Article

Hybridization between Saga pedo (Pallas 1771) and Saga rammei Kaltenbach 1965 (Orthoptera: Tettigonlidae)

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  • Groupement d'Etudes Entomologiques Méditerranée
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Abstract

Since 2004, hybridizations in captivity were tested between Saga pedo (Pallas 1771), a parthenogenetic species, and various bisexual closely related species of the Balkans: Saga hellenica Kaltenbach 1967, Saga rammei Kaltenbach 1965 and Saga campbelli Uvarov 1921. Mating with formation of spermatophores were noted in all cases. The first hatching, resulting from a female of S. pedo with a male of S. rammei, occurred in April 2006.

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... Hybrids (S. rammei =6S. pedo R)obtained from matings in captivity were also described, based on their morphometric characterisation [31]. ...
... Hybrids (S. rammei =6S. pedo R)obtained from matings in captivity were also described, based on their morphometric characterisation [31]. The aim of the present work was to determine the evolutionary relationships between the European Saga species, and to shed light on the likely origin of the most peculiar species of the genus, the parthenogenetic bush cricket. ...
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Twelve of the 13 bushcricket species of the Saga genus are bisexuals and diploids, except the parthenogenetic and tetraploid bush cricket, Saga pedo. Despite a continuous research effort stretching through the 1900s, the taxonomic relationships of the Saga species are still disputed. In this study, our primary aim was to reveal natural relationships of the European Saga species and three of their Asian relatives, with special attention to the problematic taxonomy of two subspecies: S. campbelli campbelli and S. c. gracilis. Following a phylogenetic analysis of eight species, a comprehensive study was carried out on the above three taxa by using acoustic and morphometric approaches in parallel. Our phylogenetic data showed that European Saga species evolved from a monophyletic lineage. The geographical transitional species S. cappadocica was positioned between European and Asian lineages supporting the idea that the European Saga lineage originated phylogeographically from the Asian clade. The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only. After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies. S. c. gracilis shares the same ITS2 haplotype with S. pedo, indicating that the latter could have evolved from populations of the former, probably through whole genome duplication. Based on acoustic and morphometric differences, we propose to elevate the two subspecies, S. campbelli campbelli and S. c. gracilis, to species level status, as Saga gracilis Kis 1962, and Saga campbelli Uvarov 1921. The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.
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Karyotypes of the polyploid parthenogenetic species Saga pedo from four localities in France and the Republic of Macedonia were constructed and compared. All these karyotypes consist of 70 chromosomes, which is more than twice that in other species of the genus. The chromosomes differ from each other, making the matching of homologues difficult. Karyotypes of French specimens are similar, except for differences in the heterochromatin. Compared to that of the Macedonian specimens those from French specimens differ by the shortening of a single chromosome. The difficulty experienced in identifying tetrads and even pairs of chromosomes indicates that either many chromosome rearrangements have occurred since the polyploidisation event(s) or that the addition of quite different genomes is the cause. On the other hand, that the karyotypes are similar indicates a common origin of both the Macedonian and French populations. Thus, most chromosome changes preceded the separation from their common ancestor. Both the DNA content and chromosome analyses suggest that the S. pedo karyotype is pentaploid and not tetraploid as previously proposed. This odd ploidy number rules out the hypothesis that it could only have originated by endoreduplication. It is more likely that it originated by the association of five copies of the 14,X haploid karyotype, which exists in the gametes of the closely related species, S. campbelli and S. rammei (male / female 2n = 27, X / 28, XX). Fertilization of a parthenogenetic 56, XXXX female by a 14, X spermatozoa could have resulted in the last increase in ploidy.
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Dans le cadre de ses recherches sur le genre Saga, le G.E.E.M. enregistre en mai 2009 la naissance en élevage, d’un male et d’une femelle issus du croisement d’une femelle de Saga campbelli Kaltenbach 1965 avec un mâle de Saga hellenica Kaltenbach 1967. L’analyse cytogénétique de la femelle hybride confirme son origine hybride et qu’une seule translocation robertsonienne sépare les caryotypes de S. hellenica de S. campbelli. L’habitus du mâle montre une affinité plus forte avec S. hellenica qu’avec S. campbelli.
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Environmental shifts and life-history changes may result in formerly adaptive traits becoming non-functional or maladaptive. In the absence of pleiotropy and other constraints, such traits may decay as a consequence of neutral mutation accumulation or selective processes, highlighting the importance of natural selection for adaptations. A suite of traits are expected to lose their adaptive function in asexual organisms derived from sexual ancestors, and the many independent transitions to asexuality allow for comparative studies of parallel trait maintenance versus decay. In addition, because certain traits, notably male-specific traits, are usually not exposed to selection under asexuality, their decay would have to occur as a consequence of drift. Selective processes could drive the decay of traits associated with costs, which may be the case for the majority of sexual traits expressed in females. We review the fate of male and female sexual traits in 93 animal lineages characterized by asexual reproduction, covering a broad taxon range including molluscs, arachnids, diplopods, crustaceans and eleven different hexapod orders. Many asexual lineages are still able occasionally to produce males. These asexually produced males are often largely or even fully functional, revealing that major developmental pathways can remain quiescent and functional over extended time periods. By contrast, for asexual females, there is a parallel and rapid decay of sexual traits, especially of traits related to mate attraction and location, as expected given the considerable costs often associated with the expression of these traits. The level of decay of female sexual traits, in addition to asexual females being unable to fertilize their eggs, would severely impede reversals to sexual reproduction, even in recently derived asexual lineages. More generally, the parallel maintenance versus decay of different trait types across diverse asexual lineages suggests that neutral traits display little or no decay even after extended periods under relaxed selection, while extensive decay for selected traits occurs extremely quickly. These patterns also highlight that adaptations can fix rapidly in natural populations of asexual organisms, in spite of their mode of reproduction.
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Parthenogenesis in bushcrickets has an incidence of less than 1%. In the diploid bushcricket Poecilimon intermedius, rearing indicates obligate, thelytokous parthenogenesis. Antibiotic treatment of P. intermedius was not effective in restoring male production, and negative results from PCR screening excluded feminizing endosymbionts, such as Wolbachia, as a reason for the lack of males. The geographical range of P. intermedius follows the general pattern of geographical parthenogenesis, being more northerly and much larger than in the sexual relatives. This is a rare example of geographical parthenogenesis that is not attributable to endosymbiont infection or polyploidy. Females of the parthenogenetic species show differential decay of mating-related behaviour. While interspecific matings were readily achieved in captivity, with spermatophores being transferred and sperm successfully entering the females, the parthenogenetic females exhibit no phonotaxis towards singing males.
Article
The males of two species of Palestine,Saga ephippigera Fisch. andS. gracilipes Uvar have respectively 33 and 31 chromosomes in the diploid state.S. pedo Pallas, a parthenogenetic thelytoc species largely distributed in Europe, has 68 chromosomes and probably represents a tetraploid. The cells of the three species have identical dimensions and the polyploidS. pedo is even the smallest in size.
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