Strong intraspecific phylogenetic and karyotypic diversification in Isophya modestior (Orthoptera: Tettigoniidae: Phaneropterinae)

Abstract

Abstract Isophya modestior (Orthoptera: Tettigoniidae) is a species distributed in central and south-eastern Europe, where its distribution is largely separated by two large rivers (Sava and Danube). Since previous studies on the song and morphology of the stridulatory file across its complete geographic range showed that the species is separated into two main groups, we decided to use phylogenetic and karyological analyses in order to evaluate the status of the previously analysed populations. Phylogenetic analyses showed the existence of two major clades within I. modestior with very high bootstrap values and posterior probabilities—Clade A: present on the Balkan Peninsula, Slovenia (Inner Carniola), Italy, Pannonian Serbia (Vršac Mts and Deronje) and Austria (Burgenland and Lower Austria); Clade B: present in Slovenia (Upper Carniola), Croatia and Austria (Carinthia), Pannonian Serbia (Fruška Gora Mt.) and Hungary. A comparison of chromosomes of 51 specimens revealed discrete differences between their karyotypes. The physical characteristics of the karyotypes included chromosome number (2n), sex chromosome (X) morphology and C-banding patterns. The standard chromosome complement of 50 specimens from different localities is characterized by 2n = 30 + X0 in males. In one male collected in Fruška Gora Mt. (Andrevlje), the chromosome number was reduced to 2n = 28 + neo-XY. Therefore, further cytogenetic studies involving larger samples, especially from Fruška Gora Mt., are needed in order to gain a more comprehensive view of the chromosome evolution in this group of Isophya species.