Species Distribution Models and Ecological Suitability Analysis for Potential Tick Vectors of Lyme Disease in Mexico

Species distribution models were constructed for ten Ixodes species and Amblyomma cajennense for a region including Mexico and Texas. The model was based on a maximum entropy algorithm that used environmental layers to predict the relative probability of presence for each taxon. For Mexico, species geographic ranges were predicted by restricting the models to cells which have a higher probability than the lowest probability of the cells in which a presence record was located. There was spatial nonconcordance between the distributions of Amblyomma cajennense and the Ixodes group with the former restricted to lowlands and mainly the eastern coast of Mexico and the latter to montane regions with lower temperature. The risk of Lyme disease is, therefore, mainly present in the highlands where some Ixodes species are known vectors; if Amblyomma cajennense turns out to be a competent vector, the area of risk also extends to the lowlands and the east coast

Chagas Disease Risk in Texas

Chagas disease is endemic in Texas and spread through triatomine insect vectors known as kissing bugs, assassin bugs, or cone–nosed bugs, which transmit the protozoan parasite, Trypanosoma cruzi. We examined the threat of Chagas disease due to the three most prevalent vector species and from human case occurrences and human population data at the county level. We modeled the distribution of each vector species using occurrence data from México and the United States and environmental variables. We then computed the ecological risk from the distribution models and combined it with disease incidence data to produce a composite risk map which was subsequently used to calculate the populations expected to be at risk for the disease. South Texas had the highest relative risk. We recommend mandatory reporting of Chagas disease in Texas, testing of blood donations in high risk counties, human and canine testing for Chagas disease antibodies in high risk counties, and that a joint initiative be developed between the United States and México to combat Chagas disease

Assessing Historical Fish Community Composition Using Surveys, Historical Collection Data, and Species Distribution Models

Accurate establishment of baseline conditions is critical to successful management and habitat restoration. We demonstrate the ability to robustly estimate historical fish community composition and assess the current status of the urbanized Barton Creek watershed in central Texas, U.S.A. Fish species were surveyed in 2008 and the resulting data compared to three sources of fish occurrence information: (i) historical records from a museum specimen database and literature searches; (ii) a nearly identical survey conducted 15 years earlier; and (iii) a modeled historical community constructed with species distribution models (SDMs). This holistic approach, and especially the application of SDMs, allowed us to discover that the fish community in Barton Creek was more diverse than the historical data and survey methods alone indicated. Sixteen native species with high modeled probability of occurrence within the watershed were not found in the 2008 survey, seven of these were not found in either survey or in any of the historical collection records. Our approach allowed us to more rigorously establish the true baseline for the pre-development fish fauna and then to more accurately assess trends and develop hypotheses regarding factors driving current fish community composition to better inform management decisions and future restoration efforts. Smaller, urbanized freshwater systems, like Barton Creek, typically have a relatively poor historical biodiversity inventory coupled with long histories of alteration, and thus there is a propensity for land managers and researchers to apply inaccurate baseline standards. Our methods provide a way around that limitation by using SDMs derived from larger and richer biodiversity databases of a broader geographic scope. Broadly applied, we propose that this technique has potential to overcome limitations of popular bioassessment metrics (e.g., IBI) to become a versatile and robust management tool for determining status of freshwater biotic communities

Movement, demographics, and occupancy dynamics of a federally-threatened salamander: evaluating the adequacy of critical habitat

Critical habitat for many species is often limited to occupied localities. For rare and cryptic species, or those lacking sufficient data, occupied habitats may go unrecognized, potentially hindering species recovery. Proposed critical habitat for the aquatic Jollyville Plateau salamander (Eurycea tonkawae) and two sister species were delineated based on the assumption that surface habitat is restricted to springs and excludes intervening stream reaches. To test this assumption, we performed two studies to understand aspects of individual, population, and metapopulation ecology of E. tonkawae. First, we examined movement and population demographics using capture-recapture along a spring-influenced stream reach. We then extended our investigation of stream habitat use with a study of occupancy and habitat dynamics in multiple headwater streams. Indications of extensive stream channel use based on capture-recapture results included frequent movements of >15 m, and high juvenile abundance downstream of the spring. Initial occupancy of E. tonkawae was associated with shallow depths, maidenhair fern presence and low temperature variation (indicative of groundwater influence), although many occupied sites were far from known springs. Additionally, previously dry sites were three times more likely to be colonized than wet sites. Our results indicate extensive use of stream habitats, including intermittent ones, by E. tonkawae. These areas may be important for maintaining population connectivity or even as primary habitat patches. Restricting critical habitat to occupied sites will result in a mismatch with actual habitat use, particularly when assumptions of habitat use are untested, thus limiting the potential for recovery

Final Report: Data compilation, distribution models, conservation planning, and status survey for selected fishes of concern in Texas and region

The four primary objectives of this project were to: (1) compile a dataset of georeferenced range-wide occurrence records for 6 target fish species (Notropis buccula, N. oxyrhynchus, N. girardi, Hybognathus amarus, Platygobio gracilis, Macrhybopsis tetranema, Pteronotropis hubbsi, and Percina maculata); (2) use a high quality and geographically wide-ranging subset of those data to create species distribution models (SDM’s), which convert point occurrences into a continuous probability coverage; (3) use those models in conjunction with 130 additional SDM’s (previously created) to develop modeled conservation priority areas for Texas; and (4) complete a status survey for N. oxyrhynchus and N. buccula in the mainstem of the middle Brazos River. The dataset provided, derived from 51 original sources, includes 11,082 records, of which we were able to georeference 3,675 (33%). This number of records was sufficient for constructing SDM’s for the six target species, with all models meeting quality assurance criteria. Using these models, conservation area prioritizations were developed for Texas under several guiding criteria for decision making. The field survey sampled the mainstem Brazos at 20 sites between Possum Kingdom Reservoir and Bryan, TX, collecting 65,840 fish specimens representing 46 species. Neither survey target species was collected, suggesting absence or extreme rarity of both in this reach of the Brazos at the time of sampling. Collection sites upstream of Waco, compared to those downstream of that city, were less diverse in cyprinids and more diverse in non-native species, suggesting more heavily impacted habitat upstream of Waco. All raw data used in analyses and results of analyses and the field survey are provided with the written report.Texas Parks and Wildlife Department Section 6 grant TX E-136-R, TPWD #416853Texas Natural Science Cente

Final Environmental Impact Statement: Edwards Aquifer Recovery Implementation Program Habitat Conservation Plan

Urbanization causes havoc to native ecosystems, resulting in population declines or extirpation of sensitive taxa. This can be devastating to narrow-range endemics whose distributions overlap or are enveloped by urban development. Jollyville Plateau Salamanders (Eurycea tonkawae) are aquatic neotenes restricted to karst-associated waters in a small, highly urbanized area of central Texas. Eurycea tonkawae was recently listed as threatened under the U.S. Endangered Species Act due to threats from urbanization, although the published literature on their population status is limited to a single, short-term study. Here, we attempt to remedy this dearth of knowledge by summarizing population survey data from sites that span the breadth of E. tonkawae’s range. We analyzed count data using Bayesian inference and generalized linear models, first to determine trends in abundance at eight sites from 1996–2011. Secondly, we examined differences in salamander density at these and an additional nine sites (n = 17) among urbanized and nonurbanized catchments from 2009–2012. Study sites occurred in catchments that ranged from undeveloped to completely built-out, from no-change in development to \u3e 20% increases in development. Accounting for climatic variation, we found that counts of E. tonkawae declined in areas that had the largest increases in residential development (a metric of urbanization) over a 15-y period. Additionally, densities of E. tonkawae were negatively correlated with residential development across their range. We discuss several possible mechanisms responsible for declines of E. tonkawae and highlight likely causes and potential areas of future research to aid in conservation efforts for this and other central Texas Eurycea salamanders

Final Environmental Impact Statement: Edwards Aquifer Recovery Implementation Program Habitat Conservation Plan

Urbanization causes havoc to native ecosystems, resulting in population declines or extirpation of sensitive taxa. This can be devastating to narrow-range endemics whose distributions overlap or are enveloped by urban development. Jollyville Plateau Salamanders (Eurycea tonkawae) are aquatic neotenes restricted to karst-associated waters in a small, highly urbanized area of central Texas. Eurycea tonkawae was recently listed as threatened under the U.S. Endangered Species Act due to threats from urbanization, although the published literature on their population status is limited to a single, short-term study. Here, we attempt to remedy this dearth of knowledge by summarizing population survey data from sites that span the breadth of E. tonkawae’s range. We analyzed count data using Bayesian inference and generalized linear models, first to determine trends in abundance at eight sites from 1996–2011. Secondly, we examined differences in salamander density at these and an additional nine sites (n = 17) among urbanized and nonurbanized catchments from 2009–2012. Study sites occurred in catchments that ranged from undeveloped to completely built-out, from no-change in development to \u3e 20% increases in development. Accounting for climatic variation, we found that counts of E. tonkawae declined in areas that had the largest increases in residential development (a metric of urbanization) over a 15-y period. Additionally, densities of E. tonkawae were negatively correlated with residential development across their range. We discuss several possible mechanisms responsible for declines of E. tonkawae and highlight likely causes and potential areas of future research to aid in conservation efforts for this and other central Texas Eurycea salamanders

Species Distribution Model for <i>Hybopsis amnis</i> (Maximum modeled probability of occurrence in BCW is 0.63).

<p>The figure extent is limited to BCW vicinity. The black dots show historical occurrence points in BCW vicinity for this species.</p