Towards resolving the Knautia arvensis agg. (Dipsacaceae) puzzle: primary and secondary contact zones and ploidy segregation at landscape and microgeographic scales

Abstract

Five different ploidy levels (from 2x to 6x) were found, with triploids of K. arvensis being recorded for the first time. The species also exhibited variation in the monoploid genome size, corresponding to the types of habitats occupied (grassland diploid populations had larger genome sizes than relict and subalpine diploid populations). Disregarding relict populations, the distribution of 2x and 4x cytotypes was largely parapatric, with a diffuse secondary contact zone running along the north-west margin of the Pannonian basin. Spatial segregation of the cytotypes was also observed on regional and microgeographic scales. The newly detected sympatric growth of diploids and tetraploids in isolated relict habitats most likely represents the primary zone of cytotype contact. Ploidy level was found to be a major determinant of the strength of inter-cytotype reproductive barriers. While mixed 2x + 4x populations virtually lacked the intermediate ploidy level at any ontogenetic stage, pentaploid hybrids were common in 4x +6x populations, despite the cytotypes representing different taxonomic entities.

Arbuscular mycorrhizal symbiosis on serpentine soils: the effect of native fungal communities on different Knautia arvensis ecotypes

“…(Dipsacaceae) is a common perennial herb, inhabiting dry and mesophilous meadows, pastures, shrublands, open woods, forest margins and roadsides throughout most of Europe (Štěpánek 1997). It harbours two more-or-less spatially separated (parapatric) but morphologically only weakly differentiated ploidy levels, diploid and tetraploid, which are sometimes treated as separate subspecies or varieties (Kaplan 1998;Kolář et al 2009). Knautia arvensis was selected as a good model system for studying the role of AM symbiosis in plant adaptation to serpentine conditions because: (1) it is a mycorrhizal species (Wang and Qiu 2006); (2) it inhabits both serpentine and non-serpentine substrates in Central Europe (Kaplan 1998); and (3) the serpentine populations (ecotypes) showed higher tolerance to elevated Mg concentrations (lower Ca/Mg ratio) in a hydroponic experiment than the non-serpentine populations (F. Kolář et al, unpublished data).…”

“…Knautia arvensis was selected as a good model system for studying the role of AM symbiosis in plant adaptation to serpentine conditions because: (1) it is a mycorrhizal species (Wang and Qiu 2006); (2) it inhabits both serpentine and non-serpentine substrates in Central Europe (Kaplan 1998); and (3) the serpentine populations (ecotypes) showed higher tolerance to elevated Mg concentrations (lower Ca/Mg ratio) in a hydroponic experiment than the non-serpentine populations (F. Kolář et al, unpublished data). Furthermore, both diploid and tetraploid cytotypes occur on serpentine as well as on non-serpentine sites (Kolář et al 2009), thus providing an opportunity for assessment of the interactions between mycorrhizal inoculation and genome copy number by comparison of plants of different ploidy level within the same species.…”

Breeding barriers at a diploid–hexaploid contact zone in Aster amellus

“…A diverse array of breeding barriers can mediate assortative mating in natural populations, including heterogeneity in the spatial distribution of cytotypes (van Dijk et al 1992;Husband and Schemske 1998;Kolař et al 2009) due to different microhabitat preferences (Felber-Girard et al 1996); temporal isolation due to shifts in flowering phenologies (Petit et al 1997;Marques et al 2007;Jersáková et al 2010); mechanical isolation due to differences in floral morphology (reviewed in Grant 1994); segregation resulting from divergent behaviors and preferences of pollinators (Grant 1994;Thompson et al 2004;Marques et al 2007; Thompson and Merg 2008); gametic isolation (Husband et al 2002;Mráz 2003;Brock 2004); and/or reduced fitness or sterility of the hybrids (Ramsey and Schemske 1998;Buggs and Pannell 2006;Prentis et al 2007). All together, such breeding barriers will act in concert and govern the levels of pollen flow between cytotypes, thereby determining the cytotype composition of the offspring and population.…”

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.…”