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Sexual dimorphism is almost ubiquitous in animals. A common pattern observed across multiple taxa involves differences in development time (sexual bimaturism) and body size (sexual size dimorphism) between conspecific males and females. Furthermore, a strict association of dimorphism at these traits has been documented in several taxa, where the sex showing shorter development time also has a smaller body size than the other sex. Growth and development are strongly dependent on environmental conditions during individual life-cycle in ectotherms, inducing considerable phenotypic plasticity. However, how phenotypic plasticity affects the association between sexual dimorphism in development time and body size remains unclear. Here, we tracked development time, body size, and body mass throughout the ontogeny of the mosquito Aedes mariae . The larval development of this species is strictly linked to Mediterranean Sea rock-pools, whose highly variable environmental conditions over minimal time frames make this organism-environment system ideal for exploring plasticity-led eco-evolutionary processes. We found differential plasticity between males and females, dissolving the link between dimorphism in development time and body size under increasing temperature and decreasing salinity conditions. These findings contrast with the current hypotheses proposed to explain the origin of the association between sexual bimaturism and sexual size dimorphism, highlighting the condition dependence of sexual dimorphism patterns and the need to consider phenotypic plasticity in future studies on their evolution.

Hybridization between heterospecific individuals has been documented as playing a direct role in promoting paternal leakage and mitochondrial heteroplasmy in both natural populations and laboratory conditions, by relaxing the egg-sperm recognition mechanisms. Here, we tested the hypothesis that hybridization can lead to mtDNA heteroplasmy also indirectly via mtDNA introgression. By using a phylogenetic approach, we showed in two reproductively isolated beetle species, Ochthebius quadricollis and O. urbanelliae , that past mtDNA introgression occurred between them in sympatric populations. Then, by developing a multiplex allele-specific PCR assay, we showed the presence of heteroplasmic individuals and argue that their origin was through paternal leakage following mating between mtDNA-introgressed and pure conspecific individuals. Our results highlight that mtDNA introgression can contribute to promote paternal leakage, generating genetic novelty in a way that has been overlooked to date. Furthermore, they highlight that the frequency and distribution of mtDNA heteroplasmy can be deeply underestimated in natural populations, as i ) the commonly used PCR-Sanger sequencing approach can fail to detect mitochondrial heteroplasmy, and ii ) specific studies aimed at searching for it in populations where mtDNA-introgressed and pure individuals co-occur remain scarce, despite the fact that mtDNA introgression has been widely documented in several taxa and populations.

In recent decades, our view of inter-individual diversity in insects has been deeply impacted by the discovery that they exhibit individual personalities, expressed as consistent individual differences in behavioral tendencies across time and contexts. Personality traits, such as boldness, exploration, and activity, have been documented in several species and linked to variation in multiple life history traits with consequences for insect population ecology. However, personalities remain largely unexplored in mosquito vectors. Here, we investigated the presence of personality traits in the tiger mosquito Aedes albopictus larvae. A total of 41 larvae (16 males, 18 females, 7 unsexed) were individually tested under laboratory conditions. Activity was measured by time spent in locomotion in the housing trays, exploration by the area covered in a novel environment, and boldness by the latency to re-emerge after a simulated aerial threat. All behavioral traits showed significant repeatability through time, with no significant effect of sex. Moreover, boldness, activity, and exploration were significantly correlated, with more active larvae being bolder and more exploratory. Overall, our results reveal the occurrence of personalities in mosquito vector larvae. We propose that incorporating personality into mosquito research could offer new insights into their biology and ecology, with potential implications for vector control strategies and the management of mosquito-borne diseases.

Discordance between mitochondrial and nuclear patterns of population genetic structure is providing key insights into the eco-evolutionary dynamics between and within species, and their assessment is highly relevant to biodiversity monitoring practices based on DNA barcoding approaches. Here, we investigate the population genetic structure of the fire salamander Salamandra salamandra in peninsular Italy. Both mitochondrial and nuclear markers clearly identified two main population groups. However, nuclear and mitochondrial zones of geographic transition between groups were located 600 km from one another. Recent population declines in central Italy partially erased the genetic imprints of past hybridization dynamics. However, the overall pattern of genetic variation, together with morphological and fossil data, suggest that a rampant mitochondrial introgression triggered the observed mitonuclear discordance, following a post-glacial secondary contact between lineages. Our results clearly show the major role played by reticulate evolution in shaping the structure of Salamandra salamandra populations and, together with similar findings in other regions of the species’ range, contribute to identify the fire salamander as a particularly intriguing case to investigate the complexity of mechanisms triggering patterns of mitonuclear discordance in animals.

The spotted-wing drosophila ( Drosophila suzukii ), a highly invasive agricultural pest, poses significant challenges to fruit production worldwide. Traditional chemical control methods are costly and raise concerns about resistance and environmental sustainability. The Heterospecific Sterile Insect Technique (h-SIT) has emerged as a promising alternative. Sterile heterospecific males ( Drosophila melanogaster ) can be used to suppress D. suzukii populations through reproductive interference, primarily mediated by post-zygotic isolation mechanisms. Although this approach ensures the absence of viable offspring from heterospecific matings, male sterilization through irradiation remains essential. It prevents unintended ecological effects from D. melanogaster proliferation in the release area and allows for safe large-scale implementation. Therefore, determining an optimal irradiation dose is critical for achieving high levels of male sterility and maintaining biological quality and mating performance. This study aimed to determine the optimal irradiation dose by assessing induced sterility in D. melanogaster males exposed to gamma ray doses ranging from 80–180 Gy. Subsequently, the longevity and the time spent by irradiated D. melanogaster males courting D. suzukii females were also assessed. Results showed a significant dose-dependent increase in induced sterility, with near-complete sterility at 180 Gy. However, longevity decreased with increasing doses, with males irradiated at 160–180 Gy showing a lifespan reduction of up to 50 days compared to controls. Regardless of the irradiation dose received, D. melanogaster males retained their courtship ability toward D. suzukii females, although males exposed to 160 Gy exhibited reduced courtship activity. These findings showed that, among the tested doses, 80 Gy was the most effective in preserving male longevity and mating performance, significantly reducing fertility, while 180 Gy induced the highest sterility. The potential lifespan and courtship behavior trade-offs warrant further evaluation. Future studies should evaluate field performance to refine the balance between sterility, longevity, and mating performance for effective D. suzukii population suppression.

Background The pupal stage in holometabolous insects is a critical transition between larval and adult forms, during which feeding ceases and survival depends on stored energy reserves. Mosquito pupae exhibit active diving behaviour in response to threats, which is energetically costly due to their positive buoyancy. Whether pupae are able to adjust diving behaviour according to environmental conditions, balancing predator avoidance and energy expenditure, remains poorly understood. Here, we investigated how water salinity affects the diving behaviour of Aedes mariae pupae, a species inhabiting Mediterranean rock pools characterised by highly variable salinity conditions. Methods Pupae were maintained and tested in two salinity conditions: low (50%) and high (150%). Diving behaviour was recorded following an automated mechanical stimulus, and we measured: (i) time spent underwater, (ii) pupal activity (i.e. the number of abdominal movements during the immersion and the ratio of movements to time spent underwater) and (iii) the proportion of time spent by a pupa at different depths along the height of the water column (space use). Results We found that pupae in high-salinity conditions spent 20.6% less time underwater than those in low salinity. They also performed fewer abdominal movements during dives but showed no significant differences in movements per unit time. Analysis of space use showed that pupae in high salinity spent more time in the upper part of the water column and less time in the middle and lower parts. Conclusions Ae. mariae pupae modify their diving behaviour in response to different salinity conditions, adopting energy-efficient responses to external stimuli that promote survival in variable habitats. These findings highlight the importance of pupal behavioural flexibility for overall fitness and underscore the need to investigate pupal behavioural plasticity, which remains largely unexplored. Graphical abstract

The tiger mosquito, Aedes albopictus, is one of the 100 most invasive species in the world and a vector of human diseases. In the last 30 years, it has spread from its native range in East Asia to Africa, Europe, and the Americas. Although this modern invasion has been the focus of many studies, the history of the species' native populations remains poorly understood. Here, we aimed to assess the role of Pleistocene climatic changes in shaping the current distribution of the species in its native range. We investigated the phylogeography, historical demography, and species distribution of Ae. albopictus native populations at the Last Glacial Maximum (LGM). Individuals from 16 localities from East Asia were analyzed for sequence variation at two mitochondrial genes. No phylogeographic structure was observed across the study area. Demographic analyses showed a signature of population expansion that started roughly 70,000 years BP. The occurrence of a continuous and climatically suitable area comprising Southeast China, Indochinese Peninsula, and Sundaland during LGM was indicated by species distribution modelling. Our results suggest an evolutionary scenario in which, during the last glacial phase, Ae. albopictus did not experience a fragmentation phase but rather persisted in interconnected populations and experienced demographic growth. The wide ecological flexibility of the species probably played a crucial role in its response to glacial-induced environmental changes. Currently, there is little information on the impact of Pleistocene climatic changes on animal species in East Asia. Most of the studies focused on forest-associated species and suggested cycles of glacial fragmentation and post-glacial expansion. The case of Ae. albopictus, which exhibits a pattern not previously observed in the study area, adds an important piece to our understanding of the Pleistocene history of East Asian biota.

Mosquito control is of paramount importance, in particular, in light of the major environmental alterations associated with human activities, from climate change to the altered distribution of pathogens, including those transmitted by Arthropods. Here, we used the common house mosquito, Culex pipiens to test the efficacy of MosChito raft, a novel tool for mosquito larval control. MosChito raft is a floating hydrogel matrix, composed of chitosan, genipin and yeast cells, as bio-attractants, developed for the delivery of a Bacillus thuringiensis israeliensis ( Bti )-based bioinsecticide to mosquito larvae. To this aim, larvae of Cx . pipiens were collected in field in Northern Italy and a novel colony of mosquito species (hereafter: Trescore strain) was established. MosChito rafts, containing the Bti -based formulation, were tested on Cx . pipiens larvae from the Trescore strain to determine the doses to be used in successive experiments. Thus, bioassays with MosChito rafts were carried out under semi-field conditions, both on larvae from the Trescore strain and on pools of larvae collected from the field, at different developmental stages. Our results showed that MosChito raft is effective against Cx . pipiens . In particular, the observed mortality was over 50% after two days exposure of the larvae to MosChito rafts, and over 70–80% at days three to four, in both laboratory and wild larvae. In conclusion, our results point to the MosChito raft as a promising tool for the eco-friendly control of a mosquito species that is not only a nuisance insect but is also an important vector of diseases affecting humans and animals.

Understanding the genomic consequences of hybridization is an essential research focus in global change biology. Species adapted to rapidly changing environments can offer valuable, yet largely underexplored insights in this context. Here, we present the first de novo transcriptomes of the sea-rock pools mosquitoes Aedes mariae and Aedes zammitii , two species adapted to highly variable habitats. Using RNA-seq data obtained from larval stages, we assembled and annotated 95,059,578 reads for Ae. mariae and 101,050,236 reads for Ae. zammitii , detecting 49,352 transcripts with N50 of 2,615 for the former and 43,461 transcripts with N50 of 2,570 for the latter. Validation by BUSCO confirmed the high quality of our resources. Homology alignments of predicted ORFs showed that 21,842 sequences from Ae. mariae and 21,944 sequences from Ae. zammitii mapped to the Nr, SwissProt, and TrEMBL databases, while 19,208 and 19,393 predicted ORFs, respectively, were functionally annotated using the COG and KEGG databases. These high-quality transcriptomes will provide valuable resources to investigate the role of hybridization in species adaptation to changing environments.

Background Insecticide resistance is one of the primary problems affecting vector control worldwide. Assessing the occurrence of resistant alleles and understanding their origin across the geographic range of vector species is crucial for effective resistance management. In populations of the mosquito Culex pipiens , point mutations conferring resistance to the insecticide diflubenzuron (DFB) were recently found across the Mediterranean basin. In this study, we investigated the possible occurrence of DFB resistance in Cyprus, where West Nile virus outbreaks have been documented in recent years. Methods We sequenced a fragment of the chitin-synthase 1 gene carrying the resistant mutations in individuals collected from 18 populations of Cx. pipiens in Cyprus to investigate the occurrence of DFB-resistant alleles. We then assessed the evolutionary origin of DFB-resistant alleles by reconstructing the phylogenetic relationships between susceptible and resistant alleles found across the Mediterranean basin. Results Our screening revealed the occurrence of the I1043F allele in all the districts analyzed. Notably, a new gene codon underlying the I1043F allele was detected. To our knowledge, this has not been previously reported in areas with DFB-resistance alleles in Cx. pipiens . In addition, we observed that the I1043F alleles detected in Cyprus have a different genetic background from those reported in other geographic areas, such as Italy and Turkey. Conclusions To our knowledge, this is the first time in which DFB resistance was revealed in Cx. pipiens populations occurring in Cyprus. Furthermore, we demonstrate that I1043F-resistant alleles have an independent origin in Cyprus, further supporting the hypothesis of a multiple independent origin of DFB resistance across the Mediterranean region. These results stress the need for regular resistance surveillance activities and the urgency of developing new mosquito control strategies. Graphical abstract