Colonizing the world in spite of reduced MHC variation

The major histocompatibility complex (MHC), which harbours the most polymorphic vertebrate genes, plays a critical role in the host–pathogen coevolutionary arms race. However, the extent to which MHC diversity determines disease susceptibility and long-term persistence of populations is currently under debate, as recent studies have demonstrated that low MHC variability does not necessarily hamper population viability. However, these studies typically assayed small and decimated populations in species with restricted distribution, thereby making inferences about the evolutionary potential of these populations difficult. Here, we show that MHC impoverish- ment has not constrained the ecological radiation and flourishing of falcons (Aves: Falconidae) worldwide. We found two remarkably different patterns of MHC variation within the genus Falco. Whereas MHC variation in kestrels (the basal group within the genus) is very high, falcons exhibit ancestrally low intra- and interspecific MHC variability. This pattern is not due to the inadvertent survey of paralogous genes or pseudogenes. Further, patterns of variation in mitochondrial or other nuclear genes do not indicate a generalized low level of genome-wide variability among falcons. Although a relative contribution of genetic drift cannot be completely ruled out, we propose the falcons went through an evolutionary transition, driven and maintained by natural selection, from primarily highly variable towards low polymorphic and slow-evolving MHC genes with a very specific immune function. This study highlights that the importance of MHC diversity cannot be generalized among vertebrates, and hints at the evolution of compensatory immune mechanisms in falcons to cope with emerging and continuously evolving pathogens.Peer reviewe

Post-breeding movement and activities of two streaked shearwaters in the north-western Pacific

We used miniature light-level/immersion loggers (geolocators) to study the movements and behavior of two Streaked Shearwaters (Calonectris leucomelas) during their travel away from Japan, after the breeding season. During the period from late October until late December, the tracked shearwaters moved south over subtropical pelagic waters,with low productivity. The birds traveled to the seas off northern New Guinea and the Gulf of Carpentaria, Australia, 3400-5200 km distant from Mikura Island, their breeding colony in Japan. During the wintering period (December-February), the birds were on the sea surface for 77-85% of their time on average. The migratory and wintering behavior of Streaked Shearwaters are discussed in relation to the physical and biological marine environment of the north-western Pacific

Legacy or colonization? Posteruption establishment of peregrine falcons (Falco peregrinus) on a volcanically active subarctic island

Abstract How populations and communities reassemble following disturbances are affected by a number of factors, with the arrival order of founding populations often having a profound influence on later populations and community structure. Kasatochi Island is a small volcano located in the central Aleutian archipelago that erupted violently August 8, 2008, sterilizing the island of avian biodiversity. Prior to the eruption, Kasatochi was the center of abundance for breeding seabirds in the central Aleutian Islands and supported several breeding pairs of peregrine falcons (Falco peregrinus). We examined the reestablishment of peregrine falcons on Kasatochi by evaluating the genetic relatedness among legacy samples collected in 2006 to those collected posteruption and to other falcons breeding along the archipelago. No genotypes found in posteruption samples were identical to genotypes collected from pre‐eruption samples. However, genetic analyses suggest that individuals closely related to peregrine falcons occupying pre‐eruption Kasatochi returned following the eruption and successfully fledged young; thus, a genetic legacy of pre‐eruption falcons was present on posteruption Kasatochi Island. We hypothesize that the rapid reestablishment of peregrine falcons on Kasatochi was likely facilitated by behavioral characteristics of peregrine falcons breeding in the Aleutian Islands, such as year‐round residency and breeding site fidelity, the presence of an abundant food source (seabirds), and limited vegetation requirements by seabirds and falcons