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    HL Graduate Student Award

    2021-07-21   09:15 - 10:15

    Moderator: Rulon Clark

    1.  09:15  IN-PERSON    Characterization of Texas Tortoise (Gopherus berlandieri) Home Ranges and Habitat Use in Cameron County, Texas. Daniel Guerra*, Texas State University; Joseph Veech, Texas State University; Todd Esque, U.S. Geological Survey, Western Ecological Research Center

    Species habitat use is valuable information in conservation planning for species with restricted home ranges such as Gopherus tortoises. The Texas Tortoise (Gopherus berlanderi) inhabits Tamaulipan scrublands throughout south Texas, and coastal populations have been associated with lomas,low relief clay ridges filled with mesquital scrub. Lomasare typically surrounded by salt prairie grasslands. Our study examines G. berlandieri habitat use at Palo Alto Battlefield National Historical Park in Cameron County, Texas. Eleven tortoises were outfitted with GPS loggers which took locations once an hour. GPS loggers were replaced monthly after tortoises were relocated using radio telemetry. We used three different metrics to delineate home ranges of individual tortoises: 100% Minimum Convex Polygon, 95%, and 50% Kernel Density Estimate. We conducted a ?2-analysis for each individual tortoise for each home range metric to compare tortoise use of loma and prairie habitats to the amount of each habitat type available for use. A ?2-analysis was also performed for the entire study population for each home range metric. No individual tortoise showed patterns of habitat use that were different from availability of the two habitat types, regardless of home range metric. However, the study population as a single entity exhibited habitat use that was significantly similar to the availability of loma and prairie habitat types when home ranges were estimated as 100% MCPs and 95% KDEs. These results are counter to previous studies which strongly associate G. berlandieri with loma habitat in coastal populations of south Texas.

    2.  09:30  IN-PERSON    Modeling the potential impact of climate change on range expansion in Eleutherodactylus cystignathoides. Rebecca Chastain*, University of Texas Rio Grande Valley; Teresa Patricia Feria Arroyo, University of Texas Rio Grande Valley

    The critically understudied direct-developing Eleutherodactylus cystignathoides is a notable outlier in the amphibian decline crisis currently underway, having rapidly expanded its known distribution in recent years. Originally found in the Rio Grande Valley region, E. cystignathoideshas established populations across Texas, as well as in southern Louisiana and Alabama. This expansion has largely been dismissed as ecologically neutral due to lack of evidence of negative effect; however, no investigation has occurred into the potential interactions of this species in its introduced range whatsoever, meaning its impact is virtually unknown. The dearth of information about this species’ dispersal and ecology, coupled with the documented negative impacts of other successful Eleutherodactylid invaders such as E. coquior E. planirostris, warrants investigation that preempts waiting for any potential consequences of this invasion to make themselves known. To conduct such an investigation into the potential range limits of this species as they are defined by bioclimatic variables, we used spatially rarefied presence data and selected future climate projections to develop Maxent models of the potentially suitable habitat distribution of E. cystignathoidesin the United States both now and in the future. Our models suggest the existence of presently non-invaded potentially suitable habitat under both current and future models as well as evidence that this species may experience climate-induced habitat loss in its native range. These results are cause for concern, particularly because the impact of E. cystignathoides on other, more vulnerable amphibian populations is uncharacterized in terms of its capacity to compete, displace, hybridize, or spread disease.

    3.  09:45  VIRTUAL    Impact of Individual and Population-Level Factors on Daily Movements in Anaxyrus fowleri: Can Dispersive Movements Occur at Random? Nathalie Jreidini*, McGill University; David M. Green, McGill University

    There exists a conceptual gap between studies focused on understanding animal daily movements and studies focused on understanding animal dispersal. Using a 19-year capture-recapture dataset of daily movements performed by a population of Fowler’s Toads (Anaxyrus fowleri) in Long Point, Ontario, Canada, we explored the correlation between movement distances and factors typically thought to drive dispersal. We used a mixed-effect model with predictors sex, body size, the interaction between sex and body size, and conspecific density in addition to random effect terms year (inter-annual variation) and individuality (inter-individual variation). Overall, predictors were significantly correlated with movement distances when tested as isolated factors, but the correlations were weak as the variation in movement distances explained by predictors was negligible both across all individuals (3.6%) and within sex subsets (adult females: 0.2%, adult males: 3%, juveniles: 1.9%). Random effect terms accounted for some of that variation (24%), and the variation was nested per individual (24%) and to a lesser extent per year (8%). As much of the variation in A. fowleridaily movement distances remained unaccounted for by all predictors and random effect terms, and daily movements have the potential of turning into large-scale dispersive movements, this supports the idea of randomness in animal dispersive patterns. The simultaneous exploration of several dispersal predictors on short-scale movements that amount to large-scale dispersive movements provides a link between animal movement ecology and dispersal theories, which are often regarded as separate concepts.

    4.  10:00  VIRTUAL    Time Course of Splenic Cytokines mRNA During an LPS-induced Inflammatory Response in Toads. Felipe Floreste*, University of São Paulo; Braz Titon Jr, University of São Paulo; Stefanny Titon, University of São Paulo; Sandra Muxel, University of São Paulo; Fernando Gomes, University of São Paulo; Vania Assis, University of São Paulo

    Corticosterone (CORT) and melatonin (MEL) have complex immunomodulatory effects, including cytokine production. Cytokines modulate the inflammatory response by mediating communication among leukocytes, thus orchestrating the balance between propagation and resolution of the inflammatory response. Pro-inflammatory cytokines (IL-1? and IL-6) provide leukocyte recruitment and activation for the initial stages of response, while anti-inflammatory cytokines (IL-10) inhibit the advance of inflammation at later stages, preventing autoimmune damage. However, in ectotherms, the dynamics of endocrine mediators and cytokines during the inflammatory response are still underexplored. We investigated the progression of the inflammatory response in toads (Rhinella diptycha) injected with lipopolysaccharide (LPS; 2mg/kg) or saline (APBS) at 7 pm. Toads were bled (1, 3, 6, and 18h post-injection) to measure CORT and MEL levels, and spleens were collected to quantify cytokines mRNA. Our results show increased CORT from 6h on and a trend for decreased MEL 3h post-injection in the LPS-stimulated toads. LPS-stimulated toads also showed IL-1? upregulation at 1h and 18h, and IL-6 upregulation at all time-points. IL-10 was only detected at 6h and 18h post-injection, being upregulated in both time-points in the LPS toads. Alterations in CORT and MEL levels indicate activation of the hypothalamic-pituitary-interrenal axis and evidence of an amphibian immune-pineal axis, respectively. Our molecular data agrees with inflammatory progression with pro-inflammatory cytokines expressed since the first hour and the anti-inflammatory cytokine only after 6h. However, the late IL-1? mRNA surge at 18h indicates this timeframe is still short to comprehend the inflammation resolution phase in amphibians.

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