First insights into the evolutionary history of the <I>Davallia repens</I> complex

Abstract

Davallia repens and its close relatives have been identified as a species complex in this study because of the existence of continuously morphological variation. To decipher its evolutionary history, integrated methodologies were applied in this study including morphology, cytology, reproductive biology and molecular phylogeny. Analysis of morphological characters reveals several important discriminating characteristics, such as the shape of stipe scales, frond and indusium. Both diploid and polyploid forms are present in the complex and reproduce sexually and by apogamy, respectively. The incongruence between cpDNA and nDNA phylogeny indicates a hybrid origin for most polyploid individuals. Based on the present results, we hypothesize that there were at least two ancestral lineages distributed in the Malesian region. Through hybridization, polyploidization and apogamy, some polyploid genotypes dispersed outwards to shape the extant distribution.

Low‐copy nuclear data confirm rampant allopolyploidy in the Cystopteridaceae (Polypodiales)

“…With the recent availability of data from the nuclear genome (Schuettpelz & al., 2008;Rousseau-Gueutin & al., 2009;Duarte & al., 2010;Lo & al., 2010;Chen & al., 2012;Zimmer & Wen, 2012;Cacho & Strauss, 2013;Rothfels & al., 2013a), plant systematists have novel opportunities to elucidate complex cases of reticulate evolution. Phylogenetic data from low-copy nuclear genes is proving particularly useful in groups where morphological discontinuities have been obscured by past reticulation events (e.g., Adjie & al., 2007;Brysting & al., 2007;Kim & al., 2008;Schuettpelz & al., 2008;Shepherd & al., 2008;Grusz & al., 2009;Guggisberg & al., 2009;Ishikawa & al., 2009;Beck & al., 2010;Juslén & al., 2011;Nitta & al., 2011;Chao & al., 2012;Dyer & al., 2012;Li & al., 2012;Sessa & al., 2012;Lee & Park, 2013;Zhang & al., 2013;Chen & al., 2014;Hori & al., 2014).…”

Phylogenetic analyses place the monotypic Dryopolystichum within Lomariopsidaceae

“…The collection of SITW10443 was made under the “Census and Classification of Plant Resources in the Solomon Islands” project (http://siflora.nmns.edu.tw/). Mitotic chromosomes were counted from these cultivated plants following the protocol of Chen et al (2014).…”

“…5). In Polypodiales, sporogenesis leading to the formation of 64 spores in a sporangium is by far the most common pattern of sexually reproducing species, e.g., Aspleniaceae (Gabancho et al 2010), Athyriaceae (Kato et al 1992, Takamiya et al 1999), Davalliaceae (Chen et al 2014), Dryopteridaceae (Lu et al 2006), Polypodiaceae (Wang et al 2011), Pteridaceae (Huang et al 2006), and Thelypteridaceae (Ebihara et al 2014). Cases of sporogenesis resulting in 32 spores per sporangium are known from a few Polypodiales ferns but all belong to the suborders Lindsaeineae and Pteridineae, i.e., Lindsaeaceae (Lin et al 1990), Cystodiaceae (Gastony 1981), and Ceratopteris (Pteridaceae; Lloyd 1973).…”

A current perspective on apomixis in ferns

“…Meanwhile, the development of many low‐copy, nuclear DNA markers (Ishikawa et al, ; Schuettpelz et al, ; Chen et al, ; Rothfels et al, ) has dramatically streamlined the inference of bi‐parental precursors to extant polyploid lineages, helping to elucidate the independent origins that often comprise apomictic polyploid taxa (e.g., in Cheilanthes [= Myriopteris Fée emend. Grusz & Windham], Grusz et al, ; Crepidomanes , Nitta et al, ; Astrolepis , Beck et al, ; Pteris , Chao et al, ; Asplenium , Dyer et al, ; Dryopteris , Ebihara et al, , Hori et al, ; and Davallia , Chen et al, ). More recently, the adoption of genotyping‐by‐sequencing has also proven powerful for exploring the evolution of widespread apomictic taxa and deciphering cryptic lineages in ferns (Wickell, ).…”

“…Using flow cytometry, they also documented viable polyhaploid (2.5x) gametophytes derived through apomixis from a 5x parent. Many other studies of apomictic ferns have likewise adopted flow cytometry (standardized with known chromosome counts) for genome size estimation and ploidy-level determination (Schneller & Krattinger, 2010;Ootsuki et al, 2011;Chao et al, 2012;Dyer et al, 2013;Chen et al, 2014;Hori et al, 2014Hori et al, , 2015. And though flow cytometry has greatly improved our understanding of these polyploid apomictic groups, recent work by Dyer et al (2013) cautions that inferring ploidy-level using correlations between nuclear DNA content and spore length should be restricted to intraspecific comparisons.…”