The taxonomy of Leucanthemum ircutianum (Asteraceae, Anthemideae) in the Apennine Peninsula based on AFLP fingerprinting, plastid DNA sequence variation and eco-climatological niche reconstruction

The tetraploid species Leucanthemum ircutianum (Asteraceae, Anthemideae) is represented in the Apennine Peninsula by three infraspecific taxa, L. ircutianum subsp. ircutianum, L. ircutianum subsp. asperulum and L. ircutianum subsp. leucolepis. The present study uses AFLP fingerprinting and sequencing of the petN-psbM intergenic spacer (IGS) region of the plastid genome for inferring genetic relationships among these three subspecies and aims at the elaboration of an appropriate taxonomic treatment of these taxa. Due to the amphi-Adriatic distribution of these taxa, additional samples from the Balkan Peninsula and representatives of L. ircutianum subsp. ircutianum from north-western Italy, south-eastern France, Romania and southern Germany were included. Genetic analyses reveal that L. ircutianum subsp. asperulum from southern Italy and L. ircutianum subsp. leucolepis from the Balkan Peninsula and the northern and central Apennine Peninsula are identical and should be treated as a single taxon. The observation of genetically intermediate individuals throughout the overlapping distributional ranges of L. ircutianum subspp. ircutianum and leucolepis and in a surveyed mixed stand of the two taxa indicate that these are not reproductively isolated from each other. The analysis of eco-climatological niches of the two subspecies indicates that L. ircutianum subsp. ircutianum is found in more temperate regions, whereas L. ircutianum subsp. leucolepis prefers the Mediterranean fringe of the total distributional range of the species. A hybrid-zone analysis based on AFLP 'allele frequency' clines along a transect from Germany to southern Italy is interpreted as supporting a scenario of secondary contact of the two entities after some diversification in allopatry. On the basis of our results, we provide a taxonomic treatment of the species L. ircutianum for Italy, including the designation of three lectotypes.