An Integrative Approach of Taxonomic, Morphometric and Ecological Research to Solve the Status of Cryptic Chelonian Taxa—A Case Study With Pelomedusa kobe in Rwanda

Using genetic data, we confirm for the first time the presence of the Tanzanian helmeted terrapin Pelomedusa kobe in Akagera National Park, Rwanda, extending their known distribution. Our study provides the first natural history observations, population and morphological data for this species from a wild population. As species in the genus Pelomedusa are morphologically difficult to distinguish, we gain the first insights into intraspecific and interspecific patterns of size and shape variation of plastron morphology between two morphologically-similar species living in Eastern Africa, P. kobe and P. subrufa, using geometric morphometrics. Species affiliation, rather than sex, is the dominant factor influencing size and shape variation. P. kobe exhibits female-based sexual size dimorphism (SSD), while P. subrufa shows a tendency toward male-based SSD. Furthermore, sexual shape dimorphism (SShD) was observed in P. kobe but not in P. subrufa. Our results provide the first integrative data (genetic, morphological and natural history) on P. kobe, however further information on their distribution in the park is needed for effective conservation of this data-deficient species. Our findings lay the groundwork for future ecological studies on P. kobe, potentially revealing unique adaptations and conservation needs previously overlooked due to its cryptic nature.