Does Solidago litoralis (Asteraceae) merit specific rank? Insights from cytogenetic, molecular and ecological data

Solidago litoralis (Asteraceae) is a psammophile plant endemic to the northern coasts of Tuscany, Italy. During time, different authors have considered it either as a separate species, subspecies or variety of the European S. virgaurea, but few studies of experimental taxonomy have been investigating the relationship between these two taxa. Aim of this study is to compare S. litoralis and S. virgaurea from different points of view: cytogenetic (karyotype analysis, localization of rDNA loci and genome size estimation), molecular (using two plastidial molecular markers), and ecological (by comparing functional characters). A difference in ecological responses to habitats is confirmed, even though S. virgaurea is potentially capable of assuming ecological strategies similar to those of S. litoralis. Despite this, cytogenetic and molecular analyses failed to reveal any significant difference supporting a specific distinction of S. litoralis. The latter taxon is here hypothesized as being an ecotype at the initial steps of a speciation event, better recognized at subspecific level (S. virgaurea subsp. litoralis)

Genome size shifts: karyotype evolution in Crepis section Neglectoides (Asteraceae)

Plant genome size evolution is a very dynamic process: the ancestral genome of angiosperms was initially most likely small, which led to a tendency towards genome increase during evolution. However, findings in several angiosperm lineages demonstrate mechanisms that also led to genome size contraction. Recent molecular investigations on the Asteraceae genus Crepis suggest that several genomic reduction events have occurred during the evolution of the genus. This study focuses on the Mediterranean Crepis sect. Neglectoides, which includes three species with some of the smallest genomes within the whole genus. Crepis neglecta has the largest genome in sect. Neglectoides, approximately twice the size of the two species Crepis cretica and Crepis hellenica. Whereas C.cretica and C.hellencia are more closely related to each other than to C.neglecta the karyotypes of the latter species and C.cretica are similar, while that of C.hellenica differs considerably. Here, the karyotypic organisation of the three species is investigated with fluorescence in-situ hybridisation and studied in a molecular phylogenetic framework based on the nuclear markers Actin, CHR12, CPN60B, GPCR1 and XTH23. Our findings further corroborate the occurrence of genome size contraction in Crepis, and suggest that the difference in genome size between C.neglecta and C.cretica is mostly due to elimination of dispersed repetitive elements, whereas chromosomal reorganisation was involved in the karyotype formation of C.hellenica