Contribution of geometric morphometry in the discrimination of tick species in Europe
Résumé
Ticks are vectors of infectious diseases of major importance in human and veterinary medicine. For epidemiological studies, accurate identification of ticks is crucial to define their potential role as vectors and to develop control and prevention strategies. Modern morphometric has enabled the
quantification of size and shape variations to investigate species in anatomical structures. We therefore applied landmark-based and outline-based geometric morphometric approaches to study 250 field-collected adult males and females in France and Slovakia. This research includes four
species: Ixodes hexagonus (n=39), I. ricinus (n=44), Dermacentor marginatus (n=71) and D. reticulatus (n=96). Coordinates of 16 landmarks, the contour of the external boundary of the dorsal face and the contour of the coxa1, were selected and digitized. The best scores of correct assignment, in both
sexes, were obtained by the contour of the first coxa 1 (91% of correct attribution in females, 76% in males), slightly higher than for landmark technique (72% and 80%) or the contour of the body (72% and 75%) techniques. The average level of correct species recognition by the coxa1 was satisfactory, and slightly higher for females than for males. Our results show that the outlines were very effective for identifying Dermacentor and Ixodes to genus and species level as well as for separating sexes within species. Moreover, shape differences were found between D. reticulatus population of France nd Slovakia. A molecular approach was used to validate the morphological and morphometric identification. Our results suggest that landmark-based and outline-based geomorphometric approaches could be a useful tool to allow an accurate identification of ticks at the genus and species level and deserve to be expanded.