of five major lineages. Among these, the akodontines are among the most diverse and oldest, with fossils of modern forms extending back some 6 million years in Argentina. Despite the widely recognized diversification of this lineage, most taxa are both poorly known and defined, and phylogenetic, ecologic, and life history aspects of their biology are either totally unknown or only barely so. This is particularly true for the akodontine group, a radiation of some 15 genera and about 50 species largely confined to grassland habitats from the northern Andes to the Patagonian steppes. The present research will utilize DNA sequences, obtained from several genes within the mithochrondrial genome by the technique of the Polymerase Chain Reaction, to address the following set of general goals: (1) establish an hypothesis of phylogenetic relationships among all genera and most species of the complex; (2) perform a text of the model of species formation resulting from divergence across strong habitat gradients, using selected species inhabiting the steep eastern slope of the Andes as exemplars; and (3) determine whether or not particular cranial conformations that identify highly derived taxa within this assemblage share a close common ancestor or whether this type of cranial structure has evolved repeatedly in separate lineages. The exciting aspect of this research is that, since DNA can be extracted and amplified from dried skin specimens already preserved within natural history collections, now extinct or exceedingly rare taxa can be compared in ways never before available. Five of the genera of concern, for example, are each known form very few specimens, most of which only collected once from very remote areas. This is, therefore, the first study of relationships within the group to examine all extant taxa in a comparative way.