Patterns of hybrid formation among cryptic species of bird-nest fern,Asplenium niduscomplex (Aspleniaceae), in West Malesia

Abstract

In order to clarify patterns of hybrid formation in the Asplenium nidus complex, artificial crossing experiments were performed between individuals of genetically differentiated groups based on the sequence of the rbcL gene, including A. australasicum from New Caledonia, A. setoi from Japan and several cryptic species in the A. nidus complex. No hybrid plants were obtained in crosses between nine of the 16 pairs. Even for pairs that generated hybrids, the frequency of hybrid formation was lower than expected given random mating, or only one group was able to act as the maternal parent, when the genetic distance (Kimura's two parameter) between parental individuals was at least 0.006. Sterile hybrids were produced by three pairs that were distantly related but capable of forming hybrids. Considering the results of the crosses together with the genetic distance between the parental individuals, it seems that the frequency of hybrid formation decreases rapidly with increasing divergence. The frequency of hybrid formation has not been previously examined in homosporous ferns, but it seems that a low frequency of hybrid formation can function as an important mechanism of reproductive isolation between closely related pairs of species in the A. nidus complex in addition to hybrid sterility.

Species boundaries and frequency of hybridization in the Dryopteris carthusiana (Dryopteridaceae) complex: A taxonomic puzzle resolved using genome size data

“…On the contrary, the lack of genome identity between D. carthusiana and D. expansa may reduce the likelihood of successful hybridization between them. A congruence between the frequency of interspecifi c hybridization and species relationship has been documented in several plant groups, both fl owering ( Mosseler, 1990 ) and spore-bearing ( Yatabe et al, 2009 ).…”

Phylogeny of the fern family Aspleniaceae in Australasia and the south-western Pacific

“…Section Thamnopteris was previously found not to be monophyletic with predominantly South-east Asian taxon sampling (Murakami et al 1999a;Yatabe et al 2009). In the present study, monophyly of section Thamnopteris was not supported.…”

“…Murakami 1995;Murakami et al 1999aMurakami et al , 1999bPinter et al 2002;Van den heede et al 2003;Schneider et al 2004Schneider et al , 2005Bellefroid et al 2010;Dong et al 2012), including New Zealand (Perrie and Brownsey 2005;Shepherd et al 2008aShepherd et al , 2008bPerrie et al 2010). However, the phylogenetic positions of very few Aspleniaceae from other areas of ASWP have been studied through DNA sequencing (Schneider et al 2004;Schneider et al 2005;Yatabe et al 2009). …”

Profundizando en la evolución de los helechos: un enfoque mecanicista a los principales conceptos y técnicas de estudio

“…Isozyme markers allowed much more accumulation of genetic insights to understand the mating system and consequences of outcrossing as a main mechanism favou-ring intergametophytic mating in the main homosporous fern lineages, in contrast to previous inbreeding assumptions (Soltis & Soltis 1990, Jiménez et al 2009, Yatabe et al 2009). In the decade of 1980 morphological discrimination of hybrids was improved with quantitative analysis of morphometric characters.…”

“…After a long time of discussion, and only when reliable molecular information has allowed to built a robust relationships hypothesis, this elusive "plant" has been reconstructed extrapolating likely character states from extant species (Stein et al 2010) Even when putative parentals seem to be well established by application of one or more of the above cited techniques, the ultimate, unequivocal and certain proof should come from the verification that a sexual contact is possible between gametophytes of both species. In nature, this evidence is almost impossible to achieve, but there are some striking in vitro experiments that have developed artificial hybrids by cultivating female gametophytes of one species close to male gametophytes of the other species (Herrero et al 2001, Yatabe et al 2009). This information was used along other datasets to confirm the involvement of the analysed plants in forming the hybrids.…”