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The stick insect Clonopsis gallica is a morphologically stable obligate parthenogen, ranging from North Africa to southern Europe, with a variable karyotype (54–57 chromosomes), considered diploid or triploid. Clonopsis gallica origin and relationships with Clonopsis algerica and Clonopsis maroccana remained unknown. Our Moroccan samples shared the same egg and body patterns and, in addition to C. gallica (2n = 54, XX), comprised the new bisexual Clonopsis sp. 1 (2n = 35/36, X0/XX) and the new all-female Clonopsis sp. 2 (2n = 72, XX), apparently forming a numerically polyploid series with re-diplodized karyotypes; C. gallica could thus be a triploid hybrid in origin. Furthermore, two strains of ameiotic males with 2n = 35 (X0) or 53 (X0) were found, which would maintain themselves as clonal androgens. We could conclude that in stick insects body and karyotype ‘phenotypes’ are considerably independent, thus preventing a sound taxonomy. Generally, the high heterozygosity of hybrids allows parthenogens to persist for long, particularly when hybrid polyploids are produced, as backcrosses of the hybrids to the parental species allow repeated incorporations of genetically diversified genomes. The distribution range of Clonopsis parthenogens appears to realize a sound instance of geographical parthenogenesis. Riassunto Gli insetti stecco (Phasmida) hanno attirato l’attenzione dei biologi per le varie modalita riproduttive messe in atto oltre alla anfigonia, cioe la partenogenesi, l’ibridogenesi e l’androgenesi, spesso correlate all’ibridazione interspecifica ed accompagnate dalla poliploidia. Fra gli insetti stecco del bacino mediterraneo, il genere Clonopsise noto per l’esistenza di due specie anfigoniche nord-africane (C. algerica, C. maroccana) e, soprattutto, per la partenogenetica C. gallica, ad amplissimo areale di distribuzione (nord Africa e tutta l’Europa meridionale). Nonostante le numerose e varie indagini, la sua struttura genetica, grado di ploidia e relazioni filetiche con le altre specie sono incerte o addirittura sconosciute. Nuovi campioni del Rif marocchino, miranti a chiarire alcuni aspetti di questo puzzle, hanno evidenziato l’esistenza di una nuova specie anfigonica, qui indicata come Clonopsis sp. 1 (2n = 35/36, X0/XX), un nuovo taxon partenogenetico, Clonopsis sp. 2 (2n = 72, XX), e confermato la presenza di C. gallica (2n = 54, XX); queste specie nell’insieme formano una serie numericamente poliploide 2-4n, pur mostrando tutte cariotipo strutturalmente diploide. Confrontando questo species-complex con altri noti (Bacillus, Leptynia, Sipyloidea) per risolvere la discrepanza fra numero cromosomico e struttura cariotipica, viene quindi suggerito che i partenogenetici con 54 e 72 cromosomi si siano originati come ibridi triploidi e tetraploidi, rispettivamente, innescando la partenogenesi; il loro assetto cromosomico si sarebbe poi ri-diploidizzato strutturalmente, come e accaduto per il complex S. nelida, come pure per i poliploidi di svariati vertebrati. Inoltre, il campione di Targuist ha fornito, in aggiunta alle femmine Clonopsis sp. 2, anche una femmina dell’anfigonica C. maroccana (2n = 22), di cui viene qui presentato il cariotipo per la prima volta, e due ceppi di soli maschi: 2n = 35, X0 e 2n = 53, X0. Questi maschi hanno meiosi alterata, con spermatociti che si dividono mitoticamente, producendo cosi spermi non ridotti. Viene quindi suggerito che questi maschi, analogamente a quanto osservato in Bacillus, siano androgenetici clonali, che si mantengono inseminando le femmine partenogenetiche sintopiche. La straordinaria somiglianza morfologica di corpi e uova delle specie Clonopsis contrasta notevolmente con l’elevata plasticita del loro cariotipo; cio rende comunque piu comprensibile la nota impossibilita di stabilire i rapporti filogenetici dei fasmidi in base alla citotassonomia. In alcuni gruppi risulta semmai piu attendibile una sistematica basata sull’ootassonomia. Dall’analisi dei nuovi campioni del Rif marocchino verrebbe cosi rinforzato il dato che le forme partenogenetiche, soprattutto se ibride, possono competere con le specie anfigoniche parentali, occupare areali con valenza ecologica molto diversa (da zone montuose ad aree predesertiche) e formare serie poliploidi. Infine, i ceppi androgenetici, oltre che testimoniare la varieta delle modalita riproduttive dei fasmidi, pongono anche il problema della valutazione del loro rango sistematico.

Speciation by hybridization in insects has been recently recognized on the basis of isozyme and chromosome studies showing that several species, either diploid or polyploid, have genomes that combine the genes and chromosome sets of two (or more) bisexual species. Until this evidence became available, thelytokous invertebrates were all considered uniparental derivatives of bisexual species. In this paper, we review examples including the stick insects Bacillus whitei, B. atticus, B. lynceorum, Leptynia hispanica D, Clonopsis gallica, Carausius morosus; the grasshopper Warramaba virgo; some Otiorrhynchus weevils; the planthopper Muellerianella 2-fairmairei–brevipennis; and black flies of the genera Gymnopais and Prosimulium. For several species (e.g., Warramaba virgo and Bacillus whitei), both parental taxa have been recognized, and their hybrid origin has been genetically assessed. In others (e.g., B. atticus), only one of the bisexual parental species has been detected; but their hybrid origin is supported by strong evidence, at both the isozyme and chromosome levels. For other supposed hybrid species (e.g., Clonopsis gallica, Carausius morosus), no bisexual ancestors have been detected, possibly because competition with their hybrid derivatives has made them rare or extinct. Insect hybrid species may differ in their mode of reproduction (apomictic or automictic thelytokous parthenogenesis, gynogenesis), degree of ploidy, and genetic structure (level of heterozygosity, clonal variation). The parallels between insect and vertebrate hybrid species, in which this phenomenon has been recognized and widely studied in the past 50 years, are drawn. The main problems involved in the origin and evolution of hybrid species are discussed, with particular regard to (i) changes in the maturation divisions allowing the transmission of the hybrid genome to the next generation, and (ii) their successful adaptation. The "spontaneous" and "hybrid" theories for the origin of unisexual forms are compared, with regard to hybrid species. An origin of hybrid species from occasional parthenogenetic development of hybrid eggs produced in areas of extensive interspecific hybridization (e.g., disturbed habitats) is suggested. Hybridization would not itself cause changes in the maturation divisions (which are controlled by genes of tychoparthenogenetic eggs) but only favour their selection through heterosis. The role of the so-called "heterotic" advantage (resulting from high levels of heterozygosity) and "demographic" advantage (resulting from all-female reproduction) in the evolutionary success of hybrid species is discussed. It is concluded that habitat disturbance by man is favouring both the onset of hybrid species and their successful spread.

Eggs of 6 Clonopsis gallica (Phasmatodea: Bacillidae) populations have been investigated by means of scanning electron microscopy (SEM) to detect intraspecific differences. Two main chorionic patterns have been observed: type 1 is common to 5 populations, while type 2 is found in the Motril (South Spain) sample. Type-2 sculpturing differs from type-1 in the absence of prominences on the operculum; and hemispheric, isolated mamelons replace the smooth and diffuse prominences of the common pattern on the egg capsule. This suggests that a considerable degree of difference exists in the South Spanish C. gallica . In the 5 type-1 populations, only minor and partially overlapping differences in the opercular pattern have been detected, so that the existence of subspecific taxa is very unlikely among them. Therefore, the Calabrian subspecies C. gallica affinis does not appear to be tenable. This is the 1st report on egg interpopulation differences in the Phasmatodea. These findings suggest further field search, along with karyological and gene-enzyme system analysis, within the C. gallica complex.

The scanning electron microscope morphology and the amino acid composition of the egg capsules of two Lonchodini, Lonchodes pterodactylus and Carausius morosus , are reported. In both species, the egg shows a structural organization common to all Phasmatodea so far investigated. Many details appear to be similar in the two species, such as the egg capsule tubercular sculpturing, the general features of the micropylar plate, and the presence of a well-developed opercular capitulum. These common characteristics fully support the inclusion of these two species within the same tribe. However, differences in the opercular sculpturing patterns, capitulum shape and implantation, micropylar cup conformation, the presence of tubercule-less pits on the egg capsule, and the polar mound in L. pterodactylus , indicate not only specific differences, but also at the generic level. Egg chorion characteristics therefore appear, to be of high taxonomic value in the Phasmatodea. From our analysis, it appears that the frequent anomalies of the micropylar plate in C. morosus are not directly related to the internal abdominal pressure in the female, as formerly suggested, but rather to ovariolar disturbances due to intersexuality. The chemical information obtained from amino acid analysis of the egg shell of the two species has confirmed a high glycine content, a stable quantity of serine, and trace amounts of cystine and methionine, and also showed a marked difference in tyrosine, when compared with the bacilline, Clonopsis gallica . The amino acid composition of the stick insect egg shell suggests that its proteins resemble silk proteins. Thus, the egg morphology at scanning electron microscope level and the amino acid composition data contribute to both ootaxonomy and better understanding of the phylogeny of the order.

The scanning electron microscope morphology and the amino acid composition of the egg capsule of the stick insect Clonopsis gallica have been studied. The egg capsule shows an irregular but characteristic pattern of rounded tubercules, which at higher magnifications reveal a still more detailed sculpturing. The micropylar plate shows specific structural characters, including a shallow square micropylar cup without micropylar orifices; ovariolar eggs, however, show a number (from 3 to 5) of wide, open micropyles. The opeculum does not possess the capitulum nor the pseudocapitulum, but among the prominent tubercules of the central area some aeropyles are present. The thick 3-layered chorion has a uniformly smooth internal surface; the spongy submicropylar plate possesses a tubule connecting the chorion to the vitelline membrane. The amino acid composition has revealed that glycine is the most common residue (33%), followed by serine and alanine (about 10% each), with traces of cystine and methionine. SEM features specifically identify the egg of C. gallica but also reveal some genuine similarities with the egg of B. rossius. The meaning of the existence of the micropylar orifices during egg development has been discussed. The amino acid composition is a new datum for the Cheleutoptera and it has been compared with that of insects having an orthopteroid structure. In particular, the high glycine content in C. gallica egg shell suggests a certain resemblance with the species of 5 families of Tettigonioidea, whilst there are definite differences with species of Gryllidae and Acrididae. Thus, the egg morphology and amino acid composition data can be utilized as aids in understanding the phylogeny and egg physiology in several insect orders.