Interference competition between native Iberian turtles and the exotic Trachemys scripta

Abstract

The red-eared slider, Trachemys scripta elegans, is a worldwide invasive species, currently introduced in most freshwater habitats as a consequence of the exotic pet trade. In the Iberian Peninsula, this American turtle is competing and displacing the Iberian turtles, Emys orbicularis and Mauremys leprosa. Recent studies have pointed out to diverse competitive advantages of sliders over Iberian terrapins. For instance, native turtles avoid chemical cues from T. scripta, which is more aggressive and dominant in direct competition for food and basking places. This avoidance behaviour displayed by Iberian terrapins might serve as a spacing mechanism to avoid unfavourable competitive interactions with the introduced species. Sliders also benefit from morphological and thermoregulatory advantages: they are more spherical, thus presenting a less surface to volume ratio and a greater thermal inertia that facilitates heat retention. On the other hand, introduced turtles show a more accurate assessment of predatory risk in altered habitats, and are more efficient predators of local prey than native species. These inter-specific asymmetries could contribute jointly to the greater competitive ability of introduced T. scripta, thus facilitating the expansion of this alien species in detriment of native populations of Iberian terrapins. Interferencias competitivas entre los galápagos nativos ibéricos y el galápago exótico Trachemys scripta. El galápago de Florida, Trachemys scripta elegans, es una especie invasora a nivel mundial, introducida en la mayor parte de los ecosistemas acuáticos como consecuencia del comercio masivo de mascotas. En la Península Ibérica, este galápago americano compite y desplaza a los galápagos ibéricos, Emys orbicularis y Mauremys leprosa. Estudios recientes han puesto de manifiesto la existencia de diversas ventajas competitivas del galápago de Florida sobre los galápagos nativos ibéricos. Por ejemplo, los galápagos nativos evitan ocupar espacios donde detectan secreciones químicas de los galápagos exóticos, quienes se muestran más agresivos y dominantes en la competencia directa por la comida y los recursos de asoleamiento. Este comportamiento aversivo podría ser utilizado por las especies nativas para evitar las interacciones competitivas desfavorables con la especie invasora. Los galápagos de Florida se benefician también de ventajas morfológicas y termorreguladoras: presentan una forma más esférica y por tanto una menor relación superficie-volumen y una mayor inercia térmica que facilita la retención de calor. Por otra parte, los galápagos exóticos muestran un mejor ajuste del riesgo de depredación en hábitats alterados y poseen ventajas en la captura de presas nativas. Estas asimetrías inter-específicas podrían contribuir conjuntamente a una mayor habilidad competitiva del galápa-go de Florida, facilitando la expansión de esta especie invasora en detrimento de las poblaciones nativas de galápagos ibéricos.

On a razor's edge: Status and prospects of the critically endangered Bellinger River snapping turtle, Myuchelys georgesi

“…This sub species is native to the south‐eastern USA but is now widely distributed in North America beyond its natural range and throughout the world (Kikillus, Hare, & Hartley, ). It is the invasive turtle of greatest concern globally, with a suite of adverse impacts on native turtles and other species (Ficetola, Rödder, & Padoa‐Schioppa, ; Polo‐Cavia, López, & Martin, ; Ramsay, Ng, O'Riordan, & Chou, ). Removal of non‐native slider populations has been achieved or attempted in Australia (O'Keefe, ), Europe (Valdeón, Crespo‐Diaz, Egaña‐Callejo, & Gosá, ), and the USA (Drost, Lovich, Madrak, & Monatesti, ), but confirming eradication can be difficult (García‐Díaz et al, ).…”

“…Knowledge of the size of the residual post-disease population of M. georgesi in the Bellinger River, and the body condition and growth of the survivors, is critical for planning conservation actions. For example, poor body condition as a result of malnutrition can reduce immune competence in freshwater turtles and render them more susceptible to infection (Borysenko & Lewis, 1979, though also see Polo-Cavia, Engstrom, López, & Martin, 2010).…”

“…This sub species is native to the south-eastern USA but is now widely distributed in North America beyond its natural range and throughout the world (Kikillus, Hare, & Hartley, 2010). It is the invasive turtle of greatest concern globally, with a suite of adverse impacts on native turtles and other species (Ficetola, Rödder, & Padoa-Schioppa, 2012;Polo-Cavia, López, & Martin, 2014;Ramsay, Ng, O'Riordan, & Chou, 2007).…”

Complex genetic patterns and distribution limits mediated by native congeners of the worldwide invasive red-eared slider turtle

“…To evaluate our last questions about the establishment of invasive T.s. elegans and the displacement of native turtles, we explored niche suitability and niche overlap between TSE and its congeners T. venusta, T. cataspila and T. taylori; while for worldwide comparisons, we selected a set of native turtle species from different parts of the world where invasive TSE has been documented and negative interactions have been observed: Actinemys marmorata (Western United States; Spinks et al, 2003;Silbernagel et al, 2013), Mauremys leprosa (south Europe-north Africa; Polo-Cavia et al, 2014;Meyer et al, 2015), Emys orbicularis (Europe; Cady and Joly, 2004;Polo-Cavia et al, 2014), Mauremys reevesii (Asia; Jo et al, 2017;Geng et al, 2018), Emydura macquarii and Chelodina longicollis (Australia; Burgin, 2006;Mo, 2019). A dataset of available occurrence records per species was gathered from the Global Biodiversity Information Facility (GBIF, 2015); our own collecting records in Mexico were also included.…”

“…Comparative studies between native and invasive vertebrates that explicitly include biological interactions or functional features are quite limited (Polo-Cavia et al, 2014;Espindola et al, 2019). Thus, contrasting niche suitability could be a useful tool to include, indirectly, the interaction that can occur when a species is introduced to habitats occupied by other species, based on the environmental centrality hypothesis, where fitness is expected to be highest in those sites with environments closest to the center of the fundamental niche (Martínez- Meyer et al, 2013;Osorio-Olvera et al, 2019).…”