Marina Cobolli

Isolation by distance in equilibrium and nonequilibrium populations of four talitrid species in the Mediterranean Sea.

Abstract Allozymic variation at 21–23 loci was studied in 28 populations of Talitrus saltator, 23 populations of Orchestia montagui, 13 populations of O. stephenseni, and five populations of Platorchestia platensis from the Mediterranean Basin. Different levels of gene flow (Nmθ) were detected within each species at the scale of the whole Mediterranean: O. montagui and P. platensis had low population structure, with levels of Nmθ 1, whereas the T. saltator and O. stephenseni populations have values of Nmθ < 1. The relationship between Nmθ and geographic distance was analyzed to test for the presence of an isolation by distance pattern in the spatial genetic variation within each species. A model of isolation by distance is useful to describe the pattern of genetic structuring of study species at the scale of the whole Mediterranean: geographic distance explained from 28% to 70% of the variation in gene flow. In the Aegean area all species showed an island model of genetic structuring regardless of the levels of gene flow.

Geographic variation in Talitrus saltator (Crustacea, Amphipoda): biochemical evidence

Allozyme variation of 30 populations of the amphipod Talitrus saltator collected from different localities of Atlantic and Mediterranean coasts was studied. A remarkable genetic differentiation was revealed among diverse geographic groups. Three main groups were highlighted showing values of genetic distance (average D = 0.4) frequently reported for interspecific comparisons. The estimates of gene flow calculated from the Fst values are reported. The pattern of genetic divergence between the different geographic groups is discussed taking into account the dispersal capacity of T. saltator, the pattern of the surface currents in the Mediterranean basin and the Pleistocene climatic fluctuations in the Mediterranean.

Allozymic variability and biogeographic relationships in two Leuciscus species complexes (Cyprinidae) from southern Europe, with the rehabilitation of the genus Telestes Bonaparte

Abstract Genetic variability was assessed in eight populations belonging to the Leuciscus souffla complex and in nine populations of Leuciscus cephalus, sampled in France, Italy and Greece and in one population of Leuciscus lucumonis, endemic to Italy. Twenty‐six enzymatic loci were analysed in order to clarify the genetic relationships, the patterns of colonisation of peri‐Mediterranean area and the taxonomic positions. Results indicate a more ancient penetration of the Leuciscus souffia complex in southern Europe (possibly during the Messinian ‘Lago Mare’ phase of the Mediterranean), whereas L. cephalus and L. lucumonis seem to have quite recently reached these regions (about 1Myr). These evidences are discussed in relation to the two main proposed models of primary freshwater fishes colonisation of peri‐Mediterranean area. In addition, the genetic distance suggests a generic separation between the two complexes. The genus Telestes Bonaparte, is rehabilitated to include members of the Leuciscus souffia ...

Genetic divergence and evolutionary times: calibrating a protein clock for South-European Stenasellus species (Crustacea Isopoda)

We studied genetic divergence in a group of exclusively stygobiont isopods of the family Stenasellidae. In particular, we assessed evolutionary relationships among several populations of Stellaselllls racovitzai and Stellaselllls virei. To place this study in a phylogenetic context, we used another species of Stellaselllls, S. assorgiai, as an outgroup. S. racovitzai occurs in Corsica, Sardinia and in the fossil islands of the Tuscan Archipelago, while S. virei is a polytypic species widely distributed in the central France and Pyrenean area. This vicariant distribution is believed to be the result of the disjunction of the Sardinia-Corsica microplate from the Pyrenean region and its subsequent rotation. Since geological data provide time estimates for these events, we can use the genetic distance data to calibrate a molecular clock for this group of stygobiont isopods. The calibration of the molecular clock reveals a roughly linear relationship (r = 0.753) between the genetic distances and absolute divergence times, with a mean divergence rate (19.269 Myr/DNei)different from those previously reported in the literature and provides an opportunity to shed some light on the evolutionary scenarios of other Stellaselllls species.

Genetic differentiation and biogeography in southern European populations of the genus Scardinius (Pisces, Cyprinidae) based on allozyme data

Levels of genetic differentiation and variability were assessed in several populations and species belonging to the primary freshwater fish genus Scardinius by means of electrophoretic analyses of 28 enzymatic loci. We studied one population of S. acarnanicus and one of S. graecus, both endemic to Greece, seven populations of S. erythrophthalmus from Greece, Slovenia, northern and central Italy, and the single extant population of S. scardafa, a species endemic to central Italy. Patterns of genetic relationships placed the Greek species basal in the neighbour‐joining (NJ) and maximum parsimony (MP) trees, S. scardafa and S. erythrophthalmus are sister species. Based on the molecular clock, the split between S. acarnanicus and S. graecus occurred around 4.3 Myr ago and the split between (S. acarnanicus, S. graecus) and (S. scardafa, S. erythrophthalmus) around 3.5 Myr ago, both after the Messinian lacustrine ‘Lago Mare’ phase of the Mediterranean. The separation between S. scardafa and S. erythrophthalmus was more recent (0.5 Myr ago) and was probably the result of confluences between adjacent river basins during the Pleistocene. Within S. erythrophthalmus, the Greek population showed a certain degree of genetic differentiation, whereas northern and central Italian populations were nearly indistinguishable. These findings demonstrate the impact of the artificial introduction of this species into central Italy, leading to the near extinction of the endemic S. scardafa.

Evolution of Lineages

The aim of this chapter is to offer a survey of cave animals focusing attention on the evolution of lineages. Subterranean organisms show well how preadaptations are important for the adoption of a new way of life. There are several possible routes to hypogean habits. Some of the major examples are reported comparing different scenarios for aquatic and terrestrial organisms. We further consider the origin of troglobites and discuss the models of genetic differentiation (single versus multiple origin). Moreover, the integration of morphological, ecological, genetic, and geological data appears necessary to clarify this issue. Morphological traits are analyzed in terms of variation and time of isolation. The hypotheses of constructive or regressive traits are considered, with the description of models and mechanisms. Finally, we offer a brief survey of molecular methods and markers applied to the study of evolution in subterranean habitats.

Biochemical systematics and phylogeography of the percus strictus subspecies (coleoptera, carabidae), endemic to Sardinia

Abstract Allozymic variation at 14 loci was studied in six Sardinian populations of the carabid beetle Percus strictus. These populations represent the four subspecies of P. strictus recognised on morphological grounds in the island. Clustering and multivariate analyses were able to discriminate different subspecies, supporting the morphological evidence. Genetic distance data and .P‐sta‐tistics analysis indicated a certain degree of isolation among subspecies, but not high enough to propose the splitting of the polytypic F‐strictus into different species. From molecular clock and geological data, it is inferred that the major differentiation events were due to vicariance and took place at the beginning of the Pliocene, in concomitance with sea introgressions that subdivided the island into different blocks roughly corresponding to the present ranges of the different subspecies.

Four new species of Dolichopoda Bolivar, 1880 from Southern Sporades and Western Turkey (Orthoptera, Rhaphidophoridae, Dolichopodainae).

Abstract A description of four new species of Dolichopoda Bolivar, 1880 (Orthoptera, Rhaphidophoridae) from Eastern Aegean region (Southern Sporades), including Western Turkey, is reported. This brings to a total of 11 the number of Dolichopoda species recorded for caves of the Aegean area. Overall, these species show a high degree of morphological homogeneity and they are very close to Dolichopoda paraskevi Boudou-Saltet, 1973 from Crete and Dolichopoda naxia Boudou-Saltet, 1972 from Cyclades (Naxos Island). The Western Turkish species are morphologically not closely related to the other Anatolian species; this suggests an independent origin for the taxa occurring in the Southern Taurus and Black Sea regions. These new data help to better define the already high level of diversity of the Hellenic Dolichopoda and strengthen the hypothesis that the central area of dispersal for the genus would correspond to the ancient Aegean plate.