Coexistence of Native and Invasive Freshwater Turtles: The Llobregat Delta (NE Iberian Peninsula) as a Case Study

Abstract

The global degradation of wetlands is increasing their susceptibility to invasions, which is greatly determined by a niche overlap between native and invasive species. We analyze its role in regulating the coexistence of the native Mediterranean stripe-necked terrapin Mauremys leprosa and the invasive Red-eared Slider Trachemys scripta elegans in a coastal wetland. We analyzed both water chemistry and landscape attributes, using variance-partitioning analysis to isolate the variance explained by each set of variables. Then, the influence of environmental variables on species co-occurrence patterns was assessed by using latent variable models (LVM), which account for correlation between species that may be attributable to biotic interactions or missing environmental covariates. The species showed a very low niche overlap, with clear differences in their response to environmental and landscape filters. The distribution of T. s. elegans was largely explained by landscape variables, preferring uniform landscapes within the daily movement buffer, whereas at larger scales, it was associated with a high diversity of habitats of small and uniform relative sizes. A high percentage of the distribution of M. leprosa was unexplained by the measured variables and may be related to the competitive exclusion processes with T. s. elegans. The species was positively related with large patches with high perimeter values or ecotone area at medium spatial scales, and it was benefited from a marked heterogeneity in the patches’ size at larger scale. According to latent variable models, both species had wide eutrophication and salinity tolerance ranges, but they showed different environmental preferences. T. s. elegans was related to eutrophic freshwater environments, whereas M. leprosa was related to more saline and less eutrophic waters. Our results suggest that M. leprosa modifies its habitat use in order to avoid interaction with the T. s. elegans. Thus, management actions aimed at removing the invasive species from the territory and promoting habitat heterogeneity might be needed to protect M. leprosa and avoid local extinctions.

Risk Assessment Model System for Aquatic Animal Introduction Based on Analytic Hierarchy Process (AHP)

“…Although Trachemys scripta elegans is considered one of the 100 worst IS according to the IUCN and drives native freshwater turtles to consume suboptimal resources [63,64], the degree of control of non-native species is generally higher than that of pathogens. It is necessary to strengthen the supervision of the introduction and cultivation of Trachemys scripta elegans; prevent escape, diffusion, and random breeding; and strictly manage the areas where the Trachemys scripta elegans population settles, as Trachemys scripta elegans can coexist harmoniously with native species [65]. (5) The risk grade of Ambystoma mexicanum is low.…”

Aboriginal Tribe’s Knowledge of the Endangered Freshwater Turtle Cuora amboinensis in Car Nicobar, a Remote Oceanic Island in the Bay of Bengal

“…Turtles are also known as a good indicator of climate change [66], as climate change could possibly impact turtle populations [67][68][69]. The wetlands, which are important habitats of such species, should also be conserved and managed as they provide a permanent habitat for turtles [70]. Such habitats are vulnerable to anthropogenic impacts hence habitat management should be a key priority in future conservation efforts [71], along with the understanding of the spatial ecological information of the species [72].…”