Abstract

Gastridium P. Beauv. is a Mediterranean-Paleotropical member of the Poaceae family, whose species number and diversity are still imperfectly known. We examined patterns of DNA diversity at two plastid (trnH-psbA, trnL-F) and one nuclear (ITS) DNA markers in 44 individuals of the four taxa (Gastridium lainzii, G. phleoides, G. scabrum, G. ventricosum) recently recognised by different authors, based on morpho-ecological descriptors. Diversity data were explored with multiple statistical and phylogenetic tools, and integrated with available GenBank sequences of Gastridium and closely related genera. Despite the limited variability detected, evidence of within-taxon genetic cohesion and estimates of molecular divergence comparable with those of species in the same subtribal lineage (Agrostidinae) were recovered. The identified plastid genealogies are congruent with a subdivision of the genus into four distinct species, coherently with collected morphological descriptors. Phylogenetic reconstructions with ITS were less corresponding to the four taxa, possibly due to reticulation and polyploidization. The broader plastid and nuclear tree topologies were consistent with previous assessments, highlighting the overall little resolution of species and genera within Agrostidinae, and the close relationships shared by Gastridium and Triplachne. The hypothesis of closely related, but separately evolving, lineages within Gastridium is discussed, suggesting a re-evaluation of its current taxonomy.

摘要

Gastridium P. Beauv。是禾本科的地中海-古热带成员，其物种数量和多样性仍不完全清楚。我们研究DNA多样性的图案在两个质体（TRN H- PSB A，TRN L-F）和一个核（ITS）DNA中的四个分类单元44组的个体标记（Gastridium lainzii，G. phleoides，G. scabrum，G. ventricosum）最近基于形态生态描述符被不同作者认可。利用多种统计和系统发育工具探索多样性数据，并与胃Gas的可用GenBank序列整合和密切相关的属。尽管检测到的变异性有限，但仍获得了与同一部落宗族（Agrostidinae）中的物种相比的分类内遗传凝聚力和分子差异估计的证据。所识别的质体谱系与该属细分为四个不同的物种，与所收集的形态学描述符一致。用ITS进行的系统发育重建对应于四个分类单元的可能性较小，这可能是由于网状结构和多倍体化所致。较宽的质体和核树拓扑结构与以前的评估相一致，强调了农杆菌科中物种和属的总体分辨率不高，以及胃tri和Triplachne的密切关系。讨论了腹足纲内密切相关但又不断发展的世系的假说，这提示了对其当前分类法的重新评估。