Evidence for TTAGG telomere repeats and rRNA gene clusters in leafhoppers of the genus Alebra (Hemiptera: Auchenorrhyncha: Cicadellidae)

The leafhopper genus Alebra Fieber, 1872 comprises a complex of morphologically similar species. The chromosome complements (karyotypes) of five Alebra species, i.e. A. albostriella, A. coryli, A. viridis, A. wahlbergi and a new, yet undescribed species, provisionally named Taxon 1, were here investigated, three of these species (A. coryli, A. viridis, and Taxon 1) for the first time. The techniques applied included standard chromosome staining, fluorescence in situ hybridization (FISH) for mapping of 18S rDNA and telomeric repeats (in every species), C-banding, AgNOR-banding and CMA3 /DAPI- staining (in A. viridis). The species have a holokinetic type of chromosomes, as in other hemipterans. Karyotypes of all species are remarkably conserved with 2n = 22 + X(0)/XX (male/female), one large and 10 medium pairs of autosomes and the X chromosome similar in size to larger chromosomes within this group. In every species, FISH identified the “classical” insect telomere repeat of TTAGG and rRNA gene clusters located on the homologues of a medium-sized pair of autosomes, presumably number 5. Thus, speciation in Alebra has apparently not involved significant karyotypic changes. In A. viridis, rDNA sites were both Ag- and CMA3 -positive and were located at an interstitial position. C-banding revealed heterochromatic bands in the X chromosome and also in all but four pairs of autosomes, the bands were located at one telomere of a chromosome. C-bands were positive for CMA3 and negative for DAPI, suggesting that C-heterochromatin is mainly enriched in GC-pairs.info:eu-repo/semantics/publishedVersio

Geographical patterns of chromosomal differentiation in the brachypterous grasshopper Podisma sapporensis (Orthoptera : Acrididae)

The distribution patterns of the X0/XX and neo-XY/neo-XX chromosome races, subraces, and "hybrids" between subraces of the grasshopper P. sapporensis were analyzed. The origin of the observed variation is Robertsonian translocations between a sex chromosome and an autosome, and chromosome rearrangements. The fixation levels of inversions varied depending on geographic regions. No hybrid population is known implying that a strong reproductive isolation system exists in hybrids between the different chromosomal races. The probable reasons for the purity of X0 and neo-XY chromosome races and high chromosome polymorphism in contact zones between chromosomal subraces are discussed. The presence of isolating barriers between chromosome races indicates a review of the taxonomic structure of P. sapporensis is required. It is proposed to divide P. sapporensis into two sibling species, which differ in the chromosome mechanisms of the sex determination system. The analysis of the distribution of chromosomal races and subraces of P. sapporensis allows a reconstruction of the history of this species in the Okhotsk sea region