The exponential increase in biological invasions worldwide, driven by globalisation and climate change is listed among the five biggest threats to the Earth's biodiversity. This trend poses a significant threat to the conservation of endangered species and ecosystems worldwide. The Mediterranean Sea emerges as notably affected by this phenomenon. Since the opening of the Suez Canal, a considerable amount of alien species have been entering the Mediterranean from the Red Sea, and their spread has been favoured by the consequences of climate change. Focusing on two successful Lessepsian fish invaders: Siganus rivulatus, a long-standing invader and Pterois miles a newly established invader, we aim to investigate the trends of different types of genetic diversity during the colonisation of the Mediterranean Sea. Our first objective is to investigate how the different timing and speed of invasion have shaped genetic diversity distribution and genetic load accumulation in these two invasive species. We also know that these species are adapting to significantly lower temperature and salinity levels than those in which they usually thrive. Our goal is to understand whether these two species are using the same gene combinations to adapt to the new environmental conditions. Lastly, considering different possible climate change scenarios, we aim to develop reliable predictive models to infer the possible future trajectories of these invasions, taking into account how non-neutral diversity may influence the invasive potential of these species. Preliminary results reveal a dramatic decline in genetic diversity moving from the source population to the northern bound of the invasive range with the Mediterranean population representing just a small portion of the total diversity present in the Red Sea suggesting that the colonisation of the Mediterranean is attributable to a single and rapid invasive event.

The recurrent climatic fluctuations of the Quaternary resulted in subsequent glacial and interglacial periods characterized by repeated changes in environmental conditions and resource availability. Several biotopes disappeared entirely or changed considerably leading to either extinction, survival in glacial refugia or adaptation to new habitats. Those environmental and distribution shifts likely had genetic consequences, with rapid demographic changes causing loss in genetic diversity. Patterns of demographic variation are reflected in the genome of a species which can be studied to estimate fluctuations in effective population size (N_e) using Pairwise Sequentially Markovian Coalescent (PSMC). The combination of PSMC and environmental niche modelling (ENM), which reconstruct changes in a species’ distribution using paleoclimatic data, can provide insights into the effects of environmental variations on the life history of a species and eventually help understand its vulnerability to climate changes. Among vertebrates, turtles are one of the most endangered group due to illegal trade, habitat loss, pollution, and climatic alterations, which are already affecting several of their physiological and phenological characteristics. We used whole-genome sequencing data from 22 species of turtles to infer variation in effective population size through time and checked for correlation between N_e, heterozigosity, IUCN category and habitat availability during the Marine Isotope Stage 19, the last interglacial period, the last glacial maximum and the early Holocene. All species experienced a drastic decrease in Ne at the start of the last glacial period, which was correlated to a decrease in temperature. On the other hand, no correlation was found between extent of habitat availability, effective population size, extinction risk as defined by IUCN categories and heterozygosity.

According to evolutionary theories, each species adapts different strategies and makes trade-offs to maximize fitness. Even within the same species, individuals may follow diverse strategies, some bolder and more demanding than others. However, defining the driving forces that enhance this diversity still requires investigations.

This study aimed to examine the interplay between extrinsic environmental factors and individual pace of life using Gammarus insensibilis as the study organism, a detritivorous species in Italian lagoons. To this aim, cohorts with initial different densities were maintained for 45 days in laboratory experimental trials characterized by a constant resource supply, i.e. 20g of 15-day microbially conditioned Phragmites australis leaves. The population densities varied, corresponding to the individual-to-resource ratio, from 0.75 to 12.5 individuals per gram of resource. Resources were changed, and individuals were counted every 15 days. After 45 days, individual standard metabolic rates, recorded body mass, and maturity stage were measured.

Results showed an inverse relationship between cohort density and individuals’ pace of life. Individuals reared in the lowest cohort density, compared to those in higher densities, had a greater average body mass, reached maturity faster, and had a higher baseline standard metabolic rate. Significant inter-individual variation in growth and metabolic rates was observed within each cohort, with the biggest individual ~10 times bigger than the smallest. Conclusively, this study revealed that the pace of life is modulated continuously across a spectrum of resource availability, with an increased resource-to-individual ratio resulting in a faster pace of life suggesting a wider range of individual personality outcomes. Our findings contribute to understanding the adaptive potential of population-level energy budgets influenced by the relative abundance of individuals with diverse energetic and life history outcomes.

Theory and empirical evidence support the idea that species adaptation to new environmental conditions may occur by two main routes: standing variation or de novo mutations. In origin from standing variation, adaptive polymorphisms are already present in the population before the selective pressure, and they will increase under positive selection. On the contrary, an adaptation from de novo mutations involves polymorphisms that originate in the populations once an environmental change has occurred. To date, a heated debate about the relative role of these two alternative routes is still occurring, mainly because we rarely can study populations before selection takes place.

Here, we exploited the information frozen in the genome of historical samples to disentangle between the two scenarios, putting them in the case of the diflubenzuron resistance in the mosquito Culex pipiens. Diflubenzuron is a chitin-synthesis inhibitor intensively used in northern Italy against mosquito vectors since 2007. In 2015, target-site resistance to this compound was detected in Cx. pipiens populations for the first time. By analysing current and historical samples, we showed that target-site resistance was already present in the populations of Cx. pipiens in the 1980s, thus pre-dating the use of diflubenzuron against this species. Concurrently by characterizing the morphology and behaviour of susceptible and resistant phenotypes in absence of insecticides, we revealed potentially advantageous traits associated with resistance. Taken together, our results support the importance of standing variation in adaptation and suggest that multiple selective pressures beyond insecticides may have favoured resistant individuals within populations.

Predicting species’ responses to climate change is a pressing need hampered by our limited knowledge of spatiotemporal ecological and evolutionary dynamics. We combine landscape genomics, demographic reconstructions, and species distribution models to assess the ecological responses to past climate fluctuations and to future climate in an Afro-Palearctic migratory raptor, the lesser kestrel (Falco naumanni). We uncover two evolutionary and ecologically distinct lineages (European and Asian), whose demographic history, evolutionary divergence, and historical distribution range were profoundly shaped by past climatic fluctuations. Using future climate projections, we find that the Asian lineage is at higher risk of maladaptation, range contraction, increased migration distance, and consequently greater extinction risk than the European lineage. Our results emphasise the importance of providing historical context as a baseline for understanding species’ responses to contemporary climate change, and demonstrate that incorporating intraspecific genetic variation improves the ecological realism of climate change vulnerability assessments.

Understanding population structure, genetic diversity, and adaptation in fish species is pivotal for fisheries genomics. This knowledge is crucial for effective fisheries management, conservation efforts, and to understand environmental impacts on fish populations.

This study employed ddRAD sequencing to identify and genotype single nucleotide polymorphism markers (SNPs) in European hake (Merluccius merluccius) population samples obtained during MED_UNITs project. Over 1,700 specimens from 41 sampling locations were analyzed, including extensive coverage of the Mediterranean Sea and one Atlantic location. Following reference-based assembly and quality filtering, we identified about 1,000 high-quality SNPs for downstream differentiation analyses. A comparison of the samples, based on all the SNPs, revealed significant genetic differentiation not only between the Atlantic and the Mediterranean Sea samples, but also within the Mediterranean. We observed significant differences between the Western, Central, and Eastern Mediterranean populations, as well as between the Levantine and Aegean Sea samples. Admixture analysis identified four genetic clusters, exhibiting varying frequencies in a west-to-east pattern within the Mediterranean. By employing the Population Branch Statistic, we identified SNPs putatively under selection in the admixed populations using an outgroup-case-control approach. The availability of individual phenotypic and environmental data allowed investigation of their correlation with SNPs. Notably, several putatively selected SNPs exhibited correlations with different individual parameters in independent comparisons supporting the possibility that these genetic variants lie in genomic regions with functional relevance, and they might be involved in response to the environment.

Our study offers new insights by revealing a significant degree of genetic structure within the Mediterranean region that extends previous results, which had only identified these differences through the analysis of outlier genetic loci. Additionally, the study highlights the adaptive genomic variation that underlies the observed population structure, thus providing valuable insights for the formulation of sound conservation strategies and development of sustainable fisheries practices.