Biology subjects

Escudero, N.

Publications and source records attributed to Escudero, N..

16 recordsLinked to original sources

bioRxiv2026

Sea stickleback genome reveals repeated chromosomal rearrangements in sticklebacks

Sticklebacks (Gasterosteidae) encompass model organisms which are of particular interest for evolutionary and ecological genomics. Within Gasterosteidae, chromosome number is variable (2n=40-46) and independent fusions of homologous chromosomes have been proposed. The sea stickleback (or fifteen-spined stickleback, Spinachia spinachia ) has the lowest known number of chromosomes (2n=40) and hence is crucial in understanding chromosome evolution among sticklebacks, but is so far missing in genomic datasets. Here, we present a high-quality diploid genome assembly of S. spinachia. PacBio HiFi and Hi-C reads were assembled into a genome of 407.5 Mb in size, consisting of 20 chromosomes, with an N50 of 6.6 Mb and 98.96% complete single-copy BUSCO genes. A phylogenetic tree inferred across five stickleback species and four outgroup genomes from 19,156 genes, alongside synteny analyses and ancestral chromosome reconstructions, confirms S. spinachia as the sister species to the four-spined stickleback (Apeltes quadracus) and not as the sister group to all other sticklebacks as once thought. It has one species-specific chromosome fusion and shares two fusions with the three-spined stickleback (Gasterosteus aculeatus), none of which are present in its sister species. One of these fusions is also present in Pungitius, leading to reinterpretion of this fusion as ancestral to Gasterosteidae, with subsequent fission in Apeltes. This implies a lower ancestral chromosome number in Gasterosteidae (2n=44) than previously thought. The other fusion shared with G. aculeatus presents a case of convergence. Our results suggest that karyotype evolution in Gasterosteidae has been shaped by ancestral chromosome fusion, convergent fusion, and secondary fission.

evolutionary biology↗

bioRxiv2026

ERGA-BGE reference genomes of Hyalomma lusitanicum and its obligate Francisella endosymbiont as a genomic resource for One Health research

Hyalomma lusitanicum is a characteristic tick species of the western Mediterranean region, with a well-established distribution across the Iberian Peninsula. It is strongly associated with wild ungulates, particularly red deer, as well as livestock, to which it can transmit a wide range of pathogens, including viruses, bacteria, and protozoa. Here, we present three genomic resources for H. lusitanicum: a scaffold-scale nuclear genome, the complete mitochondrial genome, and the complete genome of its associated Francisella bacterial endosymbiont. The nuclear genome assembly spans 1.81 Gb and comprises 59 scaffolds, with a scaffold N50 of 153.6 Mb (L50 = 5) and no gaps, indicating high contiguity and completeness with a gene annotation completeness BUSCO score of 97.1 %. Genome annotation of the nuclear assembly identified 20,638 protein-coding genes, 1,422 non-coding genes, and 5,775 pseudogenes. A total of 18 scaffolds were assembled as putative chromosomes, exceeding the 11 chromosomes inferred as ancestral; however, synteny analyses suggest that several scaffolds likely represent fragmented portions of the same chromosome, probably due to incomplete Hi-C scaffolding. Despite this, the assembly represents one of the most complete tick nuclear genomes generated to date. In addition, we report the complete genome of a Francisella endosymbiont (1.51 Mb, 1,679 genes), characterized by a high proportion of pseudogenes and reduced genome size, consistent with patterns of genome reduction associated with obligate symbiosis. Together, these genomic resources provide a framework to investigate local adaptation and host-symbiont evolution, and to support improved surveillance, control, and management strategies for species of public health relevance.

genomics↗

bioRxiv2026

Lungfish comparative genomics reveals ancient gene networks co-opted for life on land

The transition from water to land was a defining event in vertebrate evolution, requiring major changes in physiology and gene regulation. Lungfish, the closest extant relatives of tetrapods, offer a unique window into this process through their capacity for estivation, a physiological state that mirrors key demands of terrestrial life. Here, we constructed and compared gene co-expression networks across five vertebrate species using multi-tissue transcriptomic data. Focusing on estivating lungfish tissues, we identified conserved modules enriched in core functions, including metabolic regulation, RNA processing, and protein turnover. We further show that a subset of retained ohnologs from the vertebrate 2R-WGD act as network hubs under directional selection in key phylogenetic branches. These genes, involved in membrane trafficking, cytoskeletal regulation, water balance, and stress response, illustrate how duplicated, dosage-sensitive genes were co-opted to meet the physiological demands of terrestrial adaptation. Together, our findings support a model in which ancient whole-genome duplications supplied raw material later shaped by selection and network rewiring to enable extreme physiological adaptations such as estivation. TeaserAncient duplicated gene networks in lungfish estivation reveal how vertebrates repurposed genomic toolkits to adapt to land.

evolutionary biology↗

bioRxiv2025

Independent genomic trajectories shape adaptation to life on land across animal lineages

How animals repeatedly adapted to life on land is a central question in evolutionary biology. While terrestrialisation occurred independently across animal phyla, it remains unclear whether shared genomic mechanisms underlie these transitions. Here, we combine large-scale comparative genomics, machine learning, and multi-omics data, including proteomics and transcriptomics from stress experiments relevant to terrestrial environmental challenges in 17 species, to investigate the genomic basis of animal terrestrial adaptation. Gene co-expression networks reveal that genes relevant to stress are largely lineage-specific, yet converge in function through the co-option of gene families pre-dating terrestrialisation events. Phylogenomic and machine learning analyses support a dominant role for early-evolving genes, enriched in stress-related functions, paired with a higher gene loss than gain at terrestrialisation nodes. Our findings support a model of lineage-specific genomic changes involving mostly conserved genes that converged at the functional level during the independent transitions to terrestrial life.

evolutionary biology↗

bioRxiv2025

ERGA-BGE genome of Noah's Ark shell (Arca noae Linnaeus, 1758), a Mediterranean bivalve species

Arca noae, also known as the Noahs Ark clam, is a bivalve mollusk found in the shallow coastal waters of the Mediterranean Sea and the eastern Atlantic Ocean. This species plays a crucial ecological role by filtering plankton and organic particles from the water, helping maintain water quality and supporting nutrient cycling in marine ecosystems. It is also an important food source for various marine predators, including fish and crustaceans, thereby contributing to the coastal food web. Arca noae is notably resilient to environmental stressors, such as temperature fluctuations, changes in salinity, and pollution, making it a valuable model species for studying how bivalves adapt and respond to stress. While it is not commonly harvested commercially, Arca noae is of great interest to marine researchers due to its ability to thrive in diverse coastal habitats. The reference genome of Arca noae will thus provide important evolutionary insights. The entirety of the genome sequence was assembled into 19 contiguous chromosomal pseudomolecules. This chromosome-level assembly encompasses 1.5 Gb, composed of 257 contigs and 119 scaffolds, with contig and scaffold N50 values of 20.5 Mb and 84.7 Mb, respectively.

genomics↗

bioRxiv2025

ERGA-BGE genome of Coenonympha oedippus: an IUCN endangered European butterfly species occurring in two ecotypes

The reference genome of the False ringlet (Coenonympha oedippus) will serve as a valuable resource for uncovering the genetic mechanism underlying the species' adaptability to two ecologically distinct habitats. Through this genome we might be able to determine whether (i) each ecotype is monophyletic, indicating that the ecological divergence represents an early stage of speciation, (ii) the ecotypes have evolved through divergent evolution of habitat preference, or (iii) the differences between ecotypes are solely due to phenotypic plasticity or epigenetic variation. This reference genome is also a prerequisite for the planning, design, and implementation of conservation measures for this endangered species, taking into account its intraspecific diversity. Furthermore, it holds broader implications for population genomic studies of the species-rich genus Coenonympha, which includes some of the most endangered butterfly taxa in Europe. The complete genome sequence was assembled into 30 contiguous chromosomal pseudomolecules (sex chromosomes included). This chromosome-level assembly encompasses 0.39 Gb, composed of 385 contigs and 62 scaffolds, with contig and scaffold N50 values of 2.8 Mb and 14.2 Mb, respectively.

genomics↗

bioRxiv2025

ERGA-BGE Reference Genome of Loboptera subterranea: a cave adapted cockroach endemic to the Canary Islands

Species of the genus Loboptera from the Canary Islands are adapted to life in subterranean environments, except Loboptera canariensis and Loboptera decipiens which inhabit epigean, often influenced by human activities. The genome of Loboptera subterranea provides a valuable resource for understanding the genetic basis of how the Canarian Loboptera species evolved and thrived in subterranean environments. A total of 14 contiguous chromosomal pseudomolecules were assembled from the genome sequence. This chromosome-level assembly encompasses 2.7 Gb, composed of 486 contigs and 90 scaffolds, with contig and scaffold N50 values of 13.1 Mb and 202.7 Mb, respectively.

genomics↗

bioRxiv2025

ERGA-BGE genome of Cheirolophus tagananensis: an IUCN endangered shrub endemic to the Canary Islands

The reference genome of Cheirolophus tagananensis, locally known as the Cabezon de Taganana, will provide an exceptional opportunity to establish a new framework to develop comparative genomic tools. These tools will help uncover the genetic basis of rapid plant radiations and microevolutionary adaptation processes of insular species on oceanic islands. This genomic resource will also contribute to facilitate the establishment of better informed in situ and ex-situ conservation strategies for this narrow endemic in the face of potential habitat degradation, and support taxonomic studies to better understand genetic diversity at the population, species, and genus levels. A total of 16 contiguous chromosomal pseudomolecules were assembled from the genome sequence. This chromosome-level assembly encompasses 0.62 Gb, composed of 421 contigs and 235 scaffolds, with contig and scaffold N50 values of 4.0 Mb and 36.5 Mb, respectively.

genomics↗

bioRxiv2025

ERGA-BGE genome of Pinctada radiata (Leach, 1814): one of the first Lessepsian migrants

Pinctada radiata, commonly known as the Gulf pearl oyster, is a species of pearl oyster found primarily in the warm waters of the Red Sea, the Persian Gulf, and parts of the Indian Ocean. Pinctada radiata contributes to marine ecosystems by filtering water, which helps maintain water quality and supports other marine life. This species is the first bivalve Lessepsian migrant, having migrated from the Red Sea to the Mediterranean Sea via the Suez Canal. The reference genome of Pinctada radiata could help identify genes enabling adaptation to varying temperatures and salinities, facilitating survival in diverse and newly colonized habitats allowing comparisons with other bivalves to uncover shared and unique genetic adaptations. Additionally, the genome could support targeted management practices and conservation initiatives, such as habitat restoration and selective breeding, ensuring the long-term sustainability of P. radiata. The entirety of the genome sequence was assembled into 14 contiguous chromosomal pseudomolecules. This chromosome-level assembly encompasses 0.93 Gb, composed of 220 contigs and 44 scaffolds, with contig and scaffold N50 values of 8.1 Mb and 63.8 Mb, respectively.

genomics↗

bioRxiv2025

ERGA-BGE genome of Stigmatoteuthis arcturi Robson, 1948: the jewelled squid

The Stigmatoteuthis arcturi reference genome offers a valuable resource for understanding the evolutionary patterns of oceanic squids, who perform important ecological roles as both predators and prey in mesopelagic and deep-sea environments, while their genomes remain understudied. The entirety of the genome sequence was assembled into 46 contiguous chromosomal pseudomolecules. This chromosome-level assembly encompasses 3.25 Gb, composed of 1,268 contigs and 497 scaffolds, with contig and scaffold N50 values of 11.0 Mb and 74.6 Mb, respectively.

genomics↗

bioRxiv2025

Genomic exaptation and regulatory landscape shifts as key mechanisms enabling flatworm terrestrialization

Understanding the genomic toolkit that facilitated animal terrestrialization--the transition from aquatic to terrestrial environments--is crucial for unravelling the evolutionary processes behind the origin and diversification of terrestrial biodiversity. Despite its significance, the genomic foundations driving the physiological and metabolic adaptations required for life on land remain largely unexplored across most terrestrial animal phyla. Planarians (phylum Platyhelminthes) represent an ideal model for studying terrestrialization, as only one terrestrial lineage, the family Geoplanidae (order Tricladida) is known to exist. Here, we used an integrative approach combining genomics, transcriptomics, and proteomics to investigate the genetic underpinnings potentially facilitating adaptation to terrestrial environments. Our analysis revealed a significant burst of gene gain preceding the diversification of terrestrial planarians and their split from freshwater relatives, in the branch leading to Tricladida. Upon exposure to abiotic stress, terrestrial and freshwater planarians exhibited distinct genetic toolkits: most differentially expressed genes emerged in orthologous groups gained specifically in the branch leading to Tricladida, over half of which showed signs of strong directional selection in terrestrial flatworms, indicating their adaptive importance for land colonization. Transcriptomic analyses further revealed contrasting stress responses: terrestrial planarians upregulated ancient genes whose origin predates the Geoplanidae lineage to cope with abiotic stress, while freshwater planarians downregulated a separate set of ancestral genes. Our genomic, transcriptomic, and proteomic data consistently show that the genetic toolkit for abiotic stress response in terrestrial planarians is highly differentiated from that of their freshwater counterparts, with significant regulatory shifts as well. Overall, our findings suggest a burst of gene gain in the Tricladida lineage, with co-option of these genes, rather than clade-specific innovations, playing a critical role in the origin and diversification of terrestrial flatworms. This underscores genomic exaptation and regulatory landscape shifts as key mechanisms enabling terrestrialization within Platyhelminthes. This study offers the first genome-wide insight into the genetic toolkit underlying flatworm terrestrialization and contributes broadly to understanding the genomic basis of animal terrestrialization.

evolutionary biology↗

bioRxiv2025

Disentangling the evolutionary history of terrestrial planarians through phylogenomics

Triclads (Platyhelminthes, Tricladida) are found in marine, freshwater, and terrestrial habitats worldwide except Antarctica. Terrestrial planarians are grouped into the family Geoplanidae, which is subdivided into the subfamilies Geoplaninae, Bipaliinae, Rhynchodeminae, and Microplaninae. Some of these subfamilies result from taxonomic rearrangements based on molecular phylogenies inferred from a few molecular markers. However, the diagnosis of Rhynchodeminae was not aligned with the morphology of all its representatives. While the subfamilies are recovered as monophyletic in recent molecular phylogenies, robust hypotheses regarding the relationships between them remain unknown. In this study, we employ for the first time a phylogenomic framework to investigate the evolutionary relationships among the subfamilies, starting by obtaining the first transcriptomes for 15 species of terrestrial planarians. A total of 16 different datasets, comprising nearly two thousand single-copy genes inferred from transcriptomic data, were analyzed using various phylogenetic inference methods. We recovered, for the first time, a well-supported topology of phylogenetic relationships among Geoplanidae subfamilies, positioning Bipaliinae and Microplaninae as a clade sister to Rhynchodeminae + Geoplaninae. Internal relationships within the genus Microplana were not supported in our analyses. The subfamily Rhynchodeminae, represented in our phylogeny by species from the tribes Rhynchodemini and Caenoplanini, is re-diagnosed to align with previous taxonomic rearrangements. This study not only represents a significant step forward in the phylogenetic resolution of Geoplanidae but also provides important insights into the broader evolutionary dynamics shaping land planarian diversity. HighlightsO_LIFirst transcriptomes of multiple terrestrial planarians sequenced. C_LIO_LIFirst molecular phylogeny of terrestrial planarians at subfamily level based on transcriptomic data. C_LIO_LIHighly supported topology for phylogenetic interrelationship among terrestrial planarians subfamilies. C_LIO_LIUnclear interrelationships between species from the genus Microplana. C_LIO_LIThe subfamily Rhynchodeminae is re-diagnosed at the morphological level. C_LI

evolutionary biology↗

bioRxiv2024

ERGA-BGE Reference Genome of the Striped Field Mouse (Apodemus agrarius), a Widespread and Abundant Species in Central and Eastern Europe

The reference genome of Apodemus agrarius provides a valuable resource for phylogenetic studies of rodents, particularly mice, and for understanding factors that influence the geographical distribution of the species across East Asia and East Europe. A total of 25 contiguous chromosomal pseudomolecules were assembled from the genome sequence (23 autosomes and 2 sex chromosomes). This chromosome-level assembly encompasses 2.6 Gb, composed of 242 contigs and 60 scaffolds, with contig and scaffold N50 values of 35 Mb and 119 Mb, respectively.

genomics↗

bioRxiv2024

ERGA-BGE Reference Genome of the Northern chamois (Rupicapra rupicapra): Europe's most abundant mountain ungulate

The reference genome of Rupicapra rupicapra (subsp. rupicapra) provides insights into the genetic makeup that enabled this iconic mountain ungulate to adapt to its harsh environment, including its ability to survive in extreme weather and high altitudes--factors that are increasingly important in the face of climate change. A total of 29 contiguous chromosomal pseudomolecules were assembled from the genome sequence. This chromosome-level assembly encompasses 2.62 Gb, composed of 124 contigs and 76 scaffolds, with contig and scaffold N50 values of 77 Mb and 101 Mb, respectively.

genomics↗

bioRxiv2024

A punctuated burst of massive genomic rearrangements by chromosome shattering and the origin of non-marine annelids

The genomic basis of cladogenesis and adaptive evolutionary change has intrigued biologists for decades. Here, we show that the tectonics of genome evolution in clitellates, a clade composed of most freshwater and all terrestrial species of the phylum Annelida, is characterised by extensive genome-wide scrambling that resulted in a massive loss of macrosynteny between marine annelids and clitellates. These massive rearrangements included the formation of putative neocentromeres with newly acquired transposable elements and preceded a further period of genome-wide reshaping events, potentially triggered by the loss of genes involved in genome stability and homeostasis of cell division. Notably, while these rearrangements broke short-range interactions observed between Hox genes in marine annelids, they were reformed as long-range interactions in clitellates. Our findings reveal extensive genomic reshaping in clitellates at both the linear (2D) and three-dimensional (3D) levels, suggesting that, unlike in other animal lineages where synteny conservation constrains structural evolution, clitellates exhibit a remarkable tolerance for chromosomal rearrangements. Our study thus suggests that the genomic landscape of Clitellata resulted from a rare burst of genomic changes that ended a long period of stability that persists across large phylogenetic distances.

evolutionary biology↗

bioRxiv2023

The European Reference Genome Atlas: piloting a decentralised approach to equitable biodiversity genomics

A global genome database of all of Earths species diversity could be a treasure trove of scientific discoveries. However, regardless of the major advances in genome sequencing technologies, only a tiny fraction of species have genomic information available. To contribute to a more complete planetary genomic database, scientists and institutions across the world have united under the Earth BioGenome Project (EBP), which plans to sequence and assemble high-quality reference genomes for all [~]1.5 million recognized eukaryotic species through a stepwise phased approach. As the initiative transitions into Phase II, where 150,000 species are to be sequenced in just four years, worldwide participation in the project will be fundamental to success. As the European node of the EBP, the European Reference Genome Atlas (ERGA) seeks to implement a new decentralised, accessible, equitable and inclusive model for producing high-quality reference genomes, which will inform EBP as it scales. To embark on this mission, ERGA launched a Pilot Project to establish a network across Europe to develop and test the first infrastructure of its kind for the coordinated and distributed reference genome production on 98 European eukaryotic species from sample providers across 33 European countries. Here we outline the process and challenges faced during the development of a pilot infrastructure for the production of reference genome resources, and explore the effectiveness of this approach in terms of high-quality reference genome production, considering also equity and inclusion. The outcomes and lessons learned during this pilot provide a solid foundation for ERGA while offering key learnings to other transnational and national genomic resource projects.

genomics↗