Reticulate evolution in the Pteris fauriei group (Pteridaceae)

Abstract

The Pteris fauriei group (Pteridaceae) has a wide distribution in Eastern Asia and includes 18 species with similar but varied morphology. We collected more than 300 specimens of the P. fauriei group and determined ploidy by flow cytometry and inferred phylogenies by molecular analyses of chloroplast and nuclear DNA markers. Our results reveal a complicated reticulate evolution, consisting of seven parental taxa and 58 hybrids. The large number of hybrid taxa have added significant morphological complexity to the group leading to difficult taxonomic issues. The hybrids generally had broader ranges and more populations than their parental taxa. Genetic combination of different pairs of parental species created divergent phenotypes of hybrids, exhibited by both morphological characteristics and ecological fidelities. Niche novelty could facilitate hybrid speciation. Apogamy is common in this group and potentially contributes to the sustainability of the whole group. We propose that frequent hybridizations among members of the P. fauriei group generate and maintain genetic diversity, via novel genetic combinations, niche differentiation, and apogamy.

New taxonomic treatments in the Pteris fauriei group (Pteridaceae)

“…Chao et al (2017) emphasized that widely ovate sterile lamina (the ratio of length to width approximately 5:4) was the critical diagnostic character of P. latipinna. Simultaneously, P. austrotaiwanensis was found to be distinct from P. latipinna based on the molecular data from two cpDNA regions (Chao et al, 2021) and nrDNA sequences (Chao et al 2022), and thus was designated as a species, despite its similarity to P. latipinna in morphology and habitat. From the study of Chao et al (2017Chao et al ( , 2021, we can see that it is difficult to delimit P. fauriei var.…”

“…Based on the results of Chao et al (2021Chao et al ( , 2022 and Zhang & Zhang (2018), thirty-seven samples representing 21 taxa in the P. fauriei group, including one sample of outgroup P. puberula Ching (1941: 52) were selected for phylogenetic study (Table 2). Twelve Pteris samples were collected from the field by us and five chloroplast DNA (cpDNA) regions (atpA, matK, rbcL, rps4-trnS & trnL-trnF) were obtained using the primers and protocol in Zhang et al (2015).…”

“…Twelve Pteris samples were collected from the field by us and five chloroplast DNA (cpDNA) regions (atpA, matK, rbcL, rps4-trnS & trnL-trnF) were obtained using the primers and protocol in Zhang et al (2015). The cpDNA sequences of other Pteris samples were downloaded from GenBank mentioned in previous studies (Chao et al, 2014;Zhang et al, 2015;Chao et al, 2017;Zhang & Zhang 2018, Chao et al, 2021. DNA sequences were aligned with BioEdit v7.2.5 and manually edited.…”

“…According to Yang (2011), lophate decoration, ornate-lophate decoration, distal ridges, proximal ridges and laesural ridges were regarded as the ridge-like decorations. The sexual Pteris plants produce 64 spores per sporangium and apogamous plants produce 32 or fewer spores per sporangium (Chao et al 2022), which was used to infer the reproductive mode of each sample in this study.…”

“…Pteris fauriei var. chinensis was later treated as a synonym of P. latipinna without molecular evidence, but based on their type materials, which were considered to be identical (Chao et al, 2021). Chao et al (2017) emphasized that widely ovate sterile lamina (the ratio of length to width approximately 5:4) was the critical diagnostic character of P. latipinna.…”