How does invasion degree shape alpha and beta diversity of freshwater fish at a regional scale?

FFreshwater ecosystems appear more vulnerable to biodiversity loss due to several anthropogenic disturbances and freshwater fish are particularly vulnerable to these impacts. We aimed to (1) identify the contribution of land use, spatial variables, and invasion degree in determining freshwater fish alpha (i.e., species richness) and beta (i.e., local contributions to beta diversity, LCBD) diversity, evaluating also the relationship between invasion degree and nestedness ((Formula presented.) nes) and turnover ((Formula presented.) sim) components of beta diversity. (2) Investigate the relationship between alpha diversity and LCBD, under the hypothesis that alpha diversity and LCBD correlate negatively and (3) investigate the relationship between species contributions to beta diversity (SCBD) and species occurrence, hypothesizing that non-native species show a lower contribution to beta diversity. The linear mixed models and the partition of R2 retained the invasion degree as the most important variables explaining alpha and beta diversity, having a positive relationship with both diversity components. Furthermore, land use related to human impacts had a positive influence on alpha diversity, whereas it showed a negative effect on LCBD. Regression model further showed that invasion degree related positively with (Formula presented.) sim, but negatively with (Formula presented.) nes, suggesting that non-native species were involved in the replacement of native species in the fish community. Alpha diversity and LCBD showed a weak positive correlation, meaning that sites with low species richness have higher LCBD. SCBD scaled positively with species occurrence highlighting that rarer species contribute less to SCBD. Finally, native and exotic species contributed similarly to beta diversity. These results suggest that invasion degree plays a central role in shaping alpha and beta diversity in stream fish, more than land use features reflecting habitat alteration or other geospatial variables. Furthermore, it is important to evaluate separately the native and the non-native components of biotic communities to identify linkages between invasion dynamics and biodiversity loss.Peer reviewe

Extended Main-Sequence Turnoff and Red Clump in intermediate-age star clusters: A study of NGC 419

With the goal of untangling the origin of extended main-sequence turnoffs (eMSTOs) and extended red clumps (eRCs) in star clusters, in this work we present the study of the intermediate-age cluster NGC 419, situated along the Bridge of the Small Magellanic Cloud. To this aim, we analyzed multi-epoch, high angular resolution observations acquired with the Hubble Space Telescope for this dynamically young cluster, which enabled the determination of precise proper motions and therefore the assessment of the cluster membership for each individual star in the field of view. With this unprecedented information at hand, we first studied the radial distribution of kinematically selected member stars in different eMSTO subregions. The absence of segregation supports the rotation scenario as the cause for the turnoff color extension and disfavors the presence of a prolonged period of star formation in the cluster. A similar analysis on the eRC of NGC 419 confirms the absence of segregation, providing further evidence against an age spread, which is at odds with previous investigations. Even so, the currently available evolutionary models including stellar rotation fail at reproducing the two photometric features simultaneously. We argue that either shortcomings in these models or a different origin for the red clump feature, such as a nonstandard differential mass loss along the red giant branch phase, are the only way to reconcile our observational findings with theoretical expectations.Comment: 6 pages, 8 figures, Accepted for publication on A&

Blue Stragglers as tracers of the dynamical state of two clusters in the Small Magellanic Cloud: NGC 339 and NGC 419

The level of central segregation of Blue Straggler stars proved to be an excellent tracer of the dynamical evolution of old star clusters (the so-called "dynamical clock"), both in the Milky Way and in the Large Magellanic Cloud. The $A^{+}$ parameter, used to measure the Blue Stragglers degree of segregation, has in fact been found to strongly correlate with the parent cluster central relaxation time. Here we studied the Blue-Straggler population of two young stellar systems in the Small Magellanic Cloud, namely NGC 339 (which is 6 Gyr old) and NGC 419 (with an age of only 1.5 Gyr), in order to study their dynamical state. Thanks to multi-epoch, high angular resolution Hubble Space Telescope observations available for both clusters, we took advantage of the stellar proper motions measured in the regions of the two systems and we selected a population of likely cluster members, removing the strong contamination from Small Magellanic Cloud stars. This enabled us to study, with unprecedented accuracy, the radial distribution of Blue Stragglers in these two extragalactic clusters and to measure their dynamical age. As expected for such young clusters, we found that both systems are poorly evolved from the dynamical point of view, also fully confirming that the $A^{+}$ parameter is a sensitive "clock hand" even in the dynamically-young regime.Comment: 12 pages,11 figures, Accepted for publication by Ap

a method to identify bimodal weight length relations possible ontogenetic diet and or metabolism shift effects in anguilla anguilla actinopterygii anguilliformes anguillidae

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Long-term fish monitoring underlines a rising tide of temperature tolerant, rheophilic, benthivore and generalist exotics, irrespective of hydrological conditions

The invasion of exotic species is one of the main threats to worldwide biodiversity and can be aided by changes in environmental conditions. We hypothesized that a temporal trend of decreasing discharge and increasing temperature might have favored the invasion of warm-adapted, lentic exotic fish species in the lower Po River, northern Italy. We used presence/absence data over a long-term period (over 20 years) to investigate the dynamics of exotic fish invasion along water temperature and discharge gradients. Mean annual discharge and temperature did not show a clear trend and did not affect exotic fish species invasion, which progressed with time irrespective of these factors. The total number of species fluctuated without a clear trend, which underlined a progressive substitution of native species with exotic ones. Perhaps surprisingly, the community composition changed over time towards more temperature tolerant but also rheophilic, benthivore and generalist fish species. These results highlight how species interactions could be one of the main factors driving the invasion. Furthermore, our data underlines a continuously rising tide of exotics, which questions the success of past control strategies. Considering the current conservation resources limitations, priority should be given to the development of prevention strategies in order to avoid new species introductions

Status of the fish communities and need for management in the Po River Delta

The term “delta”, have used as a synonym for transitional water bodies, includes the terminal stretch of rivers, estuaries, deltas, fjords and lagoons, as defined by the EU WFD directive. Wetlands are sites of high biodiversity and productivity, with great ecological interest, functional richness and great exploitation of renuwable resources. Recently, these ecosystems have suffered a serious decline worldwide due to human disturbances. The Po River delta (Adriatic Sea, Italy) and the related coastal lagoons are not an exception. In the last twenty years, extensive phenomena of eutrophication and related dystrophic crises, introduction of alien species and the development of new fishing and aquaculture practices have further contributed to the breakdown of biological communities and, in particular, of fish ones. The aim of this study was to update the general status of the fish communities in the Po Delta of Emilia-Romagna, both in composition and trophic structure, and to identify the main problems of fisheries related to the physical evolution of the environment and the change in human activities. The results show that freshwater and transitional water suffered from different pressures: freshwater communities are affected by a progressive invasion of exotic species, which has intensified starting from more than 30 years ago. Whereas, fish communities in transitional water do not suffer of exotic fish invasions, but their overexploitation and play a central role in fish community changes. The cases of eels and the fishery of Comacchio are presented and analized as study cases

Knowledge extraction by using an ontology-based annotation tool

This paper describes a Semantic Annotation Tool for extraction of knowledge structures from web pages through the use of simple user-defined knowledge extraction patterns. The semantic annotation tool contains: an ontology-based mark-up component which allows the user to browse and to mark-up relevant pieces of information; a learning component (Crystal from the University of Massachusetts at Amherst) which learns rules from examples and an information extraction component which extracts the objects and relation between these objects. Our final aim is to provide support for ontology population by using the information extraction component. Our system uses as domain of study “KMi Planet”, a Webbased news server that helps to communicate relevant information between members in our institute

MnM: ontology driven tool for semantic markup

An important precondition for realising the goal of a semantic web is the ability to annotate web resources with semantic information. In order to carry out this task, users need appropriate representation languages, ontologies, and support tools. In this paper we present MnM, an annotation tool which provides both automated and semi-automated support for annotating web pages with semantic contents. MnM integrates a web browser with an ontology editor and provides open APIs to link to ontology servers and for integrating information extraction tools. MnM can be seen as an early example of the next generation of ontology editors, being web-based, oriented to semantic markup and providing mechanisms for large-scale automatic markup of web pages

Immunocytochemical and ultrastructural identification of adenohypophyseal cells in Ctenopharyngodon idella (Cypriniformes: Cyprinidae) during gonadal differentiation

The adenohypophysis was studied by immunocytochemical and ultrastructural methods in juvenile grass carp (Ctenopharyngodon idella) from natural reproduction in Northern Italian rivers. The adenohypophysis included the rostral pars distalis (RPD), the proximal pars distalis (PPD) and the pars intermedia (PI), all deeply penetrated by branches of the neurohypophysis (Nh). The prolactin (PRL), adrenocorticotropic (ACTH), somatotropic (GH), thyrotropic (TSH), gonadotropic type I (GtH I) and type II (GtH II), somatolactin (SL), melanotropic (MSH) and endorphin (END) cells were identified with antisera raised against piscine and human pituitary hormones. In juveniles of 51–69 mm of total body length (TL) with undifferentiated gonads, the PRL cells, arranged in thick strands, occupied most of the RPD. The ACTH and GH cells organized in cords bordering Nh were, respectively, confined to RPD and PPD. The TSH cells were scattered among ACTH cells in RPD and among GH cells in PPD. Cells simultaneously immunoreactive to anti-follicle stimulating hormone and to anti-croaker gonadotropin were intermingled among GH and TSH cells, which were mostly in the dorsal PPD. The SL cells were detected in PI layers bordering the Nh. The MSH and END cells were intermingled in PI and, unlike what observed in other teleosts, their respective antisera did not cross-react. In individuals of 78–112 mm TL with gonads at the beginning of differentiation, the GtH II cells were detected in PPD; all other cell types increased in number. These results, supported by ultrastructural investigations, suggest that SL and GtH II cells are directly involved in gonadal differentiation in C. idella

Natural recruitment contributes to high densities of grass carp Ctenopharyngodon idella (Valenciennes, 1844) in Western Europe

Introductions of grass carp, well known for their potentially negative ecosystem effects, have been performed in several countries around the world. As the species was considered unable to reproduce naturally under non-native environmental conditions, little attention was initially given to its invasive potential. We studied an area in northern-Italy where, contrary to expectations, introductions that were performed in the early 80s still exert a considerable pressure on aquatic macrophytes. In order to reveal whether the observed population dynamics are the result of natural events or stocking we analysed the density, age- and size-structure of the grass carp population and the migration pathways available to it. Telephone surveys were also used to check for fish transport from national and international suppliers. We also sampled potential spawning and nursery areas for young individuals and, when some were captured, we applied stable isotope analyses to discriminate their origin. We found that the population of large individuals likely originated solely from early stocking. We also documented the first analytical evidence of grass carp recruitment in the study area and, to our knowledge, in Western Europe. Therefore the species has the potential to become invasive in these areas and more detailed studies are needed to assess this potential. Further management should account at least for natural recruitment and potential negative environmental effects, controlling the species where needed.peerReviewe