Geographic differentiation in male calling song of Isophya modestior (Orthoptera, Tettigoniidae, Phaneropterinae)

Abstract

We studied the songs and morphology of the stridulatory file of Isophya modestior across its complete geographic range, in order to test our hypothesis that the male calling song of the species shows strong differentiation between the northern (Pannonian) and southern (Balkan) parts of its distribution range, reflecting its disjunct distribution. Our analyses confirm this hypothesis, separating analyzed specimens of I. modestior into two main groups - one present in the central part of the Balkan Peninsula (representing Isophya modestiorsensu stricto), with the second group occurring in the Pannonian Basin, Dinarides, Slovenia and NE Italy. The most reliable difference between the groups is the duration of the main syllable, the number of stridulatory teeth and number of pulses in the main syllable, where all values are higher in specimens from the Balkan Peninsula. Additional analyses showed that within the second group, there are differences in analyzed characters between specimens from the Pannonian Basin and specimens from the Dinaric area, the latter ones having intermediate song characteristics, closer to the group from the Balkan Peninsula. Our study shows that detailed bioacoustic analyses can help to unravel patterns of intraspecific differentiation and thus provide a useful tool for taxonomic studies.

The taxonomic status of recently described Isophya taxa from Serbia (Tettigoniidae, Phaneropterinae)

“…Our study shows that all recently described species and subspecies of Isophya from Serbia are phylogenetically not distinct from I. modestior. Specimens analyzed in this study confirmed the considerable morphological and bioacoustic variation found among different populations, which correspond with the results presented in previous publications (Ivković et al 2022(Ivković et al , 2023 Although the species is missing in some parts of its wider distribution (Fig. 7; Supp.…”

“…The calling songs in all new analysed specimens were similar to those described in Ivković et al (2022), single diminuending syllables, with one after-click in some specimens (Fig. 5).…”

“…Previous studies on I. modestior showed high phylogenetic, karyotypic and bioacoustic variability across its distributional range (Ivković et al 2022(Ivković et al , 2023. Analyses of the male calling songs and morphology of the stridulatory file showed that the species is separated into two main groups -Group A present in the central part of the Balkan Peninsula (representing Isophya modestior sensu stricto), and Group B occurring in the Pannonian Basin, Dinarides, Slovenia and NE Italy.…”

“…file 11I-N). They also have a higher number of teeth on the stridulatory file than populations from the Pannonian region (Ivković et al 2022;Supp. file 12), but in both cases exceptions occur.…”

“…Due to the high morphological similarity between newly described taxa and I. modestior, and the strong intraspecific variability found in previous research (Ivković et al 2022), we decided to compare bioacoustic and genetic data from specimens collected at the type localities of the recently described taxa in order to verify their taxonomic validity. Furthermore, we provide new bioacoustic data from specimens collected in Romania and Italy that were missing in our previous study (Ivković et al 2022). The morphological characters showing intra-and interpopulation variability within the species are discussed.…”