Genetic characterization ofCallosciurus(Rodentia: Sciuridae) Asiatic squirrels introduced in Argentina

Abstract

Squirrels have been traded in the pet market for several decades, and numerous species have established in the wild. The Asiatic species Callosciurus erythraeus and Callosciurus finlaysonii have been introduced into other parts of Asia, in Europe and South America. In this study, (1) we conducted a genetic characterization of C. erythraeus introduced into Argentina and compared them with native and introduced populations in Asia, and (2) we analyzed genetic variation among the four invasion foci in Argentina in order to corroborate that the pathway of invasion was a single introduction event in the country and subsequent translocations. We analyzed mitochondrial (cytochrome b, Cyt b; cytochrome oxidase c subunit I, COI and D-loop) and nuclear (recombination activating gene I, RAGI) DNA markers using the classical method (DNA barcoding gap analysis) and also the Automatic Barcode Gap Discovery method (ABGD). The markers D-loop, COI, and RAG1 indicated that the introduced squirrels from the different invasion foci formed a monophyletic group that, together with only one haplotype for the D-loop and COI markers, supported the hypothesis of one introduction event into Argentina followed by subsequent translocations. Unexpectedly, sequences from squirrels captured in Argentina were more related to C. finlaysonii than to C. erythraeus for D-loop and Cyt b markers. However, intraspecific variation among sequences of C. erythraeus belonging to different subspecies or collected in different regions was large and comparable with the distance to the sequences from Argentina. The ABGD method also indicated large genetic variability within C. erythraeus and close proximity between squirrels from Argentina and C. finlaysonii. The complex taxonomy of Callosciurus, as occurs with the sister species C. erythraeus and C. finlaysonii, requires a thorough systematic revision. A simultaneous analysis of diagnostic morphological characters and genetic markers is needed and will provide new insight regarding the worldwide invasion of Asiatic squirrels.

From a lag in vector activity to a constant increase of translocations: invasion of Callosciurus squirrels in Argentina

“…The first invasion focus that has established in Argentina subsequently functioned as a source of squirrels translocated to the other three invasion foci previously described , as was corroborated by genetic studies (Gabrielli et al 2014). The introduction events reported in this study also involved squirrels captured in the first invasion focus in Luján, occasionally involving illegal trade.…”

Preventing species invasion: A role for integrative taxonomy?

“…A similar scenario was found for introduced Callosciurus in Argentina, where exhaustive phylogenetic and DNA barcoding analyses revealed the occurrence of a new lineage more closely related to C. finlaysonii than to C. erythraeus, in contrast to what was assumed during sampling (Gabrielli et al 2014). Interestingly, the same unexpected misidentification occurred in our dataset for the 2 morphologically recognized C. erythraeus collected in Sichuan Province (China).…”

“…Surprisingly, in the CoxI dataset, the 2 MOTUs formed 2 new independent lineages never described before, whereas the French one was included into the MOTUs of C. erythraeus from Taiwan, China in the D-loop dataset (Figs 3,4). The K2P distance matrix and the comparison with the identification thresholds for sciurids species recently calculated by different authors (Gabrielli et al 2014;Ermakov et al 2015) suggest that the MOTU encompassing Italian and Belgian samples formed an independent taxonomic lineage at both markers, whose taxonomic rank (e.g. species or subspecies) needs to be further investigated.…”

“…Recent works have highlighted the growing importance of DNA barcoding in clarifying the taxonomic status and provenance of sciurid populations (see e.g. Gabrielli et al 2014;Ermakov et al 2015;Stevenson-Holt & Sinclair 2015). These studies also provide evidence for the importance of molecular surveys in management and conservation actions on sciurid species.…”

“…These markers were chosen because of their growing relevance in the field of modern integrative taxonomy (see e.g. Galimberti et al 2012a;Ermakov et al 2015) and because a huge number of D-loop sequences are available for the species group treated in this study (Gabrielli et al 2014). Moreover, the 2 markers typically show high mutation rates, which is essential to better identify similarities and differences among different species (CoxI) and even populations (D-loop).…”