ISSN: 2639-216X
Authors: Petitpierre E*
Molecular phylogenetic analyses mainly based on mtDNA and nuDNA sequences and/or, secondarily, on chromosomes and plant trophic affiliations, have been obtained in 84 species of Chrysolina and 19 of its closely related genus Oreina, belonging to 42 of the 70 described subgenera of the former and to all of the seven ones of the latter. Bayesian and Maximum likelihood phylogenetic trees showed monophyly of Chrysolina-Oreina, with four main clades of subgenera with high support values. The first clade includes subgenera Chrysolinopsis and Taeniochrysea, and the second those of Chrysomorpha, Euchrysolina, Melasomoptera and Synerga. The third is much large and composed of three subclades of subgenera, Chrysocrosita and Erythrochrysa, Colaphosoma and Maenadochrysa, and Centoptera, Fasta, the subgenera of Oreina and Timarchoptera. These three main clades enclose most species with 2n=24(Xyp) male chromosomes and an ancient trophic affiliation with Lamiaceae plants, at the root of the core of Chrysolina. However, a host shift from Lamiaceae to Asteraceae was detected in all but one subgenera of Oreina and another from Lamiaceae to Apiaceae in Oreina s. str. and in Ch. (Timarchoptera) haemochlora, a species with 2n(♂)=23(XO) chromosomes. The fourth main clade holds more than a half of subgenera and is ambiguous for ancestral host-plant reconstruction, with nine botanic families. A statistically significant shift for a second association to Apiaceae was found in a subclade with Crositops, Minckia and Threnosoma, and the species Ch. soiota, this last should be excluded from Timarchoptera and moved to Paraheliostola L. Medvedev stat. ressur. thereby these two subgenera could not be synonymous as it was recently suggested. New trophic shifts to Hypericaceae were clearly substantiated in Hypericia and Sphaeromela subclade, and to Plantaginaceae in another with Colaphodes, Ovosoma, Palaeosticta and probably Taeniosticha. A further great subclade showing a shift to Asteraceae is that of Allochrysolina, Anopachys, Apterosoma, Chalcoidea, Sibiriella and the species Ch. (Pezocrosita) convexicollis. All species in these latter subclades display high chromosome numbers, namely 2n=32(Xyp) in Sphaeromela, 2n=38(Xyp) in Hypericia, 2n=40(Xyp) in Anopachys, Chalcoidea, Colaphodes, Minckia and Ovosoma, and 2n(♂)=47(XO) in Threnosoma. Possible reversal shifts from Plantaginaceae to Lamiaceae and to Asteraceae were found in the subclades of Arctolina, Colaphoptera and Pleurosticha, whose species have low chromosome numbers, 2n=24(Xyp) or 2n=26(Xyp). Near to these previous, the subclade of Chrysolina s. str. holds species with a relative polyphagy, on four plant families, and sharing 2n(♂) =23(XO) chomosomes. Furthermore, the subclade of Stichoptera, mainly affiliated to Scrophulariaceae, is an exception among the subgenera of Chrysolina due to its high variation in chromosome numbers from 2n=22(Xyp) to 2n=34(Xyp). Finally, the rising of some subgenera of Chrysolina to the genus rank was statistically rejected with highly significant values.
Keywords: Chrysolina; Oreina; DNA; Chromosomes; Phylogenies
