The South American transition zone and the distribution of mayflies (Ephemeroptera)

NIETO, CAROLINA; MOLINERI, CARLOS; DOS SANTOS, DANIEL; EMMERICH, DANIEL; ZUÑIGA, M. DEL C.; DOMÍNGUEZ, E.

Aracruz

Congreso; XV Interna ; XIX International Symposium on Plecoptera; 2018

South America is considered a biologically hybrid continent, on its extreme south, the Andean (=Patagonic) region, with a unique biota strongly related to other temperate southern land masses (Australia-Tasmania, New Zealand, New Caledonia) exists, whilst in the remaining portion (tropical, subtropical), the Neotropical region, thrives a more complex taxocoenosis (Nearctic and Afro-Oriental related). The South American Transition Zone (STZ) has been proposed to place in the middle of these two areas, although its boundary differs among the authors. Six provinces are included in this transition zone: Paramo, Puna, Prepuna, Monte, Peruvian Desert and Atacama. The order Ephemeroptera seems to be an appropriate taxon to test the validity of the South American Transition zone. By using the Network Analysis Method (NAM) we analyzed the validity and boundary of the STZ, predicting a high fidelity of each regional biota resulting in weakly marked transition zones. We compiled a dataset including all mayfly species having at least one record in continental South America (8268 records for 661 species). The distribution of the species of Ephemeroptera in SA shows an astonishing spatial fidelity, with a strongly marked separation of the Patagonic and Neotropical regions, and they partially overlap in a narrow area, not in the STZ as proposed by previous authors but somewhat to the south and to the west. The Units of Co-occurrence found by network analysis show that the STZ is mainly occupied by Neotropical groups, and that the few Patagonic species only appear in the southern portion of the STZ. Almost the entire provinces of Puna, Coastal Desert and Paramo are not supported as part of the STZ by mayfly distribution. The transition zone between Patagonic and Neotropical mayfly fauna involves: Southern Puna and high Andes (south to 17º S latitude), Monte province, and part of Patagonian steppe until Chubut River as southern limit).