A minute ostracod (Crustacea: Cytheromatidae) from the Miocene Solimões Formation (western Amazonia, Brazil): evidence for marine incursions?

Combining morphology and molecular data to improve Drosophila paulistorum (Diptera, Drosophilidae) taxonomic status

The willistoni species subgroup has been the subject of several studies since the latter half of the past century and is considered a Neotropical model for evolutionary studies, given the many levels of reproductive isolation and different evolutionary stages occurring within them. Here we present for the first time a phylogenetic reconstruction combining morphological characters and molecular data obtained from 8 gene fragments (COI, COII, Cytb, Adh, Ddc, Hb, kl-3 and per). Some relationships were incongruent when comparing morphological and molecular data. Also, morphological data presented some unresolved polytomies, which could reflect the very recent divergence of the subgroup. The total evidence phylogenetic reconstruction presented well-supported relationships and summarized the results of all analyses. The diversification of the willistoni subgroup began about 7.3 Ma with the split of D. insularis while D.paulistorum complex has a much more recent diversification history, which began about 2.1 Ma and apparently has not completed the speciation process, since the average time to sister species separation is one million years, and some entities of the D. paulistorum complex diverge between 0.3 and 1 Ma. Based on the obtained data, we propose the categorization of the former "semispecies" of D. paulistorum as a subspecies and describe the subspecies D. paulistorum amazonian, D. paulistorum andeanbrazilian, D. paulistorum centroamerican, D. paulistorum interior, D. paulistorum orinocan and D. paulistorum transitional.

The Calibrated Phylogeny of the Drosophila fasciola Subgroup (D. repleta Group Wasserman) Indicates Neogene Diversification of Its Internal Branches

The species of the Drosophila fasciola subgroup Wasserman represent the dominant section of the Drosophila repleta group Wasserman in the American rainforests and have a broad geographical distribution in the New World. However, despite of its wide range, the D. fasciola subgroup is one of the most overlooked D. repleta subgroups. Here, we report a molecular phylogenetic analysis focused on the D. fasciola subgroup using two mitochondrial [cytochrome oxidase subunit I (COI), cytochrome oxidase subunit II (COII)] and two nuclear [elongation factor-1alpha F1 (EF-alphaF1) and transformer (tra)] genes. Overall, we found that this subgroup is a monophyletic taxon, subdivided into two main internal branches: named Fas1 and Fas2 clades. The diversification of these clades is estimated to have begun in the middle Miocene, around 12 Ma [95% high posterior density (HPD) 9.0-15 Ma], and might be associated with the colonization of South America by Central America populations after the closure of Isthmus of Panama due to the temporal congruence between these events. The terminal branches had their origins estimated to be in the Pliocene or the Plio-Pleistocene transition. For the later estimates, both the geomorphological influences and the climatic oscillations of the Pleistocene may have played a role in shaping the diversification of the D. fasciola group.

Miocene flooding events of western Amazonia

There is a considerable controversy about whether western Amazonia was ever covered by marine waters during the Miocene [23 to 5 Ma (million years ago)]. We investigated the possible occurrence of Miocene marine incursions in the Llanos and Amazonas/Solimões basins, using sedimentological and palynological data from two sediment cores taken in eastern Colombia and northwestern Brazil together with seismic information. We observed two distinct marine intervals in the Llanos Basin, an early Miocene that lasted ~0.9 My (million years) (18.1 to 17.2 Ma) and a middle Miocene that lasted ~3.7 My (16.1 to 12.4 Ma). These two marine intervals are also seen in Amazonas/Solimões Basin (northwestern Amazonia) but were much shorter in duration, ~0.2 My (18.0 to 17.8 Ma) and ~0.4 My (14.1 to 13.7 Ma), respectively. Our results indicate that shallow marine waters covered the region at least twice during the Miocene, but the events were short-lived, rather than a continuous full-marine occupancy of Amazonian landscape over millions of years.