Is Betula carpatica genetically distinctive? A morphometric, cytometric and molecular study of birches in the Bohemian Massif with a focus on Carpathian birch

Abstract

Until recently, Czech taxonomists often treated Betula carpatica as a distinct species. Several morphological traits for distinguishing B. carpatica from B. pubescens or other birches are described in literature; however, it has been proven impossible to reliably identify B. carpatica in the field. With the use of morphological and molecular approaches, we intended to assess the position of B. carpatica in the context of other birch taxa reported from the Bohemian Massif and to find more reliable morphological traits for their identification. In our dataset, we distinguished the following birch taxa referred to in the recent Czech literature: B. pendula, B. pubescens, B. carpatica, B. oycoviensis, B. nana, B. petraea and B. ×seideliana. We complemented them with triploids and several diploid and tetraploid “working units” into which we included intermediate individuals that in terms of morphology did not unambiguously match any of the abovementioned birch taxa. Holoploid genome size was measured to determine the ploidy level. To identify genetic relationships between selected taxa and “working units”, microsatellite analyses were performed. Model-based STRUCTURE analysis together with principal coordinates analysis (PCoA) based on genetic distances was performed to identify the similarities in multilocus genotype data between groups distinguished in the dataset. The applied analyses were not able clearly to distinguish any group among tetraploid individuals. In this light, it was of no use to search for any more reliable morphological traits of B. carpatica and also B. petraea. Among diploids, B. nana was always distinguished, in contrast to B. oycoviensis, which was not genetically recognized despite being usually morphologically distinct. Based on our results and a literature review, we suggest that B. carpatica and also the closely similar B. petraea should not be considered separate species. A similar conclusion seems relevant also for B. oycoviensis; however, further verification is desirable in this case.

Genetic and morphometric variability between populations of Betula ×oycoviensis from Poland and Czechia: A revised view of the taxonomic treatment of the Ojców birch

“…the Carpathian birch [32] and was selected based on studies by Kulju et al [33] and Tsuda et al [34,35].…”

“…(Czechia), and Skielek (Poland). The Czech samples of B. pendula, together with a sample of B. nana described below, were collected in 2012 and used in our previous study [32]. As benchmark species for the evaluation, we included two additional birch taxa (B. nana, also collected in 2012 at Božídarské rašeliniště in the Ore Mts., Czechia, ca.…”

“…All other transitional individuals, which combined traits of the two taxa, were determined as B. pendula/B. ×oycoviensis (a 'working unit' sensu Kuneš et al [32]). Besides the benchmark species B. nana and B. humilis, we also collected sample material from B. atrata and B. obscura, which are visually distinct darkbarked birches occurring at the sites of sampling (conducted in 2019), although the taxonomic significance of these dark-barked birches remains questioned.…”

“…Microsatellite markers were selected based on publications by Tsuda et al [34,35] and Kulju et al [33]. In total, 50 markers were tested, from which 12 polymorphic loci were selected (see S2 Table) and optimized for two multiplex groups, identically as in a previous study by Kuneš et al [32].…”

Conservation of Betula oycoviensis, an endangered rare taxon, using vegetative propagation methods

“…Only a small per-centage of individuals from the birch offspring bear the phenotype of the taxon, which is considered a hybrid species (Kubát et al 2002, Kříž 2003. Although the taxonomic status of B. oycoviensis is not clear yet (Kuneš et al 2019), it is crucial to maintain its extant populations both in the Czech Republic and elsewhere. This is important both in terms of maintaining the genetic diversity of this birch and to resolve its taxonomic status within our key taxonomic literature (Kubát et al 2002, Kříž 2003, Kaplan 2019.…”