Allozyme Variation in Diploid, Polyploid and Mixed-Ploidy Populations of the Pilosella alpicola Group (Asteraceae): Relation to Morphology, Origin of Polyploids and Breeding System

Abstract

The Pilosella alpicola group includes four species (P. alpicola s.str., P. ullepitschii, P. rhodopea and P. serbica) with allopatric distributions (Alps, Balkans, Carpathians) and contrasting cytotype patterns (diploid, diploid-polyploid and polyploid species). Whereas diploid taxa (P. ullepitschii and P. serbica) reproduce sexually, the mode of reproduction of polyploid cytotypes reflects their origin: autopolyploids of P. rhodopea reproduce sexually, while allopolyploid cytotypes of P. alpicola s.str. apomictically. We used allozymes to elucidate overall genetic variation within the group and to test their utility for taxon discrimination, assessment of polyploid origin and possible correlations with breeding systems. Variation of five allozyme systems encoded by eight polymorphic loci and 29 alleles was studied in 20 populations and 298 plants representing all taxa. Allozymes were proved to be only of limited usefulness for the taxonomic classification within the P. alpicola group. The Western Carpathian populations of P. ullepitschii formed the only genetically well-differentiated group. The same allele suite shared by all cytotypes of P. rhodopea and presence of both balanced and unbalanced heterozygotes in tetraploids was consistent with autopolyploid origins of polyploids and provided further evidence for a primary contact zone. An isolated relic population of P. rhodopea from the Southern Carpathians exhibited lowered values of genetic diversity when compared to the core area. Pronounced fixed heterozygosity was found in P. alpicola s.str., supporting its allopolyploid origin. In accordance with assumptions, genotypic variability was significantly higher in sexually reproducing diploid and diploid-polyploid taxa than in apomictic P. alpicola s.str.

Cytotype coexistence in the field cannot be explained by inter-cytotype hybridization alone: linking experiments and computer simulations in the sexual species Pilosella echioides (Asteraceae)

“…Different cytotypes may be completely separated geographically, or coexist in close proximity within a primary or secondary contact zone (e.g. [13, 14]), often intermingled within single populations [1, 12, 14–18]. …”

Allopatric distribution, ecology and conservation status of thePilosella alpicolagroup (Asteraceae)

“…Bip. (Šingliarová et al 2011a, 2011b). According to castration and isolation experiments and flow cytometric seed screening analysis, the tetra‐ and pentaploids of P. alpicola reproduce apomictically (Šingliarová et al 2011a).…”

“…Pilosella rhodopea is a karyologically variable species, ranging from diploid to pentaploid ploidy level. All cytotypes have been shown to reproduce sexually, without obvious reproductive barriers and without any morphological and genetic differentiation (Šingliarová et al 2011a, 2011b). These facts suggest that P. rhodopea polyploids have arisen by autopolyploidization (Šingliarová et al 2011a, 2011b).…”

“…Our molecular data suggest a recent and monophyletic origin (with the exception of P. alpicola s.s.) of the closely related P. alpicola taxa (Šingliarová et al 2011a, 2011b). We hypothesize that the modern range of the P. alpicola group is probably what remains from a wider and continuous primary range of their common progenitor (either one of the extant taxa or some already extinct taxon) during more favourable cold periods (Šingliarová et al 2011a).…”

Concealed diversity : taxonomical, phytogeographical and phytosociological notes on brambles (Rubus L. subgen. Rubus) in north-west Europe

“…Many field populations are heterogeneous in respect to ploidy level and/or reproductive system (Krahulcová et al 2000;Krahulcová et al 2009a;Šingliarová et al 2011), and hybrids are formed often, although uneven in different mixed populations (Krahulec et al 2008). The combination of hybridization, apomixis and clonal growth leads to the maintenance of various hybrids, having originated from backcrossing and hybridization between more than two species (Krahulcová et al 2000), and making the classification very cumbersome.…”