Females may invest more in reproduction if they acquire mates of high phenotypic quality, because offspring sired by preferred partners may be fitter than offspring sired by non-preferred ones. In this study, we tested the differential maternal allocation hypothesis in the freshwater crayfish, Austropotamobius italicus, by means of a pairing experiment aimed at evaluating the effects of specific male traits (body size, chelae size and chelae asymmetry) on female primary reproductive effort. Our results showed that females laid larger but fewer eggs for relatively small-sized, large-clawed males, and smaller but more numerous eggs for relatively large-sized, small-clawed males. Chelae asymmetry had no effects on female reproductive investment. While the ultimate consequences of this pattern of female allocation remain unclear, females were nevertheless able to adjust their primary reproductive effort in relation to mate characteristics in a species where inter-male competition and sexual coercion may mask or obscure their sexual preferences. In addition, our results suggest that female allocation may differentially affect male characters, thus promoting a trade-off between the expression of different male traits.

Given the ongoing decline of many species, it is important to perform multifactorial analyses of conservation status and to assess the effects of species extinction on ecosystem services. In this study, we used long‐term surveys to assess the influence of habitat change, landscape alteration and invasive species on extinction risk of the native crayfish Austropotamobius pallipes. We reviewed the existing literature to assess which ecosystem services are threatened by local extinction of A. pallipes and replacement with alien crayfish. We sampled 196 streams and wetlands in northern Italy. Of these, 117 received multiple surveys over a 13‐year period (2004–2017), thus allowing accurate measurement of extinction rate. Thirty‐four percent of A. pallipes populations underwent extinction between 2004 and 2017. The occurrence of alien crayfish in the catchment basin and urban growth in the landscape surrounding streams were associated with A. pallipes extinction. The probability of persistence was significantly higher in populations close to stream springs and with physical barriers (especially waterfalls) separating them from basins with alien crayfish. Extinction of native crayfish alters community structure and impairs regulating services such as detrital breakdown and pest regulation. Replacement by alien crayfish (Procambarus clarkii and Faxonius limosus) also threatens supporting and regulating services by altering nutrient cycling, food webs, sediments and erosion. The implementation of management practices that control river connectivity using selective barriers is needed to prevent further local extinction of native species. Integrating information on extinction with knowledge of impacts on ecosystem services is essential in developing more effective conservation policies.

Information was gathered on the distribution of white-clawed crayfish Austropotamobius pallipes complex in the watercourses of the Alessandria province (NW Italy), on the biological and ecological preferences of the species, and on the features of the biotopes in which it is found. A total of 409 sites on 361 watercourses connected to the main sub-basins of the Po River were analysed, with data gathered during the field research phase, conducted for three consecutive summers from 2002 through 2004. Thirteen percent of the sites investigated were found to currently house crayfish populations. The persistence in time of superficial water and natural morphology of the watercourse were found to be the chief requirements for the presence of crayfish. Data on land use, human density and other factors which potentially limit the survival of crayfish populations were also analysed. Key-words:Austropotamobius pallipes complex, freshwater crayfish, bio-ecological characteristics. STATUT DU COMPLEXE D'ESPACE D'AUSTROPOTAMOBIUS PALLIPES DANS LES COURS D'EAU DE LA PROVINCE D'ALESSANDRIA (ITALIE NORD-OCCIDENTALE) RÉSUMÉLe projet de recherche a prévu la récolte d'informations sur la répartition du complexe d'espèce Austropotamobius pallipes dans les réseaux hydrographiques de la province d'Alessandria (Italie nord-occidental), sur les caractères bio-écologiques de l'espèce et sur les caractéristiques des milieux où elle a été trouvée. Les prospections de terrain ont été faites durant trois étés consécutifs de la période 2002-2004 et ont permis d'analyser 409 sites sur 361 cours d'eau, appartenant aux principaux sous-bassins du fleuve Pô. Des populations d'écrevisses n'ont été trouvées que dans 13 % des sites prospectés. La persistance temporelle des débits hydriques superficiels et la morphologie naturelle constituent la condition essentielle pour la présence des écrevisses. En outre, les données

Assessing the population structure and understanding growth patterns is crucial to manage freshwater resources and to solve fundamental questions concerning endangered species conservation. Austropotamobius pallipes (Lereboullet, 1858)

The protection of freshwater biodiversity has become a priority task for conservation practices, as freshwater ecosystems host high levels of cryptic diversity, while also record similarly high rates of extinction. The Italian white-clawed crayfish Austropotamobius italicus is an endemic freshwater crustacean, threatened by several anthropogenic impacts such as habitat fragmentation, pollution, invasion of exotics, and climate change. Previous phylogenetic studies conducted in Italy pointed out a complex phylogeographic framework for the species, with four different subspecies currently recognized. Conservation efforts, particularly when involving restocking and reintroduction, require a detailed knowledge of their population genetics. In this study we describe the genetic structure of A. italicus populations in northern Italy (Lombardy Alpine foothills and northern Apennines) by using the informative mitochondrial marker cytochrome c oxidase subunit I, in order to assess their current evolutionary diversity and past phylogeographic history from a conservation perspective. Our results contribute to the mapping of the contact area among A. i. carsicus and A. i. carinthiacus in the Orobie Larian Prealps. More interestingly, we highlight the existence of two deeply differentiated evolutionary lineages within A. i. carsicus, showing alternative phylogeographic patterns and past demographic trends. We propose to consider these two clades as distinct molecular operational taxonomic units for the conservation of this endangered crayfish.

Genetic studies on the populations of Austropotamobius pallipes complex from Alessandria province (N-Italy), conducted on the basis of variations recorded in the sequences of mitochondrial DNA in the gene 16S RNA, have allowed to single out an overlapping zone of the distribution areas of the two taxa pallipes and italicus. In the crayfishes from a creek where both species have been ascertained to be present, the authors have applied the same molecular marker in order to investigate the distribution of the two taxa, stressing the syntopy of A. pallipes and A. italicus. Multivariate statistical techniques on 21 morphological parameters have been used in order to single out possible distinctive features of 31 crayfishes collected in this site, and of 225 crayfishes obtained from four sites in neighbouring areas. The results confirm the presence of a high morphological variability, not only at interspecific, but also at intraspecific level, which does not allow to distinguish the two species on the basis of the features measured in the present study. Key-words:Austropotamobius pallipes, Austropotamobius italicus, mitochondrial DNA, morphometry. SYNTOPIE DE A. PALLIPES ET A. ITALICUS: INVESTIGATIONS GÉNÉTIQUES ET MORPHOMETRIQUES RÉSUMÉLes études génétiques menées sur les populations du complexe d'Austropotamobius pallipes dans la province d'Alessandria (N-Italie) ont été faites sur la base des variations mesurées dans les séquences de l'ADN mitochondrial dans le gène 16S ARN. Elles ont permis de mettre en évidence une zone de superposition des distributions des deux taxa pallipes et italicus. On a utilisé le même marqueur moléculaire sur les deux espèces d'écrevisses provenant du même petit ruisseau, pour étudier leurs distributions et mettre en évidence la syntopie de A. pallipes et A. italicus. Des analyses statistiques multivariées ont été appliquées sur 21 paramètres morphologiques pour mettre en relief de possibles caractéristiques distinctives sur 31 écrevisses capturées dans ce ruisseau et

The occurrence of the signal crayfish Pacifastacus leniusculus in the Valla Stream was the first established population of this invasive species recorded in an Italian stream ecosystem. We evaluated the seasonality of diet and trophic niche of invasive signal crayfish in order to estimate the ecological role and effects on native communities of the stream ecosystem. We studied the differences in food source use between sexes, life stages and seasons using carbon and nitrogen stable isotope analyses. To supplement stable isotope analyses, we evaluated food source usage using traditional stomach content analysis. We tested the hypothesis that juveniles have a different diet, showing different trophic niches, compared to adults. Results indicated that signal crayfish adult and juvenile diets mainly rely on macroinvertebrates and periphyton in summer, shifting to mostly periphyton in autumn. Although the two age classes occupied an equivalent trophic niche, juveniles showed slightly different carbon isotope values, suggesting a somewhat ontogenetic shift consistent among seasons. No significant differences were found in adult and juvenile diets between summer and autumn seasons. Our findings suggest that signal crayfish juveniles and adults exhibited seasonal feeding habits, probably due to ecological behaviour rather than food resource availability, and that both are likely to impose similar effects on macroinvertebrate communities in this and similar stream ecosystems.

No abstract