Bighead and silver carp hybridization in the Mississippi River Basin: prevalence, distribution, and post-zygotic selection

Hybridization is a pervasive evolutionary phenomenon in plant and animal taxa. Understanding the evolutionary consequences of hybridization is dependent upon the ability to adequately detect genetically admixed individuals, characterize the maternal contribution and structure of hybrid zones, and understand post-zygotic selection acting on recombinant genotypes. Bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) are U.S. federally injurious species, and although suspected to be reproductively isolated in their native range in eastern Asia, form multi-generational hybrids within the Mississippi River Basin (MRB). My dissertation explores the complexity and structure of bighead and silver carp hybridization in the MRB through molecular marker development, implementing those markers to test for the extent of hybridization, and to assess post-zygotic effects of hybridization. I used restriction-associated DNA sequencing to develop fifty-seven species-diagnostic single nucleotide polymorphisms (SNPs) to distinguish parental bighead and silver carp from their hybrids in the MRB and China. All SNPs were isolated from conserved regions of the genome and thirty-two of fifty-seven were annotated to functional gene loci. During validation, evidence of hybridization in the Amur River, China was first documented. I developed a diagnostic mtDNA SNP and applied the nuclear SNP assay developed earlier to determine the prevalence and degree of introgression of bighead and silver carp introgression at nine locations throughout the MRB. Bighead and silver carp hybrids were present among all MRB locations (45%) and a silver carp maternal bias was present in 13 of 21 (62%) F1 hybrids, all silver carp backcrosses and maintained throughout many bighead carp backcrosses. Bighead and silver carp hybrids contained bighead and silver carp mitochondrial DNA and followed a bimodal distribution consisting primarily of parental or parental-like genotypes and phenotypes. All described hybrid categories were present among individuals from 1999-2008, with parents and late generation backcrosses representing the largest proportion of individuals. I compared body condition and reproductive potential of bighead and silver carp hybrids to test for their post-zygotic success in the MRB. Body condition (Wr) decreased as bighead and silver carp species-specific allele frequencies became more distant from parental allele frequency. Mean Wr was lowest in early generation bighead and silver carp hybrids (F1, F2, first generation backcross) compared with their respective parentals and late generation backcrosses. Despite an initial reduction in hybrid body condition, females displaying stage IV and V gonads (spawning stage gonads containing mature oocytes) and mean gonadosomatic index (GSI) of spawning stage females did not differ between parentals and hybrids throughout the MRB. Bimodal hybrid distribution indicated high densities of parentals and late generation hybrids and low densities of early generation hybrids. My results suggest that hybrids have the same reproductive potential as parents and the low frequency of early generation hybrids in the MRB is likely attributed to reproductive behavioral isolation or poor body condition, rather than genetic incompatibility. Overall, my findings provide a spatial and temporal examination of bighead and silver carp introgression in the MRB and demonstrate the importance of molecular and ecological influences in shaping this hybrid swarm

Transcriptomic comparison of invasive bigheaded carps (\u3ci\u3eHypophthalmichthys nobilis\u3c/i\u3e and \u3ci\u3eHypophthalmichthys molitrix\u3c/i\u3e) and their hybrids

Bighead carp (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix), collectively called bigheaded carps, are invasive species in the Mississippi River Basin (MRB). Interspecific hybridization between bigheaded carps has been considered rare within their native rivers in China; however, it is prevalent in the MRB. We conducted de novo transcriptome analysis of pure and hybrid bigheaded carps and obtained 40,759 to 51,706 transcripts for pure, F1 hybrid, and backcross bigheaded carps. The search against protein databases resulted in 20,336–28,133 annotated transcripts (over 50% of the transcriptome) with over 13,000 transcripts mapped to 23 Gene Ontology biological processes and 127 KEGG metabolic pathways. More transcripts were detected in silver carp than in bighead carp; however, comparable numbers of transcripts were annotated. Transcriptomic variation detected between two F1 hybrids may indicate a potential loss of fitness in hybrids. The neighbor-joining distance tree constructed using over 2,500 one-to-one orthologous sequences suggests transcriptomes could be used to infer the history of introgression and hybridization. Moreover, we detected 24,792 candidate SNPs that can be used to identify different species. The transcriptomes, orthologous sequences, and candidate SNPs obtained in this study should provide further knowledge of interspecific hybridization and introgression

Upper Mississippi River fish population monitoring and sport fish assessment in west-central Illinois, 2019

This report presents a summary of data collected during segment 06 (2019-2020) of the Upper Mississippi River fish population monitoring and sport fish assessment in west-central Illinois, an annual survey by staff of the Illinois Natural History Survey, with funds administered by the U.S. Fish and Wildlife Service and the Illinois Department of Natural Resources. Sampling for the program was conducted on 6 navigational pools of the Upper Mississippi River. All fishes collected were accurately identified, counted, measured, and weighed. The catch rates of several key species were calculated as the number of individuals collected per hour (CPUE ± standard error). Proportional size distribution (PSD) was also calculated for several key species. Catch rates and species varied among all sampling locations and sampling periods. Emerald Shiner and Gizzard Shad comprised most the individuals caught, and Common Carp and Smallmouth Buffalo accounted for the greatest proportion of the biomass collected. Sportfish Catch rates and sizes of popular sportfish species varied greatly among the navigation pools sampled during 2019. Bluegill and Channel Catfish were the most-abundantly collected sportfish species in nearly all areas along the Upper Mississippi River, although Largemouth Bass and Smallmouth Bass also appear to have robust populations. The slow but steady increase in White Bass CPUE since 2012 may warrant further investigation. Our long-term datasets allow us to observe substantial annual variations in the relative abundance and size distribution of many sportfish species, like Smallmouth Bass and White Bass. These observations could serve as a catalyst for future research investigating the effects environmental changes and management policies on the sustainability of Illinois’ sportfish populations. Invasive Species Although the main focus of the F-193-R project is to conduct monitoring to improve our understanding of population dynamics, life histories, and habitat requirements of sportfishes, the program’s sampling strategies are also useful for documenting trends in the relative abundance of non-native species occupying Illinois’ large river ecosystems. Our surveys suggest Common Carp populations are declining across the region since 2009, which may be the harbinger of good things to come for native fish populations that have been negatively affected by Common Carp. Alternatively, Silver Carp populations (below L&D 19) appear to be increasing since 2012, which may counteract any benefits native fish populations may have gained as a consequence of declining Common Carp populations. We advise that researchers be aware that our sampling protocols (e.g., restriction to main-channel habitats) may limit our probability of encountering the greatest densities of invasive species.Illinois Department of Natural Resources, Division of FIsheriesU.S. Fish and Wildlife Service Project F-193-R Segment 06unpublishednot peer reviewedOpe

Early generation hybrids may drive range expansion of two invasive fishes DataSet

Introgressive hybridization between two invasive species has the potential to contribute to their invasion success and provide genetic resiliency to rapidly adapt to new environments. Additionally, differences in the behaviour of hybrids may lead to deleterious ecosystem effects that compound any negative impacts of the invading parental species. Invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) exhibit introgressive hybridization which could influence their invasion ecology. In order to investigate the role hybrids may have in the invasion ecology of bigheaded carps, [CAA1] we examined the distribution, movements, and environmental cues for movement of two invasive fishes (bighead carp, silver carp) and their hybrids in the Illinois River (USA). Early generation hybrids (e.g., F1,F2, and first generation backcross individuals) composed a greater proportion of the population at the invasion front where abundances of bigheaded carp were low. A greater proportion of early hybrids passed through dams upstream towards the invasion front than did other hybrids and parental species. The movements and environmental cues for movement of late-generation backcrosses (more genetically similar to parental genotype) were not different from the parental species with which they shared the most alleles. Although the direction of the relationship between movement and environment was sometimes different for the parental species and associated advanced generation hybrids, these results indicate that management for parental species will also influence most hybrids. Although early generation hybrids are rare, our results indicate they may disperse towards low-density population zones (i.e., invasion fronts) or are produced at greater frequency in low density areas. These rare hybrids have the potential to produce a variety of unique genetic combinations which could result in more rapid adaptation of a non-native population to their invaded range potentially facilitating the establishment of invasive species

Discovery of an X-ray-Luminous Galaxy Cluster at z=1.4

We report the discovery of a massive, X-ray-luminous cluster of galaxies at z=1.393, the most distant X-ray-selected cluster found to date. XMMU J2235.3-2557 was serendipitously detected as an extended X-ray source in an archival XMM-Newton observation of NGC 7314. VLT-FORS2 R and z band snapshot imaging reveals an over-density of red galaxies in both angular and color spaces. The galaxy enhancement is coincident in the sky with the X-ray emission; the cluster red sequence at R-z ~ 2.1 identifies it as a high-redshift candidate. Subsequent VLT-FORS2 multi-object spectroscopy unambiguously confirms the presence of a massive cluster based on 12 concordant redshifts in the interval 1.38<z<1.40. The preliminary cluster velocity dispersion is 762+/-265 km/s. VLT-ISAAC Ks and J band images underscore the rich distribution of red galaxies associated with the cluster. Based on a 45 ks XMM-Newton observation, we find the cluster has an aperture-corrected, unabsorbed X-ray flux of f_X = (3.6 +/- 0.3) x 10^{-14} erg/cm^2/s, a rest-frame X-ray luminosity of L_X = (3.0 +/- 0.2) x 10^{44} h_70^{-2} erg/s (0.5--2.0 keV), and a temperature of kT=6.0 (+2.5, -1.8) keV. Though XMMU J2235.3-2557 is likely the first confirmed z>1 cluster found with XMM-Newton, the relative ease and efficiency of discovery demonstrates that it should be possible to build large samples of z>1 clusters through the joint use of X-ray and large, ground-based telescopes.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letters, a high-resolution version is available at http://www.astro.lsa.umich.edu/~cmullis/papers/Mullis_et_al_2005a.pdf, additional information is available at http://www.astro.lsa.umich.edu/~cmullis/research/xmmuj223

VHE Gamma Rays from PKS 2155-304

The close X-ray selected BL Lac PKS 2155-304 has been observed using the University of Durham Mark 6 very high energy (VHE) gamma ray telescope during 1996 September/October/November and 1997 October/November. VHE gamma rays with energy > 300 GeV were detected from this object with a time-averaged integral flux of (4.2 +/- 0.7 (stat) +/- 2.0 (sys)) x 10^(-11) per cm2 per s. There is evidence for VHE gamma ray emission during our observations in 1996 September and 1997 October/November, with the strongest emission being detected in 1997 November, when the object was producing the largest flux ever recorded in high-energy X-rays and was detected in > 100 MeV gamma-rays. The VHE and X-ray fluxes show evidence of a correlation.Comment: 14 pages, 6 figures, accepted for publication in Ap.

BATSE Observations of the Piccinotti Sample of AGN

BATSE Earth occultation data have been used to search for emission in the 20-100 keV band from all sources in the Piccinotti sample, which represents to date the only complete 2-10 keV survey of the extragalactic sky down to a limiting flux of 3.1 x 10^(-11) erg cm^(-2)$ s^(-1). Nearly four years of observations have been analyzed to reach a 5sigma sensitivity level of about 7.8x 10^(-11) erg cm^(-2) s^(-1) in the band considered. Of the 36 sources in the sample, 14 have been detected above 5sigma confidence level while marginal detection (3<sigma<5) can be claimed for 13 sources; for 9 objects 2sigma upper limits are reported. Comparison of BATSE results with data at higher energies is used to estimate the robustness of our data analysis: while the detection level of each source is reliable, the flux measurement maybe overestimated in some sources by as much as 35%, probably due to incomplete data cleaning. Comparison of BATSE fluxes with X-ray fluxes, obtained in the 2-10 keV range and averaged over years, indicates that a canonical power law of photon index 1.7 gives a good description of the broad band spectra of bright AGNs and that spectral breaks preferentially occur above 100 keV.Comment: 18 pages, 1 figure. Accepted for publication on Apj