Abstract：
Phylogenetic evidence indicates that free-living nematodes gave rise to parasitic nematodes where parasitism evolved independently at least 15 times. The high level of genetic and biological diversity among parasites dictates an equally high level of diversity in the transition to parasitism. We previously hypothesized that horizontal gene transfer (HGT) played an important role in the evolution of parasitism among early ancestors of Trichinella, mediated by an interplay of ecological and evolutionary pathways that contributed to persistence and diversification. We propose that host selection may have been associated with the metabolism of ammonia and engender a new paradigm whereby the reprogrammed nurse cell is capable of generating cyanate thereby enabling the importance of the Trichinella cyanase in the longevity of the cell. Parasites and parasitism have revealed considerable resilience against a backdrop of climate change and environmental perturbation. Here we provide a putative link between key periods in the evolution of Trichinella and major geological and climatological events dating back 500 million years. A useful lens for exploring such ideas, the Stockholm Paradigm, integrates Ecological Fitting (a foundation for host colonization and diversification), the Oscillation Hypothesis (recurring shifts between trends in generalization and specialization relative to host range), the Geographic Mosaic Theory of Coevolution (microevolutionary co-adaptive processes), and the Taxon Pulse Hypothesis (alternating events of biotic expansion i.e., exploitation in evolutionary and ecological time). Here we examine how one or more of these interactive theories, in a phylogenetic-historical context and in conjunction with HGT, may help explain the scope and depth of diversity among Trichinella genotypes.
摘要：
系统发育证据表明，自由生活的线虫产生了寄生线虫，其中寄生独立进化了至少15次。寄生虫之间的高度遗传和生物多样性决定了向寄生虫过渡时同样高度的多样性。我们先前假设水平基因转移（HGT）在旋毛虫早期祖先的寄生进化中起重要作用，由生态和进化途径的相互作用介导，这些途径促进了持久性和多样化。我们建议宿主的选择可能与氨的代谢有关，并产生了一种新的范例，即重新编程的护士细胞能够产生氰酸盐，从而使旋毛虫氰化酶在细胞寿命中的重要性得以体现。寄生虫和寄生虫在气候变化和环境扰动的背景下显示出相当大的复原力。在这里，我们提供了旋毛虫进化的关键时期与5亿年前的主要地质和气候事件之间的假定联系。探索这些想法的有用镜头，斯德哥尔摩范式，整合了生态拟合(寄主殖民和多样化的基础)，振荡假说(相对于宿主范围，泛化和专业化趋势之间的反复变化)，共同进化的地理马赛克理论(微观进化共同适应过程)，和TaxonPulse假说(生物扩增的交替事件，即，进化和生态时期的开发)。在这里，我们研究这些互动理论中的一个或多个，在系统发育历史背景下，结合HGT，可能有助于解释旋毛虫基因型之间多样性的范围和深度。
