PNAS:南瓜、葫芦与小果南瓜如何避免了灭绝

摘要 : 英国威大学生命科学学院一项研究提出，如果不是因为人类的驯化，南瓜、葫芦与小果南瓜的两种野生先驱可能已经灭绝了。

英国威大学生命科学学院一项研究提出，如果不是因为人类的驯化，南瓜、葫芦与小果南瓜的两种野生先驱可能已经灭绝了。Logan Kistler及其同事使用遗传分析研究了这些南瓜属的植物如何适应了大约1万年前大型哺乳动物的灭绝。尽管有许多现代驯化的南瓜属世系在农场和花园里繁盛，它们的祖先野南瓜是罕见的。对91种古代南瓜、现代野生南瓜和现代驯化南瓜样本的遗传分析表明，人类在美洲各地的几个时期驯化了这些植物。此外，目前未知的许多古代野生品种在大型食草动物灭绝之前广泛分布。这些极苦的野生南瓜的衰退恰逢人类驯化了这种植物。为了检验大型食草动物的消失是否与野生南瓜的衰退有关，这组作者分析了各种哺乳动物的苦味觉基因库。在伴随着全新世出现的环境巨变之后遗留下来的更小的哺乳动物比如今灭绝了的巨型动物有更多的苦味觉基因，后者生活在丰富的野南瓜中间，很可能通过它们的大便散布南瓜种子。这组作者提出，没有人类的驯化，某些南瓜属植物可能不会存活下来。

原文链接：

Gourds and squashes (Cucurbita spp.) adapted to megafaunal extinction and ecological anachronism through domestication

原文摘要：

The genus Cucurbita (squashes, pumpkins, gourds) contains numerous domesticated lineages with ancient New World origins. It was broadly distributed in the past but has declined to the point that several of the crops’ progenitor species are scarce or unknown in the wild. We hypothesize that Holocene ecological shifts and megafaunal extinctions severely impacted wild Cucurbita, whereas their domestic counterparts adapted to changing conditions via symbiosis with human cultivators. First, we used high-throughput sequencing to analyze complete plastid genomes of 91 total Cucurbita samples, comprising ancient (n = 19), modern wild (n = 30), and modern domestic (n = 42) taxa. This analysis demonstrates independent domestication in eastern North America, evidence of a previously unknown pathway to domestication in northeastern Mexico, and broad archaeological distributions of taxa currently unknown in the wild. Further, sequence similarity between distant wild populations suggests recent fragmentation. Collectively, these results point to wild-type declines coinciding with widespread domestication. Second, we hypothesize that the disappearance of large herbivores struck a critical ecological blow against wild Cucurbita, and we take initial steps to consider this hypothesis through cross-mammal analyses of bitter taste receptor gene repertoires. Directly, megafauna consumed Cucurbita fruits and dispersed their seeds; wild Cucurbita were likely left without mutualistic dispersal partners in the Holocene because they are unpalatable to smaller surviving mammals with more bitter taste receptor genes. Indirectly, megafauna maintained mosaic-like landscapes ideal for Cucurbita, and vegetative changes following the megafaunal extinctions likely crowded out their disturbed-ground niche. Thus, anthropogenic landscapes provided favorable growth hABItats and willing dispersal partners in the wake of ecological upheaval.

doi: 10.1073/PNAS.1516109112

作者：Logan Kistler

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