Hidden invasiveness of non-native Schlegel's Japanese gecko (Reptilia: Squamata: Gekkonidae) and three-way competition among natives and non-natives in Japan

In this study, we investigated the invasiveness of Gekko japonicus, a prevalent gecko species in Japan and an ancient non-native species, focusing on its competition with both the undescribed endemic Gekko species (referred to as Nishiyamori in Japanese) and G. hokouensis. These species are co-distributed with G. japonicus, leading us to hypothesize that G. japonicus was invasive upon its initial introduction. We employed niche analysis and population genetics through ddRAD-seq to assess the historical invasiveness of G. japonicus by comparing regions with and without interspecies competition. Our niche analysis across the Goto Islands, Hiradojima Island (colonized by G. japonicus) and the Koshikishima Islands (not colonized by G. japonicus) indicated that endemic Gekko sp. alter their microhabitat usage in response to invasions by other gecko species, despite having similar suitable habitats and microhabitat preferences. Population genetic analysis revealed significant population declines in Gekko sp. within areas of introduced competition, in contrast to stable populations in areas without such competition. These findings suggest a tripartite competitive relationship among the gecko species, with G. japonicus and G. hokouensis invasions restricting the distribution of the endemic Gekko sp. Consequently, G. japonicus may have historically acted as an invasive species. Acknowledging the historical dynamics of current biodiversity is crucial for addressing complex ecological issues and making informed conservation decisions.

Taxonomic revision of Chinemys pani (Testudines: Geoemydidae) from the Pleistocene of Taiwan and its implications of conservation paleobiology

Proper taxonomic identification is critical to our understanding of biodiversity and the underlying evolutionary history. Here we re-examine the cast of the holotype of Chinemys pani, a geoemydid turtle from the Pleistocene of Taiwan; the actual specimen was not curated appropriately after the original publication and was most likely lost. Our results provide substantial evidence to show that Chinemys pani should be identified as Mauremys reevesii. The replica, though not ideal, preserves various morphological features that allow reliable taxonomic identification of Mauremys reevesii, including the presence of three longitudinal keels on the carapace, the second to sixth neural bones anteriorly short-sided, and the lack of a movable plastral hinge. In addition, we also confirm that the original diagnostic features that established the new taxon: Chinemys pani - are polymorphic characters of Mauremys reevesii. Our taxonomic revision of a Pleistocene geoemydid turtle from Taiwan confirms the existence of the Pleistocene Mauremys reevesii. More importantly, this study offers new insights into the origin of modern biodiversity in Taiwan and gives a straightforward example of how fossils can be applied to conservation policies.

Ozobranchus jantseanus (Clitellata: Ozobranchidae) from Reeve’s Turtle, Mauremys reevesii: New Annelid Fauna in Korea

Turtle leeches have not been recorded in Korea, although they occur in geographically adjacent countries including China and Japan. This study describes a turtle leech, Ozobranchus jantseanus (Clitellata: Ozobranchidae), found from Reeve’s turtle (Mauremys reevesii) in Korea. Of the 143 Reeve’s turtles collected from the freshwater reservoir in Jinju City, Gyeongsangnam-do, Korea, 95 unidentified leeches were found in 8 (5.6%) individuals. The leeches had 22 somites with 11 pairs of externally exposed branchiae, body-sized posterior suckers, and spines on the dorsal surface. We identified these leeches as Ozobranchus jantseanus Oka, 1912 (Clitellata: Ozobranchidae). This species of turtle leeches found in Korea may fill the gap in the biodiversity of East Asian annulus.

A check list and population trends of invasive amphibians and reptiles in Taiwan

Invasive species have impacted biodiversity all around the world. Among various ecosystems, islands are most vulnerable to these impacts due to their high ratio of endemism, highly specialized adaptation, and isolated and unique fauna. As with other subtropical islands, Taiwan faces constant risk of biological invasions and is currently ranked as one of the countries most affected by invasive amphibians and reptiles. In this paper, a comprehensive checklist of all known exotic amphibians and reptiles is provided, including twelve species which have successfully colonized Taiwan and six species with a controversial status. We provide an update on the knowledge of all these species including their distribution, colonization history, threats to native animals, and population trends based on literature records, fauna surveys, and data collected during invasive species eradication and control programs. A list of species with high invasive potentials is also provided. This study reports, for the first time, a comprehensive survey of invasive herpetofauna in Taiwan, which should provide a valuable reference to other regions which might suffer from similar invasion risk.

Thermal physiological performance of two freshwater turtles acclimated to different temperatures

The thermal physiological performance of invasive species may play a crucial role in determining their invasion success. In this study, we acclimated two cohorts of hatchlings of freshwater turtles (native Mauremys reevesii and invasive Trachemys scripta elegans) from low and high-latitude collection sites, respectively, to different thermal conditions (20 and 30 °C) for 4 weeks, and then compared their thermal tolerance and locomotor performance. T. scripta elegans hatchlings could swim faster (but righted themselves more slowly), and tolerate a higher temperature and wider temperature range than M. reevesii hatchlings. Similarly, T. scripta elegans hatchlings had a greater maximal performance (P_max) value for swimming speed (but a lower P_max value for righting time) than M. reevesii hatchlings. Temperature acclimation had a significant impact on the thermal tolerance and locomotor ability of turtles, but the acclimation effect did not differ between the two species. T. scripta elegans hatchlings seemed to have a greater thermal plasticity than M. reevesii hatchlings. High-latitude individuals showed a greater low-temperature tolerance, but lower locomotor ability (longer righting time) than low-latitude ones. However, the thermal plasticity did not differ between latitudinal cohorts. Our results indicated that T. scripta elegans performed better than M. reevesii, which might contribute to its range expansion and invasive success.

Low genetic diversity in Ozobranchus jantseanus (Hirudinida: Ozobranchidae) in Japan: Possibility of introduction with their host turtles

Leeches belonging to the genus Ozobranchus are ectoparasitic on sea and freshwater turtles. The freshwater species O. jantseanus has been recorded from China and Japan. Ozobranchus jantseanus inhabiting Japan is considered to be a non-indigenous species, because their primary host, the Reeves' pond turtle, Mauremys reevesii, is thought to have been introduced in the last few centuries from adjacent Asian countries. To assess whether the Japanese populations of O. jantseanus were likely to have been introduced, their genetic diversity was investigated using mitochondrial cytochrome c oxidase subunit I sequences. The very low sequence diversity as well as the historical record of this species from Japan suggest that Japanese populations of O. jantseanus may have been artificially introduced along with their host turtles. Molecular phylogenies of COI showed that two marine Ozobranchus species formed a clade together with the freshwater O. jantseanus.