Maria Vittoria Civitelli

Chromosomal Mechanisms in the Evolution of Chiropteran Karyotype Chromosomal Tables of Chiroptera

ABSTRACTChromosomal mechanisms involved in the evolution of the karyotype were examined in Chiroptera. In particular the Robertsonian process of centric fusion-fission was thoroughly studied. On the basis of karyological and morphological observations, the Authors aim to demonstrate that the Robertsonian change does not proceed in a single direction; it just provides a cytological basis for the onset of a genetic barrier. The importance of other chromosomal changes in the karyotypic evolution of Chiroptera has also been pointed out. A complete table of karyological data in Chiroptera is provided.

I Cromosomi del Pipistrello Albolimbato

RIASSUNTOIn base alla analisi cariometrica, e stato definito il cariogramma di Pipistrellus kuhli (Natt. in Kuhl). Il cariogramma comprende 21 coppie di autosomi ed una coppia di eterocromosomi; delle 21 coppie autosomiche, tre sono di metacentrici grandi, una di piccoli metacentrici, 15 di acrocentrici, di cui una coppia mostra chiaramente una zona eterocromatica, 2 di cromosomi puntiformi. Il cromosoma X e un metacentrico di medie dimensioni, il cromosoma Y un puntiforme.E stato fatto inoltre un confronto tra il cariogramma di Pipistrellus kuhli e quelli di P. pipistrellus e P. nathusi (Bovey 1949). E stato anche fatto un confronto con i dati della cariornetria di Miniopterus schreibersii (Capanna e Civitelli 1965).

Genome size variations are related to X‐chromosome heterochromatin polymorphism in Arvicanthis sp. from Benin (West Africa)

Abstract The African grass rat, Arvicanthis sp., from Benin shows sex‐chromosome polymorphism for the presence in the karyotype of three X‐chromosome forms: subtelocentric (Xst), submetacentric (Xsm), and metacentric (Xm). Here we report statistically significant differences of diploid genome size (g.s.) among individuals, from 6.22 ± 0.06 pg to 6.80 ± 0.10 pg, depending on the X‐chromosome form. The evaluation of the total and X‐chromosome heterochromatin content alone (Xst: 2.16 ± 0.22%; Xsm: 5.02 ± 0.22%; Xm: 6.54 ± 0.28%), supports this suggestion. DNA base‐pair preferential staining revealed that heterochromatin of both autosome and sex chromosomes is AT‐rich. Digestion of genomic DNA with sixteen restriction enzymes produced DNA bands representing the repetitive fraction of the genome. When these were used as probes for fluorescence in situ hybridization (FISH), two hybridization patterns were found: a) FISH positive signals localized in the pericentromeric areas of every chromosome of the complemen...

Cariologia e Cariometria del Miniottero (Mammalia — Chiroptera)

RIASSUNTOIn base ad una precisa analisi cariometrica, e stato definito il cariogramma di Miniopterus schreibersii (Natt. in Kuhl). II cariogramma comprende ventidue coppie di autosomi ed una coppia di eterocromosomi; delle ventidue coppie autosomiche, tre sono di cromosomi metacentrici, tra loro chiaramente differenziabili per la lunghezza media e la posizione del centromero, diciassette coppie sono eli cromosomi acrocentrici e due coppie di puntiformi. Il cromosoma X e un metacentrico di medie dimensioni, il cromosoma Y e un puntiforme.

Evolutionary genetics and systematics of the garden dormouse, Eliomys Wagner 1840.1‐karyotype divergence

Abstract Data on the system of chromosomal variability of the garden dormouse, Eliomys, are reported. Ten populations from Italy, Austria, and Morocco were analyzed cytogenetically. Five different di‐ploid numbers (2n = 46, 48, 50, 52, 54) were found and the karyotypes were compared analyzing G and C banding patterns. The G‐band analysis demonstrated that the European karyotypes (2n = 48, 50, 52, 54) originated through successive Robertsonian fissions, involving the metacentric pairs 12, 13, and 7. The Moroccan population (2n = 46) lacks the smallest acrocentric pair (No. 23). The comparison of the G‐band pattern between the European and the Israeli 48 chromosome dormice revealed chromosomal rearrangement of the largest subtelocentric (pair No. 1). It is suggested that the 48 chromosome karyotype is ancestral.

Genetic divergence in the genus Arvicanthis (Rodentia: Murinae)

Allozyme variation in four species of Arvicanthis (Arvicanthis sp. from Benin, A. abyssinicus, A. blicki, and A. dembeensis from Ethiopia) was studied by means of allozyme electrophoresis at 25 presumptive gene loci. Arvicanthis sp. showed high genetic differentiation from the three Ethiopian species (D = 0.839). Conversely, little genetic differentiation (D = 0.073) was observed between the sibling species A. abyssinicus and A. blicki, which are genetically more closely related to each other than to A. dembeensis (D = 0.234). This pattern is consistent with that based on chromosome rearrangements.

Chromosomal Polymorphism in an Alpine Population of Mus Musculus L.

Abstract Una popolazione alpina di Mus musculus L. e stata studiata dal punto di vista cromosomico ed ha rivelato numeri diploidi, nei 5 individui esaminati, pari a 2n = 27, 30, 32, 37; il numero fondamentale rimane pero inalterato ed uguale a quello che caratterizza Mus musculus, NF = 40. Lo studio delle diacinesi meiotiche e del cariotipo degli ibridi F1 ed F2 e R in esperienze di incrocio con topi albini di ceppo Suisse (2n = 40; NF = 40) dimostra la presenza di almeno 4 fenotipi cromosomici aploidi: n = 12, n = 13, n = 14, ed n = 19. I rapporti con il cariotipo di Mus poschiavinus Fatio (2n = 26; NF = 40) sono stati discussi.

Les chromosomes des rongeurs du Bénin (Afrique de l’ouest): 3 murinae

The karyotype has been studied in 7 species of Murinae,i.e. Mastomys natalensis, Mastomys erythroleucus,Arvicanthis niloticus, Rattus rattus, Lemniscomys striatus, Dasymys rufulus, andPraomys tullbergi minor from forest and cultivated areas of the Republic of Benin (West Africa). The diploid numbers observed are:Mastomys natalensis 2n = 32,M. erythroleucus 2n = 38,Arvicanthis niloticus 2n = 62,Rattus rattus 2n = 38,Lemniscomys striatus 2n= 44,Dasymys rufulus 2n = 36,Praomys tullbergi minor 2n= 34. The data was discussed within the problem of chromosomal variability affecting several murinae species from Africa.RiassuntoÈ stato studiato il cariotipo di sette specie di Murini,Mastomys natalensis, Mastomys erythroleucus, Arvicanthis niloticus,Rattus rattus, Lemniscomys striatus. Dasymys rufulus ePraomys tullbergi minor, provenienti da biotopi forestall e da coltivi del Benin meridionale (Africa occidentale). I cromosomi sono stati ottenuti attraverso la comune tecnica da midollo rosso delle ossa e da cellule coltivatein vitro. I numeri diploidi osservati sono rispettivamente:Mastomys natalensis 2n= 32,M. erythroleucus 2n= 38,Arvicanthis niloticus 2n= 62,Rattus rattus 2n = 38,Lemniscomys striatus 2n = 44,Dasymys rufulus 2n= 36 ePraomys tullbergi minor 2n= 34. I dati sono stati discussi nell’ambito dei problemi di variabilità cromosomica che interessano varie specie di murini africani.

Karyotypic and genetic divergence in the Ethiopian Myomys ‐ Stenocephalemys complex (Mammalia, Rodentia)

Abstract The Ethiopian Myomys ‐ Stenocephalemys complex has long constituted a taxonomic and systematic puzzle. The species occur at different altitudes, from 1000 up to 4300 m a.s.l., and show remarkable adaptations to high altitude habitats. The four species forming the complex, M. albipes, M. ruppi, S. albocaudata and S. griseicauda, are all endemic to the country and constitute a monophyletic group. We describe their karyotypes, including their G‐ and C‐ banding patterns, and their allozyme patterns. Phylogenetic trees based on chromosomal rearrangements and al‐lozymes support the current taxonomy. Nonetheless, comparisons with genetic similarity data and other hypotheses drawn from mtDNA and geometric morphometrics show substantial disagreement, and therefore it is not possible to claim the paraphyly of Stenocephalemys which would then include Myomys.

The chromosomes of Lemniscomys barbarus (Rodentia, Muridae)

The somatic and meiotic chromosomes of Lemniscomys barbarus, belonging to an isolated Maghreb population, were studied. The karyotype was analysed using and G banding techniques and silver-staining for the nucleolus organizer regions (NORs) and was found to consist of 54 chromosomes. The constitutive heterochromatin was widely distributed throughout the centromeric regions of numerous autosomes and of the X heterochromoso mes, while two pairs of chromosomes displayed NOR bands. Karyotypic differences ascribable to pericentric inversions emerged from a comparison with Mattheys (1954) observations for the same species.