Biology subjects

Biello, R.

Publications and source records attributed to Biello, R..

11 recordsLinked to original sources

bioRxiv2026

Autozygosity and genetic load as sensitive early warnings of butterfly population decline

Insects are commonly expected to be protected from genomic erosion by high fecundity, short generation times, and large census sizes. Yet, insect populations can decline and eventually go extinct, underscoring the need for genomic indicators that provide actionable early warnings of population collapse. Here, we test this expectation by comparing contemporary and historical genomes of the Ponza grayling, Hipparchia sbordonii, an endangered butterfly endemic to the Pontine Islands in the Mediterranean, with the genomes of a widespread European congeneric species, H. semele. Using whole-genome resequencing, outgroup-based variant polarization, demographic reconstruction, runs of homozygosity, selection scans, and annotation-based genetic-load analyses, we show that H. sbordonii has undergone sustained demographic contraction, including a sharp recent decline. Despite limited temporal change in mean genome-wide heterozygosity, we observe extensive autozygosity, elevated inbreeding, and a clear shift from masked to realized genetic load in contemporary H. sbordonii. R'XY analysis revealed similar relative frequencies of high-impact derived variants in H. sbordonii and H. semele, suggesting ineffective purging during population collapse, whereas low- and moderate-impact variants were relatively enriched in H. sbordonii, particularly within candidate regions under selection. This indicates a more complex dynamic, in which functional variation has been shaped by the combined effects of drift, relaxed purifying selection, and possible local adaptation. Our study shows that declining butterfly populations bear distinctive signatures of genomic erosion, mirroring patterns well documented in vertebrates. Yet recent demographic collapse in H. sbordonii is more clearly captured by long runs of homozygosity and realized genetic load than by changes in mean genome-wide heterozygosity, highlighting their potential as early warning indicators for monitoring declining insect populations.

evolutionary biology↗

bioRxiv2026

The relationship between genomic variation and genetic load: insights from small island populations

Small populations face high extinction risks. This can be explained by several non-genetic and genetic factors, the latter including the loss of genetic diversity and evolutionary potential, as well as the accumulation of harmful mutations (genetic load). Using whole-genome data from island populations with different effective sizes, we estimated genetic variation and load and explored the relationship between these quantities. An extremely small population of the Aeolian wall lizard, Podarcis raffonei, likely isolated for tens of thousands of years, shows the lowest genome-wide heterozygosity observed in wild eukaryotes (one polymorphic site every 300 kb on average). Despite this, its realized genetic load is comparable to that observed in another larger and more genetically variable population. Both populations have lower variation and higher load than the much more abundant sister species, the Sicilian wall lizard. These observations are consistent with the hypothesis that populations experiencing severe bottlenecks may persist for extended periods with extremely low genomic variation, provided that their burden of deleterious mutations remains within tolerable bounds.

genomics↗

bioRxiv2025

Whole-Genome Population Genomics Reveals Lineage Structure and Adaptive Potential of Philaenus spumarius, the Principal Vector of Xylella fastidiosa in Europe

Philaenus spumarius (L.), the meadow spittlebug, is the principal European vector of Xylella fastidiosa. This xylem-feeding insect has a broad host range, ecological plasticity, and mobility, making it an efficient vector across diverse landscapes. Yet, major gaps remain in understanding its genetic diversity, migration patterns, and local adaptation, limiting effective control of X. fastidiosa outbreaks. To address these gaps, we worked with a global network of researchers and citizen scientists to assemble a geographically and ecologically diverse collection of P. spumarius samples. We generated a chromosome-level genome assembly for P. spumarius and high-quality assemblies for four related spittlebug species, providing a robust genomic framework for evolutionary and epidemiological studies. Resequencing 430 P. spumarius individuals from across the globe uncovered boreal, temperate, and semi-arid lineages shaped by geography and climate. The lineages vary in reproductive isolation and in the degree of mito-nuclear divergence. Iberian populations grouped with an individual identified as P. tesselatus contributing to regional genetic complexity. Genomic scans identified loci under selection in Apulian populations, including signatures in sulfotransferase (SULT) genes potentially linked to behavioural plasticity, host plant specialisation, or insecticide resistance in olive-growing regions. Migration analyses indicated limited long-distance dispersal but strong local connectivity, consistent with the rapid regional spread of X. fastidiosa. Together, these findings reveal the lineage structure and adaptive potential of P. spumarius, the key vector of X. fastidiosa in Europe. They underscore the importance of targeted surveillance of locally adapted populations and provide genomic tools for monitoring vector dynamics and mitigating emerging disease risks.

evolutionary biology↗

bioRxiv2025

One Sea, Different Whales: Genomics Sheds Light on a Small Population of Fin Whales

Whales play a crucial role in marine ecosystems, yet many populations face growing environmental pressures. Among them, the fin whale, Balaenoptera physalus, from the Mediterranean Sea remains poorly characterized at the genomic level despite its classification as Endangered and decreasing in population size due to habitat degradation, climate change, and human-induced disturbances. Previous studies based on bioacoustics and telemetry data suggest the presence of resident and migratory subgroups, but the genetic isolation of this population remains uncertain. Here, we sequenced and analysed for the first time whole genomes of the Mediterranean fin whale to provide a comprehensive genomic characterization of this population, assessing its genomic variability, genetic load, population structure and potential for adaptation to environmental stressors. By comparing genomic data from Mediterranean fin whales with populations from the North Atlantic, North Pacific, and the Sea of Cortez (also sequenced in the present study), we aim to determine the degree of genetic isolation and contextualize the Mediterranean population within a broader evolutionary and conservation framework. Our results showed that while Mediterranean fin whales form a distinct genetic cluster, they are not entirely isolated from North Atlantic populations, with gene flow persisting at low levels. Furthermore, we identified a complex substructure within the Mediterranean, supporting the existence of a resident subpopulation. Although this population preserves moderate levels of genomic diversity and adaptive potential, it remains vulnerable to genomic erosion due to continued demographic decline, limited connectivity, and increasing environmental stressors. These findings underscore the urgency of targeted conservation actions and long-term genetic monitoring, especially as climate change accelerates and introduces increasingly unpredictable selective pressures that may exacerbate the risk of genomic erosion and threaten population viability.

genomics↗

bioRxiv2025

Coexisting with humans: genomic and behavioural consequences in a small and isolated bear population

Climate and land use change have increased human-wildlife interactions, potentially reducing wild species density and prompting behavioural adaptations to urbanised environments. It is still debated if behavioural responses are mainly the result of phenotypic plasticity or if they were driven by anthropic selective pressures, especially in small populations. Our study focused on the Apennine brown bear population (Ursus arctos marsicanus), which has coexisted with humans in Central Italy for millennia. We characterised genomic diversity and identified adaptation signals distinctive to this population by comparing whole genome resequencing data across the Holarctic species range. We show that Apennine brown bears possess a unique genomic diversity pattern including selective signatures at genes associated with reduced aggressiveness, possibly involving alternative splicing mechanism. Our findings suggest that even in small and long-isolated populations, selection may shape behavioural traits. We hypothesise that human-induced selection has influenced these changes, reducing conflicts and contributing to the long-term persistence of the Apennine bear and its coexistence with humans.

genomics↗

bioRxiv2023

Unravelling the mystery of endemic versus translocated populations of the endangered Australian lungfish (Neoceratodus forsteri)

The Australian lungfish is a primitive and endangered representative of the subclass Dipnoi. The distribution of this species is limited to south-east Queensland, with some populations considered endemic and others possibly descending from translocations in the late nineteenth century shortly after European discovery. Attempts to resolve the historical distribution for this species have met with conflicting results based on descriptive genetic studies. Understanding if all populations are endemic or some are the result of, or influenced by, translocation events, has implications for conservation management. In this work, we analysed the genetic variation at three types of markers (mtDNA genomes, 11 STRs, and 5,196 nuclear SNPs) using the Approximate Bayesian Computation algorithm to compare several demographic models. We postulated different contributions of Mary River and Burnett River gene pools into the Brisbane River and North Pine River populations, related to documented translocation events. We ran the analysis for each marker separately, and we also estimated the posterior probabilities of the models combining the markers. Nuclear SNPs have the highest power to correctly identify the true model amongst the simulated datasets (where the model was known), but different markers typically provided similar answers. The most supported demographic model able to explain the real dataset implies that an endemic gene pool is present in the Brisbane and North Pine Rivers where past translocations are documented. These results will inform ongoing conservation efforts for this endangered and iconic species and warrant careful consideration of future genetic management of the Australian lungfish populations.

evolutionary biology↗

bioRxiv2022

Hybridisation has shaped a recent radiation of grass-feeding aphids

Aphids are common crop pests. These insects reproduce by facultative parthenogenesis involving several rounds of clonal reproduction interspersed with an occasional sexual cycle. Furthermore, clonal aphids give birth to live apterous or winged young that are already pregnant. Together, these qualities enable rapid population growth and have facilitated the colonisation of crops globally. In several cases so-called "super clones" have come to dominate agricultural systems. However, the extent to which the sexual stage of the aphid life cycle has shaped global pest populations has remained largely unclear, as have the origins of successful lineages. Here, we used chromosome-scale genome assemblies to disentangle the evolution of two of the most significant global pests of cereals - the English (Sitobion avenae) and Indian (Sitobion miscanthi) grain aphids. We found that genome-wide divergence between S. avenae and S. miscanthi is low and that S. avenae sensu stricto is part of a larger cryptic species complex that includes multiple diverged S. miscanthi lineages. Moreover, comparison of haplotype-resolved assemblies reveals that the S. miscanthi isolate used for genome sequencing is likely a hybrid, with one of its diploid genome copies being closely related to S. avenae ([~]0.5% divergence) and the second being substantially more divergent (> 1%). Analyses of genotyping-by-sequencing (GBS) data of grain aphids from the UK and China revealed that S. avenae and S. miscanthi are part of a species complex with many highly differentiated lineages that predate the origins of agriculture. The complex consists of hybrid lineages that display a tangled history of hybridisation and genetic introgression. These data demonstrate that hybridisation has substantially contributed to grain aphid diversity, and hence, to the evolutionary potential of this important pest species.

evolutionary biology↗

bioRxiv2021

From STRs to SNPs via ddRAD-seq: geographic assignment of confiscated tortoises at reduced costs

Assigning individuals to their source populations is crucial for conservation research, especially for endangered species threatened by illegal trade and translocations. Genetic assignment can be achieved with different types of molecular markers, but technical advantages and cost saving are recently promoting the shift from short tandem repeats (STRs) to single nucleotide polymorphisms (SNPs). Here, we designed, developed, and tested a small panel of SNPs for cost-effective geographic assignment of individuals with unknown origin of the endangered Mediterranean tortoise Testudo hermanni. We started by performing a ddRAD-seq experiment on 70 wild individuals of T. hermanni from 38 locations. Results obtained using 3,182 SNPs are comparable to those previously obtained using STR markers in terms of genetic structure and power to identify the macro-area of origin. However, our SNPs revealed further insights into the substructure in Western populations, especially in Southern Italy. A small panel of highly informative SNPs was then selected and tested by genotyping 190 individuals using the KASP genotyping chemistry. All the samples from wild populations of known geographic origin were genetically re-assigned with high accuracy to the original population. This reduced SNPs panel represents an efficient molecular tool that enables individuals to be genotyped at low cost (less than {euro}15 per sample) for geographical assignment and identification of hybrids. This information is crucial for the management in-situ of confiscated animals and their possible re-allocation in the wild. Our methodological pipeline can easily be extended to other species.

genomics↗

bioRxiv2020

A chromosome-level genome assembly of the woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae)

Woolly apple aphid (WAA, Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), is a major pest of apple trees (Malus domestica, order Rosales) and is critical to the economics of the apple industry in most parts of the world. Here, we generated a chromosome-level genome assembly of WAA - representing the first genome sequence from the aphid subfamily Eriosomatinae - using a combination of 10X Genomics linked-reads and in vivo Hi-C data. The final genome assembly is 327 Mb, with 91% of the assembled sequences anchored into six chromosomes. The contig and scaffold N50 values are 158 kb and 71 Mb, respectively, and we predicted a total of 28,186 protein-coding genes. The assembly is highly complete, including 97% of conserved arthropod single-copy orthologues based on BUSCO analysis. Phylogenomic analysis of WAA and nine previously published aphid genomes, spanning four aphid tribes and three subfamilies, reveals that the tribe Eriosomatini (represented by WAA) is recovered as a sister group to Aphidini + Macrosiphini (subfamily Aphidinae). We identified syntenic blocks of genes between our WAA assembly and the genomes of other aphid species and find that two WAA chromosomes (El5 and El6) map to the conserved Macrosiphini and Aphidini X chromosome. Our high-quality WAA genome assembly and annotation provides a valuable resource for research in a broad range of areas such as comparative and population genomics, insect-plant interactions and pest resistance management.

genomics↗

bioRxiv2018

Who’s who in the western Hermann’s tortoise conservation: a STR toolkit and reference database for wildlife forensic genetic analyses

Illegal trade is threatening tortoise populations worldwide since decades. Nowadays, however, DNA typing and forensic genetic approaches allow to investigate geographic origin of confiscated animals and to relocate them into the wild, provided that suitable molecular tools and reference data are available. Here we assess the suitability of a small panel of microsatellite markers to investigate patterns of illegal translocations and to assist forensic genetic applications in the endangered Mediterranean land tortoise Testudo hermanni hermanni. We used the microsatellite panel to (i) increase the understanding of the population genetic structure in wild populations with new data from previously unsampled geographic areas (overall 461 wild individuals from 28 sampling sites); (ii) detect the presence of non-native individuals in wild populations; and (iii) identify the most likely geographic area of origin of 458 confiscated individuals hosted in Italian seizure and recovery centers. Our analysis initially identified six major genetic clusters corresponding to different geographic macro-areas along the Mediterranean range. Long-distance migrants among wild populations, due to translocations, were found and removed from the reference database. Assignment tests allowed us to allocate approximately 70% of confiscated individuals of unknown origin to one of the six Mediterranean macro-areas. Most of the assigned tortoises belonged to the genetic cluster corresponding to the area where the respective captivity center was located. However, we also found evidence of long-distance origin of confiscated individuals, especially in centers along the Adriatic coast and facing the Balkan regions, a well-known source of illegally traded individuals. Our results clearly show the role for reintroduction projects of the microsatellite panel, which was useful to re-assign most of the confiscated individuals to the respective macro-area of origin. At the same time, the microsatellite panel can assist future forensic genetic applications to detect illegal trade and possess of Testudo hermanni individuals.

genetics↗

bioRxiv2018

Genetic structure in the wood mouse and the bank vole: contrasting patterns in a human-modified and highly fragmented landscape

Habitat fragmentation related to human activities modifies the distribution and the demographic trajectory of a species, often leading to genetic erosion and increased extinction risks. Understanding the impact of fragmentation on different species that co-exist in the same area becomes extremely important. Here we estimated the impact produced by different natural and anthropic landscape features on gene flow patterns in two sympatric species sampled in the same locations. Our main goal was to identify shared and private factors in the comparison among species. 199 bank voles and 194 wood mice were collected in 15 woodlands in a fragmented landscape, and genotyped at 8 and 7 microsatellites, respectively. Genetic variation and structure were analysed with standard approaches. Effective migration surfaces, isolation by resistance analysis, and regression with randomization were used to study isolation by distance and to estimate the relative importance of land cover elements on gene flow. Genetic structure was similarly affected by isolation by distance in these species, but the isolation-by-resistance analysis suggests that i) the wood mouse has constrained patterns of dispersal across woodland patches and facilitated connectivity in cultivated areas; ii) the bank vole connectivity is hindered by urban areas, while permeability is facilitated by the presence of woodlands, and cultivated terrains. Habitat loss and fragmentation can therefore influence genetic structure of small sympatric mammal species in different ways, and predicting the genetic consequences of these events using only one species may be misleading.

genetics↗