Mathematics and Science
Bioacoustic research on Turkish bush-crickets
Orthopteran insects are popular group with entomologists and much of the research on bioacoustic studies have been carried out using members of this order. Ensiferan crickets comprise one of the most obvious groups of acoustically active orthopterans. The sounds of them are very di verse and often play a crucial role in reproduction. Males sing and females respond by approaching singing male phonotactically or by producing special acoustic response signals. Typically every species has a species-specific amplitude modulation.
The frequency content comprises both low and ultrasonic range in bush-crickets. In the genus Poecilimon, the frequence maximum is negatively correlated with body size. Sound signals with low frequencies have generally a larger range than those with high frequencies. High frequencies are strongly attenuated in dense vegetation. Using of low frequencies may be sexual selection. In many studies females have been shown to prefer larger than average males. If females judge size on the basis of properties of acoustical signals, they should prefer signals of lower than average frequency, because these might indicate larger males.
In bush-crickets, calling songs of closely related species (such as some Barbitistini species) are often very similar but with some species-specific differences particularly in temporal pattern. Many studies demonstrated that morphologically similar species, the species-specific song pattern represents the main prezygotic isolating barrier. Obviously, not only the calling song becomes different during speciation, but also the male and female genitalia. What kinds of characters are likely to evolve first? Forexample, obviously morphological evolution in Poecilimon syriacus-group, especially that of male genital structures, is faster than the evolution of song characters. Evolutionary speed between morphology and behaviour was already observed in other groups of tettigoniids and may be related to the different functions of song and genitalia during mating.
Spermatophore characteristics and sperm allocation in bush-crickets
I am broadly interested in research topics involving mating behaviour and the evolution of insect mating systems. Of particular interest are questions that address the evolution of sperm allocation strategies, sexual conflict between males and females. My model animals belong to Poecilimon and Isophya.
Theoretical models predict that males should allocate sperm in response to female quality and empirical studies have shown that fecundity traits including age, mass and mating status can influence male sperm allocation strategies. We tested whether female size has an influence on sperm allocation in the bushcricket Poecilimon jonicus jonicus (Orthoptera: Phaneropterinae). Contrary to other studies, we found neither evidence of strategic sperm allocation in response to female size nor an effect of female size on spermatophore size. Male age and mating history was positively related to sperm number during sequential matings, but had no effect on spermatophylax or ampulla weight. Spermatophore weight, but not sperm number, was positively correlated with male body weight. Ampulla weight was positively correlated with spermatophylax weight.
We have been testing the body size/weight influence on sperm allocation in Isophya sikorai and some related taxa including spermatophore characteristics within the some species group and out group.
The genus Isophya Brunner von Wattenwyl
Isophya is one of the most speciose genera of the subfamily Phaneropterinae, including more than 90 species. Tha range of the genus extends from Central Europe to Iran in a west-east direction and from Central Europe/Central Asia to Levant in a North-south direction. However, most species are concentrated around the Black Sea basin, mainly in the Anatolia, Balkans and southwest Caucasus. Particularly, most of the species show a local distribution restricted to some particular topography. More than one-third of the known species of Isophya were reported from Turkey, which is considered to be the radiation centre for this genus. The genus lacks internal sclerotized male genital organs, which are very helpful for species identification. The identification of the species therefore was based mainly on morphological differences in the sahpe of pronotum, tegmina, stridulatory apparatus of male, male cerci and ovipositor.
The genus Poecilimon Fischer
The genus Poecilimon is one of largest genera of bush-crickets with at present around 140 described species. The genus was erected by Fischer 1853, with the Barbitistes jonicus Fieber (=Poecilimon jonicus jonicus) as its type. More than 70 species inhabit Anatolia, most fo them know from western and North-western part of Turkey. The majority of them are endemic to Anatolia. Its center of distribution is situated in the East Mediterranian. Some of the endemic species are found on the Aegean islands which connect Greece with Anatolia, another area with an extremely high diversity of Poecilimon.The species live in shrubby vegetation, glades and edges coniferous forest or open habitats from sea-level to above the timberline. All are short winged, like Isophya, and usually green in color. Most species of Poecilimon can be differentiated most easily by the structure of the male cerci. The relationships between many species are unknown.
Both genera are also interesting from another aspect. Bush-crickets produce their calling songs by stridulation using their fore wings. In the genera and other short-winged members of the Barbitistinae this seems to be the only function, the size of the tegmina varies greatly. In some species they are moderate size, in others small to very small and completely concealed under the pronotum.
Ordu Üniversitesi, Moleküler Biyoloji ve Genetik