Evidence of co-specificity betweenTetranychus evansiandTetranychus takafujii(Acari: Prostigmata, Tetranychidae): comments on taxonomic and agricultural aspects

Abstract

Using a combination of the cytochrome oxidase subunit I gene (COI) and internal transcribed spacer (ITS) sequence information, cross-breeding, and morphological criteria, the taxonomic status of Tetranychus takafujii was reassessed. Described from Japan and very close to Tetranychus evansi, only the male empodium II separated the two species. Six T. evansi samples collected in Brazil, France, Kenya, Spain (including the Canary Islands), Taiwan, and two samples from Japan previously species-identified as T. takafujii, were examined. DNA sequences consistently divide the samples into two groups: group I held the mites from Brazil and France and group II contained the remaining samples of T. evansi together with the two mites collected in Japan. Likewise, crossbreeding experiments detected the same two groups that were reproductively partially incompatible. However, the Japanese samples were completely compatible with the rest of the group II T. evansi samples. The empodium II shape failed to distinguish consistently between the T. evansi and T. takafujii samples, but rather highlighted its variability, questioning its utility for separating these taxa. Congruent results support the co-specificity of the two taxa. It is concluded that T. takafuji is a junior synonym of T. evansi.

Reproductive performance of seven strains of the tomato red spider mite Tetranychus evansi (Acari: Tetranychidae) at five temperatures

“…Taiwan (Ho et al 2005) and Japan (Gotoh et al 2009). In Japan, the species was first found on nightshade (Solanum nigrum L.) in 2001 and described as a new species, Tetranychus takafujii Ehara et Ohashi (2002).…”

Recent emergence and worldwide spread of the red tomato spider mite, Tetranychus evansi: genetic variation and multiple cryptic invasions

“…Second, we have detected ITS sequence hybrids (each of the ITS types corresponds to one of the two COI clades) in the same sample (from Portugal), thus showing that crosses between mites stemming from the two clades are not only possible, but exist in nature. Additional evidence of conspecificity for individuals of the two clades comes from cross breeding experiments, which demonstrated fertile F1 females, although with some incompatibility (Gotoh et al 2009). …”

“…In the case of multiple introductions which might have unequal potential for becoming invasive (Allendorf and Lundquist 2003;Jousson et al 2000;Sakai et al 2001), crosses among individuals from distant populations might generate novel genetic combinations leading to new traits which eventually results in increased invasiveness (Allendorf and Lundquist 2003;Ellstrand and Schierenbeck 2000;Facon et al 2006;Lee 2002). Hybrid vigour has been invoked to explain why some introduced populations may overcome their parents' fitness in new environments (Facon et al 2005) and the reproductive compatibility between mites from the two clades has recently been demonstrated (Gotoh et al 2009). …”

“…Given the striking lack of variation of the ITS sequences with only two majority types detected worldwide (see results below), only 1-2 mites per locality were sequenced for this fragment. PCR conditions were as described previously (Tsagkarakou et al 2007a) with modifications of annealing temperatures and primers used to amplify and sequence the ITS 1,137 base pairs (bp) and the COI 868 (bp) as described by Gotoh et al (2009). PCR amplifications were carried out in an Eppendorf Mastercycler.…”

Integrating ecology and genetics to address Acari invasions

“…Since the specimens are immediately 'frozen in action' in their habitat, we are able to gather information on their feeding habits (ecology), observe them in greater detail (morphology) and analyze their DNA (molecular criteria). This three-pronged approach may be what is needed to solve several of the problematic issues of species that previously could only be separated using molecular techniques, e.g., cryptic species, which is of much value in the case of invasion events (Gotoh et al 2009;Dowling et al 2010).…”