Natural hybridization between diploid Ficaria calthifolia and tetraploid Ficaria verna subsp. verna in central Europe

Abstract

The genus Ficaria is a taxonomically intricate group in which polyploidization and hybridization contribute to taxa diversification. In central Europe, populations of diploid F. calthifolia and tetraploid F. verna subsp. verna occasionally come into contact, which results in an interspecific triploid hybrid, as recently demonstrated using molecular markers, genome size estimation and experimental crossing. In this study, we aimed to estimate the frequency and distribution of the triploid hybrid in central Europe, to identify those phenotypic traits that can be used to discriminate between hybrid and parental taxa and compare the phenology, pollen viability, sexual and asexual reproduction and niche differentiation of the triploid hybrid and parental taxa. Flowcytometry analyses of 1171 individuals sampled from 67 localities revealed that triploid hybrids were regularly found at 89% of the sites sampled where there were sympatric populations of both parental taxa, with a mean percentage of 19.4% occurring at sites where there was a mixture of cytotypes. No pure hybrid population was found. The hybrids were intermediate between the parental taxa in most morphological characters and did not show any novel morphological characters. The characters that best differentiate the taxonomic groups were the production of axillary bulbils, aborted and well-developed achenes, leaf shape and plant habit. Almost all hybrids were sexually sterile: the pollen viability was considerably reduced (mean 8.4%) and on average 98% of the achenes were aborted. Local dispersal of the hybrids is possible through the production of bulbils in the leaf axils, although the number of bulbils per node and the mean weight of one bulbil were two and three times lower in the hybrid than in F. verna subsp. verna. The hybrid niche was intermediate between those of the parental taxa but shifted slightly towards that of F. verna subsp. verna. In addition, the taxonomic and nomenclatural treatment of the hybrid, which is described as Ficaria ×sellii Duchoslav, Popelka et Trávn., as well as a key for identifying the central European taxa of Ficaria, are presented.

Anthropogenic and natural disturbances increase local genetic diversity in an early spring geophyte (Ficaria verna Huds)

“…Despite sampling at a very local scale, we found high levels of allelic and clonal diversity in F. verna, as evidenced by high allele numbers, large ranges of allele lengths, and generally high numbers of MLGs at individual sampling sites (Table 2). Our data thus support previous observations that the species is genetically diverse (Mattingly et al, 2023;Popelka, Sochor, & Duchoslav, 2019;Reisch & Scheitler, 2009) and provide evidence that F. verna is capable of maintaining high levels of genetic diversity despite its predominantly clonal growth (Kocot et al, 2022;Popelka, Tr avníček, et al, 2019;Verheyen & Hermy, 2004). Ficaria verna has several characteristics that are beneficial for maintaining genetic diversity.…”

“…We conclude that short-distance dispersal of both generative (where available) and vegetative propagules is responsible for maintaining clonal diversity and mixing of MLGs at the local scale in F. verna, whereas dispersal of sexually produced pollen and/or seeds, even if infrequently produced (Kocot et al, 2022;Marsden-Jones & Turrill, 1952;Popelka, Tr avníček, et al, 2019), is sufficient to ensure genetic admixture at the regional scale. Due to the generally high levels of local genetic diversity and the presence of unique MLGs at all sites of F. verna, we assume that seedling recruitment is at least occasional at all study sites, although the extent to which sexually produced propagules establish is likely to vary between sites.…”

“…Fine-scale genetic structure and clonal aggregation at very small distances are likely to result from reproduction via clonal propagules produced close to the parent plant and not easily dispersed, as is the case with root tubers (Herben & Klimešov a, 2020;Vallejo-Marín et al, 2010), the second most important propagule for vegetative reproduction in F. verna (Grime et al, 1988). Similarly, bulbils (Klimešov a et al, 2017), when formed in the leaf axils of lower stem leaves (Popelka, Tr avníček, et al, 2019), may only be very locally dispersed. However, the comparatively rare and weak pattern of SGS suggests that the spread of vegetative units in F. verna is generally effective already in the range of a few meters, as exemplified by grid sampling in this study.…”

“…We conclude that the positive effect of human disturbance on the local genetic diversity of F. verna is most likely due to gap-opening processes and facilitated propagule establishment. Negative effects of human disturbance, such as mowing, on local genetic diversity are likely to be negligible due to the early flowering and fruiting time (Popelka, Tr avníček, et al, 2019) and low height of the species. The two most genetically diverse sites in our study were highly frequented and regularly mowed urban sites (B, P), suggesting that mowing does not negatively affect genetic diversity, although the only other regularly mowed site (K) showed comparatively low levels of clonal diversity.…”

Distributions of vascular plants in the Czech Republic

“…A new edition of the field guide "Key to the Flora of the Czech Republic" was published last year (Kaplan et al 2019a). Several taxonomically complicated groups were revised, and new species (Trávníček et al 2018, Király et al 2019, Lepší et al 2019 and hybrids (Hodková & Mandák 2018, Prančl et al 2018, Popelka et al 2019 were discovered. Additional plant taxa were recorded for the first time in this country, comprising previously unrecognized native ones (Roleček et al 2018, Velebil 2018 as well as introduced aliens (Danihelka 2019a, Lustyk & Doležal 2019.…”