TimeTree 5: An Expanded Resource for Species Divergence Times.

We present the fifth edition of the TimeTree of Life resource (TToL5), a product of the timetree of life project that aims to synthesize published molecular timetrees and make evolutionary knowledge easily accessible to all. Using the TToL5 web portal, users can retrieve published studies and divergence times between species, the timeline of a species' evolution beginning with the origin of life, and the timetree for a given evolutionary group at the desired taxonomic rank. TToL5 contains divergence time information on 137,306 species, 41% more than the previous edition. The TToL5 web interface is now ADA-compliant and mobile-friendly, a result of comprehensive source code refactoring. TToL5 also offers programmatic access to species divergence times and timelines through an application programming interface, which is accessible at timetree.temple.edu/api. TToL5 is publicly available at timetree.org.

Using Ancestry-Informative SNPs to Quantify Introgression of European Alleles into North American Red Foxes.

A recent study demonstrated that British red foxes introduced to the mid-Atlantic coastal plain (ACP) of the eastern United States during the late 18th century successfully interbred with indigenous American red foxes despite half a million year's divergence. However, a large disparity in frequency of European mitochondria (27%) versus Y chromosomes (1%) left unclear the magnitude of genetic exchange. We sought to quantify genomic introgression using 35 autosomal and 5 X-chromosome ancestry-informative markers (AIMs) in conjunction with diagnostic Y chromosome single nucleotide polymorphism (Y-SNP) markers to characterize the modern state of red foxes in the eastern United States and to gain insight into the potential role of reproductive barriers. European admixture was highest in the ACP and apparently restricted to the central eastern United States. We estimated only slightly (and nonsignificantly) European ancestry in autosomal than X-chromosome markers. European ancestry from autosomal and X-chromosome markers (36.4%) was higher than the corresponding mitochondrial (mt) DNA estimate (26.4%) in the ACP. Only 1 of 124 males (<1%) in the ACP had European Y chromosomes, which was similar to the neighboring regions, in which 2 of 99 (2%) males carried a European Y chromosome (the same haplotype). Although we could not rule out drift as the cause of low European Y-chromosome frequency, results were also consistent with F1 male infertility. In the future, more extensive genomic sequencing will enable a more thorough investigation of possible barrier genes on the X chromosome as well as throughout the genome.