John P. Dumbacher

Prevalence and differential host‐specificity of two avian blood parasite genera in the Australo‐Papuan region

The degree to which widespread avian blood parasites in the genera Plasmodium and Haemoproteus pose a threat to novel hosts depends in part on the degree to which they are constrained to a particular host or host family. We examined the host distribution and host‐specificity of these parasites in birds from two relatively understudied and isolated locations: Australia and Papua New Guinea. Using polymerase chain reaction (PCR), we detected infection in 69 of 105 species, representing 44% of individuals surveyed (n = 428). Across host families, prevalence of Haemoproteus ranged from 13% (Acanthizidae) to 56% (Petroicidae) while prevalence of Plasmodium ranged from 3% (Petroicidae) to 47% (Ptilonorhynchidae). We recovered 78 unique mitochondrial lineages from 155 sequences. Related lineages of Haemoproteus were more likely to derive from the same host family than predicted by chance at shallow (average LogDet genetic distance = 0, n = 12, P = 0.001) and greater depths (average distance = 0.014, n = 11, P < 0.001) within the parasite phylogeny. Within two major Haemoproteus subclades identified in a maximum likelihood phylogeny, host‐specificity was evident up to parasite genetic distances of 0.029 and 0.007 based on logistic regression. We found no significant host relationship among lineages of Plasmodium by any method of analysis. These results support previous evidence of strong host‐family specificity in Haemoproteus and suggest that lineages of Plasmodium are more likely to form evolutionarily–stable associations with novel hosts.

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

Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on mitochondrial DNA sequence

The avian family Aegothelidae (Owlet-nightjars) comprises nine extant species and one extinct species, all of which are currently classified in a single genus, Aegotheles. Owlet-nightjars are secretive nocturnal birds of the South Pacific. They are relatively poorly studied and some species are known from only a few specimens. Furthermore, their confusing morphological variation has made it difficult to cluster existing specimens unambiguously into hierarchical taxonomic units. Here we sample all extant owlet-nightjar species and all but three currently recognized subspecies. We use DNA extracted primarily from museum specimens to obtain mitochondrial gene sequences and construct a molecular phylogeny. Our phylogeny suggests that most species are reciprocally monophyletic, however A. albertisi appears paraphyletic. Our data also suggest splitting A. bennettii into two species and splitting A. insignis and A. tatei as suggested in another recent paper.

Mid-Pleistocene divergence of Cuban and North American ivory-billed woodpeckers

We used ancient DNA analysis of seven museum specimens of the endangered North American ivory-billed woodpecker (Campephilus principalis) and three specimens of the species from Cuba to document their degree of differentiation and their relationships to other Campephilus woodpeckers. Analysis of these mtDNA sequences reveals that the Cuban and North American ivory bills, along with the imperial woodpecker (Campephilus imperialis) of Mexico, are a monophyletic group and are roughly equidistant genetically, suggesting each lineage may be a separate species. Application of both internal and external rate calibrations indicates that the three lineages split more than one million years ago, in the Mid-Pleistocene. We thus can exclude the hypothesis that Native Americans introduced North American ivory-billed woodpeckers to Cuba. Our sequences of all three woodpeckers also provide an important DNA barcoding resource for identification of non-invasive samples or remains of these critically endangered and charismatic woodpeckers.

EVOLUTION OF TOXICITY IN PITOHUIS: I. EFFECTS OF HOMOBATRACHOTOXIN ON CHEWING LICE (ORDER PHTHIRAPTERA)

Birds in the genus Pitohui carry the potent neurotoxin homobatrachotoxin in their skin and feathers. In this study, I tested whether homobatrachotoxin can repel or kill chewing lice (order Phthiraptera). When individual feather lice were offered a choice of two feathers on which to feed or take shelter, the lice preferred nontoxic feathers to feathers of the most toxic pitohui species, Pitohui dichrous. Moreover, the presence of toxic P dichrous feathers significantly shortened the life span of captive feather lice. These results suggest that homobatrachotoxin repels and kills lice and may thus protect pitohuis against lice infestation.

Adenylate Kinase Intron 5: A New Nuclear Locus for Avian Systematics

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A Passerine Bird's Evolution Corroborates the Geologic History of the Island of New Guinea

New Guinea is a biologically diverse island, with a unique geologic history and topography that has likely played a role in the evolution of species. Few island-wide studies, however, have examined the phylogeographic history of lowland species. The objective of this study was to examine patterns of phylogeographic variation of a common and widespread New Guinean bird species (Colluricincla megarhyncha). Specifically, we test the mechanisms hypothesized to cause geographic and genetic variation (e.g., vicariance, isolation by distance and founder-effect with dispersal). To accomplish this, we surveyed three regions of the mitochondrial genome and a nuclear intron and assessed differences among 23 of the 30 described subspecies from throughout their range. We found support for eight highly divergent lineages within C. megarhyncha. Genetic lineages were found within continuous lowland habitat or on smaller islands, but all individuals within clades were not necessarily structured by predicted biogeographic barriers. There was some evidence of isolation by distance and potential founder-effects. Mitochondrial DNA sequence divergence among lineages was at a level often observed among different species or even genera of birds (5–11%), suggesting lineages within regions have been isolated for long periods of time. When topographical barriers were associated with divergence patterns, the estimated divergence date for the clade coincided with the estimated time of barrier formation. We also found that dispersal distance and range size are positively correlated across lineages. Evidence from this research suggests that different phylogeographic mechanisms concurrently structure lineages of C. megarhyncha and are not mutually exclusive. These lineages are a result of evolutionary forces acting at different temporal and spatial scales concordant with New Guineas geological history.

Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds

Bird species in the avian genus Pitohui contain potent neurotoxic alkaloids that may be used for defense. The genus comprises multiple species that are endemic to New Guinea and were presumed to belong to the family Pachycephalidae or Colluricinclidae, within the core corvoidea, an ancient Australasian radiation of crow-like birds. In order to understand the evolution of toxicity within the genus Pitohui, we sequenced three mitochondrial and two nuclear gene segments and reconstructed a phylogeny of the genus Pitohui and its putative relatives. We show that the genus Pitohui is polyphyletic, and consists of five different lineages. Using Bayesian ancestral state reconstruction, we estimate that toxicity likely evolved multiple times within this group. Furthermore, because the morphological and behavioral similarity among these poisonous birds appears to have evolved convergently, we hypothesize that this may be a possible example of Müllerian mimicry in birds. The Morningbird of Palau, Micronesia, that has often been included in the genus Pitohui, actually belongs in the genus Pachycephala and offers an intriguing case of pronounced evolution on a remote oceanic island.

The flight of the Passenger Pigeon: Phylogenetics and biogeographic history of an extinct species

The human-caused extinction of the Passenger Pigeon (Ectopistes migratorius) is one of the best known and documented of any bird. This event was particularly alarming because the Passenger Pigeon went from being one of the most numerous avian species in the world to extinct in a period of decades, when the last individual died in captivity in a Cincinnati Zoo in 1914. While a great deal of information exists on the likely direct and indirect causes of its demise, as well as information on life-history, the phylogenetic relationships of this species have been subject to considerable speculation. Here we use DNA sequences obtained from museum specimens to resolve the phylogenetic position of this species with respect to other pigeons and doves (Columbiformes). We show that the Passenger Pigeon is not related to the New World mourning doves (Zenaida) as many authors have suggested, but is the sister taxon of all other New World pigeons (Patagioenas). Biogeographic analysis suggests the Passenger Pigeon lineage may have colonized North America from Asia, and subsequently dispersed into South America, leading to a more extensive radiation of New World pigeons.

Skin as a Toxin Storage Organ in the Endemic New Guinean Genus Pitohui

ABSTRACT. Several bird species in the endemic New Guinean genus Pitohui contain potent defensive toxins of the batrachotoxin family of steroidal alkaloid neurotoxins. We surveyed toxin concentrations in various tissues of Hooded Pitohui (Pitohui dichrous) using radioligand binding assays. The highest concentrations were found in the skin and feathers, on the outside of the birds, where predators or parasites are likely to encounter toxins. Significant levels of toxins also were found in skeletal muscle, heart, and liver. Muscle and liver would normally be poisoned by batrachotoxins; thus, Hooded Pitohuis must be insensitive to the toxins. The presence of toxins in internal organs further argues against the hypothesis that Hooded Pitohuis merely apply toxins topically to skin and feathers. Finally, we used scanning and transmission electron microscopy to examine skin and feathers for unusual morphological or histological adaptations for storing and secreting toxins. The skin of Hooded Pitohuis appears to have typical dermal and epidermal morphology, and we speculate on possible ways in which this species may sequester and secrete toxins using typical avian skin structural features, unique among vertebrates.