Hybridization and introgression among three Aconitum (Ranunculaceae) species of different ploidy levels in the Tatra Mountains (Western Carpathians)

Abstract

Hybridization among species of Aconitum effects their morphology and ecology. In this study the hybridization between the diploid 2n(2x) = 16 (A. lasiocarpum and A. variegatum) and tetraploid 2n(4x) = 32 (A. firmum) species was documented in the Tatra Mountains (Western Carpathians) in a small, local population in a semi-natural site. The hybrid species were: homoploid A. × pawlowskii (A. lasiocarpum × A. variegatum), and triploid A. × berdaui (A. firmum × A. variegatum, 2n(3x) = 24). Chloroplast DNA (cpDNA) alleles formed two distinct haplotypes, one typical for the tetraploid and another for diploid lines, shared between the tetraploid, triploid and diploid groups, indicating introgressive hybridization. The presumed gene flow was from the tetraploid to diploid species via the triploid bridge. The only two specimens of A. × pawlowskii that harbored tetraploid (A. firmum) type cpDNA possessed bracteoles of A. firmum-type. The remaining introgressed (cpDNA and Inter Simple Sequence Repeats (ISSR)) specimens (A. variegatum) were morphologically pure, implying cryptic introgression. ISSR loci shared between the tetraploid A. firmum and diploid A. variegatum support the hypothesis of an ancient allopolyploid origin of A. firmum and the diploid species of A. variegatum-type as one of its parent.

Phylogeny of Aconitum Subgenus Aconitum in Europe

“…Hybridization is frequent in Aconitum (Kita & Ito, 2000). Present horizontal transfer of the cpDNA gene between diploid and tetraploid Aconitum species (via reverse "triploid bridge") has been reported in the Tatra Mts (Sutkowska, Boroń, et al, 2017, Zieliński, 1982a, 1982b. Such horizontal gene transfer could be responsible for the observed interchange of cpDNA between the different sections of A. subgen.…”

“…We believe that intersectional hybridization and subsequent genetic introgression are the most relevant factors responsible for the paraphyly of the tetraploid clade ( Figure 2) (Mitka et al, 2007(Mitka et al, , 2015Sutkowska, Boroń, et al, 2017;. Hybridization is frequent in Aconitum (Kita & Ito, 2000).…”

“…Aconitum L. subgen. Aconitum is known for its high morphological plasticity and extensive interspecific hybridization (Kita & Ito, 2000;Krzakowa & Szweykowski, 1976;Sutkowska et al, 2013;Sutkowska, Boroń, et al, 2017;Zieliński, 1982aZieliński, , 1982b, and the latter is considered to be a major cause of taxonomic unclarity (Kadota, 1981;Tutin et al, 1993). Various Aconitum species have been found to possess identical chloroplast DNA (cpDNA) sequences, resulting from horizontal gene transfer (Kita & Ito, 2000;Kita et al, 1995;Luo et al, 2005;Utelli et al, 2000).…”

Genetic structure of Doronicum austriacum (Asteraceae) in the Carpathians and adjacent areas: toward a comparative phylogeographical analysis of tall-herb species

“…While, geographically, the Quaternary history of the Alps has mainly been addressed, recently the attention of researchers has also been directed to the Carpathian range (reviewed in Ronikier 2011 and. The Carpathians are seen as a biodiversity hot spot due to species richness (e.g., Tasenkevich 1998), plant communities' diversity (e.g., Pawłowski 1966Coldea 1991;Stachurska-Swakoń 2009a, b;Chytrý et al 2015), endemism (e.g., Pawłowski 1970;Hurdu et al 2016; and area of taxa speciation (e.g., Cieślak et al 2000;Španiel et al 2011;Mitka et al 2015aMitka et al , 2016Sutkowska et al 2017).…”

“…According to previous studies of subalpine species, the Carpathian range plays an important role in shaping and preserving their extant genetic diversity. Available studies indicate that their phylogeographical structure across the European distribution range is shallower than that of the most alpine species, and they are representative for the history of the mountain species with larger elevational amplitude (Després et al 2002;Michl et al 2010;, 2013aEkrtová et al 2012;Frajman et al 2016;Sutkowska et al 2017). However, phylogeographical studies on two key components of tall-herb communities, Cicerbita alpina (L.) Wallr.…”