title: Species boundaries and frequency of hybridization in the Dryopteris carthusiana (Dryopteridaceae) complex: A taxonomic puzzle resolved using genome size data.
abstract: OBJECTIVE
  Genome duplication and interspecific hybridization are important evolutionary processes that significantly influence 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 interspecific hybrids have led to a continuous dispute concerning species circumscription and delimitation. •
  
  
  METHODS
  We used flow 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. •
  
  
  RESULTS
  Flow cytometric measurements revealed unique genome sizes in all species and hybrids, allowing their easy and reliable identification for subsequent morphometric analyses. Different species often formed mixed populations, providing the opportunity for interspecific 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 flora.
authors: Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic.
authors: Libor
authors: L
authors: Ekrt
authors: Renata
authors: R
authors: Holubová
authors: Pavel
authors: P
authors: Trávnícek
authors: Jan
authors: J
authors: Suda