Biology subjects

Davis, J. S.

Publications and source records attributed to Davis, J. S..

16 recordsLinked to original sources

bioRxiv2026

Melatonin Partially Attenuates Oxycodone-Induced Placental Stress Signaling and Fetal Brain Apoptosis in a Sex-Specific Manner.

BackgroundMaternal oxycodone (oxy) exposure can disrupt placental function and fetal neurodevelopment, but the molecular mechanisms remain unclear. We investigated whether prenatal oxy exposure activates inflammation and stress response pathways in the placenta and fetal brain, and if maternal melatonin supplementation attenuates these effects. MethodsFemale Sprague-Dawley rats received either saline or oxy via oral gavage for 15 days before mating (10-15mg/kg/day dose escalation) and throughout pregnancy (15mg/kg/day). From gestational day (GD) 12.5, half of the dams received melatonin (10mg/kg/day). On GD 19.5, placental and fetal brain tissues were collected. Changes in expression of markers of oxidative stress, antioxidant defense signaling, inflammation, ER stress, and apoptosis were assessed by western blotting. Data were analyzed by two-way ANOVA with Tukeys post hoc test. ResultsNeither oxy exposure nor melatonin treatment increased markers of oxidative stress or antioxidant defenses in the placenta and fetal brain. Oxy exposure increased placental IL-1{beta} expression but did not alter expression of the other inflammatory markers examined. Oxy increased phosphorylation of eIF2 and increased the phospho-eIF2:eIF2 ratio in the placentas of male fetuses, and fetal brains of both sexes. CHOP expression was increased in the placentas and brains of female, but not male fetuses after oxy exposure. Oxy exposure increased levels of cleaved caspase-3 and cleaved caspase-9 in the fetal brain, but not the placenta; melatonin treatment attenuated the oxy-induced increase in cleaved caspase-9, but not cleaved caspase-3. ConclusionPrenatal oxy exposure induced a modest inflammatory response in the placenta and activated the integrated stress response and intrinsic apoptotic signaling in the fetal brain. Maternal melatonin supplementation partially mitigated the oxy-induced upregulation of caspase-9 but did not prevent stress signaling in either tissue. These findings demonstrate the presence of sex-specific placental and fetal brain responses to prenatal oxy exposure but suggest that melatonin may not provide complete protection against oxy-induced neurodevelopmental impairment.

developmental biology↗

bioRxiv2026

Delineating the effects of prenatal oxycodone exposure and melatonin treatment on placental and fetal outcomes in pregnant rats

BackgroundPrenatal oxycodone (oxy) exposure has been associated with adverse pregnancy and fetal developmental outcomes. In this study, we assessed whether chronic prenatal oxy exposure impairs placental and fetal growth in rats and if maternal melatonin supplementation would mitigate these effects. MethodsFemale Sprague-Dawley rats received either saline or oxy via oral gavage for 15 days before mating (10-15mg/kg dose escalation) and throughout pregnancy (15mg/kg). From gestational day (GD) 12.5, half of the dams received melatonin (10mg/kg). On GD19.5, maternal and fetal blood, and maternal, placental and fetal tissues were harvested. Placental histomorphometry was assessed and immunohistochemistry for pan-cytokeratin, PCNA, CD34, -SMA, and TUNEL analysis were performed. Maternal and fetal plasma cytokines, angiogenic factors, and pregnancy hormones were measured by ELISA. Anthropometric data were analyzed using general linear mixed models and other outcomes were analyzed using univariate general linear models. ResultsOxy induced fetal growth restriction as evidenced by reduced placental weight, fetal weight, fetal-to-placental weight ratio, crown-rump length, and fetal liver weight. Melatonin also independently reduced some parameters of fetal growth but when administered with oxy it partially improved fetal outcomes including the head-to-abdominal diameter ratio. Oxy exposure increased placental labyrinth zone area, the percentage of CD34-positive cells, and maternal plasma IL-1{beta} and IL-10 concentrations and reduced the percentage of pan-cytokeratin positive cells, while both oxy and melatonin reduced maternal plasma chorionic gonadotropin levels. ConclusionPrenatal oxy exposure disrupts placental structure, labyrinth anatomy, and induces maternal systemic inflammation, associated with impaired fetal growth. The protective effects of melatonin are partial but indicate a potential brain sparing effect.

developmental biology↗

bioRxiv2025

Antibody-Protein L Functionalized Microparticles for Detection of Surface Markers in Heterogeneous Colorectal Lesions

Visualization of colorectal cancer (CRC) lesions is complicated by their location in the colon and tumor morphology. Reliance on a single surface biomarker for direct identification risks false negatives due to temporal changes and/or tumor heterogeneity. We developed a multiplexed system of complementary biomarker targets in an effort to capture a broader range of lesions with diverse temporal and/or phenotypic expression. We identified Mucin-1 (MUC1) and epithelial cell adhesion molecule (EPCAM) as useful targeting pairs by examining multiple colon tumor subtypes in a standard tissue array, and by surveying multiple CRC cell lines, both as 2D cultures and as 3D tumoroids, for the presence of the CRC surface biomarkers. We demonstrated the utility of a "universal" surface functionalization approach using Antibody-Protein L functionalized microparticles (APL-MPs) that enabled the simultaneous incorporation of antibodies recognizing MUC1 and EPCAM. Using CRC cell heterogeneous tumoroids expressing both MUC1 and EPCAM (HET-tumoroids) and orthotopic animal cancer models designed to express both surface antigens, we demonstrated that: 1) APL-MPs identified MUC1- and EPCAM-positive tumoroids in proportion to antigen expression; 2) APL-MPs detected CRC surface antigens on the luminal colon surface in vivo, and 3) concurrent targeting of multiple surface antigens enhanced the sensitivity of detection of heterogeneous CRC lesions. This approach opens the door for the use of antibody-protein L dual-targeting MPs in a variety of applications to detect heterogeneous cancer lesions. SignificanceMulti-antigen targeting of MUC1 and EPCAM with Antibody-Protein L microparticles enhances the detection sensitivity of heterogeneous colorectal cancer lesions, offering a promising strategy for the accurate visualization of tumors in complex environments.

cancer biology↗

bioRxiv2025

Rete Ovarii Epithelial Cells as an Unappreciated Cell of Origin for Pelvic and Ovarian High-Grade Serous Carcinoma

Over the past two decades, converging clinicopathologic, molecular, and evolutionary evidence has established that pelvic and ovarian high-grade serous carcinoma (HGSC) originates predominantly from tubal-type epithelia rather than the ovarian surface epithelium. Consequently, Fallopian tube secretory epithelial cells are widely recognized as the principal cell of origin for HGSC. However, the female reproductive tract contains additional tubular epithelial networks whose potential contributions to HGSC pathogenesis remain unexplored. Here, we identify the rete ovarii (RO), a complex network of intra- and extra-ovarian tubules located within the ovarian hilus and mesovarium, as an alternative candidate tissue of origin for HGSC. We demonstrate that genetic and genomic alterations in rete ovarii epithelial cells (ROECs) can drive their malignant transformation, giving rise to tumors that closely recapitulate the histologic and molecular characteristics of human HGSC. Spatially resolved single-cell transcriptomic analyses of tumors derived from Brca/Trp53/Pten-deficient ROECs (BTP-RO) reveal distinct invasive and immunosuppressive molecular programs. These findings establish ROECs as a previously unrecognized cell of origin for HGSC, expanding the landscape of potential precursor populations beyond the Fallopian tube. The RO-based HGSC model provides a powerful framework for developing origin-informed prevention strategies, early detection approaches, and targeted therapeutics.

cancer biology↗

bioRxiv2025

Genomics and reproductive biology of Leptopilina malgretoutensis Buffington, Lue, Davis & Tracey sp. nov. (Hymenoptera: Figitidae): An asexual parasitoid of Caribbean Drosophila

Drosophila and parasitic wasps in the genus Leptopilina have long been a model for understanding host-parasite interactions. Indeed, parasitic wasps are important drivers of ecological and evolutionary processes broadly, but we are generally lacking information about the diversity, natural history, and evolution of these relationships. We collected insects from the Caribbean Island of Saint Lucia, home to the eastern Caribbean dunni subgroup of Drosophila: a clade long appreciated for its recent patterns of speciation and adaptation. Here we present an integrative approach that incorporates natural history, taxonomy, physiology, and genomics to describe Leptopilina n. sp. Buffington, Lue, Davis & Tracey sp. nov. (Hymenoptera: Figitidae), a virulent parasitoid of dunni group flies, especially Drosophila antillea. Leptopilina n. sp. is nested within an early-branching clade of Leptopilina, offering insights into the evolution of this important genus of Drosophila parasitoids. We present a high-quality assembly for this wasps 1Gbp genome, and for its bacterial endosymbiont: Wolbachia strain "wLmal". Furthermore, we show that wLmal induces parthenogenesis in the wasp, and that these wasps are reliant upon their Wolbachia infections to produce female offspring. Finally, comparison to historical museum specimens indicate that Leptopilina n. sp. had been collected approximately 40 years prior from the nearby island of Guadeloupe and were also asexually reproducing. This work represents one of only a handful of studies in which field biology, taxonomy, systematics, genomics, and experimental biology are integrated into a species description: showcasing the possibilities for biodiversity research in the genomic era.

evolutionary biology↗

bioRxiv2024

Central Role for Glycolysis and Fatty Acids in LH-responsive Progesterone Synthesis

Progesterone production by the corpus luteum is fundamental for establishing and maintaining pregnancy. The pituitary gonadotropin luteinizing hormone (LH) is recognized as the primary stimulus for luteal formation and progesterone synthesis, regardless of species. Previous studies demonstrated an elevation in abundance of genes related to glucose and lipid metabolism during the follicular to luteal transition. However, the metabolic phenotype of these highly steroidogenic cells has not been studied. Herein, we determined acute metabolic changes induced by LH in primary luteal cells and defined pathways required for progesterone synthesis. Untargeted metabolomics analysis revealed that LH induces rapid changes in vital metabolic pathways, including glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway, de novo lipogenesis, and hydrolysis of phospholipids. LH stimulated glucose uptake, enhanced glycolysis, and flux of [U-13C6]-labeled glucose-derived carbons into metabolic branches associated with adenosine 5-triphosphate (ATP) and NADH/NADPH production, synthesis of nucleotides, proteins, and lipids, glycosylation of proteins or lipids, and redox homeostasis. Selective use of small molecule inhibitors targeting the most significantly changed pathways, such as glycolysis, TCA cycle, and lipogenesis, uncovered cellular metabolic routes required for LH-stimulated steroidogenesis. Furthermore, LH via the protein kinase A (PKA) pathway triggered post-translational modification of acetyl-CoA carboxylase alpha (ACACA) and ATP citrate lyase (ACLY), enzymes involved in de novo synthesis of fatty acids. Inhibition of ACLY and fatty acid transport into mitochondria reduced LH-stimulated ATP, cAMP production, PKA activation, and progesterone synthesis. Taken together, these findings reveal novel hormone-sensitive metabolic pathways essential for maintaining LHCGR/PKA signaling and steroidogenesis in ovarian luteal cells. SignificanceThe establishment and maintenance of pregnancy require a well-developed corpus luteum, an endocrine gland within the ovary that produces progesterone. Although there is increased awareness of intracellular signaling events initiating the massive production of progesterone during the reproductive cycle and pregnancy, there are critical gaps in our knowledge of the metabolic and lipidomic pathways required for initiating and maintaining luteal progesterone synthesis. Here, we describe rapid, hormonally triggered metabolic pathways, and define metabolic targets crucial for progesterone synthesis by ovarian steroidogenic cells. Understanding hormonal control of metabolic pathways may help elucidate approaches for improving ovarian function and successful reproduction or identifying metabolic targets for developing nonhormonal contraceptives.

molecular biology↗

bioRxiv2023

Characterization of m6A modifiers and RNA modifications in uterine fibroids

Uterine leiomyoma or fibroids are the most common prevalent noncancerous tumors of the uterine muscle layer. Common symptoms associated with fibroids include pelvic pain, heavy menstrual bleeding, anemia, and pelvic pressure. These tumors are a leading cause of gynecological care but lack long-term therapy as the origin and development of fibroids are not well understood. Several next-generation sequencing technologies have been performed to identify the underlying genetic and epigenetic basis of fibroids. However, there remains a systemic gap in our understanding of molecular and biological process that define uterine fibroids. Recent epitranscriptomics studies have unraveled RNA modifications that are associated with all forms of RNA and are thought to influence both normal physiological functions and the progression of diseases. We quantified RNA expression profiles by analyzing publicly available RNA-seq data for 15 known epigenetic mediators to identify their expression profile in uterine fibroids compared to myometrium. To validate our findings, we performed RT-qPCR on a separate cohort of uterine fibroids targeting these modifiers confirming our RNA-seq data. We then examined protein profiles of key m6A modifiers in fibroids and their matched myometrium. In concordance with our RNA expression profiles, no significant differences were observed in these proteins in uterine fibroids compared to myometrium. To determine abundance of RNA modifications, mRNA and small RNA from fibroids and matched myometrium were analyzed by UHPLC MS/MS. In addition to the prevalent N6-methyladenosine (m6A), we identified 11 other known modifiers but did not identify any aberrant expression in fibroids. We then mined a previously published dataset and identified differential expression of m6A modifiers that were specific to fibroid genetic sub-type. Our analysis also identified m6A consensus motifs on genes previously identified to be dysregulated in uterine fibroids. Overall, using state-of-the-art mass spectrometry, RNA expression and protein profiles, we characterized and identified differentially expressed m6A modifiers in relation to driver mutations. Despite the use of several different approaches, we identified limited differential expression of RNA modifiers and associated modifications in uterine fibroids. However, considering the highly heterogenous genomic and cellular nature of fibroids, and the possible contribution of single molecule m6A modifications to fibroid pathology, there is a need for greater in-depth characterization of m6A marks and modifiers in a larger and varied patient cohort.

cancer biology↗

bioRxiv2022

Whole-genome resequencing data support a single introduction of the invasive white pine sawfly, Diprion similis

Biological introductions are unintended "natural experiments" that provide unique insights into evolutionary processes. Invasive phytophagous insects are of particular interest to evolutionary biologists studying adaptation, as introductions often require rapid adaptation to novel host plants. However, adaptive potential of invasive populations may be limited by reduced genetic diversity--a problem known as the "genetic paradox of invasions". One potential solution to this paradox is if there are multiple invasive waves that bolster genetic variation in invasive populations. Evaluating this hypothesis requires characterizing genetic variation and population structure in the introduced range. To this end, we assemble a reference genome and describe patterns of genetic variation in the introduced white pine sawfly, Diprion similis. This species was introduced to North America in 1914, where it has undergone a rapid host shift to the thin-needled eastern white pine (Pinus strobus), making it an ideal invasion system for studying adaptation to novel environments. To evaluate evidence of multiple introductions, we generated whole-genome resequencing data for 64 D. similis females sampled across the North American range. Both model-based and model-free clustering analyses supported a single population for North American D. similis. Within this population, we found evidence of isolation-by-distance and a pattern of declining heterozygosity with distance from the hypothesized introduction site. Together, these results support a single-introduction event. We consider implications of these findings for the genetic paradox of invasion and discuss priorities for future research in D. similis, a promising model system for invasion biology.

evolutionary biology↗

bioRxiv2022

Niche-specific genome degradation and convergent evolution shaping Staphylococcus aureus adaptation during severe infections

During severe infections, Staphylococcus aureus moves from its colonising sites to blood and tissues, and is exposed to new selective pressures, thus potentially driving adaptive evolution. Previous studies have shown the key role of the agr locus in S. aureus pathoadaptation, however a more comprehensive characterisation of genetic signatures of bacterial adaptation may enable prediction of clinical outcomes and reveal new targets for treatment and prevention of these infections. Here, we measured adaptation using within-host evolution analysis of 2,590 S. aureus genomes from 396 independent episodes of infection. By capturing a comprehensive repertoire of single-nucleotide and structural genome variations, we found evidence of a distinctive evolutionary pattern within the infecting populations compared to colonising bacteria. These invasive strains had up to 20-fold enrichments for genome degradation signatures and displayed significantly convergent mutations in a distinctive set of genes, linked to antibiotic response and pathogenesis. In addition to agr-mediated adaptation we identified non-canonical, genome-wide significant loci including sucA-sucB and stp1. The prevalence of adaptive changes increased with infection extent, emphasising the clinical significance of these signatures. These findings provide a high-resolution picture of the molecular changes when S. aureus transitions from colonisation to severe infection and may inform correlation of infection outcomes with adaptation signatures.

genomics↗

bioRxiv2021

DROP: Molecular voucher database for identification of Drosophila parasitoids

Molecular identification is increasingly used to speed up biodiversity surveys and laboratory experiments. However, many groups of organisms cannot be reliably identified using standard databases such as GenBank or BOLD due to lack of sequenced voucher specimens identified by experts. Sometimes a large number of sequences are available, but with too many errors to allow identification. Here we address this problem for parasitoids of Drosophila by introducing a curated open-access molecular reference database, DROP (Drosophila parasitoids). Identifying Drosophila parasitoids is challenging and poses a major impediment to realize the full potential of this model system in studies ranging from molecular mechanisms to food webs, and in biological control of Drosophila suzukii. In DROP (http://doi.org/10.5281/zenodo.4519656), genetic data are linked to voucher specimens and, where possible, the voucher specimens are identified by taxonomists and vetted through direct comparison with primary type material. To initiate DROP, we curated 154 laboratory strains, 856 vouchers, 554 DNA sequences, 16 genomes, 14 transcriptomes, and 6 proteomes drawn from a total of 183 operational taxonomic units (OTUs): 114 described Drosophila parasitoid species and 69 provisional species. We found species richness of Drosophila parasitoids to be heavily underestimated and provide an updated taxonomic catalogue for the community. DROP offers accurate molecular identification and improves cross-referencing between individual studies that we hope will catalyze research on this diverse and fascinating model system. Our effort should also serve as an example for researchers facing similar molecular identification problems in other groups of organisms.

genomics↗

bioRxiv2020

Highly contiguous assemblies of 101 drosophilid genomes

Over 100 years of studies in Drosophila melanogaster and related species in the genus Drosophila have facilitated key discoveries in genetics, genomics, and evolution. While high-quality genome assemblies exist for several species in this group, they only encompass a small fraction of the genus. Recent advances in long read sequencing allow high quality genome assemblies for tens or even hundreds of species to be generated. Here, we utilize Oxford Nanopore sequencing to build an open community resource of high-quality assemblies for 101 lines of 95 drosophilid species encompassing 14 species groups and 35 sub-groups with an average contig N50 of 10.5 Mb and greater than 97% BUSCO completeness in 97/101 assemblies. These assemblies, along with detailed wet lab protocol and assembly pipelines, are released as a public resource and will serve as a starting point for addressing broad questions of genetics, ecology, and evolution within this key group.

evolutionary biology↗

bioRxiv2020

A shift to shorter cuticular hydrocarbons causes sexual isolation in the Drosophila americana species group

Because sensory signals often evolve rapidly, they could be instrumental in the emergence of reproductive isolation between species. However, pinpointing their specific contribution to isolating barriers, and the mechanisms underlying their divergence, remains challenging. Here we demonstrate sexual isolation due to divergence in chemical signals between two populations of Drosophila americana (SC and NE) and one population of D. novamexicana, and dissect its underlying phenotypic and genetic mechanisms. Mating trials revealed strong sexual isolation between Drosophila novamexicana males and SC Drosophila americana females, as well as more moderate bi-directional isolation between D. americana populations. Mating behavior data indicates SC D. americana males have the highest courtship efficiency and, unlike males of the other populations, are accepted by females of all species. Quantification of cuticular hydrocarbon (CHC) profiles--chemosensory signals that are used for species recognition and mate finding in Drosophila--shows that the SC D. americana population differs from the other populations primarily on the basis of compound carbon chain-length. Moreover, manipulation of male CHC composition via heterospecific perfuming--specifically perfuming D. novamexicana males with SC D. americana males--abolishes their sexual isolation from these D. americana females. Of a set of candidates, a single gene--elongase CG17821--had patterns of gene expression consistent with a role in CHC differences between species. Sequence comparisons indicate D. novamexicana and our Nebraska (NE) D. americana population share a derived CG17821 truncation mutation that could also contribute to their shared "short" CHC phenotype. Together, these data suggest an evolutionary model for the origin and spread of this allele and its consequences for CHC divergence and sexual isolation in this group.

evolutionary biology↗

bioRxiv2020

Chromatin State Dynamics Confers Specific Therapeutic Strategies in Enhancer Subtypes of Colorectal Cancer

The extent and function of chromatin state aberrations during colorectal cancer (CRC) progression is not completely understood. Here, by comprehensive epigenomic characterization of 56 tumors, adenomas, and their matched normal tissues, we define the dynamics of chromatin states during the progression of colorectal cancer. H3K27ac-marked active enhancer state could distinguish between different stages of CRC progression. By epigenomic editing, we present evidence that gains of tumor-specific enhancers for crucial oncogenes, such as ASCL2 and FZD10, was crucial for excessive proliferation. Consistently, combination of MEK plus bromodomain (BET) inhibition was found to have synergistic effects in CRC patient-derived xenograft (PDX) models. Probing inter-tumor heterogeneity, we identified four distinct enhancer subtypes (EpiC), three of which correlate well with previously defined transcriptomic subtypes (CMSs). Importantly, CMS2 can be divided into two EpiC subgroups with significant survival differences. Leveraging such correlation, we devised a combinatorial therapeutic strategy of enhancer-blocking bromodomain inhibitors with pathway-specific inhibitors (PARPi, EGFRi, and TGF{beta}i) for three EPIC groups. Our data suggest that the dynamics of active enhancer underlies colorectal cancer progression and the patient-specific active enhancer patterns govern their unique gene expression patterns which can be leveraged for precision combination therapy.

cancer biology↗

bioRxiv2020

Composition of the Lipid Droplets of the Bovine Corpus Luteum

2.Establishment and maintenance of pregnancy is dependent on progesterone synthesized by luteal tissue in the ovary. Our objective was to identify the characteristics of lipid droplets (LDs) in ovarian steroidogenic cells. We hypothesized that LDs are a major feature of steroidogenic luteal cells and store cholesteryl esters. Bovine luteal tissue was used for whole tissue analysis. Further analyses were performed on isolated ovarian steroidogenic cells: granulosa and theca cells of the follicle, and small/large luteal cells. Isolated luteal LDs were collected for lipid/protein analyses. Luteal tissue contained perilipins 2/3/5, hormone-sensitive lipase and abhydrolase domain containing 5. Luteal tissue was enriched in TGs compared to other tissues, except of adipose tissue. Large and small luteal cells were distinguished from follicular cells by the presence of LDs and LD-associated proteins. Furthermore, LDs from large luteal cells were numerous and small; whereas, LDs from small luteal cells were large and less numerous. Isolated LDs contained nearly all of the TGs and cholesteryl esters present in luteal tissue. Isolated luteal LDs were composed primarily of TG, with lesser amounts of cholesteryl esters, diglyceride and other phospholipids. Bovine luteal tissue LDs are distinct from LDs in other bovine tissues, including follicular steroidogenic cells.

cell biology↗

bioRxiv2019

Gene-specific methylation profiles for integrative methylation-expression analysis in cancer research

DNA methylation is a key epigenetic factor regulating gene expression. While promoter-associated methylation has been extensively studied, recent publications have revealed that functionally important methylation also occurs in intergenic and distal regions, and varies across genes and tissue types. Given the growing importance of inter-platform integrative genomic analyses, there is an urgent need to develop methods to construct gene-level methylation summaries that account for the potentially complex relationships between methylation and expression. We introduce a novel sequential penalized regression approach to construct gene-specific methylation profiles (GSMPs) which find for each gene and tissue type a sparse set of CpGs best explaining gene expression and weights indicating direction and strength of association. Using TCGA and MD Anderson colorectal cohorts to build and validate our models, we demonstrate our strategy better explains expression variability than standard approaches and produces gene-level scores showing key methylation differences across recently discovered colorectal cancer subtypes. We share an R Shiny app that presents GSMP results for colorectal, breast, and pancreatic cancer with plans to extend it to all TCGA cancer types. Our approach yields tissue-specific, gene-specific sparse lists of functionally important CpGs that can be used to construct gene-level methylation scores that are maximally correlated with gene expression for use in integrative models, and produce a tissue-specific summary of which genes appear to be strongly regulated by methylation. Our results introduce an important resource to the biomedical community for integrative genomics analyses involving DNA methylation.

genomics↗

bioRxiv2017

Male success against con- and heterospecific competitors indicates a positive but modest role for sexual selection as driver of speciation

For sexual selection within species to drive the evolution of reproductive isolation between lineages, sexually selected and reproductive isolating traits must both share underlying mechanisms and operate in the same direction. While some work has been done to evaluate mechanistic overlap, fewer studies have evaluated whether intraspecific sexually-selected variation is associated with elevated reproductive isolation between species. Here we evaluate this association by assessing the relationship between male reproductive success against conspecifics versus heterospecific males at each of two different mating stages. We find that male precopulatory performance (remating success following a conspecific versus a heterospecific first mating) was not associated between conspecific and heterospecific contexts, but postcopulatory success (sperm competition against conspecific versus heterospecific males) was modestly positively correlated. We discuss two lines of evidence that suggest this modest association is due to incomplete mechanistic overlap between postcopulatory competition in conspecific and heterospecific mating contexts. This study provides an explicit test of a necessary condition for sexual selection to drive speciation, and finds that while sexual selection is not individually sufficient to explain the magnitude of reproductive isolation in this system, it could nonetheless facilitate the evolution of isolation via postcopulatory sperm competition.

evolutionary biology↗