Evolution of European Cockchafers (Melolonthinae: Scarabaeidae: Coleoptera): a morphological, molecular and chromosomal study of intra- and inter-specific variations

Abstract

In cockchafers of the genus Melolontha, there is a marked intraspecific polymorphism for morphological characters, making some specimens of one species resemble another. A cytogenetic and molecular (mitochondrial COI gene sequence) study of typical and atypical forms of M. melolontha and M. hippocastani, captured at the same period and area, was performed. Karyotypes and haplotypes clearly characterize each taxon, placing atypical specimens in one or the other species unambiguously. This formally discards the role of hybridization in phenotypic resemblance, as usually proposed. Karyotypes and haplotypes were compared to those of M. pectoralis and Phyllophaga pleei, a more distantly related Melolonthinae, and some Dynastinae species, to reconstruct their ancestral karyotype. The karyotype of M. melolontha is the most derivative and that of P. pleei the most conserved among the Melolonthinae studied, which fits with the phylogeny established by COI gene analysis. Both karyotypes and COI haplotypes demonstrate the proximity of M. pectoralis and M. melolontha. The karyotype of M. melolontha is polymorphic, without relationship with morphological variations. Finally, the existence of similar morphological variations in different Melolontha species and chromosomal polymorphism in M. melolontha is discussed in relation with a network (reticulated) mode of speciation.

A South American Origin of the Genus <b><i>Dynastes</i></b> (Coleoptera: Scarabaeidae: Dynastinae) Demonstrated by Chromosomal Analyses

“…The study of the chromosomes of 82 species of Scarabaeidae [Dutrillaux and Dutrillaux, 2012] and the analysis of published data [Smith and Virkki, 1978;Yadav et al, 1979;Bione et al, 2005;Wilson and Angus, 2005;Angus et al, 2007;Arcanjo et al, 2009;Giannoulis et al, 2011] allowed us to conclude that most species possess 20 chromosomes, which probably represents the ancestral chromosome number. In our interpretation, the autosomes had a regularly decreasing size, the X was acrocentric, with the NOR on its short arm, and the Y was punctiform [Dutrillaux and Dutrillaux, 2012].…”

Chromosome mapping of 28S ribosomal genes in 11 species of Cassidinae (Coleoptera: Chrysomelidae)

“…The images of the chromosomes were taken using a Zeiss Imager A2 equipped with an Axio Cam digital camera, using Axion Vision software (Carl Zeiss AG, Jena, Germany). Silva et al, 2009;Almeida et al, 2010;Cabral de Mello et al, 2010, 2011aMendes-Neto et al, 2010;Oliveira et al, 2010Oliveira et al, , 2012aGiannoulis et al, 2011;Proença et al, 2011;Lira-Neto et al, 2012;Karagyan et al, 2012;Goll et al, 2013Goll et al, , 2015.…”

Interstitial NORs, Fragile Sites, and Chromosome Evolution: A Not So Simple Relationship - The Example of <b><i>Melolontha melolontha</i></b> and Genus <b><i>Protaetia </i></b>(Coleoptera: Scarabaeidae)

“…Thus, in these 2 species, the NOR remained at the same location as in M. melolontha . The karyotype of M. hippocastani looks different: its centromeric heterochromatin, highly amplified, is positively stained after C-banding [Giannoulis et al, 2011]. Unlike M. melolontha , all the C-banded heterochromatin is also stained by silver, which may indicate that it was formed by amplification of strictly centromeric heterochromatin such as that present in M. melolontha .…”

“…As described by Giannoulis et al [2011], the normal karyotype of M. melolontha is composed of 20 chromosomes, with pairs 1-6 and 8 being submetacentric, pair 7 acrocentric, pair 9 polymorphic (acrocentric or submetacentric), an acrocentric X, and a punctiform Y chromosome.…”