Description of helminthic fauna of Trachemys scripta (Thunberg in Schoepf, 1792) in a protected area in Northern Italy: evidence of co-introduction of non-native helminth species.

Simple SummaryAnimal personalities could affect the behavior and physiology of both native and invasive species during biological invasion. However, little is known about the personality interaction effects on foraging behavior and growth between native and invasive species. We used the red-eared slider turtle and Chinese pond turtle as models to investigate how personality interactions effect the foraging behavior and growth of both these turtle species. The results showed that the foraging behavior of M. reevesii was mainly affected by the personality of T. scripta elegans. However, the foraging behavior of T. scripta elegans was effected by both their own personality and the personalities of M. reevesii. Additionally, the growth of both M. reevesii and T. scripta elegans were not effected by the personality combinations. The results revealed the mechanisms of personality interaction effects on the foraging behavior and growth of both native and invasive species during biological invasion. This study provides empirical evidence to help understand the effects of personalities on invasion dynamics.Animal personalities play a crucial role in invasion dynamics. During the invasion process, the behavioral strategies of native species vary among personalities, just as the invasive species exhibit variations in behavior strategies across personalities. However, the impact of personality interactions between native species and invasive species on behavior and growth are rarely illustrated. The red-eared slider turtle (Trachemys scripta elegans) is one of the worst invasive species in the world, threatening the ecology and fitness of many freshwater turtles globally. The Chinese pond turtle (Mauremys reevesii) is one of the freshwater turtles most threatened by T. scripta elegans in China. In this study, we used T. scripta elegans and M. reevesii to investigate how the personality combinations of native and invasive turtles would impact the foraging strategy and growth of both species during the invasion process. We found that M. reevesii exhibited bolder and more exploratory personalities than T. scripta elegans. The foraging strategy of M. reevesii was mainly affected by the personality of T. scripta elegans, while the foraging strategy of T. scripta elegans was influenced by both their own personality and personalities of M. reevesii. Additionally, we did not find that the personality combination would affect the growth of either T. scripta elegans or M. reevesii. Differences in foraging strategy may be due to the dominance of invasive species and variations in the superficial exploration and thorough exploitation foraging strategies related to personalities. The lack of difference in growth may be due to the energy allocation trade-offs between personalities or be masked by the slow growth rate of turtles. Overall, our results reveal the mechanisms of personality interaction effects on the short-term foraging strategies of both native and invasive species during the invasion process. They provide empirical evidence to understand the effects of personality on invasion dynamics, which is beneficial for enhancing comprehension understanding of the personality effects on ecological interactions and invasion biology.

The introduction of invasive alien species (IAS) poses a significant threat to global biodiversity, ecosystem functionality, and native species, particularly in protected areas. The red-eared slider turtle (Trachemys scripta elegans) ranks among the 100 most harmful IAS globally due to its ability to adapt and widespread distribution. This study investigates the nesting ecology of T. scripta in Angitola Lake, a Ramsar site and WWF Oasis in Calabria (Southern Italy), to better understand its reproductive strategies and guide effective management actions. We examined 309 natural predated nests across diverse habitats, analyzing the role of microhabitat features such as vegetative cover, soil type, and distance from the shoreline in nest site selection. Our findings show a clear selection for mixed habitats with soil combinations like dirt/sand and dirt/clay, which offer optimal conditions for oviposition. Nesting activity was concentrated primarily within 30 meters of the shoreline, with habitat and soil selection shifting throughout the nesting season in response to environmental factors, such as water availability. However, the results of the generalized linear mixed model (GLMM) indicate that while distance from the shoreline was significantly influenced by vegetation type (with greater distance in reforested sites), soil type and the continuous variables analyzed (depth, nest diameter, number of eggs) did not show significant effects on nesting distance. The ecological plasticity demonstrated by T. scripta, allowing it to exploit a wide array of nesting microhabitats, presents a significant threat to native turtle species like Emys orbicularis and overall local biodiversity. Consequently, this study provides valuable insights into the reproductive ecology of this invasive species, highlighting the necessity for integrated management strategies to address its ecological impacts within aquatic ecosystems.

Trait divergence and the ecosystem impacts of invading species

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees C, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environment (5 degrees C) or room-temperature environment (25 degrees C). At the end of 5 months treatment, hematocrit values, plasma protein concentration, and whole-blood viscosity values were determined for each turtle. Blood viscosity measurements were determined at five shear rates (3.75, 15, 30, 75, and 150 s-1) at 5 degrees C and 25 degrees C for all animals. No significant differences were found in hematocrit or plasma protein values between cold-adapted and room temperature-adapted animals. Whole-blood viscosity between groups at any shear rate at a temperature of 5 degrees C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to cold and room temperature occurred at a shear rate of 3.75 s-1 at 25 degrees C. The whole-blood viscosity of red-eared sliders, whether adapted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate, and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these animals during hibernation.

Juvenile invasive red-eared slider turtles negatively impact the growth of native turtles: Implications for global freshwater turtle populations

Habitat degradation and species introductions are two of the leading causes of species declines on a global scale. Invasive species negatively impact native species through predation and competition for limited resources. The impacts of invasive species may be increased in habitats where habitat degradation is higher due to reductions of prey abundance and distribution. Using stable isotope analyses and extensive measurements of resource availability we determined how resource availability impacts the long term carbon and nitrogen assimilation of the invasive red-eared slider turtle (Trachemys scripta elegans) and a native, threatened species, the red-bellied turtle (Pseudemys rubriventris) at two different freshwater wetland complexes in Pennsylvania, USA. At a larger wetland complex with greater vegetative species richness and diversity, our stable isotope analyses showed dietary niche partitioning between species, whereas analyses from a smaller wetland complex with lower vegetative species richness and diversity showed significant dietary niche overlap. Determining the potential for competition between these two turtle species is important to understanding the ecological impacts of red-eared slider turtles in wetland habitats. In smaller wetlands with increased potential for competition between native turtles and invasive red-eared slider turtles we expect that when shared resources become limited, red-eared slider turtles will negatively impact native turtle species leading to long term population declines. Protection of intact wetland complexes and the reduction of introduced species populations are paramount to preserving populations of native species.

In a recent article in Ecology, Leffler et al. (2014) presented a potentially new perspective on the importance of trait differences between native and invasive exotic plants in explaining invasions in local native communities. The new perspective brought forward is that, if trait differences between invasive and native species are likely to be important in explaining exotic plant invasion, the differences must be larger than those observed between native species in the new community. A meta-analysis of previous studies searching for trait differences was presented, with the general finding that the magnitudes of trait differences between invasive and native species tend not to differ from those observed between native species only. Leffler et al. (2014) interpret this result as evidence that trait differences are highly context dependent, and that mechanisms other than trait differences are likely to be more important in most cases of invasion. We acknowledge that there is no universal explanation of successful exotic invasion into native communities. Moreover, we do not believe that invasive plant species always have trait values that differ substantially from the traits present in the native community, or that trait differences are important for invasion in all cases. However, we cannot agree with the criterion stipulated by Leffler et al. (2014), namely that a trait difference between invasive and native species can only be important to invasion success if it is greater than the differences among natives. Leffler et al. (2014) do not explain the logic behind the criterion, but a flaw of the criterion is that it will discount cases when a successfully invading species has intermediate trait values that are not represented by native species. Leffler et al. (2014) seem to focus on trait differences as representing niche differences among species. Consider the scenarios of niche differences among native and exotic invasive species in Fig. 1. If a trait is related to the niche space occupied by native species in the community and the invader, for a trait difference to be important in invasion success under the criterion of Leffler et al. (2014), only the scenario in Fig. 1a would qualify. Here, the invader occupies a niche at the extreme of the niche space, compared to native species. The average niche-related trait difference between the invasive species and the natives will be greater than the average difference among natives. However, consider Fig. 1b. Here, the invader occupies a vacant niche that is intermediate between the native species (Stachowicz and Tilman 2005), and the invader would have an intermediate, niche-related trait value not represented by the native community. However, the average trait difference between the invader and native species in Fig. 1b will be smaller than the difference among native species, and under the criterion proposed, the native-invasive trait difference would be considered unimportant. Thus, the criterion proposed by Leffler et al. (2014) cannot distinguish between cases where trait values may lie between those of native species but are still distinct and cases where they are very similar to native species. Exotic species may not only invade a community by having different niche-related traits compared to native species. Some of the traits considered in the metaanalysis of Leffler et al. (2014), e.g., biomass, are arguably traits related to fitness. Such fitness-related traits also do not have to be more different between invasive and native species than among natives, for them to be important for invasions. All that is required is for the trait difference to be large enough for invasive species to have greater fitness than the native species (Fig. 1c). If this occurs and there is niche overlap between the invasive species and a native species, then the invasive species should displace the native species (MacDougall et al. 2009). The trait difference between invasive and native species should always be greater than the average native-native difference only when the trait is related to niche space and the invader is occupying a vacant niche at the extremes of the niche space available to the whole community. Thus, cases that meet the Leffler et al. (2014) criterion could be viewed as representing only one of three possible scenarios where differences in traits between native and invasive species are potentially important, and the only scenario where native-native differences are relevant. The challenge is to understand which of the many traits we can measure are actually related to fitness and niches of invasive and native species, and then to identify whether fitness or niche differences (or perhaps even both) have led to invasion. Manuscript received 15 July 2014; revised 7 August 2014; accepted 10 September 2014. Corresponding Editor: D. C. Laughlin. 1 Ecology Lab, Department of Biology, University of Konstanz, Universitaetsstrassse 10, Konstanz D78457 Germany. 2 E-mail: wayne.dawson@uni-konstanz.de

Different responses or tolerance to thermal stress between invasive and native species can affect the outcome of interactions between climate change and biological invasion. However, knowledge about the physiological mechanisms that modulate the interspecific differences in thermal tolerance is limited. The present study analyzes the metabolic responses to thermal stress by the globally invasive turtle, Trachemys scripta elegans, as compared with two co-occurring native turtle species in China, Pelodiscus sinensis and Mauremys reevesii. Changes in metabolite contents and the expression or enzyme activities of genes involved in energy sensing, glucose metabolism, lipid metabolism, and tricarboxylic acid (TCA) cycle after exposure to gradient temperatures were assessed in turtle juveniles. Invasive and native turtles showed distinct metabolic responses to thermal stress. T. scripta elegans showed greater transcriptional regulation of energy sensors than the native turtles. Enhanced anaerobic metabolism was needed by all three species under extreme heat conditions, but phosphoenolpyruvate carboxykinase and lactate dehydrogenase in the invader showed stronger upregulation or stable responses than the native species, which showed inhibition by high temperatures. These contrasts were pronounced in the muscles of the three species. Regulation of lipid metabolism was observed in both T. scripta elegans and P. sinensis but not in M. reevesii under thermal stress. Thermal stress did not inhibit the TCA cycle in turtles. Different metabolic responses to thermal stress may contribute to interspecific differences in thermal tolerance. Overall, our study further suggested the potential role of physiological differences in mediating interactions between climate change and biological invasion.

Human influence on the environment is so extensive that virtually all ecosystems on the planet are now affected by biological invasions. And, often, ecosystems are invaded by multiple co‐occurring non‐native species. Hence, it is important to understand the impacts these invasions are producing on biodiversity and ecosystem processes.Here, we present results of a 2‐year long field experiment where we tested the effects of co‐occurring invasive C4African grasses in a Cerrado area in central Brazil. We compared plant and arthropod communities, plant biomass, and soil nitrogen dynamics and soil chemical characteristics across five experimental treatments:Urochloa decumbensremoval;Melinis minutifloraremoval; bothU.decumbensandM.minutifloraremoval;U.decumbensandM.minutiflorainvaded plots; and uninvaded Cerrado. We hypothesized that selective removal of invasive grasses would have distinct effects on the native ecosystem structure and functioning. We expected that each invasive grass would produce a different type of impact on the native ecosystem and that their impacts would be synergistic when co‐occurring.Removal ofM.minutifloradoubled native plant diversity and biomass when compared to invaded plots, whereas removal ofU.decumbensdid not alter these parameters. Cerrado plots had four times more plant species than plots cleared of invasives. Removal of invasive grasses did not affect the species richness or community composition of soil epigeal fauna. Cerrado soils had lower fertility, organic matter content and pH than invaded soils. The effects were generally higher when both invasive grasses were removed, suggesting impacts were synergistic, butM.minutiflorahad greater effects on plants and soils thanU.decumbens. Both invasive species produced negative impacts, but a single species was the main driver. We also detected persistent effects of the invasive grass species on the ecosystem after 2 years of removal.We conclude that invasive species of the same functional group have similar types of effects in native ecosystems, but the magnitude of impact was largely dependent on invasive species biomass and cover. Where multiple invasive species are present, research and management of invaded ecosystems should tackle the interacting effects of co‐occurring invaders.

Invasive species pose significant threats to biodiversity, human health, and economic systems. Freshwater turtles are popular as pets, but when released or allowed to escape into the wild, they can become invasive. A prominent example is the red-eared slider Trachemys scripta, which is recognized as a globally invasive species. Legislative tools, such as the European Union Regulation 1143/2014 on the prevention and management of invasive alien species, aim to combat these threats. This framework includes the implementation of Commission Implementing Regulation 1141/2016, which banned the trade of listed invasive species, including T. scripta. This study evaluates the effectiveness of Regulation 1143/2014 on T. scripta invasion and its consequences on other freshwater turtle invasions, using data from the CITES database and the GBIF platform. While T. scripta imports into the EU ceased after 2016, the species continues to establish and expand in the wild. This suggests that the trade ban had minimal impact on already established populations, highlighting the need for additional measures to reduce and control its spread. Simultaneously, imports and records of other freshwater turtle species have risen, indicating a shift in trade dynamics. These species are increasingly being introduced, potentially exacerbating the biological invasion problem. Despite limitations inherent to CITES and GBIF data, our findings suggest that the current European legislation has not been effective in mitigating T. scripta invasions and may have unintentionally contributed to the introduction of other invasive turtles. We recommend that the European Union develop invasive species lists tailored to each biogeographic regions of Europe to enhance the effectiveness of legislation.

Trichinella pseudospiralisinfectionin red-eared slider,Trachemys scripta,influenced by environmental temperature.

Invasive species are a significant cause of biodiversity declines on a global scale and novel species interactions often cause ecological damage through predation or competition. The red-eared slider turtle (Trachemys scripta elegans) has been introduced to wetlands globally and negatively impacts other native turtle species. In Pennsylvania, USA, the red-eared slider turtle is ecologically similar to the PA, state threatened red-bellied turtle (Pseudemys rubriventris). The objective of this dissertation is to examine the potential for competition between red-eared slider turtles and red-bellied turtles using field studies of adult free ranging turtles and manipulative studies of juvenile turtles in mesocosms. Field studies utilized intensive trapping, radio telemetry, stomach flushing, fecal sample collection and stable isotopes to determine populations sizes, spatial resource use and dietary resource use of both species. Intensive trapping and radio telemetry revealed that both species used wetland habitats ubiquitously. Dietary studies revealed that at a smaller, more highly fragmented and vegetative species depauperate wetland complex, red-eared slider turtles and red-bellied turtles overlapped extensively for dietary resources while at a larger, intact, more vegetative species rich wetland the diets of both species were partitioned. In manipulative experiments in which red-eared slider turtles and red-bellied turtles were housed in low resource availability groups and high resource availability groups with conspecifics or in mixed species groups red-eared slider turtles were competitively superior to red-bellied turtles. Field study results suggest that the potential for competition between red-eared slider turtles and red-bellied turtles varies depending on local habitat characteristics, while manipulative experiment results suggest that red-eared slider turtles are competitively superior in resource limited environments. These results combined suggest that in degraded wetland habitats, when resources become limited, red-eared slider turtles will have a competitive advantage over red-bellied turtles potentially leading to population declines. Red-eared slider turtles should not be sold outside of their native range as pets and when possible they should be removed from wetland habitats outside of their native range. Furthermore, wetland habitats should be managed and preserved to provide intact, species rich and species diverse habitats.

The purpose of the present report is to describe feasibility and gross postmortem results of oblique prefemoral ovariectomy in red-eared sliders (Trachemys scripta elegans) performed by veterinarians in a teaching environment. Sixteen red-eared sliders were included in a teaching workshop. The turtles were anesthetized and placed in dorsolateral recumbency at an oblique 45-degree angle by use of folded towels. After prefemoral access to the celom and placement of a retractor with elastic bands, the ipsilateral follicles were exteriorized via gentle maneuvering with cotton tip applicators and excised after application of titanium clips and cautery with bipolar radiosurgery. On 14 of the 16 chelonians (87.5%) surgery was successfully completed. Of the two chelonians that did not have the surgical procedure completed, one had marked celomitis with adhesion of the ovaries to the liver and one had immature ovaries. At the end of the surgical procedures all chelonians were euthanized and postmortem was performed. The 14 chelonians that had surgery completed had no evident remaining ovarian tissue on gross postmortem. A survey completed by the attendants nine months after the workshop showed that a minority of the respondents (1/17) found the procedure difficult, and that one of the seven respondents that performed the surgery after the workshop was not able to complete the procedure. This report indicated that oblique prefemoral ovariectomy in mature red-eared sliders can be effectively taught to veterinarians during a workshop, and that if the procedure is completed the chances of leaving ovarian remnants are low.

The Red-eared slider (Trachemys scripta elegans) is one of the world’s most invasive reptiles, with its spread largely driven by the global pet trade. This study examines its trade dynamics in Kerala, India, a biodiversity hotspot facing increasing invasive species threats. Using a telephonic questionnaire survey of 60 individuals engaged in the pet trade, we assessed awareness, motivations, and release practices associated with Red-eared sliders. Most turtle sales started in Kerala between 2010 and 2020, primarily via Chennai. Drivers of pet ownership included children’s fascination with exotic pets, ease of maintenance, and religious beliefs. However, awareness of ecological impacts was low, as only 32% of sellers acknowledged the risks of release, and nearly half believed there was no threat. These findings underscore the urgent need for targeted outreach, strengthened regulation, and active surveillance to mitigate the invasion risk posed by this species.

Invasive species have been identified as a major threat to native biodiversity and ecosystem functioning worldwide due to their superiority in spread and growth. Such superiority is explained by the invasional meltdown phenomena, which suggests that invasive species facilitate the establishment of more invasive species rather than native species by modifying the plant-soil feedback (PSF). We conducted a two-phase plant-soil feedback experiment using the native Prosopis cineraria and the invasive Prosopis juliflora in Oman. Firstly, we conditioned the soil by planting seedlings of native species, invasive species, native and invasive species "mixed", and unconditioned soil served as a control. Secondly, we tested the feedback of these four conditioned soil on the two species separately by measuring the productivity (total biomass) and the performance in the form of plant functional traits (plant height, specific leaf area (SLA), leaf nitrogen content (Nmass), leaf carbon content (Cmass) and specific root length (SRL) of native and invasive species as well as the nutrient availability in soil (soil organic carbon (SOC) and soil total nitrogen (STN)). We found that the native species produced more biomass, best performance, and higher SOC and STN when grown in soil conditioned by native species, additionally, it gave lower biomass, reduced performance, and lower SOC and STN when grown in the soil conditioned by invasive and mixed species. These results suggest negative PSF for native species and positive PSF for invasive species in the soil conditioned by invasive species, which can be considered as red flag concerning the restoration of P. cineraria as an important native species in Oman, as such positive PSF of the invasive species P. juliflora will inhibit the regeneration of P. cineraria.