Towards an Evolutionary Understanding of Questing Behaviour in the Tick Ixodes ricinus

Abstract

The tick Ixodes ricinus finds its hosts by climbing vegetation and adopting a sit-and-wait tactic. This “questing” behaviour is known to be temperature-dependent, such that questing increases with temperature up to a point where the vapor pressure deficit (drying effect) forces ticks down to rehydrate in the soil or mat layer. Little if any attention has been paid to understanding the questing of ticks from an evolutionary perspective. Here we ask whether populations from colder climatic conditions respond differently in terms of the threshold temperature for questing and the rate of response to a fixed temperature. We find significant variation between populations in the temperature sensitivity of questing, with populations from cooler climates starting questing at lower temperatures than populations from warmer temperatures. Cool climate populations also quest sooner when the temperature is held constant. These patterns are consistent with local adaptation to temperature either through direct selection or acclimation and challenge the use of fixed thresholds for questing in modeling the spread of tick populations. Our results also show how both time and temperature play a role in questing, but we are unable to explain the relationship in terms of degree-time used to model Arthropod development. We find that questing in response to temperature fits well with a quantitative genetic model of the conditional strategy, which reveals how selection on questing may operate and hence may be of value in understanding the evolutionary ecology of questing.

Identifying Environmental Risk Factors for Louping Ill Virus Seroprevalence in Sheep and the Potential to Inform Wildlife Management Policy

“…In support of our predictions, sheep farms had higher LIV seroprevalences if they were in areas with a warmer climate (more growing degree days per annum). Higher temperatures increase tick interstadial development rate, oviposition rate, egg development rates and tick activity ( 34 – 37 ), and warmer climates (for example, as studied using altitude) have been associated with higher tick abundance ( 9 , 20 , 21 , 27 , 38 , 39 ) and higher risk of tick-borne diseases (examples from Lyme disease risk or B. burgdorferi prevalence: ( 7 , 22 , 40 ). While growing degree days is a variable originating from plant growth, it is a measure of warmth, and is particularly relevant to ticks because the plant growing season aligns well with the tick activity season (usually April-October, depending on the area).…”

Climate change, biodiversity, ticks and tick-borne diseases: The butterfly effect

“…I probably did not elaborate a proper answer for that question, because the relationship between tick development rates and temperature is nonlinear ( Randolph, 2009 , Estrada-Peña et al., 2012 ). Categorically, Tomkins et al. (2014) stated “while the idea of fixed temperature thresholds applying across populations may be a convenient assumption from the point of view of predicting the distribution of ticks, it may lack realism”.…”

Épidémiologie de la borréliose de Lyme en France : entre incertitudes et certitudes

“…Seule l'espèce I. ricinus peut transmettre Bbsl àl 'homme en France métropolitaine avec des variations régionales, expliquées en partie par le fait qu'I. ricinus au n tropisme pour les régions humides et tempérées (entre1 0e t2 5°C) où la végétation est constituée de forêts d'arbres àf euilles caduques ou de forêts mixtes (figure1 ,c i-dessous) (Tomkins et al, 2014 ;R izzoli et al,2 014). Ainsi les tiques I. ricinus sont très peu présentes dans le sud de la France et en altitude (au-dessus de 1500 mètres).…”