Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20560, USA.
Johns Hopkins University, Baltimore, Maryland, 21218, USA.
Am J Bot. 2021 Nov;108(11):2220-2234. doi: 10.1002/ajb2.1761. Epub 2021 Nov 3.
Apomixis (asexual reproduction by seed, spore, or egg) has evolved repeatedly across the tree of life. Studies of animals and angiosperms show that apomictic lineages are often evolutionarily short-lived and frequently exhibit different distributions than their sexual relatives. However, apomixis is rare in these groups. Less is known about the role of apomixis in the evolution and biogeography of ferns, in which ~10% of species are apomictic. Apomixis is especially common in the fern genus Pteris (34-39% of species); however, because of the limited taxonomic and geographic sampling of previous studies, the true frequency of apomixis and its associations with geography and phylogeny in this lineage remain unclear.
We used spore analyses of herbarium specimens to determine reproductive mode for 127 previously unsampled Pteris species. Then we leveraged biogeographic and phylogenetic analyses to estimate the global distribution and evolution of apomixis in Pteris.
Among all Pteris species examined, we found that 21% are exclusively apomictic, 71% are exclusively sexual, and 8% have conflicting reports. Apomixis is unevenly distributed across the range of the genus, with the Paleotropics exhibiting the highest frequency, and has evolved numerous times across the Pteris phylogeny, with predominantly East Asian and South Asian clades containing the most apomictic species.
Apomixis arises frequently in Pteris, but apomictic species do not appear to diversify. Species that encompass both apomictic and sexual populations have wider ranges than exclusively sexual or apomictic species, which suggests that sexual and apomictic ferns could occupy separate ecological niches.
无融合生殖（通过种子、孢子或卵进行无性繁殖）在生命之树上多次进化。对动物和被子植物的研究表明，无融合生殖谱系通常在进化上是短暂的，并且经常表现出与有性亲属不同的分布。然而，无融合生殖在这些群体中很少见。关于无融合生殖在蕨类植物的进化和生物地理学中的作用知之甚少，其中约 10%的物种是无融合生殖的。无融合生殖在蕨类植物属凤尾蕨属（Pteris）中尤为常见（34-39%的物种）；然而，由于之前研究的分类和地理采样有限，该谱系中无融合生殖的真实频率及其与地理和系统发育的关联仍不清楚。
我们使用对标本的孢子分析来确定 127 种以前未采样的凤尾蕨属物种的繁殖模式。然后，我们利用生物地理和系统发育分析来估计无融合生殖在凤尾蕨属中的全球分布和进化。
在所检查的所有凤尾蕨属物种中，我们发现 21%的物种是纯无融合生殖的，71%的物种是纯有性生殖的，8%的物种有相互矛盾的报道。无融合生殖在该属的分布范围不均匀，热带地区的分布频率最高，并且在凤尾蕨属的系统发育中多次进化，主要的东亚和南亚分支包含最多的无融合生殖物种。
无融合生殖在凤尾蕨属中频繁发生，但无融合生殖的物种似乎没有多样化。包含有性和无性种群的物种的分布范围比纯有性或无性的物种更广，这表明有性和无性的蕨类植物可能占据不同的生态位。
