Native American gene flow into Polynesia predating Easter Island settlement

The possibility of voyaging contact between prehistoric Polynesian and Native American populations has long intrigued researchers. Proponents have pointed to the existence of New World crops, such as the sweet potato and bottle gourd, in the Polynesian archaeological record, but nowhere else outside the pre-Columbian Americas1,2,3,4,5,6, while critics have argued that these botanical dispersals need not have been human mediated7. The Norwegian explorer Thor Heyerdahl controversially suggested that prehistoric South American populations had an important role in the settlement of east Polynesia and particularly of Easter Island (Rapa Nui)2. Several limited molecular genetic studies have reached opposing conclusions, and the possibility continues to be as hotly contested today as it was when first suggested8,9,10,11,12. Here we analyse genome-wide variation in individuals from islands across Polynesia for signs of Native American admixture, analysing 807 individuals from 17 island populations and 15 Pacific coast Native American groups. We find conclusive evidence for prehistoric contact of Polynesian individuals with Native American individuals (around AD 1200) contemporaneous with the settlement of remote Oceania13,14,15. Our analyses suggest strongly that a single contact event occurred in eastern Polynesia, before the settlement of Rapa Nui, between Polynesian individuals and a Native American group most closely related to the indigenous inhabitants of present-day Colombia

Experimental investigation of flow past open and partially covered cylindrical cavities

Flows past wall-mounted cavities are found in a wide variety of applications, including side-branches, organ pipes, automobile sunroofs, inter-car gaps in trains and aircraft bays. Under certain conditions, flow excited cavities can generate large pressure fluctuations, undesirable noise and significant structural loads. To date, most of the studies have been focused on rectangular cavities while little attention has been given to cylindrical cavities despite their widespread use. Two different types of cylindrical cavities were experimentally investigated in low speed wind tunnels: an open mouth cavity and a deep cavity with a small rectangular opening. The measurements included hot wire anemometry, particle image velocimetry (PIV) and unsteady surface pressure measurements. Additionally, numerical analysis of the test section/cavity systems were carried out with the finite element program COMSOL Multiphysics and with a wave expansion method (WEM) code developed by the Trinity College Dublin. Important flow features are described by evaluating the pressure measurements conducted in several positions over the walls of an open mouth cavity, the PIV measurements performed over horizontal planes inside the cavity and the hot-wire measurements on the shear layer and on the wake of the cavity. Pressure Fourier spectra evidence the presence of the first three shear layer hydrodynamic modes at frequencies well predicted by classical formulation for rectangular cavities (Rossiter). When the cavity is open, the acoustic modes of the test section are found to be excited by the flow but when the cavity is partially covered, the shear layer hydrodynamic modes are more likely to lock on the natural frequencies of the cavity. The position of the opening has an influence on the lock-on acoustic modes. The acoustic energy generated by the shear layer is calculated by applying the vortex sound theory of Howe: the flow velocity and the vorticity are extracted from the PIV data and the acoustic particle velocity field from the WEM calculation. The acoustic sources are localised in space and quantified over an acoustic period providing insight into the sound production of flow-excited partially covered cylindrical cavities

Morphological and molecular data from Madeira support the persistence of an ancient lineage of Taxus baccata

Macaronesia is an important biodiversity hotspot in the Mediterranean bioclimatic region, hosting a number of endemics, and encompassing outstanding refugia for ancient Tertiary plant lineages. We investig past occurrence and present distribution of yew (Taxus baccata L.) in the Madeiran archipelago, providing preliminary morphological and genetic descriptions and addressing conservation issues. Fifty-eight individuals presently occur in 19 micro-populations, as probable survivors of the continued yew exploitation across the centuries. Plants were characterized and compared with Euro-Mediterranean provenances by leaf morphology, anatomy, nuclear ITS (Internal Trascribed Spacer) and plastid trnS-trnQ DNA markers. The Madeiran provenance showed peculiar leaf size and morpho-anatomical characters. DNA sequences revealed a basal position of Madeiran yew in the Baccata phylogenetic clades along with the Azorean provenance. Gathered data suggest the survival of a lineage of T. baccata different from those on the continent, and with a possible closer derivation from the species' ancestors. Such evidences provide a base for identifying a great phylo- and phytogeographical interest of the Macaronesian provenance, and confirm the role of the archipelagos to preserve relict flora and lineages. The risk of extinction of Madeiran yew also calls for conservation strategies and restoration programs for a prompt species rescue. © 2013 Copyright Dipartimento di Biologia Evoluzionistica, Università di Firenze.s