Les Christidis

Explosive avian radiations and multi-directional dispersal across Wallacea: Evidence from the Campephagidae and other Crown Corvida (Aves)

The systematic relationships among avian families within Crown Corvida have been poorly studied so far and as such been of limited use for biogeographic interpretations. The group has its origin in Australia and is thought to have colonized Africa and the New World via Asia beginning some 35 Mya when terranes of Australian origin approached Asian landmasses. Recent detailed tectonic mapping of the origin of land masses in the region around Wallaces line have revealed a particularly complex movement of terranes over the last 20-30 Myr. Thus the biogeographic dispersal pattern of Crown Corvida is a particularly exciting case for linking vicariance and dispersal events with Earth history. Here we examine phylogenetic affinities among 72 taxa covering a broad range of genera in the basal radiations within Crown Corvida with an emphasis on Campephagidae and Pachycephalidae. Bayesian analyses of nuclear DNA sequence data identified the family Campephagidae as monophyletic but the large genus Coracina is not. Within the family Pachycephalidae the genera Pachycephala and Colluricincla are paraphyletic with respect to each other. The resulting phylogeny suggests that patterns of dispersal across Wallaces line are complex and began at least 25 Mya. We find evidence of explosive radiations and multi-directional dispersal within the last 10 Myr, and three independent long distance ocean dispersal events between Wallacea and Africa at 10-15 Mya. Furthermore, the study reveals that in the Campephagidae a complex series of dispersal events rather than vicariance is the most likely explanation for the current biogeographic pattern in the region.

A new endemic family of New Zealand passerine birds: adding heat to a biodiversity hotspot

The results of phylogenetic analysis of two molecular datasets sampling all three endemic New Zealand ‘honeyeaters’ (Prosthemadera novaeseelandiae, Anthornis melanura and Notiomystis cincta) are reported. The undisputed relatedness of the first two species to other honeyeaters (Meliphagidae), and a close relationship between them, are demonstrated. However, our results confirm that Notiomystis is not a honeyeater, but is instead most closely related to the Callaeidae (New Zealand wattlebirds) represented by Philesturnus carunculatus in our study. An estimated divergence time for Notiomystis and Philesturnus of 33.8 mya (Oligocene) suggests a very long evolutionary history of this clade in New Zealand. As a taxonomic interpretation of these data we place Notiomystis in a new family of its own which takes the name Notiomystidae. We expect this new phylogenetic and taxonomic information to assist policy decisions for the conservation of this rare bird.

An unexpectedly long history of sexual selection in birds-of-paradise

BackgroundThe birds-of-paradise (Paradisaeidae) form one of the most prominent avian examples of sexual selection and show a complex biogeographical distribution. The family has accordingly been used as a case-study in several significant evolutionary and biogeographical syntheses. As a robust phylogeny of the birds-of-paradise has been lacking, these hypotheses have been tentative and difficult to assess. Here we present a well supported species phylogeny with divergence time estimates of the birds-of-paradise. We use this to assess if the rates of the evolution of sexually selected traits and speciation have been excessively high within the birds-of-paradise, as well as to re-interpret biogeographical patterns in the group.ResultsThe phylogenetic results confirm some traditionally recognized relationships but also suggest novel ones. Furthermore, we find that species pairs are geographically more closely linked than previously assumed. The divergence time estimates suggest that speciation within the birds-of-paradise mainly took place during the Miocene and the Pliocene, and that several polygynous and morphologically homogeneous genera are several million years old. Diversification rates further suggest that the speciation rate within birds-of-paradise is comparable to that of the enitre core Corvoidea.ConclusionThe estimated ages of morphologically homogeneous and polygynous genera within the birds-of-paradise suggest that there is no need to postulate a particularly rapid evolution of sexually selected morphological traits. The calculated divergence rates further suggest that the speciation rate in birds-of-paradise has not been excessively high. Thus the idea that sexual selection could generate high speciation rates and rapid changes in sexual ornamentations is not supported by our birds-of-paradise data. Potentially, hybridization and long generation times in polygynous male birds-of-paradise have constrained morphological diversification and speciation, but external ecological factors on New Guinea may also have allowed the birds-of-paradise to develop and maintain magnificent male plumages. We further propose that the restricted but geographically complex distributions of birds-of-paradise species may be a consequence of the promiscuous breeding system.

Molecular systematics and evolutionary origins of the genus Petaurus (Marsupialia: Petauridae) in Australia and New Guinea

The glider genus Petaurus comprises a group of arboreal and nocturnal marsupial species from New Guinea and Australia. Molecular data were generated in order to examine phylogenetic relationships among species within the genus and explore the time-scale of diversification and biogeographic history of the genus in Australia and New Guinea. All known species and subspecies of Petaurus (with the exception of P. biacensis) were sequenced for two mitochondrial genes (ND2 and ND4) and one nuclear marker (omega-globin gene). Phylogenetic analyses confirmed the monophyly of the genus relative to other petaurids and showed a sister relationship of P. australis to the rest of Petaurus. The analyses revealed that currently recognised species of Petaurus formed distinct mitochondrial DNA (mtDNA) clades. Considerable mtDNA diversity and seven distinct clades were identified within the species P. breviceps, with the distribution of each clade showing no correspondence with the distributional limits of known subspecies. Molecular dating analyses using BEAST suggested an early to mid-Miocene origin (18-24 mya) for the genus. Ancestral area reconstructions, using BayesTraits, did not resolve the location for the centre of origin of Petaurus, but provided evidence for at least one dispersal event from New Guinea to Australia that led to the evolution of extant Australian populations of P. breviceps, P. norfolcensis and P. gracilis. The timing of this dispersal event appears to pre-date the Pleistocene, adding to the growing number of studies that suggest faunal connections occurred between Australia and New Guinea in the Late Miocene to Pliocene period.

Evidence of taxon cycles in an Indo-Pacific passerine bird radiation (Aves: Pachycephala)

Many insular taxa possess extraordinary abilities to disperse but may differ in their abilities to diversify and compete. While some taxa are widespread across archipelagos, others have disjunct (relictual) populations. These types of taxa, exemplified in the literature by selections of unrelated taxa, have been interpreted as representing a continuum of expansions and contractions (i.e. taxon cycles). Here, we use molecular data of 35 out of 40 species of the avian genus Pachycephala (including 54 out of 66 taxa in Pachycephala pectoralis (sensu lato), to assess the spatio-temporal evolution of the group. We also include data on species distributions, morphology, habitat and elevational ranges to test a number of predictions associated with the taxon-cycle hypothesis. We demonstrate that relictual species persist on the largest and highest islands across the Indo-Pacific, whereas recent archipelago expansions resulted in colonization of all islands in a region. For co-occurring island taxa, the earliest colonists generally inhabit the interior and highest parts of an island, with little spatial overlap with later colonists. Collectively, our data support the idea that taxa continuously pass through phases of expansions and contractions (i.e. taxon cycles).

Implications of changing species definitions for conservation purposes

Summary Concern has been expressed that failure to adopt phylogenetic or related species concepts will result in biodiversity loss. Here we describe how widespread adoption of such concepts may affect conservation administration and the social contract with elected governments that fund management of threatened species. We then review threatened species legislation, showing that most laws and international conventions avoid arguments over species’ definitions altogether, thus negating arguments that such definitions should be changed to further species’ conservation.

Plumage patterns are good indicators of taxonomic diversity, but not of phylogenetic affinities, in Australian grasswrens Amytornis (Aves: Maluridae)

The grasswrens (Maluridae: Amytornis) are elusive songbirds from the arid zones of Australia. Although some other Australian bird genera are also largely restricted to arid regions, none show the level of localized taxonomic diversity seen in Amytornis. Furthermore, their cryptic plumage patterns provide excellent camouflage but make it difficult to determine whether shared patterns reflect phylogenetic relationships or adaptations to similar terrain. To resolve the systematics and patterns of ecological diversification within Amytornis, we here present the results of a phylogenetic analysis of mitochondrial and nuclear multi-locus data for all recognized species and most subspecies, using traditional concatenation-based methods as well as a coalescent-based species-tree approach. Phylogenetic patterns retrieved by the species-tree approach were highly congruent with traditional methods, although branch support was generally higher in concatenation-based analysis, suggesting that species-tree methods may furnish more conservative results. In terms of identifying taxonomic diversity there was good concordance between plumage-based assessments and DNA distances. The same concordance was not found when comparing plumage-based and DNA-based predictions of phylogenetic relationships. Four primary lineages were identified: (a) barbatus; (b) merrotsyi; (c) the textilis complex, purnelli, ballarae, goyderi and housei; and (d) woodwardi, dorotheae, and the striatus complex. There was no robust resolution of relationships between lineages. It appears that in Amytornis, plumage differentiation between discrete populations is taxonomically significant, and not greatly influenced by ecophenotypic variation. However, at the deeper phylogenetic level, similar suites of plumage characters may be phylogenetically uninformative because of homoplasy. The study reveals higher levels of taxonomic diversity in Amytornis than previously recognized, with many taxa being highly localized. Such extensive short range endemism is mainly encountered in poorly-dispersing invertebrates and is unique in Australian birds. The identification here of the additional restricted range taxa has important conservation implications.

Morphological, behavioural and genetic differentiation within the Horned Parakeet (Eunymphicus cornutus) and its affinities to Cyanoramphus and Prosopeia

Abstract We revise the taxonomy of the two parakeet taxa in the psittaciform genus Eunymphicus—E. cornutus cornutus (Horned Parakeet) and E. c. uvaeensis (Ouvéa Parakeet)—which are restricted to New Caledonia and the Loyalty Islands, in the south-western Pacific, and we investigate their relationship with the genera Cyanoramphus, considered traditionally as its closest related genus, and Prosopeia. We used three sets of characters to assess the level of differentiation between the Eunymphicus taxa: behaviour (vocalisations), morphology (biometrics and plumage coloration) and genetic (mitochondrial cytochrome b DNA sequence variation, 924 nucleotides). The analysis of vocalisations revealed significant differences, as did morphological analyses (size and number of feathers of the crest, size of the bill, and colour pattern of the head). Genetic distance between the Horned and Ouvéa Parakeets is similar to that recorded between closely related species of Cyanoramphus and both taxa possess novel and diagnostic synapomorphic substitutions. From these genetic, behavioural and morphological data, the two Eunymphicus taxa should be considered separate species, a suggestion that is supported by ecological data as well as anecdotal data on hybridisation from captive birds. Our molecular data also support the traditional view that Cyanoramphus is the closest relative of Eunymphicus, with Prosopeia a sister group to this clade. The consistency with which Platycercus clusters next to the Cyanoramphus—Eunymphicus—Prosopeia grouping suggests that Platycercus may well be the next closest relative of this clade.

Subspeciation in the Short-tailed Grasswren (Amytornis merrotsyi, Maluridae)

Abstract The Short-tailed Grasswren (Amytornis merrotsyi) is restricted to the stony spinifex (Triodia) hills of the Gawler Ranges and Flinders Ranges of South Australia. Comparisons of DNA sequences of the mitochondrial ND3 gene reveal an average of 2.1% (1.7–2.3%) sequence divergence between the two isolated populations. Genetic differentiation within populations was less, ranging from 0 to 0.6% between individuals. This pattern of genetic differentiation is comparable to that observed between other recognised subspecies of Amytornis for the same DNA locus. Detailed comparisons of morphology and plumage patterns reveal consistent and diagnosable differences between the two populations confirming earlier more limited morphological assessments. Based on the combination of molecular and morphological differences, the Gawler Ranges population is here named as a separate subspecies, A. m. pedleri subsp. nov.

Molecular Assessment of the Taxonomic Status of Cox's Sandpiper

To determine whether Calidris paramelanotos is a distinct species or a hybrid, DNA sequences from the mitochondrial cytochrome-b gene were obtained from it, as well as from C. ferruginea and C. melanotos. The sequences of the first two taxa were identical whereas that of C. melanotos differed by 9%. It is argued that C. paramelanotos is a hybrid taxon with C. ferruginea constituting the maternal parent. This conclusion, combined with comparisons of protein allozyme variation effectively rule out all but one of the crosses postulated for its hybrid origin -C. ferruginea x C. melanotos.