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Bivalves are excellent candidates for geographically based studies of the morphological variation in individuals of different populations based on the analysis of their shape profiles. In this study, we quantified the overall shell shape differences in individuals of different populations of Ruditapes decussatus and Ruditapes philippinarum in relation to their geographical and genetic distances. A total of 395 and 124 individuals of R. decussatus (nine populations) and R. philippinarum (four populations), respectively, were sampled in different Mediterranean and Atlantic coastal locations. Pictures of the left valve were taken from all individuals. Their profiles were analysed using elliptic Fourier analysis. Mean outlines were computed. In order to classify different individuals for species, the coefficients of harmonic equations were analysed by partial least square discriminant analysis and soft independent modelling of class analogy. The results showed a high percentage of correct classification (99%) between the two species in the independent test. We found that the morphological distance between R. philippinarum and R. decussatus is higher than the morphological distance among populations of the same species. The absence of correspondence between the geographical location and the pattern of morphological and genetic variation indicates the occurrence of a reaction norm in the morphological adaptation of shell shapes to different local environmental conditions

Salamandrina is a monotypic genus of the family Salamandridae endemic to Italy. Forty five individuals of the spectacled salamander, Salamandrina terdigitata, representing 11 populations throughout the whole distribution range were examined for sequence variation of three mitochondrial DNA genes encoding the 12S and 16S ribosomal RNA's and cytochrome b (1324 bp). The results indicate the existence of two genetically distinct and geographically non-overlapping mtDNA lineages. The first lineage includes the southern populations and the second one comprises the central-northern populations. The degree of genetic divergence between the two groups is high and comparable to distances calculated from homologous sequences available in GenBank between other Salamandrid species. As a result, the genus Salamandrina probably requires splitting into two species. We also compare substitution rates associated with the mitochondrial genes employed across all Salamandrids studied so far, and discuss two possible palaeogeographic scenarios which could have shaped the splitting of the two Salamandrina lineages. These findings have also important implications for management and conservations of the spectacled salamander, which is protected under several international and regional conventions and directives.

The Italian endemic genus Salamandrina has been historically regarded as monotypic but, recently, studies based on both mitochondrial and nuclear markers have indicated the existence of two distinct species of spectacled salamanders: Salamandrina perspicillata, in central and northern Italy, and Salamandrina terdigitata, in southern Italy. We analyzed nucleotide variation at mitochondrial and nuclear genes [cytochrome b, 12S and 16S rRNA, recombination activating gene (RAG 1)] in 223 individuals from 56 locations, aiming to investigate their genetic structure and recent evolutionary histories. Phylogenetic and phylogeographical analyses revealed the existence of three and two genetically distinct groups of populations in northern and southern salamander, respectively. Historical demographic analyses led to the inference of range expansion for both species in the late Pleistocene. During the last glacial stage, each salamander survived in a single refugium, namely the southern in Calabria and the northern in central Italy. At the end of this period, both lineages expanded northward and established secondary contact. Spatial distribution of RAG 1 haplotype variation revealed two differentiated population groups corresponding to the major mitochondrial (mt)DNA clades. Nuclear pattern of introgressive hybridization was more extensive than the highly limited introgression of mtDNA markers. From a conservation standpoint, southern Latium and Calabria proved to be the major genetic diversity reservoirs, thus deserving particular conservation effort

The Italian endemic genus Salamandrina was recently determined to be polytypic since two species, Salamandrina perspicillata and S. terdigitata, were recognized using both mitochondrial and nuclear genetic markers. However, data on their range is very scanty and no morphological traits are available to distinguish between these two taxa. A thorough field survey was carried out to detect and to sample new sites in areas in which Salamandrina remained unrecorded and to sample populations expected to occur in the documented range. Specimens were analyzed for variation of three mitochondrial DNA partial sequences of 12S and 16S ribosomal RNAs and cytochrome b genes. Attribution of individuals to either of the two species was therefore made on the basis of their haplotypes. Here we provide relevant information on the distribution of the two species, which were also found in areas where Salamandrina had previously been unrecorded, i.e. in the eastern Basilicata, in the region of Apulia and within the wide area which separated the two species. In the latter zone, a small area of sympatry between the two species was found. Furthermore, we analyzed the dorsal coloration pattern and size-related characters of the two species using Classification and Regression Tree analysis (CART), the results of which provided the first account of the morphological differences between Salamandrina perspicillata and S. terdigitata. The southern species, S. terdigitata, is smaller in size than S. perspicillata and differs in its coloration, mainly due to the red color on the dorsal surface of its tail.

The actual Italian production of clams is chiefly sustained by the native Tapes decussatus and the fortuitously imported Tapes philippinarum. Both species are commercialized as "Vongola verace", but the commercial value of T. philippinarum is lower. The discrimination of species by sight is usually difficult and it cannot be done by observation based on shell morphology but only when animals open their valves hence displaying the two siphons. In this study, we propose a new, noninvasive method to discriminate individuals of both species based on the analysis of the external shape of their shells. Accordingly, in sympatric populations at two sites of the Po river outlet, we have chosen individuals (63 for T. decussatus and 57 for T. philippinarum) of comparable commercial size for which a certain genetic discrimination was previously done. Pictures of the left side valve were taken for all specimens. Their profiles were analyzed with the elliptic Fourier analysis. The mean outline for each species was graphically extracted. The coefficients of the harmonic equations were analyzed by multivariate classification (partial least squares discriminant analysis [PLSDA]). Results showed a high percentage of correct classification of individuals of both species (96.6%). Contour analysis reflected the overall shell shape and thus identified morphological aspects that were difficult to recognize and quantify in sight. The high percentage of correct classifications obtained by combining the analysis of elliptic Fourier harmonics with PLSDA demonstrated the feasibility of this method to discriminate species with a high level of resemblance.

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