Current and future ecological niche of Dermacentor similis Lado (Acari: Ixodidae) in western North America.

Abstract

Dermacentor similis Lado (Acari: Ixodidae) is a newly described tick species within western North America. These ticks were previously referred to as "western Dermacentor variabilis (Say)" and were genetically distinct from D. variabilis in eastern North America. Despite the known genetic differences, the ecology of this species was not investigated separately from eastern populations of D. variabilis. Therefore, the objectives of this study were to describe the current and future areas of ecological suitability of D. similis in western North America, and to determine the bioclimatic and environmental variables of importance for ecological suitability of this species. Twenty-nine confirmed samples of D. similis from the western United States (California, Oregon, Washington, Idaho) and Canada (British Columbia) were used in species distribution model creation via MaxEnt. Seven variables were included in the final current species distribution model of D. similis: terrestrial ecoregion, degree-days below zero degrees Celsius, Hogg's climate moisture index, mean annual relative humidity, day of the year on which the frost-free period begins, precipitation as snow, and extreme maximum temperature over thirty years. Under current conditions, high levels of ecological suitability were observed in the Okanagan region of British Columbia, Washington (extending into Oregon and Idaho), and regions of coastal and inland California. Future ecological suitability were similar to the current ecological suitability under both climate scenarios (2041 to 2070, SSP2-4.5 and SSP3-7.0). The results of this study will inform public and animal health messaging and awareness.