Abstract
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 CMa 3 /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 TT agg 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 CMa 3 -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 CMa 3 and negative for daPI, suggesting that C-heterochromatin is mainly enriched in gC-pairs.
Highlights
Most previous cytogenetic studies on the suborder Auchenorrhyncha (Insecta: Hemiptera) were performed using conventional chromosome staining techniques
The male karyotype consisted of one very large pair and ten medium pairs of autosomes, whilst the X chromosome was similar in size to the larger chromosomes within this group
As revealed in the present study, the leafhopper genus Alebra presents remarkable cytogenetic uniformity in the five species studied to date, despite the fact that some species were collected from different food plants (A. albostriella from Castanea sativa, Alnus sp., Fagus sylvatica and Quercus certis; A. wahlbergi from Acer opalus, Castanea sativa and Ulmus sp.; A. coryli from Quercus frainetto and Corylus avellana) and from distant geographical localities, i.e. Greece, Portugal and Spain (Kuznetsova et al, 2013; present paper)
Summary
Most previous cytogenetic studies on the suborder Auchenorrhyncha (Insecta: Hemiptera) were performed using conventional (routine) chromosome staining techniques. This approach allows the detection of gross karyotypic alterations, such as changes in chromosome number and size, and provides an overview of chromosome behaviour during mitosis and meiosis. The genus Alebra Fieber, 1872 is classified within the subfamily Typhlocybinae Kirschbaum 1868, one of the largest and most diversified of the auchenorrhynchan family Cicadellidae (leafhoppers). The latter includes nearly 22,000 (McKamey, 2002) or even 25,000 (Dietrich & Rakitov, 2002) described species. Neither the karyotypes of Typhlocybinae nor Cicadellidae as a whole have ever been subjected to differential chromosome staining of any description
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