Hybridization and extensive mitochondrial introgression among fire salamanders in peninsular Italy

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

Exon-intron structure and sequence variation of the calreticulin gene among Rhipicephalus sanguineus group ticks

Background: Calreticulin proteins (CRTs) are important components of tick saliva, which is involved in the blood meal success, pathogen transmission and host allergic responses. The characterization of the genes encoding for salivary proteins, such as CRTs, is pivotal to understand the mechanisms of tick-host interaction during blood meal and to develop tick control strategies based on their inhibition. In hard ticks, crt genes were shown to have only one intron with conserved position among species. In this study we investigated the exon-intron structure and variation of the crt gene in Rhipicephalus spp. ticks in order to assess the crt exon-intron structure and the potential utility of crt gene as a molecular marker. Methods: We sequenced the exon-intron region of crt gene in ticks belonging to so-called tropical and temperate lineages of Rhipicephalus sanguineus (sensu lato), Rhipicephalus sp. I, Rhipicephalus sp. III, Rhipicephalus sp. IV, R. guilhoni, R. muhsamae and R. turanicus. Genetic divergence and phylogenetic relationships between the sequences obtained were estimated. Results: All individuals belonging to the tropical lineage of R. sanguineus (s. l.), R. guilhoni, R. muhsamae, R. turanicus, Rhipicephalus sp. III and Rhipicephalus sp. IV analysed showed crt intron-present alleles. However, both crt intron-present and intron-absent alleles were found in Rhipicephalus sp. I and the temperate lineage of R. sanguineus (s. l.), showing the occurrence of an intraspecific intron presence-absence polymorphism. Phylogenetic relationships among the crt intron-present sequences showed distinct lineages for all taxa, with the tropical and temperate lineages of R. sanguineus (s. l.) being more closely related to each other. Conclusions: We expanded previous studies about the characterization of crt gene in hard ticks. Our results highlighted a previously overlooked variation in the crt structure among Rhipicephalus spp., and among hard ticks in general. Notably, the intron presence/absence polymorphism observed herein can be a candidate study-system to investigate the early stages of intron gain/loss before fixation at species level and some debated questions about intron evolution. Finally, the sequence variation observed supports the suitability of the crt gene for molecular recognition of Rhipicephalus spp. and for phylogenetic studies in association with other markers

Native strains of Beauveria bassiana for the control of Rhipicephalus sanguineus sensu lato

Background Rhipicephalus sanguineus sensu lato ticks are widespread worldwide due to their adaptability to survive under different environmental conditions. They may act as vectors of a wide range of pathogens to humans and animals and their control is based on the use of chemical products on dogs and in the environment. Alternative control strategies, such as the use of entomopathogenic fungi as bio-control agents have also been investigated. The ability of native strains of Beauveria bassiana sensu lato in causing mortality in different tick species (e.g., Amblyomma cajennense and Rhipicephalus microplus) has been demonstrated. However, limited studies have assessed the use of B. bassiana for the control of R. sanguineus s.l. and none of them have employed native strains of this fungus. Here we investigated the pathogenicity of a native strain of B. bassiana (CD1123) against all developmental stages of R. sanguineus s.l.. Methods Batches of eggs, larvae, nymphs and adult ticks were immersed in a suspension of 107 conidia/ml of B. bassiana s.l., isolated from a R. sanguineus s.l. engorged female. All treatment and control groups were observed for 20 days, and the biological parameters (i.e., mortality, hatching, moulting percentage, pre-oviposition period, oviposition period and rate, eggs production efficiency, reproductive efficiency and fitness indexes) were assessed. Results The effect of the B. bassiana strain tested herein on eggs, larvae, nymphs and adults showed a significantly higher mortality than those of the control groups (p < 0.05) at 5 days post-infection. No infected eggs hatched and no infected larvae moulted. Only 15% of infected nymphs moulted into adults. All biological parameters of treated groups differed significantly (p < 0.001) from those of control groups. Conclusions This study demonstrates that a suspension containing 107 conidia/ml of a native B. bassiana strain is highly virulent towards all life-cycle developmental stages of R. sanguineus s.l. and may be of potential interest as a biological control agent against these ticks

Profiles of relative permittivity and electrical conductivity from unsaturated soil water content models

A mathematical model of water diffusion in the vadose zone has been implemented for different types of soil textures in order to determine the soil water content (SWC) profiles in dependence of depth and time. From these profiles, obtained for different soils, we derived the characteristic electrical parameters, such as relative permittivity (epsilonr) and electrical conductivity (sigma), and their variation in time, employing empirical relations available in the scientific literature. The simulation through mathematical models has been performed taking into account different types of soils characterized by the percentage composition of sand, clay and silt in the textural triangle, which provides some physical and chemical properties that affect the water retention in the soil. The resulting simulated profiles of SWC and consequently permittivity and conductivity profiles, span over a certain range of values suggesting the best techniques and the limits in geophysical investigation. Moreover this a-prior knowledge helps in the elaboration and interpretation of permittivity and conductivity data obtained by the measurements. Permittivity and conductivity profiles are particularly useful in some environmental applications when the soil textures are (or supposed to be) known as in the typical case of landfill leachate dispersion. Since the soil textures beneath or nearby a disposal waste are characterized by a SWC, the values of (epsilonr) and (sigma) at various depth can be directly inferred

Living and dead foraminiferal assemblages from an active submarine canyon and surrounding sectors. The Gioia Canyon system (Tyrrhenian Sea, Southern Italy)

Living (rose Bengal stained) and dead benthic foraminiferal assemblages were studied from 23 stations located between 60 and 670 m depth along the Gioia Canyon and the adjacent continental shelf and slope (Southern Tyrrhenian Sea). The aim of this study is to investigate the relationships among sedimentary processes, hydrological patterns and benthic foraminiferal distribution, in a highly dynamic environment. High sedimentation rates on the shelf and occasional turbidity flows along the canyon, lead to unstable environmental conditions at the seafloor that reflect on the microbenthic community influencing faunal density, diversity, species composition and distribution inside the sediment. The foraminiferal distribution seems to be controlled by sedimentary processes, nutrient supply and organic matter recycling, which in turn are strongly controlled by the seasonal variability of riverine inputs and current dynamics in the Gulf of Gioia. From the inner shelf to the upper continental slope (550 m depth), the living foraminiferal assemblage is dominated by agglutinated taxa, likely favored by the high terrigenous supply. Frequent eutrophic taxa (Valvulineria bradyana and Nonionella turgida) tolerant high turbidity (Leptohalysis scottii,) and low oxygen (Bolivina spp. and Bulimina spp.) are recorded on the edge of the inner shelf, where channeling, deposition of coastal deposits and occasional sediment gravity flows occur. In the outer sector of the shelf a turnover of species is observed; L. scottii replaced by the opportunistic species Reophax scorpiurus, and taxa indicative of high energy conditions (Cassidulina spp.) become dominant in association with mesotrophic species like Globocassidulina subglobosa. Along the continental slope, lower sedimentation rates and more stable environmental conditions support richer and more diversified foraminiferal assemblage. The abundance of Bulimina marginata indicates eutrophic conditions at the shallower station (300 m depth) whereas at greater depth (550 m) typical open slope species dominate (Gyroidina spp., Uvigerina mediterranea). Within the Gioia Canyon, benthic assemblage indicates environmental conditions similar to those observed in other Mediterranean and extra-Mediterranean canyons. The assemblage is characterized by eutrophic and low oxygen taxa (Bolivina spp., Bulimina spp.) in relation to periodical fluxes of sediment and organic matter. Similar relationships arise from the analysis of dead foraminiferal assemblages. However, the comparison between living and dead faunas highlight compositional and structural changes related to taphonomic processes

The tangled evolutionary legacies of range expansion and hybridization

Spatial sorting of dispersal-enhancing traits has been implicated in substantial directional changes in the phenotypic and genotypic makeup of populations undergoing range expansion. We explore here the evolutionary consequences of such changes when two divergent lineages come into secondary contact. We combine instances from the study of contemporary range expansions and historical hybridizations, and highlight links between dispersal, sexual, and physiological traits during the non-equilibrium conditions imposed by range expansions. We argue that a stronger research focus on processes of spatial sorting of multiple traits will improve our understanding of subsequent hybridization dynamics and their evolutionary outcomes, including genomic introgression and speciation

Paternal leakage and mtDNA heteroplasmy in Rhipicephalus spp. ticks

Paternal leakage of mitochondrial DNA (mtDNA) and heteroplasmy have been recently described in several animal species. In arthropods, by searching in the Scopus database, we found only 23 documented cases of paternal leakage. Therefore, although arthropods represent a large fraction of animal biodiversity, this phenomenon has been investigated only in a paucity of species in this phylum, thus preventing a reliable estimate of its frequency. Here, we investigated the occurrence of paternal leakage and mtDNA heteroplasmy in ticks belonging to one of the most significant tick species complexes, the so-called Rhipicephalus sanguineussensu lato. By developing a multiplex allele-specific PCR assay targeting a fragment of the 12S rRNA ribosomal region of the mtDNA, we showed the occurrence of paternal leakage and mtDNA heteroplasmy in R. sanguineuss.l. ticks originated from experimental crosses, as well as in individuals collected from the field. Our results add a new evidence of paternal leakage in arthropods and document for the first time this phenomenon in ticks. Furthermore, they suggest the importance of using allele-specific assays when searching for paternal leakage and/or heteroplasmy, as standard sequencing methods may fail to detect the rare mtDNA molecules

Native strains of Beauveria bassiana for the control of Rhipicephalus sanguineus sensu lato

Abstract Background: Rhipicephalus sanguineus sensu lato ticks are widespread worldwide due to their adaptability to survive under different environmental conditions. They may act as vectors of a wide range of pathogens to humans and animals and their control is based on the use of chemical products on dogs and in the environment. Alternative control strategies, such as the use of entomopathogenic fungi as bio-control agents have also been investigated. The ability of native strains of Beauveria bassiana sensu lato in causing mortality in different tick species (e.g., Amblyomma cajennense and Rhipicephalus microplus) has been demonstrated. However, limited studies have assessed the use of B. bassiana for the control of R. sanguineus s.l. and none of them have employed native strains of this fungus. Here we investigated the pathogenicity of a native strain of B. bassiana (CD1123) against all developmental stages of R. sanguineus s.l.. Methods: Batches of eggs, larvae, nymphs and adult ticks were immersed in a suspension of 10 7 conidia/ml of B. bassiana s.l., isolated from a R. sanguineus s.l. engorged female. All treatment and control groups were observed for 20 days, and the biological parameters (i.e., mortality, hatching, moulting percentage, pre-oviposition period, oviposition period and rate, eggs production efficiency, reproductive efficiency and fitness indexes) were assessed

Additional file 1: of Exon-intron structure and sequence variation of the calreticulin gene among Rhipicephalus sanguineus group ticks

Figure S1. Alignment of the full sequence of the crt region amplified in the Rhipicephalus spp. individuals analysed (coded as in Table 1). Nucleotides in orange boxes belong to exon regions in 5′ and 3′ splice donor regions. Nucleotides in light grey boxes belong to intron region in 5′ and 3′ splice donor regions. Nucleotides in black boxes indicate sequence identity in intron region. Asterisks show nucleotide identity in exon regions. Numbers indicate the nucleotide position of the R. sanguineus (s.l.) crt sequence AY395275 [25]. Abbreviations: R.s. Trop. lin., Rhipicephalus sanguineus (s.l.) “Tropical lineage”; R.s. Temp. lin., Rhipicephalus sanguineus (s.l.) “Temperate lineage”. (TIF 1069 kb

Potential role of ATP-binding cassette transporters against acaricides in the brown dog tick Rhipicephalus sanguineus sensu lato.

ATP-binding cassette (ABC) transporters have been shown to be involved in pesticide detoxification in arthropod vectors and are thought to contribute to the development of drug resistance. Little is currently known about the role they play in ticks, which are among the more important vectors of human and animal pathogens. Here, the role of ABC transporters in the transport of fipronil and ivermectin acaricides in the tick Rhipicephalus sanguineus (Ixodida: Ixodidae) was investigated. Larvae were treated with acaricide alone and acaricide in combination with a sub-lethal dose of the ABC transporter inhibitor cyclosporine A. The LC50 doses and 95% confidence intervals (CIs) estimated by mortality data using probit analysis were 67.930p.p.m. (95% CI 53.780-90.861) for fipronil and 3741p.p.m. (95% CI 2857-4647) for ivermectin. The pre-exposure of larvae to a sub-lethal dose of cyclosporine A reduced the LC50 dose of fipronil to 4.808p.p.m. (95% CI 0.715-9.527) and that of ivermectin to 167p.p.m. (95% CI 15-449), which increased toxicity by about 14- and 22-fold, respectively. The comparison of mortality data for each separate acaricide concentration showed the synergic effect of cyclosporine A to be reduced at higher concentrations of acaricide. These results show for the first time a strong association between ABC transporters and acaricide detoxification in R.sanguineus s.l