Flow cytometry confirms reticulate evolution and reveals triploidy in Central European Diphasiastrum taxa (Lycopodiaceae, Lycophyta)

Abstract

Diploid hybrids have retained their genetic and morphological identites throughout their Central European range, and thus no indications for diploid backcrossing were found. The triploid hybrids have probably originated from backcrossing between a diploid gametophyte of a hybrid (derived from a diplospore) and a haploid gametophyte of a diploid parental species. By repeated crossing events, reticulate evolution patterns arise that are similar to those known for a number of ferns.

Continuous Morphological Variation Correlated with Genome Size Indicates Frequent Introgressive Hybridization among Diphasiastrum Species (Lycopodiaceae) in Central Europe

“…A possible strong influence of aneuploidy could also be ruled out based on results of morphometrics, where absolute genome size explains a major part of the observed variation. In addition, our genome size values correspond to the results of an independent flow cytometric survey of the same taxa of Diphasiastrum [20]. Possibility of samples with different ploidy level occurrence is highly improbable due to generally lower range of genome size values.…”

“…This study of a limited sample set also indicates that certain levels of recent hybridization and backcrossing exist within European Diphasiastrum , however, leaving unknown its frequency and variation patterns in natural populations. On the contrary, discrete variation in genome size in several parts of Europe indicates only primary hybridization with no hint of backcrossing (except for a few rare triploid hybrids) or introgression [20]. Nevertheless, as introgression leads to continuous patterns of variation in species traits (including genome size; [61], sufficiently large and carefully designed sampling is crucial for its discovery.…”

The Genus Diphasiastrum and Its Lycopodium Alkaloids

“…They are spore forming, slow-growing vascular plants dating back to the late Silurian geological period about 300-400 million years ago. Fossil records show that they lived amongst the earliest known land plants and contributed to a large part of the vegetation on Earth in pre-angiosperm times [2][3][4]. Although many species and groups of club mosses are now extinct, a small part of them has survived.…”

Distributions of vascular plants in the Czech Republic

“…In general, the central-European genus Diphasiastrum comprises three diploid species, namely D. alpinum, D. complanatum and D. tristachyum, and their diploid hybrids D. ×issleri, D. ×oellgaardii, D. ×zeilleri, previously considered as separate species. The hybrids are capable of at least partial spontaneous reproduction, may occur independently of the parental species (Bennert 1999) and are even able to form triploid hybrids with them (Bennert et al 2011). The previously supposed introgressive hybridization within the species and hybrids (Aagaard et al 2009, Hanušová et al 2014 was not confirmed recently (Schnittler et al 2019).…”

“…Because D. complanatum, D. tristachyum and the three hybrids with their involvement are morphologically not sharply separated, their identification is often difficult (Hanušová et al 2014). Despite the fact that all these taxa are homoploid, the genome size can be used for identification (Bennert et al 2011); however, there are also overlaps in this character (Hanušová et al 2014). In the Czech Republic members of the D. complanatum agg.…”