Ecoregions In Texas Research Articles

Effects of release strategy, source population, and age on reintroduced scaled quail reproduction

AbstractTranslocation is one strategy to reestablish populations of scaled quail (Callipepla squamata). Initial reproductive success post‐translocation is important for establishing short‐lived species such as quail, but factors influencing reproductive success are poorly understood. We evaluated the effect of source population and variation in delayed release strategy (1−9 weeks) on nest initiation and nest survival of wild‐caught, translocated scaled quail. We trapped and translocated scaled quail in 2016–2017 from source populations in the Edwards Plateau and Rolling Plains ecoregions of Texas, USA, to a large contiguous (>40,000 ha) release site in Knox County, Texas. We used a multi‐state mark‐recapture model with state uncertainty to test for effects of release treatment, source population, age, release location, and year on nest initiation and survival. Increased length of holding time decreased re‐nesting effort. Yearlings were more likely to initiate nests than adults and the probability of re‐nesting was lower during the year with drought conditions. There was no effect of source population on any of the parameters we evaluated. Future scaled quail reintroduction efforts may benefit from prioritizing translocation of yearlings and conducting translocations when drought conditions are not forecasted.

Imidacloprid exposure is detectable in over one third of wild bird samples from diverse Texas ecoregions

Avian decline is occurring globally with neonicotinoid insecticides posed as a potentially contributing factor. Birds can be exposed to neonicotinoids through coated seeds, soil, water, and insects, and experimentally exposed birds show varied adverse effects including mortality and disruption of immune, reproductive, and migration physiology. However, few studies have characterized exposure in wild bird communities over time. We hypothesized that neonicotinoid exposure would vary temporally and based on avian ecological traits. Birds were banded and blood sampled at eight non-agricultural sites across four Texas counties. Plasma from 55 species across 17 avian families was analyzed for the presence of 7 neonicotinoids using high performance liquid chromatography-tandem mass spectrometry. Imidacloprid was detected in 36 % of samples (n = 294); this included quantifiable concentrations (12 %; 10.8–36,131 pg/mL) and concentrations that were below the limit of quantification (25 %). Additionally, two birds were exposed to imidacloprid, acetamiprid (18,971.3 and 6844 pg/mL) and thiacloprid (7022.2 and 17,367 pg/mL), whereas no bird tested positive for clothianidin, dinotefuran, nitenpyram, or thiamethoxam, likely reflecting higher limits of detection for all compounds compared to imidacloprid. Birds sampled in spring and fall had higher incidences of exposure than those sampled in summer or winter. Subadult birds had higher incidences of exposure than adult birds. Among the species for which we tested more than five samples, American robin (Turdus migratorius) and red-winged blackbird (Agelaius phoeniceus) had significantly higher incidences of exposure. We found no relationships between exposure and foraging guild or avian family, suggesting birds with diverse life histories and taxonomies are at risk. Of seven birds resampled over time, six showed neonicotinoid exposure at least once with three showing exposures at multiple time points, indicating continued exposure. This study provides exposure data to inform ecological risk assessment of neonicotinoids and avian conservation efforts.

Influence of cropland on resource selection by pronghorn

AbstractPronghorn (Antilocapra americana) are a grassland specialist that have experienced a >60% reduction in their historical range due to habitat fragmentation and encroachment of woody vegetation. Pronghorn populations are increasing in the Texas Panhandle despite conversion of grassland to cropland (27–43% of the regional landscape) and associated fragmentation. We hypothesized that pronghorn avoid cropland when selecting seasonal home ranges and avoid cropland within their home ranges. We captured 64 adult pronghorn of equal sex ratios in both the High Plains (n = 32) and Rolling Plains (n = 32) ecoregions of Texas, USA, during February 2017 and fitted them with iridium satellite global positioning system (GPS) collars. We collared 27 additional pronghorn in 2018 to account for mortalities and collar failures. We estimated resource selection functions for the High Plains and Rolling Plains populations using mixed‐effects logistic regression at the home range (second order) and within home range (third order) scales separately for each ecoregion and season (fawning, summer, rut, and winter). Our hypothesis that pronghorn avoid cropland was supported in the Rolling Plains ecoregion at the home range scale; otherwise, cropland was inconsistently and seasonally important in resource selection. Furthermore, pronghorn often avoided paved roads more strongly than cropland. At the home range scale during 2017–2019, female pronghorn in the High Plains selected cropland during rut and winter. Males exhibited weak selection for cropland during rut. Within home ranges in the High Plains, female pronghorn avoided cropland during fawning in 2017, during rut in 2017 and 2018, and during winter 2019 but selected areas closer to cropland in winter 2017 and fawning 2018. Males selected areas farther from cropland during all sampling dates in 2017 and winter 2019. Avoidance and selection of cropland within home ranges also varied among seasons and years in the Rolling Plains. Overall, pronghorn avoided cropland when selecting home ranges in the Rolling Plains and cropland was otherwise inconsistently and only seasonally important in resource selection at the home range and within home range scales. We speculate that loss of pronghorn habitat to cropland in the High Plains and Rolling Plains of Texas may outweigh temporary nutritional benefits from seasonal use of crops.

Prevalence of Trypanosoma cruzi, the Etiologic Agent of Chagas Disease, Infection in Texas Skunks (Mammalia: Mephitidae).

Background: Chagas disease is one of the world's most neglected tropical diseases, infecting over six million people across the Americas. The hemoparasite Trypanosoma cruzi is the etiological agent for the disease, circulating in domestic, peridomestic, and sylvatic transmission cycles that are maintained by triatomine vectors and a diversity of wild and synanthropic hosts. Public health and wildlife management interventions targeting the interruption of T. cruzi transmission rely on an understanding of the dynamics driving the ecology of this zoonotic pathogen. One wildlife host that purportedly plays a role in the transmission of Chagas disease within the southern United States is the striped skunk (Mephitis mephitis), although infection prevalence in this species is poorly understood. Materials and Methods: To this end, we conducted a PCR-based surveillance of T. cruzi in 235 wild skunks, representing 4 species, across 76 counties and 10 ecoregions in Texas, United States, along with an evaluation of risk factors associated with the infection. Results: We recovered an overall T. cruzi prevalence of 17.9% for all mephitid taxa aggregated, ranging between 6.7% for plains spotted skunks (Spilogale putorius interrupta) and 42.9% for western spotted skunks (Spilogale gracilis). We report the first cases of T. cruzi infection in plains spotted and American hog-nosed skunks (Conepatus leuconotus), of important note for conservation medicine since populations of both species are declining within Texas. Although not statistically significant, we also detected trends for juveniles to exhibit greater infection risk than adults and for differential sex biases in T. cruzi prevalence between taxa, which align with variations in species-specific seasonal activity patterns. No geographic or taxonomic risk factors were identified. Conclusion: Our study contributed key data for population viability analyses and epidemiologic models in addition to providing a baseline for future T. cruzi surveillance among skunks and other wildlife species.

Cropping system diversity and tillage intensity affects wheat productivity in Texas

AbstractWheat (Triticum aestivum L.) production in Texas depends heavily on conventional tillage (CT) and a long summer fallow period, which contributes to soil degradation. This study compared the impact of reducing tillage intensity (CT, no‐tillage, and strip‐tillage) combined with summer cropping to CT–summer fallow on wheat establishment, grain production, and herbage mass from 2016 to 2020 in three Texas ecoregions (Coastal Plains, Southern High Plains, and Blackland Prairie). Tillage and summer cropping resulted in variable impacts on wheat stand establishment, grain yield, and herbage mass across years and locations. At Beeville, in the Coastal Plains, wheat grain and herbage mass yields were not impacted by tillage. Sorghum (Sorghum bicolor [L.] Moench) cropping resulted in less wheat grain yield in 2020. In 1 yr at Lubbock in the Southern High Plains, wheat grain yield was greater with CT than reduced tillage. Sorghum summer cropping resulted in lower wheat grain yield than cover crop mixture or cowpea (Vigna unguiculata [L.] Walp.) in 2017, but yield was greater in 2020. At Thrall, in the Blackland Prairie, wheat stand establishment and yield with reduced tillage were greater than CT in 2016, whereas CT was greater in 2017 and 2020. Sorghum or cover cropping resulted in reduced wheat grain yield compared with fallow in 2018, but sorghum and sesame (Sesamum indicum L.) resulted in increased yield compared with fallow in 2019 and 2020. Summer cropping in wheat production systems rarely had a negative impact on wheat production compared with summer fallow in all three ecoregions.

Texas professionals are employing a one health approach to protect the United States against biosecurity threats

Texas is a geographically large state with large human and livestock populations, many farms, a long coastal region, and extreme fluctuations in weather. During the last 15 years, the state of Texas has frequently suffered disasters or catastrophes causing extensive morbidity and economic loss. These disasters often have complicated consequences requiring multi-faceted responses. Recently, an interdisciplinary network of professionals from multiple academic institutions has emerged to collaborate in protecting Texas and the USA using a One Health approach. These experts are training the next generation of scientists in biopreparedness; increasing understanding of pathogens that cause repetitive harm; developing new therapeutics and vaccines against them; and developing novel surveillance approaches so that emerging pathogens will be detected early and thwarted before they can cause disastrous human and economic losses. These academic One Health partnerships strengthen our ability to protect human and animal health against future catastrophes that may impact the diverse ecoregions of Texas and the world.

Evaluating Mesquite Distribution Using Unpiloted Aerial Vehicles and Satellite Imagery

Encroachment of woody plant species on rangelands is of critical concern for rangeland health and function. Recent advances in unpiloted aerial vehicles (UAVs) technology have opened new opportunities for natural resource personnel to quantify features within the landscape. Our goal was to combine information derived from UAV and Sentinel-2 imagery to quantify the presence and spatial distribution of mesquite (Prosopis glandulosa). The specific objectives were to 1) evaluate the accuracy of UAVs to estimate mesquite height and 2) classify mesquite using a combination of height metrics and spectral information by combining UAV and Sentinel-2 remote sensing data. We conducted our study in three different ecoregions in Texas. We collected on-site tree height field measurements and created two UAV-derived height outputs at 50 m and 100 m above ground level (AGL). We then used a random forest classification with data derived from the UAV to inform Sentinel-2 imagery of mesquite locations to assess its presence at the landscape level. Linear regression analysis showed that 50-m AGL mesquite height estimates from UAV explained 95% of the variability. Variability explained from 100 m AGL height estimates was slightly lower at 92%. Accuracy assessments from using UAV training data to predict mesquite presence using Sentinel-2 imagery yielded overall accuracy of > 80% for all sites, user accuracies up to 86%, and producer accuracies up to 92%. UAV-derived heights of mesquite were reliable. UAV imagery can be used as training data for Sentinel-2 satellite imagery to assess mesquite presence on Texas rangelands. Being able to combine the high spatial resolution of the UAV imagery with the high temporal resolution of the Sentinel-2 satellite imagery could improve our ability to use UAVs to monitor rangelands.

Effective Management Practices for Increasing Native Plant Diversity on Mesquite Savanna-Texas Wintergrass-Dominated Rangelands

Throughout the Rolling Plains and Cross Timbers ecoregions of Texas, native grassland plant communities have been converted into low-diversity plant communities by long-term, intensive overgrazing by cattle and fire suppression. Much of the historical plant community has become dominated by annuals, Texas wintergrass (Nassella leucotricha), and honey mesquite (Prosopis glandulosa). This degradation has been so severe that many native bird species, including Northern bobwhite (Colinus virginianus), have experienced drastic population declines. We conducted a small-plot study to determine effective management actions for transforming mesquite savanna−Texas wintergrass communities to diverse native plant communities supportive of native wildlife species. We tested multiple management practices following mechanical mesquite brush removal, including seeding, timed treatments of herbicide, prescribed burns, and high-intensity, short-duration cattle grazing. Results indicated that plots receiving early spring treatments of herbicide followed by burning and grazing over 2 consecutive yr best reduced cool-season grasses and promoted overall restoration goals by increasing native warm-season grass and forb establishment.

Winter habitats of bats in Texas.

Few studies have described winter microclimate selection by bats in the southern United States. This is of particular importance as the cold-adapted fungus, Pseudogymnoascus destructans, which causes the fatal bat disease white-nose syndrome (WNS), continues to spread into southern United States. To better understand the suitability of winter bat habitats for the growth of P. destructans in this region, we collected roost temperature and vapor pressure deficit from 97 hibernacula in six ecoregions in Texas during winter 2016-17 and 2017-18. We also measured skin temperature of Rafinesque's big-eared bats (Corynorhinus townsendii), Townsend's big-eared bats (C. townsendii), big-brown bats (Eptesicus fuscus), southeastern myotis (Myotis austroriparius), cave myotis (M. velifer), tri-colored bats (Perimyotis subflavus), and Mexican free-tailed bats (Tadarida brasiliensis) during hibernation to study their use of torpor in these habitats. We found that temperatures within hibernacula were strongly correlated with external air temperatures and were often within the optimal range of temperatures for P. destructans growth. Hibernacula and skin temperatures differed among species, with Rafinesque's big-eared bats, southeastern myotis, and Mexican free-tailed bats occupying warmer microclimates and having higher torpid skin temperatures. For species that were broadly distributed throughout Texas, hibernacula and skin temperatures differed within species by ecoregion; Tri-colored bats and cave myotis in colder, northern regions occupied colder microclimates within hibernacula and exhibited colder skin temperatures, than individuals of the same species in warmer, southern regions. These data illustrate the variability in microclimates used as hibernacula by bats in Texas and suggest similar variation in susceptibility to WNS in the state. Thus, monitoring microclimates at winter roosts may help predict where WNS may develop, and where management efforts would be most effective.

Predicting West Nile virus transmission in North American bird communities using phylogenetic mixed effects models and eBird citizen science data

BackgroundWest Nile virus (WNV) is a mosquito-transmitted disease of birds that has caused bird population declines and can spill over into human populations. Previous research has identified bird species that infect a large fraction of the total pool of infected mosquitoes and correlate with human infection risk; however, these analyses cover small spatial regions and cannot be used to predict transmission in bird communities in which these species are rare or absent. Here we present a mechanistic model for WNV transmission that predicts WNV spread (R0) in any bird community in North America by scaling up from the physiological responses of individual birds to transmission at the level of the community. We predict unmeasured bird species’ responses to infection using phylogenetic imputation, based on these species’ phylogenetic relationships with bird species with measured responses.ResultsWe focused our analysis on Texas, USA, because it is among the states with the highest total incidence of WNV in humans and is well sampled by birders in the eBird database. Spatio-temporal patterns: WNV transmission is primarily driven by temperature variation across time and space, and secondarily by bird community composition. In Texas, we predicted WNV R0 to be highest in the spring and fall when temperatures maximize the product of mosquito transmission and survival probabilities. In the most favorable months for WNV transmission (April, May, September and October), we predicted R0 to be highest in the “Piney Woods” and “Oak Woods & Prairies” ecoregions of Texas, and lowest in the “High Plains” and “South Texas Brush County” ecoregions. Dilution effect: More abundant bird species are more competent hosts for WNV, and predicted WNV R0 decreases with increasing species richness. Keystone species: We predicted that northern cardinals (Cardinalis cardinalis) are the most important hosts for amplifying WNV and that mourning doves (Zenaida macroura) are the most important sinks of infection across Texas.ConclusionsDespite some data limitations, we demonstrate the power of phylogenetic imputation in predicting disease transmission in heterogeneous host communities. Our mechanistic modeling framework shows promise both for assisting future analyses on transmission and spillover in heterogeneous multispecies pathogen systems and for improving model transparency by clarifying assumptions, choices and shortcomings in complex ecological analyses.

Molecular prevalence and ecoregion distribution of select tick-borne pathogens in Texas dogs.

Tick-borne diseases (TBD), caused by borrelial, rickettsial and babesial pathogens, are common across the United States and can cause severe clinical disease in susceptible hosts, such as domestic dogs. However, there are limited TBD molecular epidemiological reports for dogs in Texas, and none for the non-Lyme borrelial pathogen responsible for causing tick-borne relapsing fever (TBRF). Therefore, data to support the prevalence of TBRF in the canine population is inadequate. This study aimed to characterize the molecular prevalence of 11 causative agents responsible for three TBD groups within domestic dogs with an emphasis on pathogen distribution within Texas ecoregions. A total representative number of 1,171 whole-blood samples were collected opportunistically from two Texas veterinary diagnostic laboratories. A layerplex real-time PCR assay was utilized to screen the dog samples for all 11 pathogens simultaneously. The overall molecular infection prevalence of disease was 0.68% borrelial, 1.8% rickettsial and 0.43% babesial pathogens, for a TBD total of 2.73% across Texas. Higher molecular prevalence was observed when analysed by ecoregion distinction, including 5.78% rickettsial infections by Ehrlichia canis and Anaplasma platys in the Rolling Plains ecoregion, and an average of 1.1% Borrelia turicatae and 1.0% Babesia gibsoni across detected ecoregions. To our knowledge, our findings indicate the first molecular detection of A. platys in Texas, and the first report of coinfections with E. canis and A. platys in dogs of Texas. The zoonotic concerns associated with TBDs, in conjunction with dogs' implication as an effective sentinel for human disease, highlight the importance of characterizing and monitoring regions associated with active infections in dogs. Surveillance data obtained from this study may aid public health agencies in updating maps depicting high-risk areas of disease and developing preventative measures for the affected areas.

Efficacy of Seven Invasive-Bermudagrass Removal Strategies in Three Texas Ecoregions

Efficacy of Seven Invasive-Bermudagrass Removal Strategies in Three Texas Ecoregions

Escherichia coli Concentration as a Function of Stream Order and Watershed Size.

This research examines the relationship of concentrations to stream order and watershed size and considers the implications on water quality standards. To assess geospatial effects, data were obtained from 743 monitoring stations in the Central Great Plains, Cross Timbers, and South Central Plains ecoregions of Texas and Oklahoma. Median and geometric mean concentrations were analyzed for correlation with stream order and watershed size at each site. Comparison of the three ecoregions revealed concentrations were highest in the westernmost Central Great Plains and lowest in the easternmost South Central Plains. Similarly, the strength of 's correlation with stream order and watershed area decreased with ecoregion moving west to east. Thus, incorporating ecoregion approaches when defining stream water quality standards is supported. Analysis showed no significant relationship of stream order or watershed size to concentrations in least-impacted watersheds (i.e., watersheds with minimal wastewater discharge and urbanization). Conversely, analysis of data from all sites showed a weak negative relationship between concentration and stream order and watershed size, with concentration generally decreasing with increasing stream order and watershed size. However, variability in smaller watersheds and lower-order streams supports continued use of site-specific studies to determine appropriate standards. Three-parameter exponential models provided an approach to estimate concentrations using Shreve stream order and watershed area and identify outlier streams potentially affected by anthropogenic activities where further investigation or remediation may be warranted.

Weed control and overstory reduction improve survival and growth of under‐planted oak and hickory seedlings

Weed control and overstory reduction are important silvicultural treatments for improving survival and growth of under‐planted oak and hickory seedlings. Mast‐producing trees in the bottomland forests of the blackland prairie and Post Oak Savannah ecoregions of Texas have declined in abundance. Oaks and hickories have been replaced by more shade‐tolerant species, including green ash (Fraxinus pennsylvanica Marshall) and sugarberry (Celtis laevigata Willd.), which do not produce significant hard mast for priority wildlife species. A split‐plot experiment design was installed on three sites at Richland Creek Wildlife Management Area in Freestone County, Texas, studying the effects of canopy coverage and competition control on survival and growth of bur oak (Quercus macrocarpa Michx.), Shumard oak (Quercus shumardii Buckl.), and pecan (Carya illinoinensis (Wagenh.) K. Koch) seedlings. Uprooting by hogs shortly after planting resulted in greater than 90% mortality of pecan on the two lower elevation sites. Year one survival of Shumard oak was significantly higher than bur oak. However, bur oak was more preferred by hogs than Shumard oak. Year one growth of bur oak was significantly greater than Shumard oak. Severe flooding during the second growing season caused complete mortality on the lower two sites. None of the species were well suited to such prolonged (3–4 months) inundation as seedlings. On the remaining site, density reduction and weed‐barrier mats improved growth and survival while herbaceous weed control with herbicides actually reduced both growth and survival.

Using Feathers to Evaluate Adverse Effects of Metals on Northern Bobwhites (Colinus virginianus) in Texas.

Northern bobwhites (Colinus virginianus) have been declining across the range of the species primarily due to habitat loss and habitat fragmentation. There is increasing concern regarding effects related to elevated environmental contaminants, including pesticides and metals. Elevated concentrations of some metals are known to have adverse effects on reproduction, development, and survival in birds; however, little research has been conducted on metal exposure in wild bobwhites. We analyzed metal concentrations in the feathers of 60 bobwhites from 3 ecoregions in Texas and evaluated differences between age-class, gender, and location with the objective of determining if bobwhites in Texas are at increased risk of exposure to elevated metal concentrations. We found feather Pb concentrations above the established effect threshold of 4.0µg/g dry weight at which sublethal and reproductive effects have been reported in birds. More than 25% (n = 16) of the samples analyzed had Pb concentrations above the effect threshold, including four that were five times above the threshold. We also observed slightly elevated feather Cd concentrations, above 0.1µg/g dry weight, in 17% (n = 11) of the bobwhites analyzed. On average, juvenile bobwhites had higher concentrations of Ba, Co, Fe, Mn, Sr, and V compared to adults (p < 0.05). Additionally, concentrations of Al, Be, Co, Fe, Hg, Ni, Se, Sr, and Tl differed significantly between sampling locations, indicating a potential relationship between metal levels and local agricultural practices. The results of our study indicate a potential risk of sublethal effects of Pb and to a lesser extent Cd in bobwhites in Texas.

Selecting Cool‐Season Forage Grasses for Yield, Seasonal Yield Distribution, and Nutritive Value in the Blacklands and Rolling Plains Ecoregions of Texas

Core Ideas The study evaluated seven cool‐season crops for their forage yield and quality in the Blacklands and Rolling Plains of Texas. There was significant interaction of crop species and environment on forage yield and quality. Triticale has wide range of adaptability in both the Blacklands and Rolling Plains ecoregions. Site‐specific recommendation of best adapted forage crop species would help the producers achieve higher forage productivity and profitability. Selection of suitable cool‐season crop species for winter forage production is a critical management decision in many ecoregions of the United States, including Texas. A study was conducted during 2004 to 2007 in the Blacklands and Rolling Plains ecoregions of Texas using seven cool‐season crops to determine the site‐specific crop choice to maximize forage yield and nutritive value. The seven crop species tested in these two ecoregions included: barley (Hordeum vulgare L.), hard red wheat (Triticum aestivum L.), oat (Avena sativa L.), rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), soft red wheat (Triticum aestivum L.), and triticale (×Triticosecale Wittmack). The results indicated that crop choice for maximizing the forage yield and nutritive value varied with environment. In the Blacklands, oat and triticale produced greater forage yields than other crop species (P &lt; 0.05). In the Rolling Plains, ryegrass yielded more forage during years of above‐average precipitation, whereas rye and triticale produced more forage during drier years. Seasonal forage yield distribution varied among different site‐years of the Blacklands and Rolling Plains ecoregions. Triticale was demonstrated to be the crop that performed most consistently at both ecoregions of Texas. Rye and barley had greater nutritive value and mineral composition in the Blacklands, whereas ryegrass had greater mineral composition in the Rolling Plains (P &lt; 0.05). Given this information, producers in the Blacklands and Rolling Plains ecoregions can make informed decisions on selection of suitable forage crops to be grown on their farms to achieve greater forage yield and nutritive value, and to match up their specific management and livestock requirements.

PREVALENCE AND INTENSITY OF THE SINUS ROUNDWORM ( SKRJABINGYLUS CHITWOODORUM) IN RABIES-NEGATIVE SKUNKS OF TEXAS, USA.

: Estimates of the distribution and prevalence of the sinus roundworm ( Skrjabingylus chitwoodorum) have been based largely on the inspection of skunk (Mephitidae) skulls showing damage from infections. We examined 595 striped skunks ( Mephitis mephitis) and nine hog-nosed skunks ( Conepatus leuconotus) that had tested negative for rabies by the Texas Department of State Health Services (US) between November 2010 and April 2015 to determine species of Skrjabingylus, prevalence and intensity of infection, and distribution of infection in Texas by county. We expected ecoregions with more precipitation to have higher rates of infection than more-arid ecoregions. Prevalence of S. chitwoodorum in striped skunks was 48.7%, with a mean intensity of 19.4 (SD=24.44, range=1-181) nematodes. There was a bias for the left sinus. The prevalence of infection varied among ecoregions of Texas, but it was not correlated with precipitation. Infection intensity did not vary among ecoregions. The prevalence of sinus roundworms in rabies-negative skunks suggested that behavioral changes because of skrjabingylosis might have been responsible for the submission by the public of some skunks for rabies testing.

Measuring canopy loss and climatic thresholds from an extreme drought along a fivefold precipitation gradient across Texas.

Globally, trees are increasingly dying from extreme drought, a trend that is expected to increase with climate change. Loss of trees has significant ecological, biophysical, and biogeochemical consequences. In 2011, a record drought caused widespread tree mortality in Texas. Using remotely sensed imagery, we quantified canopy loss during and after the drought across the state at 30-m spatial resolution, from the eastern pine/hardwood forests to the western shrublands, a region that includes the boundaries of many species ranges. Canopy loss observations in ~200multitemporal fine-scale orthophotos (1-m) were used to train coarser Landsat imagery (30-m) to create 30-m binary statewide canopy loss maps. We found that canopy loss occurred across all major ecoregions of Texas, with an average loss of 9.5%. The drought had the highest impact in post oak woodlands, pinyon-juniper shrublands and Ashe juniper woodlands. Focusing on a 100-km by ~1,000-km transect spanning the State's fivefold east-west precipitation gradient (~1,500 to ~300mm), we compared spatially explicit 2011 climatic anomalies to our canopy loss maps. Much of the canopy loss occurred in areas that passed specific climatic thresholds: warm season anomalies in mean temperature (+1.6°C) and vapor pressure deficit (VPD, +0.66kPa), annual percent deviation in precipitation (-38%), and 2011 difference between precipitation and potential evapotranspiration (-1,206mm). Although similarly low precipitation occurred during the landmark 1950s drought, the VPD and temperature anomalies observed in 2011 were even greater. Furthermore, future climate data under the representative concentration pathway 8.5 trajectory project that average values will surpass the 2011 VPD anomaly during the 2070-2099 period and the temperature anomaly during the 2040-2099 period. Identifying vulnerable ecological systems to drought stress and climate thresholds associated with canopy loss will aid in predicting how forests will respond to a changing climate and how ecological landscapes will change in the near term.

Field Application of Sustained-Yield Harvest Management for Northern Bobwhite in Texas

Sustained-yield harvest (SYH) is considered a potentially viable strategy for managing harvest of northern bobwhites (Colinus virginianus). However, application of SYH has not been evaluated for northern bobwhites. We evaluated the application of using SYH as a harvest management strategy for bobwhite during the 2007 2008 and 2008 2009 hunting seasons in 2 ecoregions of Texas (Rolling Plains, South Texas Plains). We collected field data at 3 study sites/ecoregion (900 1,900 ha each; 2 hunted sites and 1 control) to estimate 4 demographic parameters (fall and spring density, overwinter survival in the absence of hunting, and harvest rate). We used these data to parameterize the additive harvest model for bobwhites and compare predictions of spring abundance of the model with field estimates. The additive harvest model, compared to field estimates, consistently underestimated spring population density (mean 6 SE) by 55.7 6 17.8% (2007 2008) and 34.1 6 4.9% (2008 2009) in the Rolling Plains, and by 26.4 6 25.3% (2007 2008) and 49.1 6 2.1% (2008 2009) in the South Texas Plains. Implementing SYH in the field, despite its potential benefits, will be challenging given the need for reliable estimates of 3 key population parameters (fall and spring density, and natural mortality in the absence of hunting) and the high variation often associated with them. Conservative harvest prescriptions based on the lower 95% CIs of fall density estimates may permit sustainable harvest despite variation in density estimates.

Seroprevalence of Borrelia burgdorferi antibodies in white-tailed deer from Texas.

Lyme Disease is caused by the bacterial pathogen Borrelia burgdorferi, and is transmitted by the tick-vector Ixodes scapularis. It is the most prevalent arthropod-borne disease in the United States. To determine the seroprevalence of B. burgdorferi antibodies in white-tailed deer (Odocoileus virginianus) from Texas, we analyzed serum samples (n = 1493) collected during the 2001–2015 hunting seasons, using indirect ELISA. Samples with higher sero-reactivity (0.803 and above) than the negative control group (0.662) were further tested using a more specific standardized western immunoblot assay to rule out false positives. Using ELISA, 4.7% of the samples were sero-reactive against B. burgdorferi, and these originated in two eco-regions in Texas (Edwards Plateau and South Texas Plains). However, only 0.5% of the total samples were sero-reactive by standardized western immunoblot assay. Additionally, both ELISA and standardized western immunoblot assay results correlated with an increased incidence in human Lyme Disease cases reported in Texas. This is the first longitudinal study to demonstrate fluctuation in sero-reactivity of white-tailed deer to B. burgdorferi sensu stricto antigens in southern United States. Future ecological and geographical studies are needed to assess the environmental factors governing the prevalence of Lyme Disease in non-endemic areas of the southern United States.