A biogeographic study of South American Melanoplinae: pattern of diversification along the Andes Mountain Chain

DINGHI, P.A.; CONFALONIERI, V.A.; CIGLIANO, M.M.

Kunming

Congreso; 11th International Congress of orthopterology; 2013

The International Orthopterist Society

Melanoplinae is one of the largest subfamilies and, one of the main components of the Acrididae fauna in the American Continent (except in the rain forest biomes). The systematics of this group is controversial, with different authors recognizing different numbers of tribes, and an evolutionary history that remains unclear. Three scenarios have been proposed to explain the early biogeographic history of the Melanoplinae. The first posed a Eurasian origin of the group followed by migrations to North America, and then South America (Amédégnato, 1977). The second proposed an ancient Laurentian origin with the Nearctic region as centre, from which migrations began towards the Palaearctic and the Neotropic regions (Vickery, 1987). The third one, which is based on molecular studies (Amédégnato et al., 2003), suggests a South American origin followed by a substantial number of northward, eastward and/or westward migrations. The Andes, the world?s longest mountain chain, seems to be the main basis for speciation and diversification events for this group, harboring a great taxonomic and ecological diversity. Despite their young age, it is highly diverse due to recent geological uplift. Doan (2003) proposed a South-to-North Speciation Hypothesis (SNSH) for speciation of high Andean taxa, following a South-to-North pattern generally coinciding with the progression of final uplift of the Andes. According to this scenario, a phylogenetic hypothesis of relationships of a taxonomic group occurring in the high Andes would show a branching pattern in which the southernmost species diverged first, followed by the more northern species, and so on in a northerly pattern. Early studies based on the morphological diversification of Ponderacris (Melanoplinae), posited a North-to-South progression of speciation (Ronderos & Carbonell, 1971) but recently, Pocco et al. (2012) postulated just the opposite direction for this same genus: i.e. a South-to-North speciation pattern, in accordance with the progressive Andean uplift. Considering these issues, a molecular phylogenetic approach was carried out in order to test the different scenarios proposed for the Melanoplinae diversification in South America, especially for those distributed along the Andes Mountain chain, and also to solve some taxonomic controversies within the group. To these purposes, COI and NADH2 mitochondrial genes from several Melanoplinae species collected from Argentina to Venezuela along the Andes, were sequenced and analyzed. The following genera were included (sorted by tribe and bio-region): Jivarus Giglio-Tos, Urubamba Bruner and Nahuelia Liebermann (Jivarini), which are distributed in the Venezuela and Ecuador ´Páramos´, and in Argentinean Patagonic Andes; Maeacris Ronderos (Jivarini) from the Peruvian ´Puna´; Coyacris Ronderos, Chlorus Giglio-Tos, Ponderacris Ronderos & Cigliano, Boliviacris Ronderos & Cigliano, Baeacris Rowell & Carbonell (Dichroplini), all from the ´Yungas´ of Argentina, Perú and Bolivia; Orotettix Ronderos & Carbonell (Dichroplini), distributed in the Peruvian ´Puna´; Chibchacris Hebard, Timotes Roberts (Dichroplini) from the Venezuelan ´Páramos´; and finally, the insertae sedis genera Pediella Roberts, Huaylasacris Cigliano, Pocco & Lange, Tiyuantiyana (Cigliano, unpublished), all from Peruvian ´Puna´; and Meridacris Roberts, from the Venezuelan ´Páramos´. Locusta migratoria (L.) and several Melanoplus Stål (Melanoplini) species from North America were used as outgroup. The latter corresponding sequences were downloaded from the GeneBank. Bayesian and Maximum Parsimony (MP) searches were performed. The evolutionary model selected for the Bayesian search was GTR. Both searching criteria yielded similar topologies. Six distinct monophyletic clades were recovered. Maeacris (Jivarini) and the insertae sedis genus Tiyuantiyana resolves as the most basal sister group. Then, a cluster formed by the two insertae sedis genera Pediella and Huaylasacris emerge basally to the rest groups. These basal clades belong both to the Peruvian ´Puna´, supporting a South American origin for the Melanoplini, and to this region as the primary centre. The rest tribes resolve as follows: (Dichroplini, (Jivarini, Melanoplini)). Again, a South to North pattern of diversification was observed within both ´Jivarini´ and Dichroplini groups. Within the former, the most basal species is distributed in Patagonia (Argentina), and the most derivate in the Venezuelan ´Páramos´. Within Dichroplini, the most basal species belongs to the Yungas of Argentina, Bolivia and Perú, and the most derivate to the Venezuelan ´Páramos´. Finally, the position of North American Melanoplini also supports the South American origin and posterior dispersion to the north. On the other hand, the taxonomic status of the Jivarini tribe is again questioned. This preliminary study suggests the need of a reformulation and/or creation of new taxonomic entities in order to maintain the natural groups within this subfamily. Summarizing, the biogeographical history of each main evolutionary group show similar direction of diversification, congruently supporting the SNSH. However, further analyses will be necessary in order to determine if this process was in concert with the Andes geological uplift. Bibliography: - Amédégnato, C., 1977. Etude des Acridoidea centre et sud americains (Catantopinae sensu lato). Anatomie des génitalia, classification, répartition, phylogénie. Unpublished Thesis, University of Paris VI, 385 pp. - Amédégnato, C., Chapco, W., Litzenberger, G., 2003. Out of South America? Additional evidence for a southern origin of melanopline grasshoppers. Mol. Phylogenet. Evol. 29, 115?119. - Doan, T. 2003. A south-to-north biogeographic hypothesis for Andean speciation: evidence from the lizard genus Proctoporus (Reptilia, Gymnophthalmidae). J. of Biogeogr. 30, (3), 361-374 - Ronderos, R. & Carbonell, C. (1971) Revisión de las especies del grupo Peruvianus del genero Dichroplus Stal (Orthoptera: Acrididae, Cantantopinae). Revista de la Sociedad Entomológica Argentina, 33, 13?31. - Vickery, V.R., 1997. Classification of orthoptera (sensu stricto) or caelifera. In: Gangwere, S.K., Muralirangan, M.C., Muralirangan, M. (Eds.), The Bionomics of Grasshoppers, Katydids and their Kin. CAB International, New York, pp. 5?40.