Thirty years of invasion: the distribution of the invasive crayfish Procambarus clarkii in Italy

The presence of the red swamp crayfish Procambarus clarkii in Italy is documented since 1989, but no comprehensive data are available on its spread through time at the national scale. New confirmed records for Procambarus clarkii are continuously arising in recent years across the country. By reviewing the scientific and grey literature, we obtained an up-to-date map of the species invasion in Italy. This information can help to monitor and understand the spread of this highly invasive crayfish and to implement more effective management measures.

Using citizen science to monitor non-native species: the case of Lethocerus patruelis (Stål, 1855) (Hemiptera: Belostomatidae) in Italy

Findings of Lethocerus patruelis (Stål, 1855) in Southern Italy have become frequent in the last decades. We collected records of Lethocerus patruelis observations in Italy using scientific literature, citizen science programs, and social networks as data sources to create a complete and up-to-date dataset. This dataset is made of 59 Lethocerus patruelis observations from the Apulia, Basilicata, Calabria, and Abruzzi regions, 32 of which were previously unpublished, spanning from 1997 to 2020. Half of these records comes from biodiversity dedicated Facebook groups, citizen science programs and online forums, underlining the usefulness of unconventional data sources to gather data on species with poorly known distributions. The existence of Lethocerus patruelis viable populations in Italy remains unclear.&nbsp

Thirty years of invasion: the distribution of the invasive crayfish Procambarus clarkii in Italy

The presence of the red swamp crayfish Procambarus clarkii in Italy is documented since 1989, but no comprehensive data are available on its spread through time at the national scale. New confirmed records for Procambarus clarkii are continuously arising in recent years across the country. By reviewing the scientific and grey literature, we obtained an up-to-date map of the species invasion in Italy. This information can help to monitor and understand the spread of this highly invasive crayfish and to implement more effective management measures.

Datasets and script for niche comparisons and GLMMs

   Species distribution models are often used to predict the potential distributions of invasive species outside their native ranges and rely on the assumption of realized niche conservatism. Analyses observed that freshwater invasive species often show high degrees of niche expansion, suggesting limited reliability of species distribution models. However, observed niche shifts can arise because of both actual niche shifts, determined by biological factors, and apparent shifts, due to methodological issues. We compared metrics of niche dynamics calculated using different sets of variables to identify factors that could influence the rate of niche shifts. We collected presence-only data for 40 freshwater invasive animal species, then measured niche shift dynamics using 14 different combinations of environmental variables. Shifts were assessed measuring niche overlap, expansion, and unfilling, and testing for niche conservatism. We then built generalized linear mixed models relating niche shifts to methodological choices and biological features. Our results showed that methodological choices strongly affected all the considered niche dynamics metrics, while the effects of biological features were less prominent. Moreover, different niche dynamic measures sometimes provided contradictory assessments of niche conservatism. Niche analyses are powerful tools to predict areas at risk of invasion, but inappropriate methodological choices can lead to apparent niche shifts, questioning niche models reliability and biological interpretation. The high rate of niche expansion observed in freshwater invasive species highlights the importance of delineating objective criteria to determine the set of variables to be used in niche dynamic assessments. We provide dataset and scripts used to perform niche comparisons between native and exotic distribution for 40 freshwater invasive species and generalised linear mixed models (GLMMs). Species occurrences ("observations.zip") were downloaded from iNaturalist (https://www.inaturalist.org/). The areas used as native and exotic backgrounds ("backgrounds.zip") were created using IUCN Red List distribution data (https://www.iucnredlist.org), literature data, and the Freshwater Ecoregions of the World (Abell et al. 2008, available at: https://www.feow.org/). Niche comparisons were performed using the ecospat package (Di Cola et al. 2017). The file neded to perform niche comparisons are found in the "spbg.zip" folder, and they are needed to run the "niche_comparison_c.R"  script. GLMMs were performed to test the effects of methodological choices (bioclimatic variables, chemical variables, distance-weighted variables, limited background selection, number of parameters) and of biological features (taxonomical group, native range extent, exotic range extent, residence time) on nine measures resulting from niche comparisons. These models were performed using  the ‘lme4’ (Bates et al., 2015) and the ‘GLMMtmb’ packages (Brooks et al., 2017). The script used to perform GLMMs is provided as "glmm.R" and it needs the "data_table.RData" file.</p

Assessing Population Trends of Species with Imperfect Detection: Double Count Analyses and Simulations Confirm Reliable Estimates in Brown Frogs

Most animal species are detected imperfectly and overlooking individuals can result in a biased inference of the abundance patterns and underlying processes. Several techniques can incorporate the imperfect detection process for a more accurate estimation of abundance, but most of them require repeated surveys, i.e., more sampling effort compared to single counts. In this study, we used the dependent double-observer approach to estimate the detection probability of the egg clutches of two brown frog species, Rana dalmatina and R. latastei. We then simulated the data of a declining population at different levels of detection probability in order to assess under which conditions the double counts provided better estimates of population trends compared to na&iuml;ve egg counts, given the detectability of frog clutches. Both species showed a very high detection probability, with average values of 93% for Rana dalmatina and 97% for R. latastei. Simulations showed that not considering imperfect detection reduces the power of detecting population trends if detection probability is low. However, at high detection probability (&gt;80%), ignoring the imperfect detection does not bias the estimates of population trends. This suggests that, for species laying large and easily identifiable egg clutches, a single count can provide useful estimates if surveys are correctly timed

Condition- and context-dependent variation of sexual dimorphism across lizard populations at different spatial scales

The evolution of sexual dimorphism (SD) is driven by intricate interplays between sexual and natural selection. When it comes to SD variation within populations, however, environmental factors play a major role. Sexually selected traits are expected to be strongly dependent on individual body condition, which is influenced by the local environment that individuals experience. As a consequence, the degree of SD may also depend on resource availability. Here, we investigated the potential drivers of SD expression at two sexually dimorphic morphometric traits, body size (snout vent length) and head shape (head geometric morphometrics), in the Italian wall lizard (Podarcis siculus). We assessed the existence of condition- and context-dependent SD across ten islands of the Aeolian archipelago (southern Italy), at within- and among-population scales. We observed strong geographical variation of SD among islands, and tested three potential SD predictors related to resource availability (individual body condition, ecosystem productivity, temperature). Body condition and ecosystem productivity were the main drivers of body size SD variation, and body condition was also the main driver for head shape SD. Our results highlight that the expression of SD in the Italian wall lizard is both condition- and context-dependent. These results are congruent at within- and among-populations scales highlighting that spatial multi-scale analysis represents a useful approach to understand patterns of SD expression