Gennaro Aprea

Mitochondrial DNA variation in the caramote prawn Penaeus (Melicertus) kerathurus across a transition zone in the Mediterranean Sea

In this study we analysed mitochondrial DNA variation in Penaeus kerathurus prawns collected from seven locations along a transect across the Siculo–Tunisian region in order to verify if any population structuring exists over a limited geographical scale and to delineate the putative transition zone with sufficient accuracy. Partial DNA sequences of COI and 16S genes were analysed. In contrast to the highly conservative 16S gene, the COI sequences exhibited sufficient diversity for population analysis. The COI gene revealed low levels of haplotype and nucleotide diversities. The size of the annual landings of this commercial species suggests large population sizes. Hence, the low genetic diversity detected in this study could indicate a possible reduction in effective population sizes in the past. We detected significant genetic differentiation between eastern and western populations likely due to restricted gene flow across the Siculo–Tunisian boundary. We discuss the different evolutionary forces that may have shaped the genetic variation and suggest that the genetic divide is probably maintained by present-day dispersal limitation.

Ancient tetraploidy and slow molecular evolution in Scaphiophryne: ecological correlates of speciation mode in Malagasy relict amphibians

Karyotypes of three microhylid frog species of the Malagasy relict genus Scaphiophryne were studied: Scaphiophryne gottlebei, S. madagascariensis and S. spinosa. The latter two showed a plesiomorphic ranoid karyotype of 2n = 26. In contrast, tetraploidy was demonstrated in S. gottlebei, which constitutes an exceptional state among Malagasy amphibians. A combination of different banding techniques and of rDNA-FISH provided evidence for allopolyploidy in the species and for a completed subsequent functional and structural diploidization. Phylogenetic analysis of mitochondrial 16S rDNA sequences revealed a significant deceleration of nucleotide substitution rates in Scaphiophryne. The tetraploidy of S. gottlebei probably occurred early in their radiation. Ecological and behavioural patterns of Scaphiophryne probably favoured intraspecific gene flow and hybridization events, thereby leading to slow molecular substitution rates and to allopolyploid chromosome speciation in S. gottlebei.

Chromosomal and molecular analysis of some repeated families in Discoglossus Otth, 1837 (Anura, Discoglossidae): Taxonomic and phylogenetic implications

Abstract We conducted a cytogenetic and molecular analysis in six out of the eight Discoglossus taxa CD. pictus pictus, D. p. auritus, D. sardus, D. montalentii, D. galganoi galganoi and D. g. jean‐neae) All the taxa possessed 2n = 28 biarmed chromosomes, except D. pictus pictus where the 13th pair was acrocentric, and the NORs were located on the short arm of the 7th pair in all the taxa but D. galganoi, where they were on the short arm of the 13th pair. Heterochromatin was detected by banding methods (C‐band‐ing, base‐specific fluorochromes, replication patterns and digestions with restriction enzymes). The techniques used were able to discriminate among all the Discoglussus taxa studied, identifying several heterochromatin families with marked differences in chromosome location and/or in the behaviour of the banding techniques used. The differentiation of these heterochromatin families can have either a phylogenetic (as is the case with A+T rich cen‐tromeric heterochromatin) or an adaptive (G+C rich in...

Evidence for chromosome and Pst I satellite DNA family evolutionary stasis in the Bufo viridis group (Amphibia, Anura).

The West Palearctic green toads, Bufo viridis, represent a species complex. Apart from tetraploid populations, which form at least one separate species, evidence exists for relevant differentiation among diploid populations. We present the results of a chromosomal (C-, Ag-NOR-, Replication pattern, DAPI and CMA3 banding) and molecular study (isolation and characterization of a satellite DNA family) carried out on a number of Central Asian, European and North African populations. For comparative purposes, our molecular analysis was also extended to specimens of three additional Bufo species (B. bufo, B. mauritanicus and B. cf. regularis), as well as two rare African bufonids (Werneria mertensis and Wolterstoffina sp.). Our results demonstrate a remarkable karyological and molecular evolutionary stasis in the Bufo viridis complex. In fact, all chromatinic markers showed the same pattern and/or composition in all specimens, independently of their origin and ploidy levels. Even the NOR loci were invariably two and located on the telomeric regions of two chromosomes of the sixth pair, or quartet. Furthermore, very similar patterns of genomic hybridization of a monomeric unit of the Pst I satellite DNA family (named pBv) were observed in all diploid and tetraploid populations, as well as in B. bufo and B. mauritanicus. Finally, pBv hybridizes with monomeric units of Pst I satellite DNA in all species studied, including Werneria and Wolterstorffina, which are thought to have separated from Bufo as early as in the Mesozoic.

A chromosomal study of Eumeces and Scincus, primitive members of the Scincidae (Reptilia, Squamata)

Abstract Standard karyotypes and NOR chromosomal localizations were compared in species of the genera Eumeces and Scincus. A remarkable karyological heterogeneity was revealed within the genus Eumeces, as well as a resemblance between the karyotypes of some Palaearctic species of this genus (E. schneidern, E. algeriensis) and those of species of the genus Scincus (S. scincus and S. hem‐prichii). An XY sex‐chromosome NOR‐associated heteromorphism was identified in S. scincus.

Karyology of the Antarctic scallop Adamussium colbecki, with some comments on the karyological evolution of pectinids.

Karyotype, location of the nucleolar organiser region (NOR) and heterochromatin presence and composition were studied in the Antarctic scallop Adamussium colbecki Smith, 1902. The karyotype exhibits 2n = 38 chromosomes with 11 pairs of metacentrics, 5 of submetacentrics, one subtelocentric and two telocentrics. Ag–NOR, CMA3, DA/MM and NOR–FISH evidenced paracentromeric NORs on the short arm of 2nd pair chromosomes. Digestion with three restriction endonucleases followed by sequential staining with Giemsa, CMA3 and DAPI evidenced on all chromosomes centromeric heterochromatin positive for both DAPI and CMA3. In situ hybridisation analysis showed the presence of an AT-rich satellite DNA in the centromeric heterochromatin of several chromosomes. A mosaicism was detected in the germinal cell lines of one specimen, as in six of the 20 plates examined the set had 37 chromosomes with a missing pair of telocentrics and an unpaired metacentric. Comparison of the chromosome sets of all the pectinids studied to date and comparison with a phyletic tree obtained from molecular mitochondrial genes studies yielded good agreement between karyotype morphology and taxonomic classification.

Karyological and genetic variation in Middle Eastern lacertid lizards, Lacerta laevis and the Lacerta kulzeri complex: a case of chromosomal allopatric speciation.

AbstractKaryological (standard and C, Ag-NOR and Alu-I banding methods) and mtDNA analyses (cytochrome b and 12S rRNA) were conducted on specimens from eight allopatric populations of the Lacerta kulzeri complex. Parallel analyses were performed for comparison on Lacerta laevis specimens. Karyological and molecular studies support the morphological and ethological evidence indicating the specific separation between Lacerta laevis and Lacerta kulzeri In the Lacerta kulzeri complex, chromosomal analysis substantiated an interpopulation differentiation roughly along a north–south trend, mainly regarding the sex chromosome morphology and heterochromatin.The cytochrome b and 12S rRNA gene analyses showed minor genetic differences that were considerably smaller than those commonly found in genetically isolated populations. The L. kulzeri populations from Barouk, Druze and Hermon show a mean genetic distance that, in other saurians, characterises subspecies.The conditions found in L. laevis and L. kulzeri are reminiscent of Kings model of chromosomal primary allopatry and support the hypothesis that in these lacertid lizards chromosome variations can become fixed before the accumulation of the genetic mutations.

Progressive differentiation of the W sex‐chromosome between oviparous and viviparous populations of Zootoca vivipara (Reptilia, Lacertidae)

Abstract Populations of Zootoca vivipara appear karyologically well differentiated by heterochromatin distribution both in autosomes and sex‐chromosomes; allopatric oviparous populations possess few elements with centromeric heterochromatin and W acrocen‐tric sex‐chromosomes with heterochromatin only on the centromere; Alpine, as well as central‐western European viviparous populations possess conspicuous centromeric bands of heterochromatin on all of the chromosome pairs and a metacentric W chromosome with paracentromeric and telomeric heterochromatin bands; viviparous populations, living east and possibly north of the Carpathian Mountains, have many elements with interstitial and telomeric heterochromatin and an acrocentric W chromosome with telomeric and subtelomeric heterochroma. These data suggest an origin and evolution of sex‐chromosomes in this species, that, interestingly, parallels the recent hypothesis (Heulin et al., 1993) on the rise and evolution of viviparity and speciation in Zootoca.

Chromosome Data for Malagasy Poison Frogs (Amphibia: Ranidae: Mantella) and Their Bearing on Taxonomy and Phylogeny

Abstract We compared chromosome morphologies for 11 species of Malagasy poison frogs, genus Mantella, and three outgroup taxa (genus Mantidactylus) using conventional and fluorescence staining techniques. All species studied had a karyotype of 2n=26, with five larger and eight smaller chromosome pairs. The 11th pair was acrocentic in Mantella nigricans which represents the first such observation in the genus. The nucleolus organizer region (NOR) was located at secondary constrictions on chromosome pair 2 in all Mantella studied and in Mantidactylus grandisonae (while located on other chromosomes in all other species of Mantidactylus studied so far). Heterochromatin distribution was highly variable among Mantella species; C-bands positively staining with DAPI and CMA3 were observed. The possible structure of these bands, seemingly containing both A+T rich and C+G rich heterochromatin, is discussed. Phylogenetic reconstruction using chromosomal characters provided very little information. Evolution of the characters studied is probably either too fast (heterochromatin arrangement) or too slow (NOR location) to match the main cladogenetic events among Mantella species groups.

Cytological and molecular analysis in the rare discoglossid species, Alytes muletensis (Sanchiz & Adrover 1977) and its bearing on archaeobatrachian phylogeny

Cytogenetic and molecular data on Alytes muletensis (Amphibia: Discoglossidae) are compared with other representatives of archaeobatrachian frogs: Bombina variegata pachypus, Pelobates cultripes, Pelodytes punctatus, Xenopus laevis, and Discoglossus. A. muletensis has the karyotype typical for the genus Alytes, 38 elements with either one or two arms, some of which can be considered as ‘microchromosomes’. The NORs are located on the telomeres of the tenth chromosome pair which agrees with the state in A. obstetricians but differs from A. cisternasii reflecting phylogenetic affinities. C-banding and staining with DAPI and chromomycin A3 revealed important blocks of telomeric CMA-positive heterochromatin on the smaller chromosomes of Alytes, similar to the state found in Discoglossus. Phylogenetic analysis of 750 bp of fragments of the mitochondrial 16S and 12S rRNA genes corroborated that Discoglossus and Alytes are sister taxa which together probably form the sister group of the Bombinatorinae. Centromeric heterochromatin in Alytes may be responsible for the retention of a plesiomorphic asymmetric karyotype which independently has evolved into a symmetric karyotype through centric fusions in Bombina and Discoglossus. The HindIII satellite DNA family was present in all archaeobatrachians studied but absent in hyloid and ranoid neobatrachians.