Molecular Insight into Genetic Structure and Diversity of Putative Hybrid Swarms of Pinus sylvestris × P. mugo in Slovakia

Miroslav Klobucnik,Andrej Kormutak,Dusan Gomory,Martin Galgoci

doi:10.3390/f13020205

Abstract

The genetic structures of the four putative hybrid swarms of Pinus sylvestris × P. mugo in Slovakia were analyzed in terms of individual admixture proportions calculated via inter-primer binding site (iPBS) marker loci. This work aimed to reevaluate the hybrid swarms’ differentiation status as postulated in the previous studies at both population and genomic levels. The study confirmed intermediate divergence of each of the swarms examined. Based on 80-loci hybrid index scores, we have revealed the presence of introgressive and intermediate hybrids with frequencies corresponding to differentiation estimates. Surprisingly, irrespective of individual phenotypes, the most frequent intermediates were found in Sucha Hora (29.5%) and Obsivanka (28.6%) populations, which resemble rather pure P. mugo and were previously considered as bimodal hybrid zones with a negligible amount of hybrids. The remaining hybrid zone population Zuberec seems to be highly introgressed to P. sylvestris, while Tisovnica is clearly inclined to P. mugo. The results and different methodologies are discussed.

Highlights

Among seven introgressive hybrids of pines described within a group of hard pines and two introgressive hybrids revealed in a group of soft pines, the hybrid swarms of Scots pine (P. sylvestris L.) and dwarf mountain pine (P. mugo Turra s. str.) dominate ecologically in Central and Southern Europe [4,5]
Genetic variations of 13 populations, including Scots pine (Pinus sylvestris L.) and dwarf mountain pine (P. mugo Turra s. str.), originating from their natural habitats, along with a group of their putative hybrid swarms occurring in the four contact zones of northern
When defining individual forms by an interval width of 0.2 (Figure 3), the most frequent forms in the hybrid swarm Zuberec (H/Zu) swarm were trees of pure P. sylvestris (46.3%) and P. sylvestrislike introgressants (39.0%), which predominated considerably over true hybrids (14.6%)

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Studies addressing natural hybrid populations belong among the most important discoveries of the early 20th century, as they have laid the foundation of the modern evolutionary concept of hybridization, along with allopolyploidy and recombination and speciation [1]. With special reference to the genus Pinus, hybridization and introgression are important attributes of the reproductive behavior of pines and an indisputable part of their evolutionary history [2]. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas the introgression within a few loci may promote the adaptive divergence and facilitate speciation [3]. Among seven introgressive hybrids of pines described within a group of hard pines and two introgressive hybrids revealed in a group of soft pines, the hybrid swarms of Scots pine (P. sylvestris L.) and dwarf mountain pine (P. mugo Turra s. str.) dominate ecologically in Central and Southern Europe [4,5]

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