Mississippi River Drainage Research Articles

A Genetic Assessment of Missouri's Lake Sturgeon after 30 Years of Restoration Releases

AbstractThe Lake Sturgeon Acipenser fulvescens is native to three major watersheds in the USA: the Great Lakes, Hudson Bay, and Mississippi River drainages. However, they have declined across much of their range due to overfishing, pollution, and major river alterations. After their near extirpation in Missouri, the Missouri Department of Conservation initiated a reintroduction program to restore the Lake Sturgeon in the state's largest waterways. From 1984 to 2015, offspring originating from Lake Winnebago (1984–2001) and from upper Mississippi River tributaries (2004–2015) were reared in captivity and released into portions of the Mississippi and Missouri rivers. After 32 years of restorative releases, we screened Lake Sturgeon samples from the state of Missouri by using 11 microsatellite loci and mitochondrial DNA control region sequences. We examined overall genetic diversity and genetic structure of Lake Sturgeon captured in the Mississippi and Missouri rivers for differences between rivers and among groups within rivers. We found high levels of genetic diversity within both rivers, with very little genetic differentiation between them. Higher‐than‐average relatedness within sample groups and heterozygote excess were consistent with the pattern expected from stocked fish and suggested that closely related fish may have aggregated at stocking sites. We detected two genetic groups in Missouri, reflecting the change in stock source. Haplotypes that may be unique to the Mississippi and Ohio River systems were observed at very low frequencies. Though largely the product of stocking, reproductively mature Lake Sturgeon will likely have sufficient genetic diversity and will have experienced selection pressures in Missouri's large rivers, making them the most appropriate source for further supplementation if it is deemed necessary. We recommend continued research and monitoring of reproductive habits and preservation of multiple spawning sites to continue the long path toward a self‐sustaining Lake Sturgeon population in Missouri's waters.

Detrital Zircon Provenance and Lithofacies Associations of Montmorillonitic Sands in the Maastrichtian Ripley Formation: Implications for Mississippi Embayment Paleodrainage Patterns and Paleogeography

We provide new detrital zircon evidence to support a Maastrichtian age for the establishment of the present-day Mississippi River drainage system. Fieldwork conducted in Pontotoc County, Mississippi, targeted two sites containing montmorillonitic sand in the Maastrichtian Ripley Formation. U-Pb detrital zircon (DZ) ages from these sands (n = 649) ranged from Mesoarchean (~2870 Ma) to Pennsylvanian (~305 Ma) and contained ~91% Appalachian-derived grains, including Appalachian–Ouachita, Gondwanan Terranes, and Grenville source terranes. Other minor source regions include the Mid-Continent Granite–Rhyolite Province, Yavapai–Mazatzal, Trans-Hudson/Penokean, and Superior. This indicates that sediment sourced from the Appalachian Foreland Basin (with very minor input from a northern or northwestern source) was being routed through the Mississippi Embayment (MSE) in the Maastrichtian. We recognize six lithofacies in the field areas interpreted as barrier island to shelf environments. Statistically significant differences between DZ populations and clay mineralogy from both sites indicate that two distinct fluvial systems emptied into a shared back-barrier setting, which experienced volcanic ash input. The stratigraphic positions of the montmorillonitic sands suggest that these deposits represent some of the youngest Late Cretaceous volcanism in the MSE.

Population Genetic Analyses of Lampsilis cardium (Bivalvia: Unionida) Reveal Multiple Post–Glacial Colonization Routes into the Great Lakes Drainage

Freshwater mussels (order Unionida) are a historically abundant component of North American freshwater ecosystems, yet are among the most imperiled faunal groups. Understanding the underlying genetic structure and how it relates to historical geographic changes is critical for development of effective conservation strategies. Here we analyze mitochondrial gene fragments (COI) and 6 microsatellite loci of the freshwater mussel Lampsilis cardium (Rafinesque, 1820) in the Great Lakes and Mississippi River drainages to assess phylogenetic structure. The mitochondrial phylogeny shows geographic structure, with one divergent clade found exclusively in the Maumee and Wabash River. Phylogenies created using the COI sequences indicate divergence between two distinct clades of putative L. cardium (uncorrected p distance = 5.22%). Results from the microsatellite analyses suggest two genetically distinct populations corresponding to at least two glacial refugia, similar to the genetic structure observed for some other freshwater mussels in the region and are largely consistent to the results of mtDNA dataset. Three COI sequences from putative L. ovata (Say, 1817) were obtained from other published studies and included the phylogenetic analysis, these rendered the sequences from putative L. cardium generated in this study non–monophyletic. This suggests that more work is needed to determine whether L. cardium and L. ovata represent two distinct species or represent two divergent populations. Despite the highly divergent COI haplotypes in two monophyletic clades, nuclear microsatellite markers failed to detect differences in allele frequencies between individuals from these two clades in regions where they co–occur (FST = 0.004). These data aid in conservation strategies for unionids, providing guidance of best practices for maintaining natural genetic structure.

Late Pleistocene range expansion of North American topminnows accompanied by admixture and introgression

AbstractAimWe used genome‐scale sampling to assess the phylogeography of a group of topminnows in the Fundulus notatus species complex. Two of the species have undergone extensive range expansions resulting in broadly overlapping distributions, and sympatry within drainages has provided opportunities for hybridization and introgression. We assessed the timing and pattern of range expansion in the context of late Pleistocene–Holocene drainage events and evaluated the evidence for introgressive hybridization between species.LocationCentral and southern United States including drainages of the Gulf of Mexico Coastal Plain and portions of the Mississippi River drainage in and around the Central Highlands.TaxonTopminnows, Genus Fundulus, subgenus Zygonectes—Fundulus notatus, Fundulus olivaceus, Fundulus euryzonus.MethodsWe sampled members of the F. notatus species complex throughout their respective ranges, including numerous drainage systems where species co‐occur. We collected genome‐wide single nucleotide polymorphisms (SNPs) using the genotype‐by‐sequencing (GBS) method and subjected data to population genetic analyses to infer the population histories of both species, including explicit tests for admixture and introgression. The methods employed included STRUCTURE, principal coordinates analysis, TreeMix and approximate Bayesian computation.ResultsGenetic data are presented for 749 individuals sampled from 14 F. notatus, 20 F. olivaceus and 2 F. euryzonus populations. Members of the species complex differed in phylogeographic structure, with F. notatus exhibiting geographic clusters corresponding to Pleistocene coastal drainages and F. olivaceus comparatively lacking in phylogeographic structure. Evidence for interspecific introgression varied by drainage.Main conclusionsPopulations of F. notatus and F. olivaceus exhibited contrasting patterns of lineage diversity among coastal drainages, indicating interspecific differences in their Pleistocene southern refugia. Phylogeographic patterns in both species indicated that range expansions into the northern limits of contemporary distributions coincided with and continued subsequent to the Last Glacial Maximum. There was evidence of introgression between species in some, but not all drainages where the species co‐occur, in a pattern that is correlated with previous estimates of hybridization rates.

Spatial genetic variation and habitat association of Rhinichthys cataractae, the longnose dace, in the Driftless Area of the upper Mississippi River basin

The Driftless Area of the upper Mississippi River drainage is a unique geographic region because of its complex geological history and the influence of recent, intensive human activities. The longnose dace, Rhinichthys cataractae, is a relatively common, small freshwater fish that is distributed in swift, cool streams within the region. The aim of this study was to determine the spatial genetic differentiation of the longnose dace and define the broad scale environmental variables that shape the distribution of the species in the southwestern portion of the Driftless Area. Genotypic data from seven microsatellite loci were analyzed for 276 individuals from 15 localities representing major drainages within the region in northeast Iowa. Broad scale environmental variables including hydrologic, soil, and climatic factors were evaluated to construct an ecological niche model (ENM) to predict the suitability of habitat for the species within the region. Results of the genetic analyses revealed two distinct, but somewhat admixed genetic clusters of longnose dace in Iowa. The genetic differentiation between localities and between drainages was low to moderate with some evidence of isolation by distance. Most of the variation was observed by differences between individuals within local populations. The ENM generated largely reflected the known distribution of the species in Iowa with a decreasing probability of suitable habitat from northern to southern drainages. Geologic factors played a key role in the model. The distribution and population structure of the longnose dace in the northeast Iowa revealed that isolation by distance, historical processes and the underlying geology are primarily responsible for the observed spatial distribution of genetic variation.

Evidence for Cogradient Growth and Survival Between Two Geographically Distinct Stocks of Muskellunge

AbstractIntraspecific genetic variation across the distribution of Muskellunge Esox masquinongy suggests the existence of divergent stocks among major river drainages. Often, stocks differentiate in response to latitudinal variation in thermal regime. Genetic variation and thermal adaptation may drive fish to either maximize growth during brief growing seasons at higher latitudes (counter‐gradient growth) or experience longer periods of slower growth at lower latitudes (cogradient growth). The strength and direction of these genetic effects matter for fish stocked outside of their native drainage and for populations experiencing changes to regional thermal regimes. We used a replicated pond experiment with uniform initial fish size and environmental conditions to compare the survival and growth of stocked age‐0 Ohio River drainage (OH) Muskellunge with those of the more northerly upper Mississippi River drainage (MISS) stock following their first winter and a year after introduction into a common environment. Both stocks had similarly high winter survival, though the MISS stock had a slower growth rate overwinter than the OH stock. Survival during the latter spring‐to‐fall period was greatly reduced for the MISS stock, however, with the differences in growth rate persisting. These findings suggest that cogradient adaptation to temperatures experienced during early life stages in native environments results in a disadvantage for high‐latitude stocks of Muskellunge in thermal regimes warmer than those they have historically experienced in their native drainages.

Right practice, right place: A conservation planning toolbox for meeting water quality goals in the Corn Belt

O n August 2, 2014, the residents of Toledo, Ohio, were warned that their drinking water was potentially contaminated with microcystin, an algal-related toxin that can cause various illnesses and liver damage, and unsafe to drink (Bullerjahn et al. 2016). They were the latest victims of a series of water quality crises in the United States, many (including the Toledo event) attributable in large part to nutrients lost from agricultural landscapes. Meanwhile, hypoxia in the Gulf of Mexico continues unabated (USEPA 2015), with the 2017 dead zone being the largest recorded (NOAA 2017). In response to these crises, states in the Mississippi River and Great Lakes drainage basins are undertaking ambitious efforts to achieve 40% to 45% reductions in nutrient losses from agriculture. There is a growing consensus that in-field conservation practices, such as improved nutrient management, conservation tillage, and cover crops, will not, singly or together, achieve the 45% nutrient reduction goals (Schilling and Wolter 2009; Iowa Nutrient Reduction Strategy 2013). Meeting these water quality goals will require combining in-field nutrient management practices with downstream nutrient removal practices, such as bioreactors and filter strips at the edges of fields and wetland creation and floodplain restoration below fields (McLellan et al.

Differences in Stocking Success among Geographically Distinct Stocks of Juvenile Muskellunge in Illinois Lakes

AbstractMuskellunge Esox masquinongy are broadly distributed across the northern United States and southern Canada. Intraspecific genetic variation suggests the existence of divergent stocks related to residence in major river drainages. Populations and stocks have likely adapted to specific environmental conditions associated with geographic location, especially latitude and the associated thermal regime. In this study, we examined differences in survival and growth among stocks of juvenile Muskellunge stocked into lakes throughout Illinois. Muskellunge from the Ohio River drainage stock, the upper Mississippi River drainage stock, and the current mixed Illinois broodstock were used for comparisons. Stocking mortality was related to temperature and was greatest for Illinois and Ohio River drainage fish that were stocked during the early fall. Mississippi River drainage fish experienced high mortality over the first summer after stocking, resulting in the lowest abundance during the second fall poststocking. In addition to low catch rates, Muskellunge from the Mississippi River drainage were significantly smaller than fish from the Illinois and Ohio River drainage stocks by the second fall. Populations from similar latitudes and climate (Illinois and Ohio) performed the best in terms of survival and growth and should be utilized in future stockings.Received October 7, 2016; accepted March 15, 2017 Published online May 4, 2017

Concentrations of select dissolved trace elements and anthropogenic organic compounds in the Mississippi River and major tributaries during the summer of 2012 and 2013

The Mississippi River drainage basin includes the Illinois, Missouri, Ohio, Tennessee, and Arkansas rivers. These rivers drain areas with different physiography, population centers, and land use, with each contributing a different suites of metals and wastewater contaminants that can affect water quality. In July 2012, we determined 18 elements (Be, Rb, Sr, Cd, Cs, Ba, Tl, Pb, Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) and chlorophyll-a (Chl-a) in the five major tributaries and in the Upper Mississippi River. The following summer, we determined both trace elements and 25 trace organic compounds at 10 sites in a longitudinal study of the main stem of the Mississippi River from Grafton, Illinois to Natchez, Mississippi. We detected wastewater contaminants, including pharmaceuticals and endocrine disrupting compounds, throughout the river system, with the highest concentrations occurring near urban centers (St. Louis and Memphis). Concentrations were highest for atrazine (673ngL-1), DEET (540ngL-1), TCPP (231ngL-1), and caffeine (202ngL-1). The Illinois, Missouri, and Yazoo rivers, which drain areas with intense agriculture, had relatively high concentrations of Chl-a and atrazine. However, the Ohio River delivered higher loads of contaminants to the Mississippi River, including an estimated 177kgday-1 of atrazine, due to higher flow volumes. Concentrations of heavy metals (Ni, V, Co, Cu, Cd, and Zn) were relatively high in the Illinois River and low in the Ohio River, although dissolved metal concentrations were below US EPA maximum contaminant levels for surface water. Multivariate analysis demonstrated that the rivers can be distinguished based on elemental and contaminant profiles.

Booms, Blooms, and Doom: The Life of the Gulf of Mexico Dead Zone

Booms, Blooms, and Doom:The Life of the Gulf of Mexico Dead Zone Jack E. Davis (bio) For fourteen weeks in the winter and early spring of 2016, snow and rain kept falling on the Midwestern states. There were a few dry days in between many wet ones, but the usual long spells failed to come. Weather trackers had never seen the Midwest escape drought for such an extended period. Not surprisingly, precipitation exceeded annual averages for much of the region. In April, eight inches of rain soaked northwestern Missouri, where no more than three were normal, and in the first two weeks of the month, snowfall in northern Ohio reached up to seventeen inches above average.1 Midwestern farmers welcomed the moistening of the soil, just as long as the rain stopped before the ground turned too muddy for planting. The rain stopped. By the first of May, the majority of the corn crop was in the ground, surpassing a five-year average, and soybeans were close behind. These were the region's principal cash crops. The growing season was off to a nice start. But what was good for farmers of the Midwest was bad for sea life down in the northern Gulf of Mexico, hundreds of miles from the growing fields. In June, a two-decker headline in Mother Jones warned that the Gulf "is about to experience a 'dead zone' the size of Connecticut," nearly 6,000 square miles. Typically, the seasonal dead [End Page 156] zone kept to Delaware dimensions, its length running the front of Louisiana, reaching toward Texas in one direction, Alabama in the other, and some 40 miles into the Gulf.2 Scientists discovered the Gulf of Mexico dead zone in the 1970s, as an annual summer event. Within a few years they tracked down its principal source to chemical fertilizer runoff from the Mississippi River drainage basin, which taps forty percent of the contiguous United States, a total of thirty–one states. The area includes the Midwest and most of the High Plains, America's agricultural heartland. Corn, the biggest crop in the region and a fertilizer hog, was the principal contributor to the Gulf's woes. In the twenty–first century, with the increased production of corn-based ethanol, scientists saw a spike in fertilizer use and in the size of the dead zone. From the beginning, the ethanol connection made interesting copy for the media. Federal assistance greatly expanded the additive's presence in the domestic fuel inventory, and scientists looking for answers to reducing the dead zone, operating on federal grants in many cases, were sobered by the eclipsing power of the marketplace. But there is an important backstory here that remains adrift from the news-generating narrative. Long before ethanol's ascendency, the dead zone came to life in postwar America and of age with the baby boom generation. A defining facet in the boomer experience was the changing culinary landscape, an overall distressing development for Americans and the Gulf together. The diet of the new generation spiraled away from nutritional goodness and took a fateful turn into rivers and streams in the direction of the Gulf. Ultimately, the diminishing physical health of Americans translated into the diminishing health of their backyard sea. ________ journalists came up with the name "dead zone" in the 1980s for what scientists were abstrusely calling hypoxic coastal waters. The oxygen level in such areas, some several hundred acres and others [End Page 157] several thousand square miles, periodically drops to a level too low to support marine life. The results are mass die offs of sea creatures, especially bottom dwellers. Behind the morbidity lies an excessive infusion of nutrients. The overloading stimulates phytoplankton blooms, and, eventually, all this new minuscule life begins to die and sink to the bottom, often with other decaying organic matter. Performing its custodial role in the ecosystem, bacteria steps in to break down the dead, generating carbon dioxide as it consumes massive quantities of oxygen, leaving sea creatures to suffocate. Dead zones are worldwide. Some are natural, others the fallout of human activities. The former have been around for time immemorial. Alabama's Mobile Bay...

Signature of postglacial colonization on contemporary genetic structure and diversity of Quadrula quadrula (Bivalvia: Unionidae)

Contemporary species distributions and geographic patterns of genetic structure largely reflect pre-historic events, often with subsequent alterations from human influences. The geographic genetic structure of a relatively common and widespread unionid species, Quadrula quadrula, was investigated to reconstruct its postglacial history. Hypotheses regarding colonization routes of Q. quadrula into the Great Lakes basin after the most recent glacial retreat were tested. Samples were collected from Q. quadrula at sites spanning hypothesized glacial refugia and postglacial expansion routes in the Mississippi River drainage, including the Ohio and Missouri rivers, and the Great Lakes. Broad-scale phylogeography and population structure were assessed by sequencing a fragment of the mitochondrial CO1 gene and genotyping eight microsatellites. Results of analyses showed marked differences among the Great Lakes, Mississippi River, and Ohio River drainages, and suggested colonization of the Great Lakes basin from a Mississippian source. Populations showed patterns of isolation by distance: geographic and genetic distances were significantly correlated among Great Lakes populations based on colonization through the Chicago–Illinois outlet, but not when following the Wabash–Maumee outlet. All evidence indicates that postglacial colonization of the Great Lakes basin occurred almost exclusively through the Chicago–Illinois outlet, with subsequent expansion into the lower Great Lakes.

Status of Lake Sturgeon (Acipenser fulvescensRafinesque 1817) in North America

Summary Lake Sturgeon is a potamodromous, fluvial-dependent species from the family Acipenseridae, and one of the largest freshwater fishes within its North American range extending to the Great lakes, Mississippi River, and Hudson Bay drainages. Like almost all other sturgeon species, Lake Sturgeon populations throughout its range suffered mass declines or extirpation in the late 1800s into the early 1900s, due to extensive overexploitation and habitat loss and alteration. However, Lake Sturgeon are still present in low to high densities throughout their native range due primarily to factors including: the species long life span and resiliency, the remote location of many northern populations, long-term pro-active management programs effectively controlling exploitation, improved habitat and water-quality conditions, and recovery programs that have been in effect since the late 1970s. Recovery programs initiated in the late 1970s are now just beginning to show signs of natural recruitment from populations re-built with stocked fish. Large sustainable recreational Lake Sturgeon fisheries with annual harvests of up to 45 000 kg and a commercial fishery with an annual harvest of up to 80 000 kg still exist and are maintained for Lake Sturgeon due primarily to rigid regulations, harvest controls, enforcement, and user involvement. The prognosis for the species is generally good, although habitat loss and maintaining public interest in the species management and recovery continue to be the greatest threats to local and regional populations. Hydropower development, especially in the northern part of the species’ range, is especially challenging due to the potential negative impact this type of development can have on a long migrating fish like Lake Sturgeon. Advances in understanding Lake Sturgeon life history, habitat requirements, and distribution within and among water systems has strongly indicated that dams and Lake Sturgeon can co-exist, if the correct planning and necessary mitigative techniques are employed at each site on a case-by-case basis.

Mapping Lake Sturgeon Spawning Habitat in the Upper Tennessee River using Side‐Scan Sonar

AbstractThe Lake Sturgeon Acipenser fulvescens is a fish species that was once dispersed widely throughout the Mississippi River drainage but was largely extirpated from the southern portions of its range by overfishing and habitat degradation. There is an ongoing restoration effort to reestablish the Lake Sturgeon to rivers of the southeastern United States. Reintroduced juvenile Lake Sturgeon now occupy several reservoirs separated from each other by hydroelectric dams along the upper Tennessee River. To complete their life history, Lake Sturgeon will migrate upriver from reservoir habitats to more lotic habitats and spawn over coarse rocky substrate, even in the tailwaters of impassable dams. Using low‐cost, consumer‐grade, side‐scan sonar and a GIS, we mapped the substrate of four tailwaters that may be future spawning locations for Lake Sturgeon. We used video imagery collected from random locations within the mapped areas to validate our digitization of sonar imagery. We calculated the area of four substrate classes displayed in the maps to evaluate that aspect of the suitability of each of the tailwaters for Lake Sturgeon spawning. The revised maps showed that the best spawning substrate (unembedded, coarse, rocky substrate, 6–25 cm in diameter) comprised 17.0–30.5% of the total area mapped at each tailwater, while the least suitable substrate class (fine sediment, <0.2 cm in diameter) comprised 6.2–30.7% of the mapped areas. Our results suggest that any future spawning events by Lake Sturgeon below each of these dams are likely to encounter some suitable spawning substrate patches, while management opportunities exist to supplement tailwater areas with suitable spawning substrate.Received March 11, 2016; accepted May 30, 2016 Published online August 31, 2016

Critical thermal maxima of juvenile alligator gar (Atractosteus spatula, Lacépède, 1803) from three Mississippi-drainage populations acclimated to three temperatures

Local adaptation may cause thermal tolerance to vary between nearby but distinct populations of a species. During the summer of 2013, alligator gar Atractosteus spatula spawned from broodstock collected from three populations within the Mississippi River drainage separated by a 5° latitudinal gradient were acclimated to three temperatures (25, 30, and 35°C). Ten fish from each population were acclimated at each temperature. CTMax was determined at each temperature for each population, using five fish for each population-acclimation temperature pairing. CTMax for each population-acclimation temperature pairing was compared using two-factor anova. CTMax increased significantly with acclimation temperature (F2,40 = 600.5, P < 0.001) but population had no significant effect (F2,40 = 1.882, P = 0.166). Temperature tolerance appears to be consistent across populations of alligator gar, with no evidence of local adaptation.

Acoustical deterrence of Silver Carp (Hypophthalmichthys molitrix)

The invasive Silver Carp (Hypophthalmichthys molitrix) dominate large regions of the Mississippi River drainage and continue to expand their range northward threatening the Laurentian Great Lakes. This study found that complex broadband sound (0–10 kHz) is effective in altering the behavior of Silver Carp with implications for deterrent barriers or potential control measures (e.g., herding fish into nets). The phonotaxic response of Silver Carp was investigated using controlled experiments in outdoor concrete ponds (10 × 4.9 × 1.2 m). Pure tones (500–2000 Hz) and complex sound (underwater field recordings of outboard motors) were broadcast using underwater speakers. Silver Carp always reacted to the complex sounds by exhibiting negative phonotaxis to the sound source and by alternating speaker location, Silver Carp could be directed consistently, up to 37 consecutive times, to opposite ends of the large outdoor pond. However, fish habituated quickly to pure tones, reacting to only approximately 5 % of these presentations and never showed more than two consecutive responses. Previous studies have demonstrated the success of sound barriers in preventing Silver Carp movement using pure tones and this research suggests that a complex sound stimulus would be an even more effective deterrent.

Next-generation genomic shotgun sequencing indicates greater genetic variability in the mitochondria of Hypophthalmichthys molitrix relative to H. nobilis from the Mississippi River, USA and provides tools for research and detection

We characterized variation within the mitochondrial genomes of the invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) from the Mississippi River drainage by mapping our Next-Generation sequences to their publicly available genomes. Variant detection resulted in 338 single-nucleotide polymorphisms for H. molitrix and 39 for H. nobilis. The much greater genetic variation in H. molitrix mitochondria relative to H. nobilis may be indicative of a greater North American female effective population size of the former. When variation was quantified by gene, many tRNA loci appear to have little or no variability based on our results whereas protein-coding regions were more frequently polymorphic. These results provide biologists with additional regions of DNA to be used as markers to study the invasion dynamics of these species.

Forecasting changes in water quality in rivers associated with growing biofuels in the Arkansas‐White‐Red river drainage, USA

AbstractExcess nutrients from agriculture in the Mississippi River drainage, USA have degraded water quality in freshwaters and contributed to anoxic conditions in downstream estuaries. Consequently, water quality is a significant concern associated with conversion of lands to bioenergy production. This study focused on the Arkansas‐White‐Red river basin (AWR), one of five major river basins draining to the Mississippi River. The AWR has a strong precipitation gradient from east to west, and advanced cellulosic feedstocks are projected to become economically feasible within normal‐to‐wet areas of the region. In this study, we used large‐scale watershed modeling to identify areas along this precipitation gradient with potential for improving water quality. We compared simulated water quality in rivers draining projected future landscapes with and without cellulosic bioenergy for two future years, 2022 and 2030 with an assumed farmgate price of $50 per dry ton. Changes in simulated water quantity and quality under future bioenergy scenarios varied among subbasins and years. Median water yield, nutrient loadings, and sediment yield decreased by 2030. Median concentrations of nutrients also decreased, but suspended sediment, which is influenced by decreased flow and in‐stream processes, increased. Spatially, decreased loadings prevailed in the transitional ecotone between 97° and 100° longitude, where switchgrass, Panicum virgatum L., is projected to compete against alternative crops and land uses at $50 per dry ton. We conclude that this region contains areas that hold promise for sustainable bioenergy production in terms of both economic feasibility and water quality protection.

Phylogeography ofRhinichthys cataractae(Teleostei: Cyprinidae): pre-glacial colonization across the Continental Divide and Pleistocene diversification within the Rio Grande drainage

The longnose dace, Rhinichthys cataractae, is a primary freshwater fish inhabiting riffle habitats in small headwater rivers and streams across the North American continent, including drainages east and west of the Continental Divide. The mitochondrially encoded cytochrome b gene (1140 bp) and 2298–2346 bp of the nuclear-encoded genes S7 and RAG1 were obtained from 87 individuals of R. cataractae (collected from 17 sites throughout its range) and from several close relatives. Phylogenetic analyses recovered a monophyletic R. cataractae species-group that contained Rhinichthys evermanni, Rhinichthys sp. ‘Millicoma dace’, and a non-exclusive R. cataractae. Within the R. cataractae species-group, two well-supported lineages were identified, including a western lineage (containing R. evermanni, R. sp. ‘Millicoma dace’ and individuals of R. cataractae from Pacific slope drainages) and an eastern lineage (containing individuals of R. cataractae from Arctic, Atlantic, and Gulf slope drainages). Within the eastern lineage of R. cataractae, two well-supported groups were recovered: a south-eastern group, containing individuals from the Atlantic slope, southern tributaries to the Mississippi River, and the Rio Grande drainage; and a north-eastern group, containing individuals from the Arctic slope and northern tributaries to the Mississippi River. Estimates of the timing of divergence within the R. cataractae species-group, combined with ancestral area-reconstruction methods, indicate a separation between the eastern and western lineages during the Pliocene to early-Pleistocene, with a direction of colonization from the west of the Continental Divide eastward. Within the southern portion of its range, R. cataractae likely entered the Rio Grande drainage during the Pleistocene via stream capture events between the Arkansas River (Mississippi River drainage) and headwaters of the Rio Grande. A close relationship between populations of R. cataractae in the Rio Grande drainage and the adjacent Canadian River (Mississippi River drainage) is consistent with hypothesized stream capture events between the Pecos (Rio Grande drainage) and Canadian rivers during the late-Pleistocene. The population of R. cataractae in the lower Rio Grande may have become separated from other populations in the Rio Grande drainage (upper Rio Grande and Pecos River) and Canadian River during the late-Pleistocene, well before initiation of recent and significant anthropogenic disturbance within the Rio Grande drainage. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 317–333.

U-Pb ages of detrital zircons from the Tertiary Mississippi River Delta in central Louisiana: Insights into sediment provenance

The sources of the tremendous amount of Cenozoic siliciclastic sediment deposited in the Gulf of Mexico region remain debated because of a lack of definitive provenance-identifying characteristics. In an effort to build on prior provenance analysis, we present 101–160 single-grain detrital zircon U-Pb ages for each of 10 outcrop samples from Upper Paleocene to Upper Miocene sandstones from a ∼10,000 km 2 swath of central Louisiana corresponding to the ancient Mississippi River Delta, the largest Cenozoic depocenter in the northern Gulf of Mexico region. Sample depositional age control is derived from biostratigraphy and/or regional lithostratigraphic correlation. U-Pb ages in each of the samples range from Cenozoic to Archean, and correspond to the ages of various geologic terranes that underlie the modern Mississippi River drainage basin. However, the prominence of various age distributions changes systematically through the Cenozoic stratigraphy, and pronounced shifts in the abundance of certain age distributions between stratal packages appear to be correlated to shifts in heavy mineral assemblages recorded across the northern Gulf of Mexico coastal plain. Comparison of coastal plain detrital zircon age distributions to age distributions from North American sedimentary cover and the ages of major North American crystalline basement rocks, aided by a sediment mixing model, illuminates the provenance of each of the stratal packages, and suggests that (1) the Mississippi River catchment has resembled its present configuration, at least in the east-west dimension, for much, if not all, of the Cenozoic, and (2) depositional episodes on the Louisiana coastal plain characterized by high sediment supply also corresponded to high proportions of sediment sourcing from the Sevier-Laramide region of the interior western United States. Sediment supply to the Louisiana coastal plain by the paleo–Mississippi River has generally been high during the Cenozoic, except for an anomalous low during the Middle Eocene, when the abundance of sediment derived from the Rocky Mountain region decreased dramatically relative to sediment derived from the Appalachian region.

Phylogeography and Genetic Variability of the Freshwater Mussels (Bivalvia: Unionidae) Ellipse,Venustaconcha ellipsiformis(Conrad 1836), and Bleeding Tooth,V. Pleasii(Marsh 1891)

Abstract: Following the retreat of the last Pleistocene glaciers ∼10,000 years before present, aquatic organisms re-colonized previously uninhabitable regions from various glacial refuges. Glaciations had major impacts shaping patterns of genetic diversity and population structure for organisms throughout North America. Knowledge of genetic population structure is critical for successful conservation programs involving an increasingly threatened freshwater fauna. Due to variations in life history and ecology, species-specific planning may be the most effective method for preserving rare or threatened species. The Ellipse mussel (Venustaconcha ellipsiformis) and its congener the Bleeding Tooth mussel (V. pleasii) are species of conservation concern through much of their respective ranges in the Midwestern United States. The Ellipse is found in small to medium rivers from the northern Ozark highlands north to the Upper Mississippi River drainage and into tributaries of Lake Michigan and Lake Huron. Mitochon...