Damian Bourne MSc Student, Colautti Lab Morphometric variation in Ixodid ticks at an expanding range edge Ixodid ticks (Acari: Ixodidae) are important vectors of zoonotic disease that have devastating impacts on human health and well-being. Therefore, it is essential that effective monitoring protocols be put into place to map tick abundance and richness within certain areas. Although research into the most important tick species across Eastern, Ontario is abundant, up-to-date studies looking into the morphological features that contribute to observed diversity are lacking. Geometric morphometrics is a powerful tool that allows researchers to compare shape variation between groups. This study utilizes geometric morphometrics to survey important tick species within Eastern Ontario and explore the morphological diversity that defines them. A total of 518 ticks were sampled over a 6-year period representing two medically important species known to harbour harmful pathogens: D. variabilis and I. scapularis. Morphometrics utilizing principal component analyses of these two species found that the chosen common dorsal and ventral landmarks accurately categorized individuals by their respective species and sex. Furthermore, I. scapularis females showed significantly different morphologies across locations possibly representing diverse environmental pressures that need to be considered in management protocols. Supervised machine learning algorithms were also utilized and found that the selected landmarks accurately assigned individuals to their respective groups. Additionally, this analysis identified individuals with abnormal morphologies that may represent novel or cryptic species. Future research should combine both morphometric and genetic approaches to increase the robustness of species identification and provide additional evidence for tick diversity that may lead to better mitigation and management solutions for these critical vectors of zoonotic disease.
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