Species boundaries and frequency of hybridization in the Dryopteris carthusiana (Dryopteridaceae) complex: A taxonomic puzzle resolved using genome size data

Abstract

and 4 Institute of Botany, Academy of Sciences of the Czech Republic, Pr ů honice 1, CZ-252 43 Pr ů honice, Czech Republic• Premise of the study : Genome duplication and interspecifi c hybridization are important evolutionary processes that significantly infl uence phenotypic variation, ecological behavior, and reproductive biology of land plants. These processes played a major role in the evolution of the Dryopteris carthusiana complex. This taxonomically intricate group composed of one diploid ( D. expansa ) and two allotetraploid ( D. carthusiana and D. dilatata ) species in Central Europe. Overall phenotypic similarity, great plasticity, and the incidence of interspecifi c hybrids have led to a continuous dispute concerning species circumscription and delimitation.• Methods : We used fl ow cytometry and multivariate morphometrics to assess the level of phenotypic variation and the frequency of hybridization in a representative set covering all recognized species and hybrids.• Key results : Flow cytometric measurements revealed unique genome sizes in all species and hybrids, allowing their easy and reliable identifi cation for subsequent morphometric analyses. Different species often formed mixed populations, providing the opportunity for interspecifi c hybridization. Different frequencies of particular hybrid combinations depended primarily on evolutionary relationships, reproductive biology, and co-occurrence of progenitors.• Conclusions : Our study shows that genome size is a powerful marker for taxonomic decisions about the D. carthusiana complex and that genome size data may help to resolve taxonomic complexities in this important component of the temperate fern fl ora.

Variation in genome size in the Valeriana officinalis complex resulting from multiple chromosomal evolutionary processes

“…Genome size additivity in hybrids among taxa differing in nuclear DNA content is not exceptional and has been detected in several plant genera (e.g. Elytrigia: Mahelka et al 2005; Dryopteris: Ekrt et al 2010;Amaranthus: Jeschke et al 2003;Cerastium: Vít et al 2014). The increase in relative genome size could not be explained in this study by chromosome addition, because genetically admixed and thus supposedly hybrid individuals analysed for chromosome number were eutetraploid (with one individual possibly hypo-tetraploid).…”

“…Approaches applied involve reconstruction of the actual process of hybridization by comparison of genome sizes observed and expected in a given situation and evolutionary scenario (e.g. the genome size of the F1 expected from the fusion of meiotically reduced parental gametes), and correlation of genome size with data providing independent evidence for hybridization, like the morphological differentiation of parents (Ekrt et al 2010, Vít et al 2014.…”

Lantana camara L. (sensu lato): an enigmatic complex

“…Variation in chromosome numbers in genus Lantana encourages the use of genome size as a species-specific marker. Genome size has been well-applied to resolve notable species complexes such as Reynoutria (Mandák et al 2003); Knautia arvensis (Kolář et al 2009); Dryopteris carthusiana (Ekrt et al 2010); Callitriche (Prančl et al 2014) and, identification of invasive alien taxa (see Suda et al 2010). Further, documentation of population cytotype structure of the invasive genets and their geographical distribution is central to monitor complex constituents' invasion potential.…”

What We Do (and Don't) Know About Ferns: <I>Dryopteris</I> (Dryopteridaceae) as a Case Study

“…In recent years the efforts of a number of researchers have made Dryopteris one of the better-understood fern genera (e.g. Geiger and Ranker 2005;Li and Lu 2006a;Ekrt et al 2010;Juslén et al 2011;Sessa et al 2012a, b, c;Zhang 2012;Roux 2012;Lee and Park 2013;Sessa and Givnish 2014;Testo et al 2015), and have positioned it as a potential model for understanding biogeographic patterns and the dynamics of polyploid complexes in ferns. Ferns, with ca.…”