Journal of Heredity最新文献

Preserving genetic diversity and adaptive potential while avoiding inbreeding depression is crucial for the long-term conservation of natural populations. Despite demographic increases, traces of past bottleneck events at the genomic level should be carefully considered for population management. From this perspective, the peninsular Italian wolf is a paradigmatic case. After being on the brink of extinction in the late 1960s, peninsular Italian wolves rebounded and recolonized most of the peninsula aided by conservation measures, including habitat and legal protection. Notwithstanding their demographic recovery, a comprehensive understanding of the genomic consequences of the historical bottleneck in Italian wolves is still lacking. To fill this gap, we sequenced whole genomes of 13 individuals sampled in the core historical range of the species in Central Italy to conduct population genomic analyses, including a comparison with wolves from two highly-inbred wolf populations (i.e. Scandinavia and Isle Royale). We found that peninsular Italian wolves, despite their recent recovery, still exhibit relatively low genetic diversity, a small effective population size, signatures of inbreeding, and a non-negligible genetic load. Our findings indicate that the peninsular Italian wolf population is still susceptible to bottleneck legacies, which could lead to local inbreeding depression in case of population reduction or fragmentations. This study emphasizes the importance of considering key genetic parameters to design appropriate long-term conservation management plans.

Pathogen species are experiencing strong joint demographic and selective events, especially when they adapt to a new host, for example through overcoming plant resistance. Stochasticity in the founding event and the associated demographic variations hinder our understanding of the expected evolutionary trajectories and the genetic structure emerging at both neutral and selected loci. What would be the typical genetic signatures of such a rapid adaptation event is not elucidated. Here, we build a demogenetic model to monitor pathogen population dynamics and genetic evolution on two host compartments (susceptible and resistant). We design our model to fit two plant pathogen life cycles, "with" and "without" host alternation. Our aim is to draw a typology of eco-evolutionary dynamics. Using time-series clustering, we identify three main scenarios: 1) small variations in the pathogen population size and small changes in genetic structure, 2) a strong founder event on the resistant host that in turn leads to the emergence of genetic structure on the susceptible host, and 3) evolutionary rescue that results in a strong founder event on the resistant host, preceded by a bottleneck on the susceptible host. We pinpoint differences between life cycles with notably more evolutionary rescue "with" host alternation. Beyond the selective event itself, the demographic trajectory imposes specific changes in the genetic structure of the pathogen population. Most of these genetic changes are transient, with a signature of resistance overcoming that vanishes within a few years only. Considering time-series is therefore of utmost importance to accurately decipher pathogen evolution.

Facultative parthenogenesis (FP), or asexual reproduction by sexually reproducing female animals, has been reported across several clades of vertebrates and is increasingly being recognized as a reproductive mechanism with significant implications for the genetic variation of captive and wild populations. The definitive identification of parthenogens requires molecular confirmation, with large genomic datasets necessary to accurately parse the parthenogenetic mechanism (i.e. endoduplication, gametic duplication, terminal fusion automixis, or central fusion automixis). Current methods for inferring FP from large genomic datasets are statistically intensive, require competency in R scripting for their execution, and are not designed for detection of facultative parthenogenesis or screening of large numbers of mother/offspring pairs, whereas small datasets (i.e. microsatellites) that can be evaluated visually lack the power to discriminate among FP mechanisms. Here, we present the user-friendly software program, ParthenoGenius, that uses intuitive logic to infer the presence and mechanism of FP from even large genomic datasets comprising many mothers and offspring. ParthenoGenius runs relatively quickly and does not require the researcher to have knowledge of R scripting or statistics. ParthenoGenius was tested on eight empirical datasets and in each case identified parthenogens (and parthenogenic mechanism when present) consistent with results of previous studies or corroborating evidence. ParthenoGenius will facilitate the rapid screening of large genomic datasets comprising many mothers and offspring for the presence and mechanism of parthenogenesis, improving our understanding of the frequency and phylogenetic distribution of FP across the animal kingdom.

Heterosis occurs in individuals when genetic diversity, e.g., heterozygosity, increases fitness. Many advanced eusocial insects evolved mating behaviors, including polyandry and polygyny, which increase inter-individual genetic diversity within colonies. The possibility of this structure of diversity to improve group fitness has been termed social heterosis. Neither the independence of individual and social heterosis nor their relative effect sizes have been explicitly measured. Through controlled breeding between pairs of Western honey bee queens (Apis mellifera L.; n = 3 pairs) from two distinct populations, we created inbred colonies with low genetic diversity, hybrid colonies with high heterozygosity, and mixed colonies (combining inbred workers from each population) with low heterozygosity and high social diversity. We then quantified two independent traits in colonies: survival against bacterial challenge and maintenance of brood nest temperature. For both traits, we found hybrid and mixed colonies outperformed inbred colonies but did not perform differently from each other. During immune challenge assays, hybrid and mixed colonies experienced hazard ratios of 0.49 (95% CI [0.37, 0.65]) and 0.69 (95% CI [0.50, 0.96]) compared to inbred colonies. For nest temperatures, hybrid and mixed colonies experienced 1.94 ± 0.97 °C and 2.82 ± 2.46 °C less thermal error and 0.14 ± 0.11 °C2 and 0.16 ± 0.06 °C2 less thermal variance per hour than inbred lines. This suggests social and individual heterosis operate independently and may have similar effect sizes. These results highlight the importance of both inter- and intra-individual diversity to fitness, which may help explain the emergence of polyandry/polygyny in eusocial insects and inform breeding efforts in these systems.

Conservation of threatened species can benefit from an evaluation of genes in the Major Histocompatibility Complex (MHC), whose loci encode proteins that bind pathogens and are often under strong selection to maintain diversity in immune response to diseases. Despite this gene family's importance to disease resistance, little is known about these genes in reptiles including snakes. To address this issue, we assembled and annotated a highly-contiguous genome assembly for the timber rattlesnake (Crotalus horridus), a pit viper which is threatened or endangered in parts of its range, and analyzed this new genome along with three other rattlesnake genomes to characterize snake MHC loci. We identified highly-duplicated MHC class I and class IIβ genes in all species typified by a genomic architecture of discrete gene clusters localized on chromosome 2. Number of loci varied between species from 14 to 23 for MHC I and from 8 to 32 for MHC IIβ and was greater than previously identified in the few non-genome-based studies of reptile MHC to date. We present evidence of the gene family's complex evolutionary history, with extensive duplication and loss concurrent with speciation resulting in incomplete lineage sorting. The differences in gene number between species combined with a dynamic evolutionary history suggests that gene family expansion/contraction via rapid duplication/gene loss may represent an important mechanism for generating genetic diversity in rattlesnake MHC. Our work demonstrates the utility of whole genome sequences for identifying functional genetic variation in the form of MHC genes relevant for conservation genomic studies in threatened snakes.

Within the arachnids, chromosome-level genome assemblies have greatly accelerated the understanding of gene family evolution and developmental genomics in key groups, such as spiders (Araneae), mites and ticks (Acariformes and Parasitiformes). Among other poorly studied arachnid orders that lack genome assemblies altogether are the clade Pedipalpi, which is comprised of three orders that form the sister group of spiders, which diverged over 400 Mya. We close this gap by generating the first chromosome-level assembly from a single specimen of the vinegaroon Mastigoproctus giganteus (Uropygi). We show that this highly complete genome retains plesiomorphic conditions for many gene families that have undergone lineage-specific derivations within the more diverse spiders. Consistent with the phylogenetic position of Uropygi, macrosynteny in the M. giganteus genome substantiates the signature of an ancient whole genome duplication.

A high-quality reference genome is quite valuable in assessing the conservation status of a rare species when adequate data from other sources are unavailable. Bats comprise almost a fifth of all mammals and contribute greatly to ecosystem. However, due to the nocturnal and elusive habits, it is difficult to obtain the accurate census population size of a rare bat species and assess its conservation status. Here, we generate a chromosome-level genome assembly for the king horseshoe bat (Rhinolophus rex) and assess its conservation status by comparing the genome-wide summary statistics to other related species. The genome assembly size was 2.1 Gb (contig N50: 75.26 Mb) and 99.9% of the total sequences were anchored onto 30 autosomes, X and Y chromosomes. Despite lower genome-wide heterozygosity and recent inbreeding, R. rex did not exhibit higher genetic load comparing to the other two Rhinolophus species. Historical demography analysis revealed that R. rex maintained a long term (~2 million years) stable population size (~150,000). In the future whole-genome sequencing data from more individuals will be needed to comprehensively assess the conservation status at recent timescales. We also reconstructed the ancestral karyotype of Rhinolophus as 2n=54 and found that Robertsonian fissions and fusions were the main mechanism of chromosomal rearrangements in this genus. Overall, our study shows important implications of reference-quality genomes in both conservation genomics and comparative genomics.

Genomic markers are essential tools for studying species of conservation concern, yet non-model species often lack a reference genome. Here we describe a methodology for identifying and genotyping thousands of SNP loci in the southern damselfly (Coenagrion mercuriale), a bioindicator of freshwater stream quality classified as near-threatened, with locally declining populations. We used a hybrid approach combining reduced representation sequencing and target enrichment. First, we identified putative SNP loci using ddRADseq and de novo assembly. Then, single primer enrichment technology targeted 6,000 of these SNPs across 1,920 individuals. Challenges encountered included sequence recapture failure, coverage depth discrepancies, and aberrant FIS values. We provide recommendations to address such issues. After multiple filtering steps, 2,092 SNPs were retained and used to analyse the genetic structure of 131 individuals belonging to 11 populations in France, comparing central and marginal populations. Genetic differentiation was lower among central populations, with no sign of inbreeding. As compared to microsatellite loci, SNPs exhibited greater resolution in detecting fine-scaled genetic structure, identifying putative hybrids in adjacent populations. In this study, we emphasise the difficulties of large-scale SNP genotyping in non-model species via a hybrid method that ultimately did not offer the expected cost and time saving compared to classical ddRAD approaches. However, SNPs showed greater power than previously available markers in identifying conservation units or admixture events, and the panel of reusable probes we describe here offers the potential to improve conservation efforts through future diachronic studies or finer estimations of key parameters like effective population size.

The winter ant, Prenolepis imparis, is one of the most common, widespread, and conspicuous ant species in North America. P. imparis is well adapted to cold climates, and consequently, is often noted as the only active ant species during colder months. This specialized life history makes P. imparis a useful model organism for exploring thermal physiology and understanding the potential impacts of a warming climate on insects. Phylogeographic studies have revealed deeply divergent lineages across North America, as well as a single collection of an apparent social parasite in California. In light of its distinctive cold adaptation and recently discovered geographic diversity, a better understanding of the underlying genetic patterns of the winter ant is valuable to future conservation efforts for this species. Here, we present a high-quality genome assembly of P. imparis from Santa Clara County, California. This genome assembly consists of 787 scaffolds spanning 327.3 Mb, with contig N50 of 901.9 kb, scaffold N50 of 18.7 Mb, and BUSCO completeness of 96.5%. This genome assembly provides an essential foundation for future studies of the winter ant and will be particularly useful for understanding the genetic basis of thermal adaptation, cold resistance, chemical ecology, and the resilience of organisms in response to a changing climate.

Urbanization impacts the structure and viability of wildlife populations. Some habitat generalists, such as bobcats (Lynx rufus), maintain populations at the intersection of wild and urban habitats (wildland urban interface, WUI), but impacts of urbanization on bobcat social structure are not well understood. Although commonly thought to establish exclusive home ranges among females, instances of mother-daughter home range sharing have been documented. We combined GPS localities with genomic relatedness inferences from double-digest restriction site associated DNA sequencing (ddRADseq) to investigate mother-daughter home range sharing in bobcats (n = 38) at the WUI in the Tucson Mountains, Arizona, USA. We found the highest relatedness among females, which showed stronger isolation by distance than males and the population as a whole. Using mother-daughter relationships inferred from pedigree reconstruction, we found extensive mother-daughter home range sharing, compared to other females. Every mother identified as having at least one daughter, shared home ranges with one daughter, while other confirmed daughters established adjacent home ranges. Our results provide substantial support for the mother-daughter home range sharing hypothesis, as well as evidence of spatiotemporal overlap between mothers and daughters, adding to the body of research complicating the solitary felid paradigm. These results additionally challenge the notion of home range partitioning by prior rights land tenure, suggesting a role of matrilineal land tenure in home range establishment of daughters. Habitat fragmentation due to human population growth and urbanization thus has the potential to alter landscape genetic structure and social dynamics in bobcats.