Biology subjects

Mandeville, E. G.

Publications and source records attributed to Mandeville, E. G..

10 recordsLinked to original sources

bioRxiv2025

Extensive multi-species hybridization between Leuciscidae minnow species

Anthropogenic disturbances can disrupt ecosystems and alter species population dynamics. Interspecific hybridization is common between genetically related organisms, especially once reproductive barriers such as spatial isolation have been removed. We used genotyping- by-sequencing data to assess outcomes of hybridization between several Leuciscidae minnow species and to identify to what extent land use type and environmental variables influence the frequency of hybridization. We found that both two-species and multi-species hybridization was widespread; hybrids were sampled at all 25 sampling sites and made up almost 30% of all individuals sampled. While most species hybridized with at least one other sampled species, the amount of hybridization was variable. We used logistic regression to estimate the influence of anthropogenic disturbance on hybridization, and found significant but weak relationships between hybridization and environmental factors. This research improves our understanding of hybridization dynamics in species-rich clades like the Leuciscidae with low reproductive isolation, and points to the need for additional work to better understand predictors of hybridization in multi-species hybrid zones.

evolutionary biology↗

bioRxiv2024

The ambiguity of "hybrid swarm": inconsistent definitions and applications in existing research

1Hybridization is common in wild taxa and often increases in frequency following anthropogenic disturbance to an environment. Next-generation sequencing techniques make genomic analysis of a large number of individuals feasible, vastly improving the analysis for and promoting a greater frequency of studies on hybridization. However, terminology surrounding hybridization can be inconsistent; in particular, the term "hybrid swarm" has been used extensively in the literature but lacks a consistent definition. In this paper, we conducted a comprehensive review of the literature that uses the term "hybrid swarm" in reference to hybridization between taxa and challenged putative definitions of the term. We found that the term "hybrid swarm" is used in a variety of contexts, including some contradictory to other literature, and that there is little consensus on what constitutes a hybrid swarm in terms of hybrid outcomes, frequency relative to disturbances, or duration of existence. We dissuade researchers from use of the term "hybrid swarm" and instead suggest more specific and clear terminology to describe aspects of hybridization. Consequently, we hope that this paper promotes consensus surrounding hybridization terminology and improves the quality of future research on hybridization.

evolutionary biology↗

bioRxiv2023

The first chromosome-level annotated reference genome for Chrosomus eos, the northern redbelly dace

Hybridization amongst teleost fish species is an ongoing phenomenon with unclear implications. Chrosomus eos, the northern redbelly dace, is a species with an especially complex and fascinating history of hybridization with the closely related species Chrosomous neogaeus, the finescale dace. The two species historically hybridized during the last glacial maximum, forming a rare unisexual F1 hybrid lineage that utilizes gynogenetic reproduction. This hybridization event is currently thought to have only occurred during the glacial period, with subsequent dispersal of parents and hybrids into contemporary ranges during glacial recession and a cessation of further hybridization. All three maintain sympatric relationships, with limited evidence suggesting recent or contemporary hybridization between the parental species. To enable future research, a novel, high-quality, chromosome-level genome was produced through Dovetail Genomics and analyzed for completeness and the syntenic relationship between itself and the high-quality, well cited zebrafish Danio rerio genome.

genomics↗

bioRxiv2023

A high-quality reference genome for the common creek chub, Semotilus atromaculatus

Creek chub (Semotilus atromaculatus) are a leuciscid minnow species commonly found in anthropogenically disturbed environments, making them an excellent model organism to study human impacts on aquatic systems. Genomic resources for creek chub and other leuciscid species are currently limited. However, advancements in DNA sequencing now allow us to create genomic resources at a historically low cost. Here, we present a high quality 239 contig reference genome for the common creek chub, created with PacBio HiFi sequencing. We compared the assembly quality of two pipelines: Pacific Biosciences Improved Phase Assembly (IPA; 873 contigs) and Hifiasm (239 contigs). Quality and completeness of this genome is comparable to the zebrafish (Danioninae) and fathead minnow (Leuciscidae) genomes. The creek chub genome is highly syntenic to the zebrafish and fathead minnow genomes, and while our assembly does not resolve into the expected 25 chromosomes, synteny with zebrafish suggests that each creek chub chromosome is likely represented by 1-4 large contigs in our assembly. This reference genome is a valuable resource that will enhance genomic bio-diversity studies of creek chub and other non-model leuciscid species common to disturbed environments.

genomics↗

bioRxiv2022

Selection leads to remarkable variability in the outcomes of hybridization across replicate hybrid zones

Hybrid zones have been viewed as an opportunity to see speciation in action. When hybrid zones are replicated, it is assumed that if the same genetic incompatibilities are maintaining reproductive isolation across all instances of secondary contact, those incompatibilities should be identifiable by consistent patterns in the genome. In contrast, changes in allele frequencies due to genetic drift should be idiosyncratic for each hybrid zone. To test this assumption, we simulated 20 replicates of each of 12 hybrid zone scenarios with varied genetic incompatibilities, rates of migration, selection and different starting population size ratios of parental species. We found remarkable variability in the outcomes of hybridization in replicate hybrid zones, particularly with Bateson-Dobzhansky-Muller incompatibilities and strong selection. We found substantial differences among replicates in the overall genomic composition of individuals, including admixture proportions, inter-specific ancestry complement, and number of ancestry junctions. Additionally, we found substantial variation in genomic clines among replicates at focal loci, regardless of locus-specific selection. We conclude that processes other than selection are responsible for some consistent outcomes of hybridization, whereas selection on incompatibilities can lead to genomically widespread and highly variable outcomes. We highlight the challenge of mapping between pattern and process in hybrid zones and call attention to how selection against incompatibilities will commonly lead to variable outcomes. We hope that this study informs future research on replicate hybrid zones and encourages further development of statistical techniques, theoretical models, and exploration of additional axes of variation to understand reproductive isolation.

evolutionary biology↗

bioRxiv2022

Identification of sex-determining loci in hybridizing Catostomus fish species

1Despite the near-universality of gonochorism (separate sexes) in eukaryotic organisms, the underlying mechanisms of sex determination are poorly understood and highly variable in some taxa. Sex determination mechanisms may promote or impede reproductive isolation depending on whether mechanisms are similar between related species, so identifying genomic regions associated with sex determination is especially relevant for understanding evolutionary diversification and hybridization between closely related species. In Catostomus fishes, contemporary hybridization is variable and extensive, but factors influencing hybridization dynamics are not fully understood. In the present study, we aim to describe the genetic basis of sex determination in bluehead (Catostomus discobolus) and white suckers (Catostomus commersonii ) to understand the potential impact of sex determination on reproductive isolation. We used genotyping-by-sequencing data from Catostomus species and their hybrids to identify regions of the genome associated with sex using a genome-wide association study and the identification of sex-specific loci. We identified a genetic basis of sex determination in Catostomus fishes, with a region of the genome significantly associating with sex in bluehead suckers. This region is suggestive of a master sex-determining region in bluehead suckers but is not significant in white suckers, implying that either the sex-determining region of the genome differs in these two species that hybridize, or that sample size was insufficient to identify this genomic region in white suckers. By describing and comparing sex-determination systems across Catostomus fish species, we highlight the relationship between sex determining systems and hybridization in closely related fish species.

evolutionary biology↗

bioRxiv2021

Limited evidence of a genetic basis for sex determination in the common creek chub, Semotilus atromaculatus

1Sexual reproduction is almost universal in the animal kingdom; therefore, each species must have a mechanism for designating sex as male or female. Fish especially have a wide range of sex determining systems. While incompatible systems are thought to increase reproductive isolation, interspecific hybridization is common among groups such as cyprinid minnows, thus, studies such as this can provide insight into hybridization and evolutionary diversification of this clade. In the present study, we aimed to identify a genetic basis for sex determination in the common creek chub (Semotilus atromaculatus) using genotyping-by-sequencing (GBS) data. No sex-associated markers were found by RADSex or a GWAS using GEMMA, however, our Weir and Cockerham locus-specific FST analysis and discriminant analysis of principal components revealed some genetic differentiation between the sexes at several loci. While no explicit sex determination mechanism has been yet discovered in creek chub, these loci are potential candidates for future studies. This study also highlights technical challenges involved in studying sex determination in species with extremely variable mechanisms.

evolutionary biology↗

bioRxiv2021

Ecological outcomes of hybridization vary extensively in Catostomus fishes

Hybridization has been studied extensively to learn about speciation and mechanisms of reproductive isolation, but increasingly we recognize that hybridization outcomes vary geo-graphically and can depend on the environment. At the same time, hybridization can reshape biotic interactions in an ecosystem, leading to ecological shifts where hybridization occurs. Identifying how hybrid individuals function ecologically would link evolutionary outcomes of hybridization to ecological consequences, but relatively few studies have focused on ecological traits of hybrids. We described the feeding ecology of several Catostomus fish species and their hybrids by using stable isotopes ({delta}13C and{delta} 15N) as a proxy for diet and habitat use, and compared two native species, an introduced species, and three interspecific hybrid crosses. We replicated this comparison spatially, including hybrids and parental species from seven rivers in the Upper Colorado River basin where parental species co-occur and the opportunity for hybridization exists. Although relationships between native species in isotopic space varied, individual native species did not fully overlap in isotopic space in any river sampled, suggesting little overlap of resource use between these historically sympatric species. The introduced species overlapped with one or both native species in every river, suggesting similar resource use and potential for competition. Hybrids occupied intermediate, matching, or more extreme (transgressive) isotopic space relative to parental species, and were isotopically variable within and among rivers. We suggest that ecological outcomes of hybridization, like genomic outcomes of hybridization, are likely to vary across locations where a pair of species hybridizes. This variation implies that hybridization might have large unpredictable, idiosyncratic ecological effects on fish assemblages where hybrids occur. Although we found little evidence that hybrids are at a disadvantage ecologically--there were no significant declines in body condition relative to parental species--it is nevertheless possible that abiotic or biotic attributes of a river might constrain the range of interspecific hybrids that are successful, thus contributing to variation in hybridization outcomes across rivers.

evolutionary biology↗

bioRxiv2020

Model-based genotype and ancestry estimation for potential hybrids with mixed-ploidy

Non-random mating among individuals can lead to spatial clustering of genetically similar individuals and population stratification. This deviation from panmixia is commonly observed in natural populations. Consequently, individuals can have parentage in single populations or involving hybridization between differentiated populations. Accounting for this mixture and structure is important when mapping the genetics of traits and learning about the formative evolutionary processes that shape genetic variation among individuals and populations. Stratified genetic relatedness among individuals is commonly quantified using estimates of ancestry that are derived from a statistical model. Development of these models for polyploid and mixed-ploidy individuals and populations has lagged behind those for diploids. Here, we extend and test a hierarchical Bayesian model, called entropy, which can use low-depth sequence data to estimate genotype and ancestry parameters in autopolyploid and mixed-ploidy individuals (including sex chromosomes and autosomes within individuals). Our analysis of simulated data illustrated the trade-off between sequencing depth and genome coverage and found lower error associated with low depth sequencing across a larger fraction of the genome than with high depth sequencing across a smaller fraction of the genome. The model has high accuracy and sensitivity as verified with simulated data and through analysis of admixture among populations of diploid and tetraploid Arabidopsis arenosa.

genetics↗

bioRxiv2018

Machine learning to classify animal species in camera trap images: applications in ecology

1. Motion-activated cameras (\"camera traps\") are increasingly used in ecological and management studies for remotely observing wildlife and have been regarded as among the most powerful tools for wildlife research. However, studies involving camera traps result in millions of images that need to be analyzed, typically by visually observing each image, in order to extract data that can be used in ecological analyses.\n\n2. We trained machine learning models using convolutional neural networks with the ResNet-18 architecture and 3,367,383 images to automatically classify wildlife species from camera trap images obtained from five states across the United States. We tested our model on an independent subset of images not seen during training from the United States and on an out-of-sample (or \"out-of-distribution\" in the machine learning literature) dataset of ungulate images from Canada. We also tested the ability of our model to distinguish empty images from those with animals in another out-of-sample dataset from Tanzania, containing a faunal community that was novel to the model.\n\n3. The trained model classified approximately 2,000 images per minute on a laptop computer with 16 gigabytes of RAM. The trained model achieved 98% accuracy at identifying species in the United States, the highest accuracy of such a model to date. Out-of-sample validation from Canada achieved 82% accuracy, and correctly identified 94% of images containing an animal in the dataset from Tanzania. We provide an R package (Machine Learning for Wildlife Image Classification; MLWIC) that allows the users to A) implement the trained model presented here and B) train their own model using classified images of wildlife from their studies.\n\n4. The use of machine learning to rapidly and accurately classify wildlife in camera trap images can facilitate non-invasive sampling designs in ecological studies by reducing the burden of manually analyzing images. We present an R package making these methods accessible to ecologists. We discuss the implications of this technology for ecology and considerations that should be addressed in future implementations of these methods.

ecology↗