Unraveling the diversification history of Trimerotropis pallidipennis (Oedipodinae: Acrididae) species group in South America: a delimitation analysis reveals new genetic lineages.

GUZMAN N. V.; CIGLIANO M. M.; PIETROKOVSKY S. ; CONFALONIERI V.A.

Congreso; 11th International Congress of Orthopterology; 2013

The Trimerotropis pallidipennis species complex represents a group of band-winged grasshoppers distributed over North and South America. As diagnostic characters are vague and intraspecific variability is high, the taxonomic status of the South American representatives of this group have a high degree of uncertainty, making taxonomic decisions based only on morphological traits difficult. Originally, six species had been described:T. pallidipennis, with the subspecies T. pallidipennis pallidipennis (Burmeister, 1838) and T. pallidipennis andeana Rehn, 1939; Trimerotropis ochraceipennis (Blanchard, 1851), Trimerotropis atacamensis (Philippi, 1860), Trimerotropis chloris (Philippi, 1863), Trimerotropis flavipennis (Philippi, 1863) and Trimerotropis irrorata (Philippi,1863). Yet, the latter four names are now considered synonyms of T. ochraceipennis(Amedegnato & Carbonell, 2001), while T. pallidipennis andeana has been raised to the status of species (Otte, 1995). More recently, an analysis of species delimitation based on molecular markers revealed that the complex would be composed by at least three distinct genetic linages:Trimerotropis from North America, Trimerotropisochraceipennis from Chile and an undescribedTrimerotropis species from Argentina (Husemann et al., 2013). Peruvian specimens taxonomically assigned to T. andeana resolved as paraphyletic, i.e. they joined either to T pallidipennis from Argentina or T. ochraceipennis.Moreover, these genetic lineages can also be distinguished on cytological grounds: in Trimerotropis sp. from Argentina the four medium chromosomes are polymorphic for inversions, a karyotypic feature that differentiates this species from North American T. pallidipennis, in which the same chromosomes are always monomorphic. In contrast, in T. ochraceipennistwo of the medium-sized chromosomes are fixed for submetacentric state. Finally, the karyotype of Peruvian specimens remains unknown. In this study, we performedphylogenetic and coalescent analysesin order to establishthe species status of Peruvian specimens (i.e. T.andeana), by sequencing two mitochondrial and one nuclear gene for multiple specimens belonging to each genetic linage of Trimerotropis and from T. andeana along its entire distribution. Our results indicate that Peruvian specimens are clustered in at least two different genetic lineages: one of them is formed by those individuals collected at the northwest of Perú, at lower altitudes near the sea coast;and the other includes those individuals collected at higher altitudes along the Andes mountains, and also those individuals from Chile, taxonomically identified as T. ochraceipennis. Interestingly, the new genetic lineage from Perú identified in this study has the same karyotype as T.pallidipennis from North America. Previous studies indicated a North American origin of the species complex and suggested that colonization of South America would have occurred during the Pleistocene after the closure of the Isthmus de Panama.Subsequent diversification in South America was the result of range expansion and vicariance, possible in response to later Plesitocene glaciations.