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At least 1,387 records · Page 77Linked to original sources

USGS2023

White perch health relative to urbanization and habitat degradation in Chesapeake Bay tributaries. II. Hepatic and splenic macrophage aggregates

Macrophage aggregate (MA) abundance in fish is a useful general biomarker of contaminant exposures and environmental stress. Hepatic and splenic MAs were evaluated in semi-anadromous white perch Morone americana (Gmelin, 1789) from the urbanized Severn River (S) and the more rural Choptank River (C), Chesapeake Bay. Fish were collected from different sites in the annual migratory circuit in each river that corresponded to active spawning in late winter-early spring, summer regenerating, autumn developing, and winter spawning-capable phases. An age-associated progressive increase in the total volume of MAs (MAV) was evident in the liver and spleen. Mean hepatic MAV (range in seasonal means, C: 6.4-23.1 mm 3 ; S: 15.7-48.7 mm 3 ) and mean splenic MAV (C: 7.3-12.6 mm 3 ; S: 16.0-33.0 mm 3 ) differed significantly among seasons and were significantly greater in females and in Severn River fish. Age and river were the most influential factors, suggesting that increased MAV in Severn River fish resulted from chronic exposures to higher concentrations of environmental contaminants. Hepatic MAV was directly related to the relative volume of copper granules in the liver. Less influential factors on splenic MAV included fish condition, trematode infections, and granulomas, indicating possible functional differences in MAs by organ. While organ volumes were strongly linked to gonadosomatic index (GSI) and reproductive phase, the reason for seasonal differences in MAV was less clear. Water temperature, salinity, and dissolved oxygen were not significantly related to MAV, and indicators of reproductive phase (hepatosomatic index and GSI) were significant but less important in explaining variation in MAV.

Chesapeake Bay watershed↗

USGS2023

High female desert tortoise mortality in the western Sonoran Desert during California’s epic 2012–2016 drought

We conducted population surveys for desert tortoises Gopherus agassizii at 2 nearby sites in the western Sonoran Desert of California, USA, from 2015-2018, during the driest ongoing 22 yr period (2000-2021) in the southwestern USA in over 1200 yr. We hypothesized that drought-induced mortality would be female-biased due to water and energy losses attributable to egg production during protracted periods of resource limitation. At the higher-elevation, cooler, wetter Cottonwood site from 2015-2016, the sex ratio of live adult tortoises was biased toward males and the sex ratio of tortoises estimated to have died during the intensified drought conditions from 2012-2016 was essentially even. At the lower-elevation, warmer, drier Orocopia site from 2017-2018, the sex ratio of live adult tortoises was biased toward males and the sex ratio of tortoises with estimated times of death from 2012-2016 was biased toward females. High female mortality at the Orocopia site may have resulted from the interaction of drought effects and the bet-hedging reproductive strategy of tortoises wherein they continue to produce clutches of eggs in drought years. Annual reproductive output results in an estimated loss of up to 13.5% of female tortoise body mass including over 0.20 l of water. Combined with dehydration during severe droughts, these losses may compromise their ability to survive droughts lasting more than 2 yr. The low tortoise density and high mortality of females observed may reflect reduced survival of tortoises near the southern edge of their range due to climate change, including protracted and intensified droughts.

Western Sonoran Desert↗

USGS2012

Bioenergetics model for estimating food requirements of female Pacific walruses ( Odobenus rosmarus divergens )

Pacific walruses Odobenus rosmarus divergens use sea ice as a platform for resting, nursing, and accessing extensive benthic foraging grounds. The extent of summer sea ice in the Chukchi Sea has decreased substantially in recent decades, causing walruses to alter habitat use and activity patterns which could affect their energy requirements. We developed a bioenergetics model to estimate caloric demand of female walruses, accounting for maintenance, growth, activity (active in-water and hauled-out resting), molt, and reproductive costs. Estimates for non-reproductive females 0–12 yr old (65−810 kg) ranged from 16359 to 68960 kcal d −1 (74−257 kcal d −1 kg −1 ) for years with readily available sea ice for which we assumed animals spent 83% of their time in water. This translated into the energy content of 3200–5960 clams per day, equivalent to 7–8% and 14–9% of body mass per day for 5–12 and 2–4 yr olds, respectively. Estimated consumption rates of 12 yr old females were minimally affected by pregnancy, but lactation had a large impact, increasing consumption rates to 15% of body mass per day. Increasing the proportion of time in water to 93%, as might happen if walruses were required to spend more time foraging during ice-free periods, increased daily caloric demand by 6–7% for non-lactating females. We provide the first bioenergetics-based estimates of energy requirements for walruses and a first step towards establishing bioenergetic linkages between demography and prey requirements that can ultimately be used in predicting this population’s response to environmental change.

Marine Ecology Progress Series↗

USGS2024

Photogrammetry-based body condition for monitoring an Arctic marine mammal experiencing habitat loss

Monitoring animal body condition can provide insight on population responses to environmental change. Pacific walruses ( Odobenus rosmarus divergens ) are experiencing loss of their sea ice habitat which has decreased the time that females spend foraging during a critical period of pregnancy and lactation. Here we investigate the potential for body condition to track demographic change and be monitored via two-dimensional aerial imagery by (1) examining whether walrus somatic growth and body mass data tracked estimated historic demographic changes, (2) collecting morphometric and body mass data and aerial imagery of walruses in human care to determine if sex, age group, and body size and condition can be determined from imagery, and (3) examining aerial imagery from a large coastal haulout used primarily by females and young to estimate potential sample sizes of measurable walruses. Body mass and growth in body length decreased between the last 1970s and early 1980s concurrent with a period when the population apparently approached carrying capacity and subsequently declined. Measures from aerial imagery (1) accurately distinguished reproductive age females from subadults and adult males and (2) enabled body mass estimates with 6-7% error using either areal footprint or a combination of length and width. We found a mean of 216 ± 77 walruses appropriately positioned for measurement from aerial surveys of the haulout enabling measurements of ≥7000 individuals annually via repeated daily imagery. Our results suggest that body mass of reproductive age females and growth of dependent young may be useful indicators to augment monitoring of the Pacific walrus population and can be achieved via non-invasive aerial imagery collections.

Alaska↗

USGS2007

Characteristics of vesicomyid clams and their environment at the Blake Ridge cold seep, South Carolina, USA

Spatial distributions and patchiness of dominant megafaunal invertebrates in deep-sea seep environments may indicate heterogeneities in the flux of reduced chemical compounds. At the Blake Ridge seep off South Carolina, USA, the invertebrate assemblage includes dense populations of live vesicomyid clams (an undescribed species) as well as extensive clam shell beds (i.e. dead clams). In the present study, we characterized clam parameters (density, size-frequency distribution, reproductive condition) in relation to sulfur chemistry (sulfide and sulfate concentrations and isotopic compositions, pyrite and elemental sulfur concentrations) and other sedimentary metrics (grain size, organic content). For clams >5 mm, clam density was highest where the total dissolved sulfide concentration at 10 cm depth (ΣH 2 S 10cm ) was 0.4 to 1.1 mmol l –1 ; juvenile clams (<5 mm) were most dense where ΣH 2 S 10cm was lowest. Clams were reproductively capable across a broad range of ΣH 2 S 10cm (0.1 to 6.4 mmol l –1 ), and females in the sampled populations displayed asynchronous gametogenesis. Sulfide concentrations in porewaters at the shell–sediment interface of cores from shell beds were high, 3.3 to 12.1 mmol l –1 , compared to <1 mmol l –1 sulfide concentrations at the clam–sediment interface in live clam beds. Concentration profiles for sulfide and sulfate in shell beds were typical of those expected where there is active microbial sulfate reduction. In clam beds, profiles of sulfide and sulfate concentrations were also consistent with rapid uptake of sulfide by the clams. Sulfate in shell beds was systematically enriched in 34 S relative to that in clam beds due to microbial fractionation during sulfate reduction, but in clam beds, sulfate δ 34 S matched that of seawater (~20‰). Residual sulfide values in clam and shell beds were correspondingly depleted in 34 S. Based on porewater sulfide concentrations in shell beds at the time of sampling, we suggest that clam mortality may have been due to an abrupt increase in sulfide concentration and sulfide toxicity, but other alternatives cannot be eliminated.

California↗

USGS2006

Size dimorphism, molt status, and body mass variation of prairie falcons nesting in the Snake River Birds of Prey National Conservation Area

Thirty-nine bald eagles found sick or dead in 13 States during 1969 and 1970 were analyzed for pesticide residues. Residues of DDE, dieldrin, polychlorinated biphenyls (PCB's), and mercury were detected in all bald eagle carcasses; DDD residues were detected in 38; DDT, heptachlor epoxide, and dichlorobenzophenone (DCBP) were detected less frequently. Six eagles contained possible lethal levels of dieldrin in the brain, and one contained a lethal concentration of DDE (385 ppm) in the brain together with 235 ppm of PCB's. Autopsy revealed that 18 bald eagles were illegally shot; other causes of death were impact injuries, electrocution, emaciation, and infectious diseases.

Journal of Raptor Research↗

USGS2017

No substitute for survival: Perturbation analyses using a Golden Eagle population model reveal limits to managing for take

Conserving populations of long-lived birds of prey, characterized by a slow life-history (e.g., high survival and low reproductive output), requires a thorough understanding of how variation in their vital rates differentially affects population growth. Stochastic population modeling provides a framework for exploring variation in complex life histories to better understand how environmental and demographic variation within individual vital rates affects population dynamics. Specifically, we used life-stage simulation analysis (LSA) to identify those life-history characteristics that most affect population growth and are amenable to management actions. The Golden Eagle ( Aquila chrysaetos ) is a wide-ranging raptor of conservation concern, which has been adopted as a focal species for conservation planning. Golden Eagle population trends in western North America currently appear stable. Yet an expanding human footprint that may increase mortality stimulated our investigation into the ability of populations to sustain reduced survival. We fit mixed-effects models to published estimates of vital rates to estimate the mean and process variation of productivity (young fledged per pair) and survival for use in a LSA framework. As expected, breeding adult survival had the greatest relative effect on population growth, though productivity explained the most variation in growth. Based on perturbation analyses, we demonstrate that even minor reductions in breeding adult survival (<4.5%) caused otherwise stable populations to decline. Despite its importance, precise estimates of spatial and temporal variation in breeding adult survival are poorly documented. Importantly, we found that the ability for increases in reproductive output to compensate for decreased survival was very limited. To maintain stable populations, declines in survival >4% required increases in productivity that generally exceed the evolutionary potential for Golden Eagles. Our findings support the current U.S. Fish and Wildlife conservation strategy which mitigates eagle “take” via efforts to reduce mortality elsewhere.

Journal of Raptor Research↗

USGS2023

Patterns of water use by raptors in the southern Great Plains

There is a paucity of data evaluating water use by raptors. Although raptors are believed to satisfy their water requirements through metabolic processes, they are known to experience reduced reproductive success during periods of drought, and there is evidence of water being important for site occupancy in arid landscapes. Several raptor species have a seasonal or year-round presence in west Texas, a drought-prone, semi-arid region of the Southern Great Plains. We examined species-specific timing of free water use by common raptors in this region, and examined environmental conditions associated with water use. We collected 4549 camera trap-days of data across 4 yr at ten human-made water sources placed for cattle. We recorded 14 species of raptors among the 1177 detections of raptors visiting water sources; of these, 1084 raptors (92.1%) perched at tanks, and 93 (7.1%) flew by tanks. Of the raptors that perched at tanks, 63.5% drank and 20.8% both bathed and drank. Barn Owls ( Tyto alba ; 35.6%), Swainson's Hawks ( Buteo swainsoni ; 32.0%), and Northern Harriers ( Circus hudsonius ; 21.0%) were the predominate species detected. Visits by Northern Harriers and Swainson's Hawks increased with increasing temperature and decreasing precipitation. Visits by Barn Owls increased with increasing drought severity. Further, detections per 100 trap-days increased substantively across our 4-yr study period during which the region experienced one of the worst droughts on record. Although our data do not demonstrate these raptors require free water, they do reveal an increasing use of free water in relation to hotter and drier conditions. How this influences survival and reproduction remains unknown, but may become a pressing question because current climate models predict the study area will experience increases in heat and decreases in precipitation.

Journal of Raptor Research↗

USGS2025

Rare milkvetch (Astragalus) persistence at a utility-scale solar energy facility in the Mojave Desert

Utility-scale solar energy (USSE) development is driving the projected growth in global renewable energy capacity but comes with environmental tradeoffs. New, alternative construction methods are promoted to minimize impacts to soils, vegetation, and hydrology; however, the disturbance created by these methods requires further investigation. We evaluated the population of a rare annual species, threecorner milkvetch ( Astragalus geyeri var. triquetrus ), at the Gemini Solar Project in the Mojave Desert, USA, two years after construction. Gemini was required to minimize disturbance in the threecorner milkvetch habitat, providing a unique opportunity to study the plant population and life history characteristics of a rare plant species under novel construction methods. Our objectives were to compare plant population characteristics of threecorner milkvetch inside and outside the Gemini footprint and in different photovoltaic (PV) panel microsites (interspace, panel dripline, under panel). We hypothesized that 1) threecorner milkvetch would have lower survival, reproduction, and growth, and a later phenology, inside compared to outside the facility, and 2) that these negative effects on plant demography and phenology would intensify with increasing proximity to photovoltaic panels in the solar array due to an increasing effect of disturbance and reduction of light and water availability. The results of this 1-year study during a favorable year of rainfall demonstrate the persistence of a rare Mojave annual plant species within an altered environment at a USSE facility. We found that threecorner milkvetch had an earlier phenology, grew larger, and had a higher fecundity at Gemini compared to plants off-site. Survivorship between the two populations, however, was not significantly different. Although growth and reproductive metrics were not correlated with distance to panel, minimal threecorner milkvetch emergence occurred directly under the PV panels and along their driplines, indicating a potential loss of suitable habitat if this pattern becomes more widespread in space or through time. Novel construction techniques for USSE could be considered moving forward to minimize impact on aboveground vegetation and maintain viable seed banks. The results of this study can assist land managers in making decisions about USSE development as the demand grows.

Nevada↗

USGS2021

Variability of lipids and fatty acids in Pacific walrus blubber

The variability of lipid content and fatty acid (FA) composition across blubber depth and body sites are important considerations for condition and diet studies of marine mammals. We investigated lipid and FA variability among inner and outer blubber layers, three body sites, four study years, and lactation status of adult female Pacific walruses ( Odobenus rosmarus divergens ) using blubber samples collected from subsistence-harvested walruses in spring 2007–2010. Percent lipid content did not differ between the inner and outer blubber layers at the rump, flank, or sternum of walruses. Although FA composition differed between the inner and outer blubber layers, the difference was consistent across body sites, and differences between layers within individual FAs were small (<2%). Lipid content at the sternum of lactating females was 6% higher than non-lactating females, consistent with known variation in body condition among these reproductive classes. Across study years, lipid content varied 18% and individual FAs varied 6%, likely reflecting population-level interannual variability in energy budgets and small differences in diet among years. Consistency in blubber lipid content across blubber depth and body sites and detectable variation in blubber lipid content among reproductive classes and years suggests the potential for lipid content to be a useful indicator of walrus body condition. In addition to information on condition, FA composition of blubber samples could potentially provide insights into changes in walrus diet that may be expected to occur from changes in their access to prey resources resulting from continued sea ice loss.

Frontiers in Marine Science↗

USGS2024

Fish health altered by contaminants and low water temperatures compounded by prolonged regional drought in the Lower Colorado River Basin, USA

The goal of this study was to assess health of male Common Carp (carp, Cyprinus carpio ) at four sites with a wide range in environmental organic contaminant (EOC) concentrations and water temperatures in Lake Mead National Recreation Area NV/AZ, US, and the potential influence of regional drought. Histological and reproductive biomarkers were measured in 17–30 carp at four sites and 130 EOCs in water per site were analyzed using passive samplers in 2010. Wide ranges among sites were noted in total EOC concentrations (>10Xs) and water temperature/degree days (10Xs). In 2007/08, total polychlorinated biphenyls (tPCBs) in fish whole bodies from Willow Beach (WB) in the free-flowing Colorado River below Hoover Dam were clearly higher than at the other sites. This was most likely due to longer exposures in colder water (12–14 °C) and fish there having the longest lifespan (up to 54 years) for carp reported in the Colorado River Basin. Calculated estrogenicity in water exceeded long-term, environmentally safe criteria of 0.1–0.4 ng/L by one to three orders of magnitude at all sites except the reference site. Low ecological screening values for four contaminants of emerging concern (CEC) in water were exceeded for one CEC in the reference site, two in WB and Las Vegas Bay and three in the most contaminated site LVW. Fish health biomarkers in WB carp had 25% lower liver glycogen, 10Xs higher testicular pigmented cell aggregates and higher sperm abnormalities than the reference site. Sperm from LVW fish also had significantly higher fragmentation of DNA, lower motility and testis had lower percent of spermatozoa, all of which can impair reproduction. Projections from a 3D water quality model performed for WB showed that EOC concentrations due to prolonged regional drought and reduced water levels could increase as high as 135%. Water temperatures by late 21st century are predicted to rise between 0.7 and 2.1 °C that could increase eutrophication, algal blooms, spread disease and decrease dissolved oxygen over 5%.

Arizona, Nevada↗

USGS2021

Non-native Pond Sliders cause long-term decline of native Sonora Mud Turtles: A 33-year before-after study in an undisturbed natural environment

Using a before-after study design in a stable, largely undisturbed pond habitat and a dataset spanning 33 years, we document and describe the decline of native Sonora mud turtles (Kinosternon sonoriense) after the introduction of non-native pond sliders (Trachemys scripta). The Sonora mud turtle population in Montezuma Well in central Arizona, USA, declined to less than 25% of previous numbers, from 372 ± 64 in 1983 to 80 ± 21 in 2011. We trapped and removed the non-native turtles between 2007 and 2012 and after removal of the non-natives, the Sonora mud turtle population increased to 139 ± 34 in 2015. The native turtles also significantly increased basking activity after removal of the non-natives, paralleling results of small-scale mesocosm studies showing that pond sliders negatively affect basking rates of native turtle species. Reproductive rates of female Sonora mud turtles (numbers of females with eggs) were lower during the period of peak non-native turtle abundance, and increased after removal of the non-native turtles. We hypothesize that the reduction in effective reproductive rate links interference competition (reflected in reduced basking rates) to the long-term decline of the native mud turtles. Results from the undisturbed natural system of Montezuma Well provide new insights on the overall occurrence, magnitude, and mechanisms of negative effects of introduced pond sliders on native turtle species. Sonora mud turtles are very different in their morphology, behavior, and ecology from pond sliders and from native turtles in other studies, suggesting that impacts of non-native pond sliders are more pervasive than previously thought.

Aquatic Invasions↗

USGS2014

GIS-based rapid-assessment of bighead carp Hypophthalmichthys nobilis (Richardson, 1845) suitability in reservoirs

Broad-scale niche models are good for examining the potential for invasive species occurrences, but can fall short in providing managers with site-specific locations for monitoring. Using Oklahoma as an example, where invasive bighead carp (Hypophthalmichthys nobilis) are established in certain reservoirs, but predicted to be widely distributed based on broad-scale niche models, we cast bighead carp reproductive ecology in a site-specific geospatial framework to determine their potential establishment in additional reservoirs. Because bighead carp require large, long free-flowing rivers with suitable hydrology for reproduction but can persist in reservoirs, we considered reservoir tributaries with mean annual daily discharge ≥8.5 cubic meters per second (m3 /s) and quantified the length of their unimpeded portions. In contrast to published broad-scale niche models that identified nearly the entire state as susceptible to invasion, our site-specific models showed that few reservoirs in Oklahoma (N = 9) were suitable for bighead carp establishment. Moreover, this method was rapid and identified sites that could be prioritized for increased study or scrutiny. Our results highlight the importance of considering the environmental characteristics of individual sites, which is often the level at which management efforts are implemented when assessing susceptibility to invasion.

Oklahoma↗

USGS2019

Ligation and division of ductus deferens does not produce long term sterility in most bighead carp or grass carp

Invading species are most easily eradicated or controlled if detected early and rapid action can be taken, but locating and eradicating small numbers of aquatic invaders is extremely difficult. Bighead carp ( Hypophthalmichthys nobilis ) and grass carp ( Ctenopharyngodon idella ) are Asian cyprinids that have been widely introduced and are considered undesirable and detrimental invasive species in many parts of their introduced range. The relatively novel “Judas fish” technique is used to locate aggregations of fish in the wild by strategically releasing individuals equipped with surgically implanted transmitters. However, releasing Judas fish that are capable of reproducing is problematic because it could add to the invasion problem by contributing to recruitment if not recaptured. We thus tested whether surgical ligation and division of the ductus deferens could effectively sterilize adult diploid bighead and grass carp. If effective, surgical sterilization would result in a superior Judas fish by maintaining the reproductive motivation derived from intact gonads while blocking the reproductive potential. This technique was initially successful, but ultimately most individuals were able to recanalize the surgically-severed ducts and produce milt, and were thus potentially able to reproduce during the following spawning season. Thus, ligation and division of the ductus deferens does not seem to be a viable procedure to sterilize bighead carp or grass carp for deployment as Judas fish where long term sterility of the fish is paramount in importance.

Missouri↗

USGS2007

Potential strategies for recovery of lake whitefish and lake herring stocks in eastern Lake Erie

Lake Erie sustained large populations of ciscoes ( Salmonidae : Coregoninae ) 120 years ago. By the end of the 19 th century, abundance of lake whitefish ( Coregonus clupeaformis ) had declined drastically. By 1925, the lake herring (a cisco) population (Coregonus artedii) had collapsed, although a limited lake herring fishery persisted in the eastern basin until the 1950s. In the latter part of the 20 th century, the composition of the fish community changed as oligotrophication proceeded. Since 1984, a limited recovery of lake whitefish has occurred, however no recovery was evident for lake herring. Current ecological conditions in Lake Erie probably will not inhibit recovery of the coregonine species. Recovery of walleye ( Sander vitreus ) and efforts to rehabilitate the native lake trout ( Salvelinus namaycush ) in Lake Erie will probably assist recovery because these piscivores reduce populations of alewife ( Alosa psuedoharengus ) and rainbow smelt ( Osmerus mordax ), which inhibit reproductive success of coregonines. Although there are considerable spawning substrates available to coregonine species in eastern Lake Erie, eggs and fry would probably be displaced by storm surge from most shoals. Site selection for stocking or seeding of eggs should consider the reproductive life cycle of the stocked fish and suitable protection from storm events. Two potential sites in the eastern basin have been identified. Recommended management procedures, including commercial fisheries, are suggested to assist in recovery. Stocking in the eastern basin of Lake Erie is recommended for both species, as conditions are adequate and the native spawning population in the eastern basin is low. For lake herring, consideration should be given to match ecophenotypes as much as possible. Egg seeding is recommended. Egg seeding of lake whitefish should be considered initially, with fingerling or yearling stocking suggested if unsuccessful. Spawning stocks of whitefish in the western basin of Lake Erie could be utilized.

Journal of Great Lakes Research↗

USGS2007

Egg thiamine status of Lake Ontario salmonines 1995-2004 with emphasis on lake trout

Alewives (Alosa pseudoharengus), the major prey fish for Lake Ontario, contain thiaminase. They are associated with development of a thiamine deficiency in salmonines which greatly increases the potential for developing an early mortality syndrome (EMS). To assess the possible effects of thiamine deficiency on salmonine reproduction we measured egg thiamine concentrations for five species of Lake Ontario salmonines. From this we estimated the proportion of families susceptible to EMS based on whether they were below the ED20, the egg thiamine concentration associated with 20% mortality due to EMS. The ED20s were 1.52, 2.63, and 2.99 nmol/g egg for Chinook salmon (Oncorhynchus tshawytscha), lake trout (Salvelinus namaycush), and coho salmon (Oncorhynchus kisutch), respectively. Based on the proportion of fish having egg thiamine concentrations falling below the ED20, the risk of developing EMS in Lake Ontario was highest for lake trout, followed by coho (O. kisutch), and Chinook salmon, with the least risk for rainbow trout (O. mykiss). For lake trout from western Lake Ontario, mean egg thiamine concentration showed significant annual variability during 1994 to 2003, when the proportion of lake trout at risk of developing EMS based on ED20 ranged between 77 and 100%. Variation in the annual mean egg thiamine concentration for western Lake Ontario lake trout was positively related (p < 0.001, r2 = 0.94) with indices of annual adult alewife biomass. While suggesting the possible involvement of density-dependent changes in alewives, the changes are small relative to egg thiamine concentrations when alewife are not part of the diet and are of insufficient magnitude to allow for natural reproduction by lake trout.

Journal of Great Lakes Research↗

USGS2009

Differential phytosociological interactions involving male and female atriplex bonnevillensis

Wind-pollinated dioecious plants often exhibit spatial segregation of the sexes. This partial niche separation has most often been explored using abiotic niche axes. However, if the sexes are truly separated in space, then they are apt to encounter different plant species that may heavily affect growth and reproduction. Also, to the extent that their niches differ, the sexes may respond differently to the same co-occurring species. Here we examine interspecific interactions that influence male and female reproductive potential in Atriplex bonnevillensis. Using Emlen's interaction assessment, a technique which assesses species interactions based on cover classes, we show that Salsola species compete significantly with females but not males, while Halogeton glomeratus competes with males but not females. The effect of competition only became apparent when we corrected for site-specific fertility. These results imply that differential competition must be considered when studying dioecious plants that display spatial segregation of the sexes.

Western North American Naturalist↗

USGS2014

Sylphella puccoon gen. n., sp. n. and two additional new species of aquatic oligochaetes (Lumbriculidae, Clitellata) from poorly-known lotic habitats in North Carolina (USA)

Three new species of Lumbriculidae were collected from floodplain seeps and small streams in southeastern North America. Some of these habitats are naturally acidic. Sylphella puccoon gen. n., sp. n. has prosoporous male ducts in X-XI, and spermathecae in XII-XIII. Muscular, spherical atrial ampullae and acuminate penial sheaths distinguish this monotypic new genus from other lumbriculid genera having similar arrangements of reproductive organs. Cookidrilus pocosinus sp. n. resembles its two subterranean, Palearctic congeners in the arrangement of reproductive organs, but is easily distinguished by the position of the spermathecal pores in front of the chaetae in X-XIII. Stylodrilus coreyi sp. n. differs from congeners having simple-pointed chaetae and elongate atria primarily by the structure of the male duct and the large clusters of prostate cells. Streams and wetlands of Southeastern USA have a remarkably high diversity of endemic lumbriculids, and these poorly-known invertebrates should be considered in conservation efforts.

North Carolina↗