Tracing the phylogeography of human populations in Britain based on 4th-11th century mtDNA genotypes.

Some of the transitional periods of Britain during the first millennium A.D. are traditionally associated with the movement of people from continental Europe, composed largely of invading armies (e.g., the Roman, Saxon, and Viking invasions). However, the extent to which these were migrations (as opposed to cultural exchange) remains controversial. We investigated the history of migration by women by amplifying mitochondrial DNA (mtDNA) from ancient Britons who lived between approximately A.D. 300-1,000 and compared these with 3,549 modern mtDNA database genotypes from England, Europe, and the Middle East. The objective was to assess the dynamics of the historical population composition by comparing genotypes in a temporal context. Towards this objective we test and calibrate the use of rho statistics to identify relationships between founder and source populations. We find evidence for shared ancestry between the earliest sites (predating Viking invasions) with modern populations across the north of Europe from Norway to Estonia, possibly reflecting common ancestors dating back to the last glacial epoch. This is in contrast with a late Saxon site in Norwich, where the genetic signature is consistent with more recent immigrations from the south, possibly as part of the Saxon invasions.

Phylogenetic evidence for colour pattern convergence in toxic pitohuis: Müllerian mimicry in birds?

Bird species in the genus Pitohui are chemically defended by a potent neurotoxic alkaloid in their skin and feathers. The two most toxic pitohui species, the hooded pitohui (Pitohui dichrous) and the variable pitohui (Pitohui kirhocephalus), are sometimes strikingly patterned and, in certain portions of their geographical ranges, both species share a nearly identical colour pattern, whereas in other areas they do not. Müllerian mimicry (the mutual resemblance of two chemically defended prey species) is common in some other animal groups and Pitohui birds have been suggested as one of the most likely cases in birds. Here, we examine pitohui plumage evolution in the context of a well-supported molecular phylogeny and use a maximum likelihood approach to test for convergent evolution in coloration. We show that the 'mimetic' phenotype is ancestral to both species and that the resemblance in most races is better explained by a shared ancestry. One large clade of P. kirhocephalus lost this mimetic phenotype early in their evolution and one race nested deep within this clade appears to have re-evolved this phenotype. These latter findings are consistent with the hypothesis that Müllerian mimicry is driving the evolution for a similar colour pattern between P. dichrous, but only in this one clade of P. kirhocephalus

Batrachotoxin alkaloids from passerine birds: a second toxic bird genus (Ifrita kowaldi) from New Guinea.

Batrachotoxins, including many congeners not previously described, were detected, and relative amounts were measured by using HPLC-mass spectrometry, in five species of New Guinean birds of the genus Pitohui as well as a species of a second toxic bird genus, Ifrita kowaldi. The alkaloids, identified in feathers and skin, were batrachotoxinin-A cis-crotonate (1), an allylically rearranged 16-acetate (2), which can form from 1 by sigmatropic rearrangement under basic conditions, batrachotoxinin-A and an isomer (3 and 3a, respectively), batrachotoxin (4), batrachotoxinin-A 3'-hydroxypentanoate (5), homobatrachotoxin (6), and mono- and dihydroxylated derivatives of homobatrachotoxin. The highest levels of batrachotoxins were generally present in the contour feathers of belly, breast, or legs in Pitohui dichrous, Pitohui kirhocephalus, and Ifrita kowaldi. Lesser amounts are found in head, back, tail, and wing feathers. Batrachotoxin (4) and homobatrachotoxin (6) were found only in feathers and not in skin. The levels of batrachotoxins varied widely for different populations of Pitohui and Ifrita, a result compatible with the hypothesis that these birds are sequestering toxins from a dietary source.

Homobatrachotoxin in the genus Pitohui: chemical defense in birds?

Three passerine species in the genus Pitohui, endemic to the New Guinea subregion, contain the steroidal alkaloid homobatrachotoxin, apparently as a chemical defense. Toxin concentrations varied among species but were always highest in the skin and feathers. Homobatrachotoxin is a member of a class of compounds collectively called batrachotoxins that were previously considered to be restricted to neotropical poison-dart frogs of the genus Phyllobates. The occurrence of homobatrachotoxin in pitohuis suggests that birds and frogs independently evolved this class of alkaloids.