Detection of cryptic diversity in lizards (Squamata) from two Biosphere Reserves in Mesoamerica.

A combined approach based on karyology and DNA taxonomy allowed us to characterize the taxonomic peculiarities in 10 Mesoamerican lizard species, belonging to six genera and five families, inhabiting two Biosphere Reserve in Chiapas, Mexico: La Sepultura Biosphere Reserve, and Montes Azules Biosphere. The karyotypes of four species, Phyllodactylus sp. 3 (P. tuberculosus species group) (2n = 38), Holcosus festivus (Lichtenstein et von Martens, 1856) (2n = 50), Anolis lemurinus Cope, 1861 (2n = 40), and A. uniformis Cope, 1885 (2n = 29-30) are described for the first time, the last one showing a particular X1X1X2X2/X1X2Y condition. In Aspidoscelis deppii (Wiegmann, 1834) (2n = 50) and Anolis capito Peters, 1863 (2n = 42), we found a different karyotype from the ones previously reported for these species. Moreover, in A. capito, the cytogenetic observation is concurrent with a considerable genetic divergence (9%) at the studied mtDNA marker (MT-ND2), which is indicative of a putative new cryptic species. The skink Scincella cherriei (Cope, 1893), showed high values of genetic divergence (5.2% at 16S gene) between the specimens from Montes Azules and those from Costa Rica and Nicaragua, comparable to the values typical of sister species in skinks. A lower level of genetic divergence, compatible with an intraspecific phylogeographic structure, has been identified in Lepidophyma flavimaculatum Duméril, 1851. These new data identify taxa that urgently require more in-depth taxonomic studies especially in these areas where habitat alteration is proceeding at an alarming rate.

The Sicilian Wolf: Genetic Identity of a Recently Extinct Insular Population.

Historically, many local grey wolf (Canis lupus) populations have undergone substantial reductions in size or become extinct. Among these, the wolf population once living in Sicily, the largest island in the Mediterranean Sea, was completely eradicated by human activity in the early decades of the 20th century. To gain a better understanding of the genetic identity of the Sicilian wolf, we used techniques for the study of ancient DNA to analyze the mitochondrial (mt) variability of six specimens stored in Italian museums. We were able to amplify a diagnostic mtDNA fragment of the control region (CR) in four of the samples. Two of the samples shared the same haplotype, differing by two substitutions from the currently most diffused Italian wolf haplotype (W14) and one substitution from the only other Italian haplotype (W16). The third sample showed a previously unreported wolf-like haplotype, and the fourth a haplotype commonly found in dogs. All of the wolf haplotypes analyzed in this study belonged to the mitochondrial haplogroup that includes haplotypes detected in all the known European Pleistocene wolves and in several modern southern European populations. Unfortunately, this endemic island population, which exhibited unique mtDNA variability, was definitively lost before it was possible to understand its taxonomic uniqueness and conservational value.

The first cytogenetic description of Euleptes europaea (Gené, 1839) from Northern Sardinia reveals the highest diploid chromosome number among sphaerodactylid geckos (Sphaerodactylidae, Squamata).

The karyotype of a sphaerodactylid gecko Euleptes europaea (Gené, 1839) was assembled for the first time in this species. It is made of 2n = 42 gradually decreasing in size chromosomes, the highest chromosome number so far acknowledged in the family Sphaerodactylidae. The second chromosome pair of the karyotype appears slightly heteromorphic in the male individual. Accordingly, FISH with a telomeric probe revealed an uneven distribution of telomeric repeats on the two homologues of this pair, which may be indicative of an XY sex-determination system in the species, to be further investigated.

5S ribosomal RNA genes in six species of Mediterranean grey mullets: genomic organization and phylogenetic inference.

This paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus.

Mitochondrial phylogeny reveals differential modes of chromosomal evolution in the genus Tatera (Rodentia: Gerbillinae) in Africa.

The African gerbils of the genus Tatera are widespread and abundant throughout sub-Saharan Africa. There is still today a certain controversy concerning the taxonomy of these rodents and very few attempts have been made to assess their systematic relationships. The present paper introduces findings based on the partial sequences of cytochrome b (495 bp) and the 16S rRNA (469 bp) mitochondrial genes of six (T. robusta, T. nigricauda, T. vicina, T. leucogaster, T. valida, and T. kempi) species together with two additional taxa. We also report the karyotypes of T. vicina and T. leucogaster. We propose that T. vicina should be considered as a valid species and show the monophyly of the robusta species group, with the exclusion of T. leucogaster. Our results show there is a different chromosomal evolutionary pattern within the two major lineages, which is recognizable through molecular phylogenetics. One is characterized by karyotype stability and the other by a considerable number of chromosomal rearrangements. The lineage divergence coincides with the formation of the East African Rift. The processes that led to the origin of the East African species seem to be related to the subsequent climatic changes, which caused cyclic contraction and expansion of the savannah biomes. Furthermore, geological activities that characterized East Africa during Plio-Pleistocene may also have contributed to lineage divergence.

Chromosomal and molecular characterization of Aethomys kaiseri from Zambia and Aethomys chrysophilus from Tanzania (Rodentia, Muridae).

Aethomys is a common and widespread rodent genus in the African savannas and grasslands. However, its systematics and taxonomy are still unclear as no study has covered the entire range. In fact it might not be a monophyletic genus and perhaps should be split into two subgenera, Micaelamys and Aethomys. In this paper, we present findings based on the cytogenetics and the entire cytochrome b sequence of two species from Zambia (A. kaiseri) and Tanzania (A. chrysophilus), and we compare them with the sequences of a South African species (A. namaquensis) and other allied muroid genera. Comparison of the banded chromosomes revealed complete G-band homology between the autosomes of the two species. However, the X and Y chromosomes clearly differ in size and in C- and G-banding, being much larger in A. kaiseri. Comparison of the cytochrome b sequences places the separation between A. kaiseri and A. chrysophilus at 4.49 Mya, a period of intense speciation in other African muroids. The resulting phylogeny strongly supports the idea of a paraphyletic group, suggesting the need to elevate the previously described subgenera to the genus rank.

Comparative structure analysis of vertebrate U17 small nucleolar RNA (snoRNA).

Intron-encoded U17 RNA is a member of the H/ACA box class of small nucleolar RNAs (snoRNAs) involved in ribosomal RNA (rRNA) maturation. U17 snoRNA shows typical characteristics of guide RNAs, which specify sites of pseudouridylation on the precursor rRNA (pre-rRNA). However, in spite of the presence of H and ACA boxes and short regions complementary to the pre-rRNA, its secondary structure does not show any evident pseudouridylation pocket. Moreover, its length is larger than the typical one of snoRNAs and it shows a more complex secondary structure compared to the canonical hairpin-hinge-hairpin-tail architecture. Greater knowledge of eukaryotic U17 snoRNA structure is needed to understand its precise function. Comparative molecular studies of this snoRNA with different vertebrates is still limited to a few cases. With the aim of increasing our understanding of the U17 snoRNA secondary structure, we cloned the U17 snoRNA coding sequence from 10 additional vertebrate taxa. On the basis of structure homology derived from sequence comparison and thermodynamic prediction, we propose a vertebrate consensus secondary structure and novel conserved sequence boxes for U17 snoRNA. Host gene localization of U17 coding sequence and its ability to serve as a guide sequence for RNA/RNA interaction has been evolutionarily traced from fish to mammals. It is interesting to note that turtle U17 snoRNAs show a noncanonical ACA box, mainly consisting in the GCA box. Microinjections in X. laevis oocytes of in vitro synthesized turtle transcripts containing the U17 RNA sequence which have canonical ACA, wild-type GCA, and mutated CCA and UCA boxes resulted in efficient production of mature U17 snoRNA.