Diphasiastrum species have been assumed to produce homoploid hybrids whose reproductive competence is still a matter of debate. Using flow cytometry, Bennert et al. demonstrate that the three Central European primary hybrids are consistently homoploid. Their nuclear DNA amounts are invariable and intermediate between the parents; no indications for diploid backcrossing are found. Higher DNA amounts [...]

Polyploidy is a major evolutionary force generating new plant species. Hunt et al. explore the dynamics of allopolyploid speciation in the western Mediterranean rock fern Asplenium majoricum at a site where it occurs sympatrically with its diploid parents and their diploid hybrid. Analysis of genetic diversity in allotetraploid and progenitor populations shows recurrent formation of [...]

Coexistence of multiple cytotypes of an orchid Large-scale cytotype surveys have indicated that intraspecific ploidy diversification is much more common than previously thought. Trávníček et al. examine inter- and intrapopulational ploidy diversity in the fragrant orchid, Gymnadenia conopsea agg., in Central Europe and find that this species represents a remarkable example of ploidy coexistence in [...]

Genetic relationships between sympatric and allopatric Casearia Casearia sylvestris var. sylvestris inhabits humid, dense forests, while var. lingua is restricted to xeric habitats, yet despite differences in morphology and habitat preference, intermediate forms exist in transitional environments, complicating the delimitation of the taxa. Cavallari et al. examine nine microsatellite markers and conclude that the two [...]