A review of the systematics of the tick family Argasidae (Ixodida)

Abstract

The tick family Argasidae is a complex and diverse assemblage of about 190 species. Taxa within the Family Ixodidae had received considerable attention by contemporary researchers, but currently there is no consensus about the relevant morphological features for the determination of argasid species nor there is consensus on the appropriate genus for about 130 species. As a result, many species of Argasidae have not been yet adequately described. The generic and subgeneric arrangements are still a matter of discussion and currently there is no strict description of supraspecific systematics of this group. In this review, we introduce the competing proposals for the systematics of the family Argasidae, together with an overview of prominent morphological, ecological and behavioural features, which are of interest in a synthesis of the family. Special attention is paid to previous attempts to systematize the group based on cladistic analysis, outlining the possible pros and cons of such a method. We also present the largest phylogenetic tree of the family in terms of the number of species resolved by molecular biology based on 16S rDNA. This tree provides support for some of the previously proposed systematic arrangements based on morphology alone, and shows no basic differences with other previously published trees using either nuclear or mitochondrial, coding or non-coding genes. Our main conclusion is that we are still far from an accurate view of the main evolutionary lines of the family. There is thus an urgent need to obtain additional material to, first, explore the relative position of the different species in the phylogenetic arrangement of the family, and second, to capture adequate morphological features which could support a systematic key, necessary for any kind of faunistic or epidemiological studies.