Ecological hybrid speciation in central-European species of Bolboschoenus

Abstract

Divergent natural selection is known to facilitate speciation in many taxa. The genus Bolboschoenus (Cyperaceae) is a model group for investigating ecological and homoploid hybrid speciation. Four taxa of Bolboschoenus occur in central Europe: the halophyte B. maritimus and glycophytes B. laticarpus, B. planiculmis and B. yagara. These species differ in their ecological niches. Such ecological and/or geographical isolation is critical for homoploid hybrid speciation. The determination of species of Bolboschoenus is based on morphological characters of the inflorescence and on achene shape and anatomy. On the basis of its intermediate morphology, chromosome number and ecological amplitude B. laticarpus is thought to be a hybrid. In order to determine the validity of morphological species and the possible hybrid origin of B. laticarpus we used amplified fragment length polymorphisms (AFLPs) as molecular markers and compared different genetic groups defined using STRUCTURE analysis with morphological data. The morphological classification of central-European species of Bolboschoenus was confirmed. Plants of heterogeneous genotypes were also found to be intermediate individuals resulting from spontaneous hybridization. Hybrid origin of B. laticarpus, which is genetically and morphologically intermediate between B. yagara and B. planiculmis, was elucidated. Inflorescence characters were less important for determining species than anatomical characters of achenes (widths of the exocarp and mesocarp).K e y w o r d s: AFLP, Bolboschoenus, central Europe, hybridization, model-based clustering, morphometrics, speciation IntroductionThe evolutionary histories of groups of closely related species of plants have been the focus of interest of much research in recent years, especially the process of speciation (Kaplan et al. 2013, Kolář et al. 2014, 2015. Moreover, questions concerning reproductive isolating mechanisms and the genetics and genomics of speciation have been highlighted by a major European initiative as the main subjects for further research (Butlin et al. 2012). Ecological speciation is one of the main modes of speciation (Schluter 2001). It occurs as a result of reproductive isolation due to divergent selection of organisms in different environments and can arise even where species occur sympatrically (Sobel et al. Preslia 89: 17-39, 2017 17 doi: 10.23855/preslia.2017.017 2009). Studying microevolution within groups of closely related species differing in ecology may thus reveal the role of such environmental differences in their origin. Hybridization can result in both gene flow among plant taxa and generation of new species. Some families and genera have relatively high numbers of hybrids, with the family Cyperaceae being one of them (Ellstrand et al. 1996).The European species of Bolboschoenus (Asch.) Palla (Cyperaceae) provide an example of a putative hybrid complex for which ecological selection, geographic isolation and hybridization are thought to have been important in their speciation, with the...

Cirsium ×sudae

“…In addition, the parental species were well recognized even in a robust dataset containing 13 different species. The applicability of this technique for studying hybridization events was demonstrated recently by Čertner et al (2015), Hulber et al (2015), Szczepaniak et al (2016), Zelener et al (2016), An et al (2017), Píšová et al (2017) and others. In the genus Cirsium it was also used for the molecular confirmation of a new hybrid by Segarra-Moragues et al (2007).…”

Pedunculate Club-rush Bolboschoenus laticarpus (Cyperaceae) ‒ an overlooked native or a spreading neophyte?

“…(= B. planiculmis (F. Schmidt) T. V. Egorova). Detailed molecular studies by Píšová et al (2017) have demonstrated this to be the case: B. laticarpus is genetically and morphologically intermediate between B. yagara and B. planiculmis and is a stable hybridogenous species.…”

Morphological and Physiological Traits Related to the Response and Adaption of Bolboschoenus planiculmis Seedlings Grown Under Salt-Alkaline Stress Conditions

“…Plants of genus Bolboschoenus are commonly distributed in saline wetlands, and often occupy a wide range of habitats, including both coastal and inland salt marshes (Ljevnaić-Mašić et al, 2020). The ecological properties of these species such as their dispersal abilities and distribution as well as their relationships with habitat conditions, have been are investigated (Hroudová et al, 2007;Píšová et al, 2017). Bolboschoenus maritimus, for example, is regarded as a halophyte usually inhabiting saline habitats.…”