Parapatric hybridization in the chromosomal speciation of the house mouse

Chromosomal races of the house mouse ( Mus domesticus ) occur extensively in Italy. The present paper reports results of studies on a hybrid zone in Central Italy on a chromosomal race with a 2 n = 22 karyotype and surrounding populations with a standard 2 n = 40 karyotype. Karyotypic and morphometric patterns of variation in this area are discussed in an attempt to contribute to an understanding of the chromosomal speciation in this species. Data are compared, where possible, with other findings on the same hybrid zone. Finally, it is suggested that changes in behavioural traits (inter-male aggression and female socio-sexual preferences) may help in promoting complete genetic isolation.     

Morphological and ecological differences in two electrophoretically detected species of Cliona (Porifera, Demospongiae)

The taxonomie status of different morphotypes generally ascribed to the species of boring sponge Cliona viridis is examined. Morphometric, ecological and genetic differences between two morphotypes living sympatrically on rocky shores of the Ligurian Sea are considered. Morphotype 1 is characterized by small, well separated papillae (α stage), exclusively boring into the crust of coralline algae on the exposed rocky bottoms of the upper sublittoral zone. Morphotype 2 shows bigger papillae, often connected by portions of encrusting tissue ( β stage), and is predominantly found boring into organogenic concretions in slightly lighted habitats. Measurements of tylostyles indicate that morphotype 1 has spicules significantly smaller than morphotype 2. Electrophoretic analysis shows that the two morphotypes are fixed for different alleles at all four loci scored, indicating absence of gene flow between the two populations, i.e. they appear to be distinct biological species.     

Predicting microhabitat selection in juvenile Atlantic salmon Salmo salar by the use of logistic regression and classification trees

1. We compared the capacity of logistic regression (LR) and classification tree (CT) models to predict microhabitat use and the summer distribution of juvenile Atlantic salmon, Salmo salar, in two reaches of a small stream in eastern Quebec. 2. The models predicted the presence or absence of salmon at a location on the basis of habitat features (depth, current velocity, presence of instream and overhead cover, substratum particle size, and distance to stream bank) measured at that location. Models were validated by means of crossover field tests evaluating the performance of models developed for one reach (calibration trials) when applied to the other reach (validation trials). Model performance was evaluated with regard to accuracy, generality and ease of use and interpretation. Prediction maps based on habitat features were also built to compare the observed position of fish with those predicted by LR and CT models. 3. The spatial distribution of active fish differed markedly from that of resting fish, apparently as a result of the selection for water greater than about 30 cm depth by active fish and for the presence of rocky cover by resting fish. 4. All models made accurate predictions, validated by crossover trials. For both LR and CT models, the prediction maps reflected well the actual fish distributions. However, CT models were easier to build and interpret than LR models. CT models also had less variable performance and a smaller decline in predictive capability in crossover trials (for fish at rest), suggesting that they may be more transferable than LR models.     

The Basic Karyotype of Lotus tenuis C-banding and Feulgen Studies

The basic karyotype of L. tenuis is illustrated. The study ofFeulgen stained metaphases has shown that the chromosome complementconsists of four pairs of median chromosomes and two pairs ofsubmedian chromosomes. Two nucleolar constrictions characterizethe first homologous pair. The C-banding pattern includes largepericentric bands in each chromosome pair and a terminal bandin the short arm of chromosome 3 Lotus tenuis, chromosome morphology, C-banding     

Seasonal Trends of Nitrate Reductase, Carboxylating Enzymes, and Water-soluble Proteins in Two Field-grown Cultivars of Triticum

Nitrate reductase, RuDP¹ carboxylase, PEP carboxylase, and water-solubleproteins have been studied during the vegetative cycles of onesoft and one hard wheat cultivar. Nitrate reductase was similarin amount and in pattern of variation in both varieties, thevariations being related to the phenological state of the plant,because the seasonal trend was not in phase in the two varieties.The pattern of change in water-soluble proteins was significantlydifferent in the two cultivars, namely in the consistent declineshown by the upper leaves of soft wheat. RuDP carboxylase was almost identical in amount and absolutelyin phase between the two varieties, showing a dependence onseasonal factors, possibly through a photoperiodic effect. Thechanges in PEP carboxylase were similar in the two wheats andgenerally synchronous. The fluctuation in the RuDP carboxylase/PEPcarboxylase ratio was due primarily to the increase in RuDPcarboxvlase activity.     

Offspring performance in dynamic habitats: key factors for a riparian carabid beetle

Abstract.  1. Knowledge of the ecology of carabid species is largely restricted to adults, although larval mortality is assumed to be the key factor in overall mortality. As low-mobility larvae are unable to avoid unfavourable conditions, habitat selection of reproducing adults should be clearly affected by the habitat factors which determine offspring performance.
2. The present study examines the key habitat factors governing the distribution patterns of Bembidion velox larvae and adults on the river banks of the River Elbe by means of habitat suitability models. The validity of the determined habitat factors for offspring performance and survival was tested in laboratory experiments.
3. In the field, B. velox adults as well as larvae show a strong association with semi-terrestrial, sandy, open soil habitats.
4. In the laboratory, overall mortality of larvae reared in different substrates was lowest in sand of medium grain size mixed with fine and coarse sand. The first larval instars in particular reacted sensitively to variations in grain size. Furthermore, flood resistance of eggs was demonstrated, as 90% of larvae hatched under permanently flooded conditions.
5. Short development times were recorded, with 4–7 days for hatching of young larvae from eggs after oviposition and approximately 28 days for the development of adults from newly hatched larvae. This probably increases the survival probability for the pre-imaginal stages in dynamic habitats.
6. In conclusion, it can be said that reproductive success is strongly dependent on oviposition site selection by adults as this reflects the ecological demands of the immature stages.     

TWO NEW SPECIES OF THE GENUS ISLAMIA RADOMAN, 1973 FROM ITALIAN ISLANDS (PROSOBRANCHIA, HYDROBIIDAE)

Two new Italian species of the genus Islamia (Prosobranchia:Hydrobiidae), one living in eastern Sicily (I. cianensis), andone on Elba Island (Tuscan Archipelago, Italy) (I. gaiteri)are described. The two species are distinguished on the basisof shell and anatomical characters, mainly those of the malegenitalia. I. cianesis n. sp. is characterized by a valvatoidshell and a penial lobe with internal band of glandular tissuenot distinct in its lower portion from the penis body but bulgingapically as a small knob. I. gaiteri n. sp. is characterizedby a planispiral shell and a small lateral penial lobe withoutinternal glandular tissue. (Received 20 December 1993; accepted 27 June 1994)     

Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean

Brandano, M. & Policicchio, G. 2011: Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean. Lethaia, Vol. 45, pp. 315–328. A ⁸⁷Sr/⁸⁶Sr analysis of selected pectinid shells has been performed to refine the stratigraphical framework of the Burdigalian transgressive event. Samples were collected from shallow water successions of the Western Mediterranean area (North‐Eastern Sardinia, Southern Corsica, Central Apennines). The Western Mediterranean is the result of the interaction between the European and the African plates. Sardinia and Corsica were extended and rifted apart from the Iberian Peninsula during the opening of the Liguro‐Provencal basin, between 30 and 15 Ma. In the outcrops of Northern Sardinia and Southern Corsica, Burdigalian deposits nonconformably overlie Varisican granites. In the central Apennines the Burdigalian deposits paraconformably overlie the Cretaceous platform. These are transgressive deposits, characterized by the presence of Miogypsina globulina, which points out early to middle Burdigalian age. The Sr isotope ages indicate that marine transgression in Northern Sardina and Southern Corsica took place between 18.6 and 18.3 Ma, which could correspond to the eustatic sea level rise of the Bur3 third‐order sequence. In the Central Apennines the Burdigalian transgression was anticipated (18.8 Ma) by subsidence input linked to the eastward migration of the orogenic system. This input allowed the Miocene carbonate ramp to develop on the Cretaceous platform substrate, while successive eustatic rise controlled the evolution of the stratigraphical architecture. The following regressive phase is recorded in both the Apennine and Corsica successions. The end of this phase is dated between 17.6 and 17.5 Ma and corresponds to sea level drop corresponding to the occurrence of the Mi 1b event. □Burdigalian, pectinids, strontium stratigraphy, transgression, Western Mediterranean     

Pliocene and Pleistocene events shaping the genetic diversity within the central corridor of the Brazilian Atlantic Forest

Dinoponera lucida (Formicidae; Ponerinae) is an extinction‐threatened species of ant which is endemic in the central corridor of the Atlantic Forest. We used mitochondrial sequences of the Cox1, Cox2 and Cytb genes in order to infer some aspects of the evolutionary history and phylogeography of this ant. High genetic divergence and population structure were observed for the whole species. The current pattern of D. lucida diversity seems to be shaped during different geological times: middle Pliocene, early Pleistocene and mainly late Pleistocene, when the reduction of populations generated a structure pattern of the genetic variation of this species. Our data show that this structure results from the maintenance of populations of D. lucida within very small putative refuges to the south of the central Bahia refugium. We thus argue that, for some Atlantic forest endemic species, especially those resistant to very small fragments of forest, such as D. lucida, the small putative refuges were as important as, or even more important than, larger and stable refuges for the creation and maintenance of diversity, adding another piece to the puzzle of the mechanisms underlying local endemism. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 949–960.     

Structured populations of the oriental fruit moth in an agricultural ecosystem

Intercontinental trade has led to multiple introductions of invasive pest species at a global scale. Molecular analyses of the structure of populations support the understanding of ecological strategies and evolutionary patterns that promote successful biological invasions. The oriental fruit moth, Grapholita (=Cydia) molesta, is a cosmopolitan and economically destructive pest of stone and pome fruits, expanding its distribution range concomitantly with global climate warming. We used ten newly developed polymorphic microsatellite markers to examine the genetic structure of G. molesta populations in an agricultural ecosystem in the Emilia‐Romagna region of northern Italy. Larvae collected in eight sampling sites were assigned to a mosaic of five populations with significant intra‐regional structure. Inferred measures of gene flow within populations implicated both active dispersal, and passive dispersal associated with accidental anthropogenic displacements. Small effective population sizes, coupled with high inbreeding levels, highlighted the effect of orchard management practices on the observed patterns of genetic variation within the sampling sites. Isolation by distance did not appear to play a major role at the spatial scale considered. Our results provide new insights into the population genetics and dynamics of an invasive pest species at a regional scale.