Project description:Illumina reads generated using ddRAD-Seq for white-footed mice sampled along an urban-to-rural gradient in the NYC metropolitan area
Project description:How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we find that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia. Native Americans diversified into two basal genetic branches around 13 KYA, one in North and South America and the other restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians and Australo-Melanesians, the latter possibly through the ancestors of Aleutian Islanders. Putative relict populations in South America, including the historical Pericúes and Fuego-Patagonians, are not directly related to modern Australo-Melanesians.
Project description:The Lyme disease spirochete Borrelia burgdorferi drives a range of acute and chronic maladies in humans and other incidental hosts infected with the pathogen. However, the primary vertebrate reservoir, Peromyscus leucopus appears spared from any symptomology following infection. This has led to a common hypothesis that P. leucopus and B. burgdorferi exist symbiotically: P. leucopus restrain their immune response against the microbe and enable the enzootic cycle while B. burgdorferi avoids causing damage to the host. While aspects of this hypothesis have been tested, the exact interactions that occur between P. leucopus and B. burgdorferi during infection remain largely unknown. Here we utilized an inbred colony of P. leucopus in order to compare B. burgdorferi (B31) fitness in these rodents to the traditional B. burgdorferi murine models—C57BL/6J and C3H/HeN Mus musculus, which develop signs of inflammation akin to human disease. We find that in contrast to our expectations, B. burgdorferi were able to reach much higher burdens in M. musculus, and that the overall kinetics of infection differed between the two rodent species. Surprisingly, we also found that P. leucopus remained infectious to larval Ixodes scapularis for a far shorter period than either M. musculus strain. In line with these observations, we found that P. leucopus does launch a modest but sustained inflammatory response against B. burgdorferi in the skin, which we hypothesize leads to reduced bacterial viability and infectivity in these hosts. These observations provide new insight into the nature of reservoir species and the B. burgdorferi enzootic cycle.