Browsing by Author "McIntyre, Nancy E. (TTU)"
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Item Evaluation of speculated reproductive habitat for Somatochlora calverti (Corduliidae), a rare and range-restricted dragonfly(2024) Girgente, Hannah E. (TTU); McIntyre, Nancy E. (TTU)Globally, freshwater ecosystems and the organisms that depend on them are at risk. Dragonflies and damselflies (collectively, “odonates”) have a history of being used as bioindicators of freshwater habitat quality due to their wide range in environmental sensitivities across species and because they are relatively accessible. However, the nymphal stage is severely understudied compared to the adult stage, which inhibits conservation efforts. Somatochlora calverti is a rare species of dragonfly in the family Corduliidae; members of the genus Somatochlora are notoriously difficult to find and collect in the field as nymphs and adults. Somatochlora calverti is known primarily from the Florida panhandle but has been documented in Alabama, Georgia, and South Carolina. The nymph of this species is speculated to use seepage streams analogous to sympatric congeners; however, the nymph has never been collected in the field and, therefore, its specific microhabitat is unknown. We conducted a review from a suite of informational sources to generate a holistic consensus on what is defined to be suitable reproductive habitat for S. calverti. Sources identified eight major environmental characteristics that are likely to harbor S. calverti: shallow seepage streams, including steephead ravines, with undercut banks and mats of Sphagnum moss adjacent to intact sandhill forest. These ecosystems are being lost and degraded by anthropogenic activity, which has considerable impacts on the persistence of habitat specialists, including S. calverti, and managers’ ability to conserve them.Item Habitat-distribution modeling of a recolonizing Black Bear, Ursus americanus, Population in the Trans-Pecos region of Texas(2009) Rice, Mindy B. (TTU); Ballard, Warren B. (TTU); Fish, Ernest B. (TTU); McIntyre, Nancy E. (TTU); Holdermann, DavidBlack Bears (Ursus americanus) were once widespread across Texas, but their numbers were reduced in the early 1900s. Recolonization of the Trans-Pecos region of Texas has occurred via bears migrating northward from Mexico. Recent bear sightings have increased in this area. This could be an indication that the population in Texas is beginning to recover, but the population will continue to expand only if there is suitable habitat to occupy. To help identify suitable habitat and restoration areas, we developed a predictive habitat-distribution model by using records of Black Bear sightings from 1996 to 2003 to map the species' distribution. Using Bayesian statistics, we modeled the probability of occurrence of Black Bears in the Trans-Pecos region based on sighting locations. We used GIS layers for land use/landcover, elevation, water sources, and road networks to obtain covariates in our modeling. We used a 10-fold cross-validation to test the effectiveness of using sighting data. Our results indicated a negative association with bare areas, agriculture, and grassland landcovers. In addition, southern aspect, elevation, distance to water, slope, and western aspect also influenced suitable habitat. Both the original and validation datasets correctly classified bear sightings 93.9% and 93.7% of the time, respectively. Our model can be used to target restoration efforts to enhance the ability of the Black Bear to expand in the Trans-Pecos region. It can also identify private landowners most likely to be affected by the expansion of Black Bears for education and cooperative efforts.Item Identifying structural connectivity priorities in eastern Paraguay’s fragmented Atlantic Forest(2021) de la Sancha, Noé U.; Boyle, Sarah A.; McIntyre, Nancy E. (TTU)The Atlantic Forest of eastern Paraguay has experienced extensive recent deforestation. Less than one-third of the region is forested, and the remaining forest largely consists of isolated remnants with potentially disrupted connectivity for forest fauna. We used a graph theory approach to identify those forest remnants that are important in maintaining landscape structural connectivity for mammals in this fragmented forest. We quantified structural connectivity for forest remnants over the period 2000–2019 at three levels: the entire network of Atlantic Forest remnants in eastern Paraguay; at 10 smaller, nested spatial scales (40–10,000 m) encompassing a range of potential mammalian dispersal abilities; and at the level of individual remnants. We used 10 graph theory metrics to assess aspects of network complexity, dispersal-route efficiency, and individual remnant importance in supporting structural connectivity. We identified forest remnants that serve as important structural connectivity roles as stepping stones, hubs, or articulation points and that should be prioritized for connectivity conservation. Structural connectivity was constrained for organisms incapable of travelling at least 9–12 km (farthest distances between nearest-neighboring forest remnants depending on whether smaller remnants were included or not) and was particularly limited for area-sensitive forest-specialist mammals. With the increased forest loss and fragmentation that is occurring, the connectivity of this system will likely be further compromised, but most of the remnants that we identified as playing important roles for structural connectivity were outside of the country’s proposed “green corridor,” indicating additional areas where conservation action can be directed.Item Quantifying the degree of bias from using county-scale data in species distribution modeling: Can increasing sample size or using county-averaged environmental data reduce distributional overprediction?(2017) Collins, Steven D.; Abbott, John C.; McIntyre, Nancy E. (TTU)Citizen-science databases have been used to develop species distribution models (SDMs), although many taxa may be only georeferenced to county. It is tacitly assumed that SDMs built from county-scale data should be less precise than those built with more accurate localities, but the extent of the bias is currently unknown. Our aims in this study were to illustrate the effects of using county-scale data on the spatial extent and accuracy of SDMs relative to true locality data and to compare potential compensatory methods (including increased sample size and using overall county environmental averages rather than point locality environmental data). To do so, we developed SDMs in maxent with PRISM-derived BIOCLIM parameters for 283 and 230 species of odonates (dragonflies and damselflies) and butterflies, respectively, for five subsets from the OdonataCentral and Butterflies and Moths of North America citizen-science databases: (1) a true locality dataset, (2) a corresponding sister dataset of county-centroid coordinates, (3) a dataset where the average environmental conditions within each county were assigned to each record, (4) a 50/50% mix of true localities and county-centroid coordinates, and (5) a 50/50% mix of true localities and records assigned the average environmental conditions within each county. These mixtures allowed us to quantify the degree of bias from county-scale data. Models developed with county centroids overpredicted the extent of suitable habitat by 15% on average compared to true locality models, although larger sample sizes (>100 locality records) reduced this disparity. Assigning county-averaged environmental conditions did not offer consistent improvement, however. Because county-level data are of limited value for developing SDMs except for species that are widespread and well collected or that inhabit regions where small, climatically uniform counties predominate, three means of encouraging more accurate georeferencing in citizen-science databases are provided.Item Socio-ecology of the marsh rice rat (Oryzomys palustris) and the spatio-temporal distribution of Bayou virus in coastal Texas(2013) Holsomback, Tyla S. (TTU); Van Nice, Christopher J. (TTU); Clark, Rachel N. (TTU); McIntyre, Nancy E. (TTU); Abuzeineh, Alisa A.; Salazar-Bravo, Jorge (TTU)Along the southeastern coast of the United States of America (USA), the marsh rice rat (Oryzomys palustris) is the primary host for the hantavirus genotype Bayou. According to the socio-ecological model for a territorial, polygamous species, females should be distributed across space and time by habitat resources and predation risks, whereas males should space themselves according to the degree of female aggregation and reproductive synchrony. To investigate how females affect the male-male transmission paradigm of Bayou virus, rodents were captured, marked, released, and re-captured in two macrohabitat types across a 30-month period. Microhabitat cover variables were quantified around the individual trap stations. A geodatabase was created from habitat and rodent capture data and analysed in a geographical information system. The ratio of breeding to non-breeding females was ~1:1, with breeding females overly dispersed and non-breeding females randomly dispersed. Spatial analyses revealed both macro- and microhabitat preferences in females. Compared to sero-negatives, higher proportions of seropositive adult males were found consistently within closer proximities to breeding females but not to non-breeding females, indicating that male locations were not driven simply by habitat selection. Activities to acquire dispersed receptive females could be an important driver of Bayou virus transmission among male hosts. To date, socio-ecological theory has received little attention as an investigative framework for studying pathogen dynamics in small, solitary mammals. Herein, we describe an interdisciplinary effort providing a novel approach to elucidate the complexity of hantavirus trafficking and maintenance in rodent populations of a coastal marsh ecosystem.Item Species as conservation umbrellas: A case study with lesser prairie-chicken (Tympanuchus pallidicinctus) in the southern Great Plains of North America(2022) Gary, Demi M. (TTU); Mougey, Krista; McIntyre, Nancy E. (TTU); Griffis-Kyle, Kerry L. (TTU)Conservation efforts often focus on a single species, but this approach is inefficient for agencies dealing with many declining species at risk of extinction. Leveraging already-funded management for additional species can help stretch limited resources to conserve more biodiversity. However, evaluation of the efficacy of such an umbrella approach is typically lacking, does not explicitly consider outcomes of management treatments, or only evaluates one or a few species. We developed a method to evaluate the ability of management for the lesser prairie-chicken (Tympanuchus pallidicinctus) to offer an umbrella of protection for non-target species at risk of decline. To accomplish this, we predicted the conservation outcomes of lesser prairie-chicken management for overlapping at-risk species and created an index of conservation benefit to evaluate the effectiveness of the lesser prairie-chicken as an umbrella species for conservation. We conducted a literature review for 77 at-risk species that overlap in range with the lesser prairie-chicken to determine the effects (benefit, cost, or neutral) of the primary conservation actions taken to manage lesser prairie-chicken habitat. We determined that 84 % of the species were expected to receive a net conservation benefit from management for lesser prairie-chicken, 8 % would incur a net cost, and 8 % would have a net balance of costs and benefits. These results suggest that the lesser prairie-chicken functions as an umbrella of protection for other grassland species, providing a net conservation benefit. Our index-based approach serves as a model for evaluating the efficacy of proposed surrogate species on a community of organisms.Item Urban areas create refugia for odonates in a semi-arid region(2021) Husband, Danielle M. (TTU); McIntyre, Nancy E. (TTU)In western Texas, most wetlands are fed from precipitation runoff, making them sensitive to drought regimes, anthropogenic land-use activities in their surrounding watersheds, and the interactive effect between these two factors. We surveyed adult odonates in 133 wetlands (49 in grassland settings, 56 in cropland, and 28 in urban areas) in western Texas from 2003–2020; 33 species were recorded. Most species were widespread generalists, but urban wetlands had the highest species richness, as well as the most unique species of any of the three wetland types. Non-metric, multidimensional scaling ordination revealed that the odonate community in urban wetlands was distinctly different in composition than the odonates in non-urban wetlands. Urban wetlands were smaller in surface area than the other wetland types, but because they were fed from more consistently available urban runoff rather than seasonal precipitation, they had longer hydroperiods, particularly during a multi-year drought when wetlands in other land-cover contexts were dry. This anthropogenically enhanced water supply was associated with higher odonate richness despite presumably impaired water quality, indicating that consistent and prolonged presence of water in this semi-arid region was more important than the presence of native land cover within which the wetland existed. Compared to wetlands in the regional grassland landscape matrix, wetlands in agricultural and urban areas differed in hydroperiod, and presumably also in water quality; these effects translated to differences in the regional odonate assemblage by surrounding land-use type, with the highest richness at urban playas. Odonates in human environments may thus benefit through the creation of a more reliably available wetland habitat in an otherwise dry region.Item Using nested connectivity models to resolve management conflicts of isolated water networks in the Sonoran Desert(2017) Drake, Joseph C. (TTU); Griffis-Kyle, Kerry (TTU); McIntyre, Nancy E. (TTU)Connectivity is essential to organisms for dispersal, mate finding, and resource access. Management conflicts may arise if the attempts to maintain connectivity in the face of habitat loss result in opening up dispersal corridors to invasive species and disease vectors to already-threatened native species. Using the mule deer (Odocoileus hemionus) and American bullfrog (Lithobates catesbeianus) as examples in a network of surface waters in the Sonoran Desert, we illustrate and propose a resolution to these conflicts. We used structural and functional metrics from graph and circuit theory to quantify landscape connectivity within a spatially nested framework under current and future climate-based scenarios at regional and local scales to project structural and functional climate impacts for both species. Results indicated that climate impacts may reduce both structural and functional potential connectivity for each species. Mule deer, however, will be impacted to a lesser degree, and the proposed management mitigation of exclusion areas will have a potential lesser impact on this species. From our results, we propose a method to create exclusion areas and site new waters to help mitigate increasing spread of invasive species like the bullfrog while maintaining resource availability and local connectivity for economically important species like the mule deer. The isolation of local clusters from invasive species may be a successful and useful way to reduce management conflicts in the Sonoran Desert isolated waters network and beyond.Item Using Remotely Sensed Imagery to Document How Land Use Drives Turbidity of Playa Waters in Texas(2016) Starr, Scott M. (TTU); Heintzman, Lucas J. (TTU); Mulligan, Kevin R. (TTU); Barbato, Lucia S. (TTU); McIntyre, Nancy E. (TTU)Sedimentation (primarily from human land use) is a major threat to runoff-fed wetlands of the Great Plains of North America (playas), but it is unknown how many playas are turbid, how prevalence of turbidity has changed over time, and how turbidity is related to surrounding land use. We used remotely sensed imagery to assess sedimentation in the waters of over 7700 playa basins in Texas on four dates during a 29-year span: 25 July 1986 (a regionally wet time), 3 May 2014 (during drought), 4 June 2014 (after the drought was broken), and 25 July 2015 (one year post-drought). Even on the wettest date examined, 64% of playa basins did not hold water. Turbidity varied over time, was already present in over half of the basins examined in 1986, and prevalence of turbidity was not simply proportional to overall wet playa abundance. There was an increase in total and irrigated cropland in our focal region and a statistically significant association between sedimentation and land use within 100 m of a playa: clear playas were associated with more urban development and pasture/grassland, and turbid playas were surrounded mostly by cropland.Item Watershed-Mediated Ecomorphological Variation: A Case Study with the Twin-Striped Clubtail Dragonfly (Hylogomphus geminatus)(2023) Girgente, Joseph S. (TTU); McIntyre, Nancy E. (TTU)Anthropogenic land-cover change is modifying ecosystems at an accelerating rate. Changes to ecomorphologically variable taxa within those ecosystems serve as early-warning signs that resources on which humans and other animals depend are being altered. One known ecomorphologically variable taxon is Hylogomphus geminatus, a species of dragonfly in the southeastern United States that shows pronounced variation in total body length across its limited geographic range. We measured total length of live as well as preserved museum specimens of H. geminatus and the sympatric species Progomphus obscurus (as a means for comparison). Both species showed significant size differences linked to HUC-8 watersheds in which they occur. H. geminatus showed additional significant differences on either side of the Apalachicola River, Florida, for all comparisons by sex. In overlapping watersheds, the species tended to show the same trends in length relative to their respective averages. Smaller body length was associated with more urban and agricultural land cover. These findings indicate that ecomorphological variation is tied to the watershed scale and point to significant variations on either side of the Apalachicola River. More thorough future analyses would be needed to verify trends in body length and identify the drivers behind them.