Isozyme variability among cryptic species ofBotrychiumsubgenusBotrychium(Ophioglossaceae)

Abstract

The systematics of Botrychium subgenus Botrychium has been controversial, primarily because reduction in frond size and complexity has limited the number of characters available for discrimination of species. The recognition of many polyploid species has magnified the difficulty of classification because allopolyploids are often morphologically intermediate between their progenitor diploids. In order to evaluate species limits and sectional boundaries, we surveyed and compared 16 of the 24 currently recognized species for isozymic variation. Little or no intrapopulational variation was detected, but the variation present was consistent with the hypothesis that Botrychium species are primarily inbreeding. Interspecific comparisons distinguished six diploid species and provided evidence of molecular differentiation between the cryptic sister species B. lunaria and B. crenulatum. Evidence of possible progenitor/descendant relationships was found for certain diploid/polyploid relationships. Using enzyme bands shared between species, realignment of the sectional assignment of several species is proposed. Anomalous banding patterns in certain individuals suggested that gene silencing or homoeologous chromosome pairing might be operating in B. minganense, B. hesperium, and B. matricariifolium. Isozyme data also showed that some populations of species presumed to be uniformly diploid possessed isozyme patterns typical of polyploids. All available molecular data indicate that members of Botrychium subgenus Botrychium are actively evolving at diploid and polyploid levels.

Living on the edge: Conservation genetics of seven thermophilous plant species in a High Arctic archipelago

“…It is somewhat surprising to observe such a strong founder/bottleneck effect in B. lunaria as we expected levels of genetic variation to be extremely low throughout the distribution range due to intragametophytic self-fertilization (see e.g. Soltis et al 1988; Hauk and Haufler 1999; Farrar 2006). Contrary to what we predicted, most B. lunaria populations actually contain many AFLP multilocus phenotypes and a higher proportion of within population genetic variation relative to among population genetic variation.…”

Independent origins of tetraploid cryptic species in the fern Ceratopteris thalictroides

“…In recent decades cytotaxonomy, enzyme electrophoresis, and DNA sequence data have revealed cryptic species in many fern lineages, such as the Adiantum pedatum complex (Paris and Windham 1988), Botrychium subg. Botrychium (Hauk and Haufler 1999), Gymnocarpium dryopteris (Pryer and Haufler 1993), Polypodium vulgare (Haufler and Windham 1991), Athyrium oblitescens (Kurihara et al 1996), Asplenium nidus complex (Yatabe et al 2001), and Ceratopteris thalictroides (Masuyama et al 2002). This flush of recent discoveries suggests that cryptic species could be common in ferns.…”

Genetic and genomic aspects of hybridization in ferns

“…Such is the case for the allotetraploid Dryopteris celsa , which has two alleles of phosphoglucoisomerase ( Pgi‐2 ) that are not expressed by either of its progenitors (Werth, ). Loss of homoeolog expression, unbalanced heterozygotes, and the presence of orphan alleles are commonly reported in fern reticulate complexes, with other well‐documented examples in Dryopteris (Darnaedi et al, ; Werth, ; Jiménez et al, ), Polypodium (Bryan & Soltis, ; Haufler et al, ), Pellaea (Gastony, ), Polystichum (Soltis et al, ), Botrychium (Hauk & Haufler, ), and Asplenium (Herrero et al, ; Van den heede et al, ).…”

“…For ten other isozyme loci examined, intraspecific variation in banding patterns in the allotetraploid species largely reflected the interspecific variation present in their putative diploid progenitors, and was offered as evidence for multiple, independent origins of the allotetraploid species (see section Multiple Origins of Hybrid Fern Taxa). Isozyme electrophoresis was subsequently used to identify the progenitors of allopolyploid species and hybrids in numerous temperate and tropical genera, including Dryopteris (Darnaedi et al, ; Werth, ; Jiménez et al, ; Stein et al, ), Cystopteris (Haufler et al, ; Haufler & Windham, ), Polypodium (Bryan & Soltis, ; Haufler & Windham, ; Haufler et al, ), Adiantum (Paris & Windham, ), Pellaea (Gastony, ), Hemionitis (Ranker et al, ), Polystichum (Soltis et al, , ; Barrington, ), Gymnocarpium (Pryer & Haufler, ), Botrychium (Hauk & Haufler, ), and other groups of Asplenium (Herrero et al, ; Van den heede et al, , ).…”

“…Notably, Werth's isozyme study of the Appalachian Asplenium complex is the first documented example of multiple origins in a vascular plant (Werth et al, , 1985b). Multiple origins have subsequently been proposed for numerous ferns such as Cystopteris tennesseensis (Haufler et al, ), Polystichum californicum (Soltis et al, ), Botrychium minganense (Hauk & Haufler, ), and Asplenium majoricum (Hunt et al, ).…”