Systematics of the oil bee genus Lanthanomelissa and its implications to the biogeography of southern grasslands

Abstract

Lanthanomelissa is a controversial taxonomic group of bees that was treated as subgenus of Chalepogenus or an independent genus. All of its species are endemic to the south-eastern grasslands of South America, an endangered and still poorly known environment. We aimed to understand the origin of this group of bees in time and space as well as the influence of Quaternary climatic fluctuations on its current distribution and possible link to the history of the Southern Grasslands. We inferred phylogenetic relationships of Lanthanomelissa species using 37 terminals and 3430 nucleotides of three mitochondrial and two nuclear markers and estimated divergence times and ancestral geographic range. We performed an ensemble with the algorithms SVM, Maxent, and Random Forest in a dataset of 192 georeferenced occurrence points using 19 WorldClim bioclimatic variables to analyse species distribution during the current and two past climatic scenarios (LIG, ∼120 kya and LGM, ∼21 kya). The results support the monophyly of the genus and taxonomic changes including the species Lanthanomelissa parva n. comb. on Lanthanomelissa, and the treatment of the goeldianus group of Chalepogenus as the genus Lanthanella. The genus originated at the Oligocene-Miocene border in the Chacoan-Pampean region, and the glacial-interglacial models indicated expansion in Last Glacial Maximum and retraction in Last Interglacial. Expansion and retraction of Lanthanomelissa distribution in the last glacial-interglacial indicated grasslands distributional shifts during periods of climate cooling and warming. The diversification of Lanthanomelissa supported the estimated expansion of southern grasslands in South America concurrently with the origin of Cerrado during the late Miocene. Their origin was approximately synchronized with their exclusive floral host, Sisyrinchium (Iridaceae).