Phylogeography of Rhipicephalus sanguineus sensu lato and its relationships with climatic factors

Abstract

Brown dog ticks morphologically identifiable as Rhipicephalus sanguineus sensu lato, are distributed world-wide and their systematics is controversial. Results of genetic and reproductive compatibility studies of geographically distinct populations of R. sanguineus s.l. indicate that the R. sanguineus complex is paraphyletic. To further elucidate systematic relationships within R. sanguineus s.l. and geographic boundaries of its lineages, we conducted a phylogeographical study of 136 tick specimens from 23 countries. Voucher specimens were morphologically identified. A phylogenetic tree was constructed using concatenated partial mitochondrial 12S and 16S rDNA gene sequences and analyzed by the Neighbor-Joining method. A set of nineteen “bioclimatic” variables within the WorldClim dataset were extracted and analyzed to assess correlations between distribution of R. sanguineus lineages and climatic variables. The following four branches are clearly recognized on the phylogenetic tree: R. sanguineus - tropical and temperate clades, R. leporis, and R. turanicus. DNA sequences of R. sanguineus from Israel differ from those of other groups. Strong association between geographical locations of major clades of R. sanguineus and temperature was identified. Tropical clade of R. sanguineus s.l. occupies areas with the annual mean temperature >20°C, whereas the temperate clade is present in areas with the annual mean temperature <20°C. Our results indicate that ticks in 2 closely related phylogenetic clades are adapted to different environmental conditions and support proposals for re-classification of R. sanguineus complex. Differences in R. sanguineus s.l. ecology and human/animal pathogens transmitted by different taxa of brown dog tick need to be studied.

East and west separation of Rhipicephalus sanguineus mitochondrial lineages in the Mediterranean Basin

“…IIa and Rhipicephalus sp. IIb in the Mediterranean Basin appear to be independent of current climatic conditions (unlike the geographical distribution of the “tropical” and “temperate” lineages of R. sanguineus : [12]).…”

“…For instance, sequences of the 12S gene of ticks from Kuwait, morphologically identified as R. leporis , were 99% similar to sequences of R. leporis from Iraq and R. sanguineus ( s.l .) from South America [12]. Based on this ambiguity, further and larger scale studies may be needed to ultimately verify that R. leporis from east and west Africa are not intraspecific morphological variants of R. sanguineus ( s.l .)…”

“…I-IV) in addition to the “tropical species” [1]. The geographical distribution of these groups has recently been shown to be associated with climate variables, such as temperature [12]. …”

Mitochondrial DNA analysis of Rhipicephalus sanguineus s.l. from the western Iberian peninsula

“…Other authors have supported and extended these findings by suggesting the existence of at least two climate‐related lineages based on climate variables correlation analysis and including a ‘tropical lineage’ and a ‘temperate lineage’ (Szabó et al ., ; Moraes‐Filho et al ., ; Sanches et al ., ; Zemtsova et al ., ). Recently, (Dantas‐Torres et al ., ) highlighted four genetically distinct morphotypes in R. sanguineus s.l ., designated as Type I (from Greece), Type II (from Italy, France, Spain and Portugal), Type III (from India) and R. sanguineus s.l .…”

“…; Burlini et al ., ; Moraes‐Filho et al ., ; Dantas‐Torres et al ., ; Liu et al ., ; Rosa et al ., ; Sanches et al ., ). This variability suggests the presence of several different species, an issue presently evaluated through genetic approaches developed in recent years, using mitochondrial ribosomal RNA (12S and 16S) molecular markers (Nava et al ., ; Dantas‐Torres et al ., ; Sanches et al ., ; Zemtsova et al ., ), cytochrome oxidase I (COI) (Moraes‐Filho et al ., ; Nava et al ., ; Dantas‐Torres et al ., ; Sanches et al ., ), and total DNA (Liu et al ., ).…”