Biology subjects

Lamichhaney, S.

Publications and source records attributed to Lamichhaney, S..

11 recordsLinked to original sources

bioRxiv2026

Multiple introductions shaped genomic diversity and demographic history of invasive box tree moth (Cydalima perspectalis) populations in North America

The box tree moth (Cydalima perspectalis) is an invasive pest of boxwood plants (Buxus spp.) that has rapidly expanded across Europe and, since its first detection in Canada in 2018, across North America. Understanding its introduction pathways and early population structure is critical for effective surveillance and management. We integrated genome-wide single nucleotide polymorphism (SNP), mitochondrial cytochrome c oxidase I (COI), and morphological data to investigate the early invasion history of C. perspectalis across North America. Genome-wide analyses revealed pronounced genetic differentiation between North American and European populations, together with substantial genetic structure within North America. Delaware was genetically distinct from other North American populations and showed greater affinity with European populations, consistent with a separate introduction history. In contrast, New York, Massachusetts, Michigan, Ohio, and Ontario showed greater genetic similarity, suggesting shared ancestry and/or regional connectivity, whereas Virginia and West Virginia exhibited additional differentiation. Mitochondrial data supported shared ancestry among most North American populations, while Delaware shared a haplotype group with the Croatian European population. D-statistic analyses identified asymmetric allele sharing among several North American and European populations, consistent with multiple introductions and subsequent admixture. Morphometric analyses revealed significant geographic variation in several body and wing traits. Together, these complementary datasets indicate that multiple introductions, regional genetic structuring, and admixture have shaped the North American invasion. These findings highlight the value of integrating genomic approaches with nursery and border surveillance to identify introduction pathways and inform targeted containment and long-term management of this emerging horticultural pest.

genomics↗

bioRxiv2025

Integrated landscape genomics reveals biogeography and climate-driven local adaptation in high-altitudes

High-elevation environments harbor unique species adapted to altitudinal and environmental extremes. However, due to logistical challenges of sampling such species throughout their distribution across steep and varied terrains, studies often lack comprehensive evidence to understand patterns of population divergence, local adaptation, and how current adaptations may influence future vulnerability. In this study, we utilized Tibetan Partridge (Perdix hodgsoniae), a high-altitude endemic bird found between 2800-5000 meters across the arid western and humid northeastern regions of the Sino-Himalayan landscape. This regions complex topography-characterized by tall mountains, deep valleys, and contrasting climatic conditions provided opportunities for investigating population divergence, local adaptation, and climate-related vulnerability. We integrated population-scale whole-genome sequencing with ecological, climatic, landscape, and morphological data to examine current patterns of local adaptation and forecast future risks. Our findings show that both biogeographic barriers and climatic variation drive rapid population divergence in P. hodgsoniae, reflected in distinct morphological traits and population genetic structure. Western populations, inhabiting dry and fragmented landscapes, exhibit adaptations to temperature extremes with low genetic diversity, reduced habitat suitability, limited gene flow, and weak connectivity--factors that increase their vulnerability to future environmental changes. In contrast, northeastern populations, living in more humid regions, show genetic adaptations linked to precipitation, maintain high genetic diversity and habitat connectivity, and may serve as evolutionary refugia under future climate scenarios. This study underscores the value of integrating genomic, ecological, and landscape data to reveal mechanisms of divergence and adaptation, and to develop robust predictions for conservation planning under rapidly changing environmental conditions.

evolutionary biology↗

bioRxiv2025

A complete reference genome assembly and annotation of the Black Redstart (Phoenicurus ochruros)

The Black Redstart (Phoenicurus ochruros) is one of the most widely distributed species, occupying diverse habitats and exhibiting remarkable altitudinal migration, making it suitable model for studying altitudinal migration and high-altitude adaptation. In this study, we present the first reference genome of Phoenicurus ochruros, generated using PacBio HiFi long-read sequencing. The nuclear genome is 1.37 Gb in length, assembled into 296 scaffolds with a scaffold N50 of 29.9 Mb. Multiple complementary genome validation approaches - including BUSCO analysis, mapping of raw PacBio HiFi reads, and comparative genomics analysis - confirmed the high contiguity and gene-space completeness of the genome. The Black Redstart genome contains one of the highest proportions of transposable elements among passerines (30.58%), second only to Bells Sparrow (Artemisiospiza belli), 31.2%. We further integrated RNA-seq data, protein homology evidence, and ab initio gene prediction to build high-quality genome annotation of 18,609 genes in the P. ochruros genome. This genomic resource provides invaluable resource for evolutionary genomics studies of passerines and explore genetic basis of high-altitude adaptation.

genomics↗

bioRxiv2024

Genomic insights into the successful invasion of the avian vampire fly (Philornis downsi) in the Galapagos Islands

Invasive species disrupt island ecosystems, posing significant threats to native species. The avian vampire fly (Philornis downsi), introduced into the Galapagos Islands, has become a major threat to endemic birds including Darwins finches, yet the genetic mechanisms of its invasion remain unclear. This study used whole-genome sequencing of P. downsi populations from Galapagos and its native range in mainland Ecuador, revealing reduced genetic diversity in Galapagos, indicative of a recent bottleneck. We found evidence of ongoing gene flow among island populations and identified regions under positive selection near genes related to neural signaling, muscle development, and metabolic processes, which may have contributed to the flys invasion success in Galapagos. These findings highlight the importance of genomic research for mitigating the impact of P. downsi on Galapagos biodiversity.

evolutionary biology↗

bioRxiv2022

Genomic Variation, Population Structure, and Gene Flow across Asian Pikas

Asian pikas have one of the most complex systematics and evolutionary history. The Himalayas is an important habitat for Asian pikas as it hosts 23 - 25% of pikas global diversity and has provided the ancestral training ground for local adaptation to high altitudes. They are one of the most abundant species in the Himalayas and Qinghai Tibetan Plateau (QTP), however genetic studies to explore their population structure and evolution are limited. Here, we utilize a population genomics approach using ~28,000 genome-wide SNP markers obtained from restriction-site associated DNA sequencing in six species of Asian Pikas (Ochotona spp.) that are distributed across the Himalayas and neighboring high-altitude mountains. We examined intra- and inter-species genetic diversity, population structure, phylogenetic history and explored processes that shaped the current genetic diversity of Pikas across the Himalayas. We identified low nucleotide diversity and high inbreeding coefficient across all species which possibly indicated decreasing population size in these species. We also identified extensive evidence of gene flow (both historic and contemporary) across these species. Our findings indicate that inter-species gene flow is a key evolutionary process that has been countering the negative effect of low genetic diversity among Asian pikas.

evolutionary biology↗

bioRxiv2022

Low mutation load in a supergene underpinning alternative male mating strategies in ruff

Ruffs are shorebirds with an elaborate lekking behavior involving three male morphs with different mating strategies: Independents, Satellites, and Faeders1,2. The latter two are heterozygous for different versions of a supergene maintained by an inversion that were estimated to have occurred about 4 million years ago3. Faeders carry an intact inversion while the Satellite allele is recombinant, both of which are expected to accumulate high mutational load because they are recessive lethals. Here we have constructed a highly contiguous genome assembly of the inversion region for both the Independent and Satellite haplotypes. The recombination event(s) between an inverted and non-inverted chromosome creating the Satellite allele must have occurred recently (within the last 100,000 years) based on the minute sequence divergence between the Satellite and Independent alleles in the recombinant regions. Contrary to expectations4,5, we find no expansion of repeats and only a very modest mutation load on the Satellite allele in the nonrecombinant region despite high sequence divergence (1.46%). The essential centromere protein CENPN gene is disrupted by the inversion, and surprisingly is as well conserved on the inversion haplotypes as on the noninversion haplotype. The results suggest that the inversion may be much younger than previously thought. The lack of mutation load despite recessive lethality can be explained by the introgression of the inversion from a now extinct lineage.

evolutionary biology↗

bioRxiv2021

Darwin's finches - an adaptive radiation constructed from ancestral genetic modules

Recent adaptive radiations are models for investigating mechanisms contributing to the evolution of biodiversity. An unresolved question is the relative importance of new mutations, ancestral variants, and introgressive hybridization for phenotypic evolution and speciation. Here we address this issue using Darwins finches, which vary in size from an 8g warbler finch with a pointed beak to a 40g large ground finch with a massive blunt beak. We present a highly contiguous genome assembly for one of the species and investigate the genomic architecture underlying phenotypic diversity in the entire radiation. Admixture mapping for beak and body size in the small, medium and large ground finches revealed 28 loci showing strong genetic differentiation. These loci represent ancestral haplotype blocks with origins as old as the Darwins finch phylogeny (1-2 million years). Genes expressed in the developing beak are overrepresented in these genomic regions. Frequencies of allelic variants at the 28 loci covary with phenotypic similarities in body and beak size across the Darwins finch phylogeny. These ancestral haplotypes constitute genetic modules for selection, and act as key determinants of the exceptional phenotypic diversity of Darwins finches. Such ancestral haplotype blocks can be critical for how species adapt to environmental variability and change.

evolutionary biology↗

bioRxiv2021

The genome sequence of the avian vampire fly (Philornis downsi), an invasive nest parasite of Darwins finches in Galpagos

The invasive avian vampire fly (Philornis downsi) is considered one of the greatest threats to the unique and endemic avifauna of the Galapagos Islands, Ecuador. The fly parasitizes nearly every passerine species, including Darwins finches, in the Galapagos. The fly is thought to have been introduced from mainland Ecuador, although the full pathway of invasion is not yet known. The majority of research to date has focused on the effects of the fly on the fitness of avian hosts and explorations of mitigation methods. A lag in research related to the genetics of this invasion demonstrates, in part, a need to develop full-scale genomic resources with which to address further questions within this system. In this study, an adult P. downsi collected from San Cristobal Island within the Galapagos archipelago was sequenced to generate a high-quality genome assembly. We examined various features of the genome (e.g., coding regions, non-coding transposable elements) and carried out comparative genomics analysis against other dipteran genomes. We identified lists of gene families that are significantly expanding/contracting in P. downsi that are related to insecticide resistance, detoxification, and potential feeding ecology and counter defense against host immune responses. The P. downsi genome assembly provides an important foundational resource for studying the molecular basis of its successful invasion in the Galapagos and the dynamics of its population across multiple islands. The findings of significantly changing gene families associated with insecticide resistance and immune responses highlight the need for further investigations into the role of different gene families in aiding the flys successful invasion. Furthermore, this genomic resource will also better help inform future research studies and mitigation strategies aimed at minimizing the flys impact on the birds of the Galapagos.

genomics↗

bioRxiv2019

Integrating natural history-derived phenomics with comparative genomics to study the genetic architecture of convergent evolution

Evolutionary convergence has been long considered primary evidence of adaptation driven by natural selection and provides opportunities to explore evolutionary repeatability and predictability. In recent years, there has been increased interest in exploring the genetic mechanisms underlying convergent evolution, in part due to the advent of genomic techniques. However, the current genomics gold rush in studies of convergence has overshadowed the reality that most trait classifications are quite broadly defined, resulting in incomplete or potentially biased interpretations of results. Genomic studies of convergence would be greatly improved by integrating deep vertical, natural history knowledge with horizontal knowledge focusing on the breadth of taxonomic diversity. Natural history collections have and continue to be best positioned for increasing our comprehensive understanding of phenotypic diversity, with modern practices of digitization and databasing of morphological traits providing exciting improvements in our ability to evaluate the degree of morphological convergence. Combining more detailed phenotypic data with the well-established field of genomics will enable scientists to make progress on an important goal in biology: to understand the degree to which genetic or molecular convergence is associated with phenotypic convergence. Although the fields of comparative biology or comparative genomics alone can separately reveal important insights into convergent evolution, here we suggest that the synergistic and complementary roles of natural history collection-derived phenomic data and comparative genomics methods can be particularly powerful in together elucidating the genomic basis of convergent evolution among higher taxa.

evolutionary biology↗

bioRxiv2017

Moderate Nucleotide Diversity In The Atlantic Herring Is Associated With A Low Mutation Rate

The Atlantic herring (Clupea harengus) is one of the most abundant vertebrates on earth but its nucleotide diversity is moderate ({pi}=0.3%), only three-fold higher than in human. The expected nucleotide diversity for selectively neutral alleles is a function of population size and the mutation rate, and it is strongly affected by demographic history. Here, we present a pedigree-based estimation of the mutation rate in the Atlantic herring. Based on whole-genome sequencing of four parents and 12 offspring, the estimated mutation rate is 1.7 x 10-9 per base per generation. There was no significant difference in the frequency of paternal and maternal mutations (8 and 7, respectively). Furthermore, we observed a high degree of parental mosaicism indicating that a large fraction of these de novo mutations occurred during early germ cell development when we do not expect a strong gender effect. The now estimated mutation rate - the lowest among vertebrates analyzed to date - partially explains the discrepancy between the rather low nucleotide diversity in herring and its huge census population size (>1011). But our analysis indicates that a species like the herring will never reach its expected nucleotide diversity for selectively neutral alleles primarily because of fluctuations in population size due to climate variation during the millions of years it takes to build up a high nucleotide diversity. In addition, background selection and selective sweeps lead to reductions in nucleotide diversity at linked neutral sites.

genomics↗

bioRxiv2017

A Model-Free Approach For Detecting Genomic Regions Of Deep Divergence Using The Distribution Of Haplotype Distances

Recent advances in comparative genomics have revealed that divergence between populations is not necessarily uniform across all parts of the genome. There are examples of regions with divergent haplotypes that are substantially more different from each other that the genomic average.\n\nTypically, these regions are of interest, as their persistence over long periods of time may reflect balancing selection. However, they are hard to detect unless the divergent sub-populations are known prior to analysis.\n\nHere, we introduce HaploDistScan, an R-package implementing model-free detection of deep-divergence genomic regions based on the distribution of pair-wise haplotype distances, and show that it can detect such regions without use of a priori information about population sub-division. We apply the method to real-world data sets, from ruff and Darwins finches, and show that we are able to recover known instances of balancing selection - originally identified in studies reliant on detailed phenotyping - using only genotype data. Furthermore, in addition to replicating previously known divergent haplotypes as a proof-of-concept, we identify novel regions of interest in the Darwins finch genome and propose a plausible, data-driven evolutionary history for each novel locus individually.\n\nIn conclusion, HaploDistScan requires neither phenotypic nor demographic input data, thus filling a gap in the existing set of methods for genome scanning, and provides a useful tool for identification of regions under balancing selection or similar evolutionary processes.

genomics↗