Thirty years of tick population genetics: A comprehensive review

Abstract

Population genetic studies provide insights into the basic biology of arthropod disease vectors by estimating dispersal patterns and their potential to spread pathogens. In wingless vectors, such as ticks, gene flow will be defined in large part by the mobility of their hosts. However, tick behaviors and life cycle strategies can limit their dispersal even on highly mobile hosts and lead to an increase in genetic structure. In this review we synthesize the published literature from three decades of tick population genetic studies. Based on studies from 22 tick species (including representatives from Amblyomma, Bothriocroton, Dermacentor, Ixodes, Ornithodoros, and Rhipicephalus), observed levels of population genetic structure in ticks varied from no structure to very high levels. In about half of the species (including representatives from Amblyomma, Bothriocroton, Dermacentor, and Ornithodoros), tick genetic structure appeared to be determined primarily by the movement capacity of hosts, with low gene flow observed in ticks that use smaller bodied less mobile hosts and high gene flow in ticks using highly mobile hosts. In a number of other species (primarily from Ixodes, Ornithodoros, and Rhipicephalus), behavioral limitations to gene flow appeared to result in greater genetic structure than expected based upon host movement capability alone. We also discuss the strengths and limitations of genetic markers and their applicability to ticks and suggest possible analyses when planning population genetic studies for ticks.

Range-wide genetic analysis of Dermacentor variabilis and its Francisella-like endosymbionts demonstrates phylogeographic concordance between both taxa

“…This important disease vector boasts an extensive and expanding range, which emphasizes the need for comprehensive phylogeographic studies to better understand its distributional patterns and characterize the relationship between these ticks and their microbiota. Multiple population genetic studies of D. variabilis have identified important phylogeographic trends for this species [5, 7, 21–23] and the bacterial pathogens that they vector; however, the breadth of these studies has been limited by geographical scope (1 to 3 states or provinces).…”

A comparative test of ixodid tick identification by a network of European researchers

“…Although these technologies are useful, they will always rely on reference specimens for which morphological identification needs to be correctly conducted (Nava et al, 2009;Araya-Anchetta et al, 2015). "Garbage sequences" obtained from unreliably identified specimens that accumulate in databanks are a source of molecular misidentification.…”

Comparative population genetics of two invading ticks: Evidence of the ecological mechanisms underlying tick range expansions

“…The use of molecular methods to trace the ancestry of invading species is well established (Templeton et al 1995, Ibrahim et al 1996, Le Roux et al 2009). For more than 30 years, molecular methods have been used to investigate tick population genetic structure (Araya-Anchetta et al 2015). Previous studies have documented the effects of host-mediated dispersal on genetic structure in the seabird tick Ixodes uriae , using microsatellite markers to determine how gene flow patterns changed depending on the host species exploited for dispersal (McCoy et al 2001, McCoy et al 2003).…”

“…Other studies have used phylogenetic analyses to determine recent population expansion, identify founder effects, and examine population structure at the expansion fronts of A. americanum and I. scapularis (Kelly et al 2014, Mechai et al 2013, Ogden et al 2011). Some broad conclusions reached by this body of work are that tick behaviors and life cycle strategies are as critical as host mobility in understanding tick population genetic structure, particularly as applied to different families of ticks (Araya-Anchetta et al 2015). …”