Ecology of Georgetown Salamanders (Eurycea naufragia) Within the Flow of a Spring Author(s): Benjamin A. Pierce, James L. Christiansen, Alexis L. Ritzer, and Taylor A. Jones Source: The Southwestern Naturalist, 55(2):291-297. 2010. Published By: Southwestern Association of Naturalists DOI: 10.1894/WL-30.1 URL: http://www.bioone.org/doi/full/10.1894/WL-30.1 BioOne (www.bioone.org) is an electronic aggregator of bioscience research content, and the online home to over 160 journals and books published by not-for-profit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. June 2010 Notes 291 ECOLOGY OF GEORGETOWN SALAMANDERS (EURYCEA NAUFRAGIA) WITHIN THE FLOW OF A SPRING BENJAMIN A. PIERCE,* JAMES L. CHRISTIANSEN,ALEXIS L. RITZER, AND TAYLOR A. JONES Department of Biology, Southwestern University, Georgetown, TX 78626 (BAP, ALR, TAJ) Texas Natural Science Center, University of Texas, Austin, TX 78705 (JLC) * Correspondent: [email protected] ABSTRACT—The Georgetown salamander, Eurycea naufragia, is a permanently neotenic salamander known only from about a dozen surface springs and caves in Williamson County, Texas. Rapid urbanization places all known populations at risk and conservation strategies are hindered by a lack of information on the ecology of the species. To better understand requirements of microhabitat and spatial distribution of E. naufragia within flows of surface springs, we conducted counts of salamanders on the surface at one locality over a 12-month period. Numbers of salamanders and percentage of cover objects occupied by salamanders varied among months, with a general trend of higher abundance in spring and summer. Few juveniles were observed, and there was no strong seasonal trend in distribution of size of salamanders. Within the flow of the spring, abundance of salamanders decreased linearly with distance from origin of the spring. Salamanders were more likely to be under rocks than under other types of cover objects and they selected larger rocks. Larger salamanders occupied larger cover objects; rocks covering multiple salamanders were larger than those covering single salamanders. RESUMEN—La salamandra Eurycea naufragia es una salamandra permanentemente neote´nica conocida solamente de una docena de manantiales superficiales y cuevas en el condado de Williamson de Texas. La ra´pida urbanizacio´n que ocurre en las a´reas donde habita la especie pone a todas las poblaciones conocidas en riesgo, pero las estrategias de conservacio´n son impedidas por falta de informacio´n ba´sica sobre su ecologı´a. Para entender mejor las necesidades del microha´bitat y la distribucio´n espacial de E. naufragia dentro de los flujos de los manantiales superficiales, contamos el nu´mero de salamandras en la superficie de una localidad por un perı´odo de doce meses. La cantidad de salamandras y el porcentaje de objetos de cubierta utilizados por las salamandras variaron de mes en mes, con una tendencia general de ma´s abundancia durante los meses de la primavera y del verano. Observamos muy pocos juveniles, y no hubo ninguna fuerte tendencia estacional en las distribuciones del taman˜o de las salamandras. Dentro del flujo del manantial, la abundancia de las salamandras disminuyo´linealmente THE SOUTHWESTERN NATURALIST 55(2):291–297 292 The Southwestern Naturalist vol. 55, no. 2 con la distancia del nacimiento del manantial. Fue ma´s probable encontrar salamandras debajo de piedras que debajo de otros tipos de objetos de cubierta y las salamandras eligieron piedras ma´s grandes. Las salamandras ma´s grandes ocuparon objetos de cubierta ma´s grandes; las piedras cubriendo mu´ltiples salamandras fueron ma´s grandes que las que cubrieron salamandras individuales. The Georgetown salamander, Eurycea naufra- some of these were 20–30 years ago and we have gia, is an endemic, spring-dwelling and cave- not been able to confirm presence of salaman- dwelling salamander restricted to the San Gabri- ders at several previously reported sites. el River drainage in central Texas. The species In spring 2007, we initiated a low-impact occurs at ca. 12 sites and its entire range is within ecological study of E. naufragia with the goal of the vicinity of Georgetown, Texas, an area that is better understanding the ecology of salamanders undergoing rapid growth and urbanization. The within flows of surface springs. Counts of E. population of Georgetown was 9,468 in 1980 but naufragia on the surface were made monthly or had increased to 44,398 in 2007 and is projected bimonthly at Swinbank Spring near Georgetown, to reach 84,000 by 2015. Published research on Williamson County, Texas, over a period of E. naufragia is limited to the original description 1 year. Counts of salamanders on the surface of its genetic and morphological characteristics were conducted 4 April, 7 June, 24 August, 21 (Chippindale et al., 2000) and general treatments September, 26 October, 30 November, and 31 of Eurycea in central Texas (e.g., Chippindale and December in 2007, and 1 February, 29 February, Price, 2005). Eurycea naufragia has been included and 28 March in 2008. For analysis of selection of as a candidate for listing as endangered (Jones, microhabitat, we also included results of one 2001), but currently is not protected by federal or count conducted at Taylor Ray Hollow Spring on state regulation. Because of its conservation status, 20 April 2007. basic information on distribution and ecology is All counts were conducted during 0800–1700 critical for management of the species. h. For each count, we established a transect Populations of E. naufragia originally were along the flow of the spring, beginning at the assigned to the wide-ranging species E. neotenes origin and extending 25 m downstream. Starting (Bishop and Wright, 1937; Sweet, 1977, 1984), at the bottom of the transect and working but analysis of molecular data (Chippindale et upstream, we overturned objects that were al., 1993, 1998, 2000; Hillis et al., 2001) submerged in the flow and potentially capable demonstrated numerous evolutionarily distinct of covering a salamander. For each potential lineages within Eurycea from central Texas. cover object, we recorded location along the Chippindale et al. (2000) determined that transect (in m), classified it to type (rock, stick, populations of Eurycea in Texas north of the leaf litter, gravel, or other), recorded its two Colorado River were monophyletic and exhibit- broadest dimensions (in cm), and recorded the ed considerable genetic divergence from other aquatic habitat in which it occurred (riffle, pool, populations of Eurycea on the Edwards Plateau. or bedrock glide). We recorded presence of E. Based on allozymes, sequences of mitochondrial naufragia and crayfish (Procambarus clarkii) under DNA, morphology, and osteology, they described cover objects. Each salamander was assigned to three species in Texas north of the Colorado one of three size classes (,2.5, 2.5–5.1, or River: E. tonkawae from the Jollyville Plateau in .5.1 cm) based on a visual estimate of its total Travis and Williamson counties, E. naufragia length from tip of snout to tip of tail. To from the San Gabriel River drainage in William- minimize disturbance to the population, we did son County, and E. chisholmensis from Salado not attempt to capture or handle salamanders Creek in Bell County. Chippindale et al. (2000) during surveys, and we returned all potential listed seven populations of E. naufragia. They cover objects examined to their original location suggested that additional populations might after observation. At the conclusion of each occur west of Georgetown and, indeed, we and count, we measured temperature (uC) and others have located salamanders at several specific conductivity (mScm21) of the water at additional sites. Currently, we are aware of past 1-m intervals along the transect. collections, observations, or both, of E. naufragia To standardize counts for sampling effort, we at 14 locations in Williamson County, Texas; calculated percentage of cover objects exam- June 2010 Notes 293 FIG. 1—Percentage of cover objects occupied by Georgetown salamanders (Eurycea naufragia) at Swinbank Spring, Williamson County, Texas, April 2007–March 2008. ined that were occupied by salamanders. Be- ered to be adult (Bruce, 1976; Najvar et al., causecountsandsurfaceareasofcoverobjects 2007). We suspect that monthly differences in were not distributed normally, we used non- abundance of salamanders are influenced by parametric statistics for analyses. Statistical tests variation in distribution of salamanders on the were conducted using SPSS statistical software surface within the flow of the spring; during (SPSS 13.0 for Windows, release 13.01, SPSS, certain months, more salamanders may be near Inc., Chicago, Illinois). This study complied the surface of the flow, where they are more with all applicable institutional animal-care likely to be observed in our counts. Differences guidelines. in abundance of food, chemistry of the water, or Numbers of salamanders observed at Swin- flow may influence abundance of salamanders bank Spring during surface counts were relative- on the surface and contribute to variation in ly small (range, 5–43). Percentage of cover abundance among months. objects occupied by salamanders at this site Percentage of cover objects occupied by varied significantly among months (Fig. 1, x2 5 crayfish also varied among months (x2 5 29.01, 80.54, df 5 9, P , 0.001), ranging from ca. 1% in df 5 9, P 5 0.001), but there was no significant December to .6% in March.