The systematics and biogeography of African tailorbirds (Cisticolidae: Artisornis) with comment on the choice of Bayesian branch-length prior when analyzing heterogeneous data

The Long-billed Tailorbird (Artisornis moreaui), one of Africa's rarest birds, has a strikingly disjunct distribution, the origin of which has long puzzled biogeographers. One small population (subspecies moreaui) occurs in sub-montane forest in the East Usambara Mountains, a sky island near the coast of northern Tanzania, and another (subspecies sousae) on Serra Jeci in northwestern Mozambique, 950km away. The African Tailorbird, the putative sister-species of Long-billed Tailorbird, also occurs in the East Usambara Mountains and on Serra Jeci, but in addition occupies all the Eastern Arc Mountain forests between these disjunct sites. Stuart (1981) hypothesized that the two tailorbird distributions could be explained by strong ecological competition, with African Tailorbird populations having eliminated Long-billed Tailorbird populations via competitive exclusion in montane forests between the East Usambara and Serra Jeci. If such competitive exclusion explains these geographic distributions, the co-occurrence of the two species in the East Usambara and at Serra Jeci may be ephemeral, with the status of Long-billed Tailorbird especially in doubt. We sought to (1) determine whether the two species of African tailorbirds are indeed sister-species, and (2) test predictions from Stuart's (1981) competitive exclusion hypothesis using genetic data. Phylogenetic analyses of our seven gene dataset (3 mtDNA, 4 introns; 4784bp) indeed place these two species together in the genus Artisornis. Instead of finding shallow divergence among African Tailorbird populations and deep divergence between Long-billed Tailorbird populations as expected from Stuart's hypothesis, we recover deep genetic divergence and geographic structure among populations of both tailorbird species. This result is consistent with long-term co-existence of the two species at East Usambara and Serra Jeci. Observational data from both the East Usambara and Serra Jeci suggest that the two species have diverged in use of forest canopy strata. From a conservation standpoint, our results suggest that extinction of the Long-billed Tailorbird as a function of competition with African Tailorbird is highly unlikely, and should not be viewed as imminent. Threats to its survival are instead anthropogenic, and conservation measures should take this into account. Finally, our empirical results suggest that mis-specification of the branch-length prior in Bayesian analyses of mitochondrial DNA data can have a profound effect on the overall tree-length (sum of branch-lengths), whereas the topology and support values tend to remain more stable. In contrast, mis-specification of the branch-length prior had a lesser impact on all aspects of the nuclear-only DNA analyses. This problem may be exacerbated when mitochondrial and nuclear DNA analyses are combined in a total evidence approach.

Phylogeny and biogeography of the imperial pigeons (Aves: Columbidae) in the Pacific Ocean

We reconstruct the phylogeny of imperial pigeons (genus Ducula) using mitochondrial and nuclear sequence data. We evaluate the most likely biogeographic scenario for the evolution of this group that colonized many islands of the Pacific Ocean. The divergence time analysis suggests that the basal divergences within Ducula occurred more recently than in the fruit doves (genus Ptilinopus), a group that is also well diversified in Oceania. The imperial pigeons colonized the Melanesian region several times independently, and the diversification within this region led to several species in sympatry, in particular in the Bismarck archipelago. Central Polynesia was also colonized several times, first by a lineage during the Miocene that led to the large D. latrans, sister to the New Caledonian endemic D. goliath, then more recently by the widespread D. pacifica, during the Pleistocene. The phylogenetic pattern obtained with the extant Ducula species showed that the Eastern Polynesian endemics do not form a monophyletic group, with the Pacific Imperial Pigeon D. pacifica sister species with good support to the Polynesian Imperial Pigeon D. aurorae. However, the impact of recent anthropic extinctions has been important for the imperial pigeons, more than for the smaller fruit doves, suggesting that several Ducula lineages might be missing today.

The evolution of north-east Atlantic gadfly petrels using statistical phylogeography

Macaronesia (north-east Atlantic archipelagos) has been host to complex patterns of colonization and differentiation in many groups of organisms including seabirds such as gadfly petrels (genus Pterodroma). Considering the subspecies of widely distributed soft-plumaged petrel for many years, the taxonomic status of the three gadfly petrel taxa breeding in Macaronesia is not yet settled, some authors advocating the presence of three, two or one species. These birds have already been the subject of genetic studies with only one mtDNA gene and relatively modest sample sizes. In this study, using a total of five genes (two mitochondrial genes and three nuclear introns), we investigated the population and phylogeographical histories of petrel populations breeding on Madeira and Cape Verde archipelagos. Despite confirming complete lineage sorting with mtDNA, analyses with nucDNA failed to reveal any population structuring and Isolation with Migration analysis revealed the absence of gene flow during the differentiation process of these populations. It appears that the three populations diverged in the late Pleistocene in the last 150 000 years, that is 10 times more recently than previous estimates based solely on one mtDNA gene. Finally, our results suggest that the Madeira petrel population is ancestral rather than that from Cape Verde. This study strongly advocates the use of nuclear loci in addition to mtDNA in demographical and phylogeographical history studies.

Ecological and evolutionary determinants for the adaptive radiation of the Madagascan vangas

Adaptive radiation is the rapid diversification of a single lineage into many species that inhabit a variety of environments or use a variety of resources and differ in traits required to exploit these. Why some lineages undergo adaptive radiation is not well-understood, but filling unoccupied ecological space appears to be a common feature. We construct a complete, dated, species-level phylogeny of the endemic Vangidae of Madagascar. This passerine bird radiation represents a classic, but poorly known, avian adaptive radiation. Our results reveal an initial rapid increase in evolutionary lineages and diversification in morphospace after colonizing Madagascar in the late Oligocene some 25 Mya. A subsequent key innovation involving unique bill morphology was associated with a second increase in diversification rates about 10 Mya. The volume of morphospace occupied by contemporary Madagascan vangas is in many aspects as large (shape variation)--or even larger (size variation)--as that of other better-known avian adaptive radiations, including the much younger Galapagos Darwin's finches and Hawaiian honeycreepers. Morphological space bears a close relationship to diet, substrate use, and foraging movements, and thus our results demonstrate the great extent of the evolutionary diversification of the Madagascan vangas.

The New Zealand Thrush: an extinct oriole

The New Zealand Thrush, or Piopio, is an extinct passerine that was endemic to New Zealand. It has often been placed in its own family (Turnagridae), unresolved relative to other passerines, but affinities with thrushes, Australaian magpies, manucodes, whistlers, birds-of-paradise and bowerbirds has been suggested based on morphological data. An affinity with the bowerbirds was also indicated in an early molecular study, but low statistical support make this association uncertain. In this study we use sequence data from three nuclear introns to examine the phylogenetic relationships of the piopios. All three genes independently indicate an oriole (Oriolidae) affinity of the piopios, and the monophyly of the typical orioles (Oriolus), figbirds (Sphecotheres), and the piopios is strongly supported in the Bayesian analysis of the concatenated data set (posterior probability = 1.0). The exact placement of the piopios within Oriolidae is, however, more uncertain but in the combined analysis and in two of the gene trees the piopios are placed basal to the typical orioles while the third gene suggest a sister relationship with the figbirds. This is the first time an oriole affinity has been proposed for the piopios. Divergence time estimates for the orioles suggest that the clade originated ca 20 million years ago, and based on these estimates it is evident that the piopios must have arrived on New Zealand by dispersal across the Tasman Sea and not as a result of vicariance when New Zealand separated from Gondwana in the late Cretaceous.

Influence of quaternary sea-level variations on a land bird endemic to Pacific atolls

Little is known about the effect of quaternary climate variations on organisms that inhabited carbonate islands of the Pacific Ocean, although it has been suggested that one or several uplifted islands provided shelter for terrestrial birds when sea-level reached its highest. To test this hypothesis, we investigated the history of colonization of the Tuamotu reed-warbler (Acrocephalus atyphus) in southeastern Polynesia, and found high genetic structure between the populations of three elevated carbonate islands. Estimates of time since divergence support the hypothesis that these islands acted as refugia during the last interglacial maximum. These findings are particularly important for defining conservation priorities on atolls that endure the current trend of sea-level rise owing to global warming.

A new Indo-Malayan member of the Stenostiridae (Aves: Passeriformes) revealed by multilocus sequence data: biogeographical implications for a morphologically diverse clade of flycatchers

Recent molecular studies on passerine birds have highlighted numerous discrepancies between traditional classification and the phylogenetic relationships recovered from sequence data. Among the traditional families that were shown to be highly polyphyletic are the Muscicapidae Old World flycatcher. This family formerly included all Old World passerines that forage on small insects by performing short sallies from a perch. Genera previously allocated to the Muscicapidae are now thought to belong to at least seven unrelated lineages. While the peculiarity of most of these lineages has been previously recognized by Linnean classification, usually at the rank of families, one, the so-called Stenostiridae, a clade comprising three Afrotropical and Indo-Malayan genera, has only recently been discovered. Here, we address in greater detail the phylogenetic relationships and biogeographic history of the Stenostiridae using a combination of mitochondrial and nuclear data. Our analyses revealed that one species, Rhipidura hypoxantha, previously attributed to the Rhipiduridae (fantails), is in fact a member of the Stenostiridae radiation and sister to the South African endemic genus Stenostira (Fairy Flycatcher). Our dating analyses, performed in a relative-time framework, suggest that the splits between Stenostira/R. hypoxantha and Culicicapa/Elminia occurred synchronously. Given that the Stenostiridae assemblage has been consistently recovered by independent studies, we clarify its taxonomic validity under the rules of the International Code of Zoological Nomenclature.

Tracing the colonization history of the Indian Ocean scops-owls (Strigiformes: Otus) with further insight into the spatio-temporal origin of the Malagasy avifauna

BACKGROUND

The island of Madagascar and surrounding volcanic and coralline islands are considered to form a biodiversity hotspot with large numbers of unique taxa. The origin of this endemic fauna can be explained by two different factors: vicariance or over-water-dispersal. Deciphering which factor explains the current distributional pattern of a given taxonomic group requires robust phylogenies as well as estimates of divergence times. The lineage of Indian Ocean scops-owls (Otus: Strigidae) includes six or seven species that are endemic to Madagascar and portions of the Comoros and Seychelles archipelagos; little is known about the species limits, biogeographic affinities and relationships to each other. In the present study, using DNA sequence data gathered from six loci, we examine the biogeographic history of the Indian Ocean scops-owls. We also compare the pattern and timing of colonization of the Indian Ocean islands by scops-owls with divergence times already proposed for other bird taxa.

RESULTS

Our analyses revealed that Indian Ocean islands scops-owls do not form a monophyletic assemblage: the Seychelles Otus insularis is genetically closer to the South-East Asian endemic O. sunia than to species from the Comoros and Madagascar. The Pemba Scops-owls O. pembaensis, often considered closely related to, if not conspecific with O. rutilus of Madagascar, is instead closely related to the African mainland O. senegalensis. Relationships among the Indian Ocean taxa from the Comoros and Madagascar are unresolved, despite the analysis of over 4000 bp, suggesting a diversification burst after the initial colonization event. We also highlight one case of putative back-colonization to the Asian mainland from an island ancestor (O. sunia). Our divergence date estimates, using a Bayesian relaxed clock method, suggest that all these events occurred during the last 3.6 myr; albeit colonization of the Indian Ocean islands were not synchronous, O. pembaensis diverged from O. senegalensis about 1.7 mya while species from Madagascar and the Comoro diverged from their continental sister-group about 3.6 mya. We highlight that our estimates coincide with estimates of diversification from other bird lineages.

CONCLUSION

Our analyses revealed the occurrence of multiple synchronous colonization events of the Indian Ocean islands by scops-owls, at a time when faunistic exchanges involving Madagascar was common as a result of lowered sea-level that would have allowed the formation of stepping-stone islands. Patterns of diversification that emerged from the scops-owls data are: 1) a star-like pattern concerning the order of colonization of the Indian Ocean islands and 2) the high genetic distinctiveness among all Indian Ocean taxa, reinforcing their recognition as distinct species.

Evolutionary history and biogeography of the drongos (Dicruridae), a tropical Old World clade of corvoid passerines

We address the phylogenetic relationships of the drongos (Dicruridae) at the species-level using sequences from two nuclear (myoglobin intron-2 and c-mos) and two mitochondrial (ND2 and cytochrome b) loci. The resulting phylogenetic tree shows that the most basal species is D. aeneus, followed in the tree by a trichotomy including (1) the Asian D. remifer, (2) a clade of all African and Indian Ocean islands species as well as two Asian species (D. macrocercus and D. leucophaeus) and (3) a clade that includes all other Asian species as well as two Australasian species (D. megarhynchus and D. bracteatus). Our phylogenetic hypotheses are compared to [Mayr, E., Vaurie, C., 1948. Evolution of the family Dicruridae (Birds). Evolution 2, 238-265.] hypothetical family "tree" based on traditional phenotypic analysis and biogeography. We point out a general discrepancy between the so-called "primitive" or "unspecialized" species and their position in the phylogenetic tree, although our results for other species are congruent with previous hypotheses. We conduct dating analyses using a relaxed-clock method, and propose a chronology of clades formation. A particular attention is given to the drongo radiation in Indian Ocean islands and to the extinction-invasion processes involved. The first large diversification of the family took place both in Asia and Africa at 11.9 and 13.3Myr, respectively, followed by a dispersal event from Africa to Asia at ca 10.6Myr; dispersal over Wallace line occurred later at ca 6Myr. At 5Myr, Principe and Indian Ocean Islands have been colonized from an African ancestor; the most recent colonization event concerned Anjouan by an immigrating population from Madagascar.

A phylogeny for the Cisticolidae (Aves: Passeriformes) based on nuclear and mitochondrial DNA sequence data, and a re-interpretation of an unique nest-building specialization

Based on some general similarities in feeding adaptations, a large number of Old World passerine birds were in the past lumped in one broad family, the Sylviidae. Recent molecular studies, starting with the DNA-DNA hybridization work by Sibley et al. [Sibley, C.G., Ahlquist, J.E., 1990. Phylogeny and Classification of Birds: A Study in Molecular Evolution, Yale University Press, New Haven, CT], have revealed that this group is in fact a paraphyletic assemblage, mainly in the superfamily Sylvioidea, and within this assemblage a distinct group (the Cisticolidae) can be identified around the genus Cisticola. In this study we try to define natural lineages within it, based on DNA sequence data from 35 ingroup taxa representing 12 putative genera. Both nuclear myoglobin intron II (630 bp in our study) and mitochondrial ND2 (1041 bp) genes were sequenced, and 1671 bp were aligned and subjected to parsimony, maximum likelihood and Bayesian analyses. The results strongly support the monophyly of a cisticolid clade, with the Malagasy warblers Neomixis constituting the deepest branch within the clade. Three major clades receive statistical support, but not all relationships between and within these are well resolved. All species of the genus Bathmocercus belong to the Cisticolidae but in two different clades. The tailorbirds appear also polyphyletic with most species of the genus Orthotomus (but O. cucullatus falling in the outgroup) and the African metopias being in two different clades. Also the genus Apalis is polyphyletic, but all other included genera seem to be confirmed as natural units. Based on these findings we resurrect the genera Scepomycter and Artisornis. Calamonastes is confirmed to be in the Cisticolidae and grouped with Camaroptera. Main basic nest types do not follow the phylogenetic branching, and notably the peculiar "tailorbird" technique of stitching leaves together around the nest is found in different parts of the phylogeny. The basic types of nests seem to be found in particular environments, and the sewing may therefore have evolved in some ancestor of the Cisticolidae and was later lost or modified in some genera or species following the spread of drier habitats from the mid-Miocene.

Nuclear and mitochondrial sequence data reveal the major lineages of starlings, mynas and related taxa

We investigated the phylogenetic relationships among the major lineages of the avian family Sturnidae and their placement within the Muscicapoidea clade using two nuclear (RAG-1 and myoglobin) and one mitochondrial gene (ND2). Among Muscicapoidea, we recovered three clades corresponding to the families Cinclidae, Muscicapidae and Sturnidae (sensu [Sibley, C.G., Monroe Jr., B.L., 1990. Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven, CT]). Within the sturnoid lineage Mimini and Sturnini are sister groups, with Buphagus basal to them. We identified three major lineages of starlings: the Philippine endemic genus Rhabdornis, an Oriental-Australasian clade (genera Scissirostrum, Gracula, Mino, Ampeliceps, Sarcops, Aplonis), and an Afrotropical-Palaearctic clade (all African taxa, Sturnus and Acridotheres). We discuss the biogeographic implications of our findings and suggest an Asiatic origin for this family. The congruence between the age of major clades, estimated by NPRS, and palaeoclimatic data present evidence for the role of climatic changes in shaping present day distribution of the group.

The African warbler genus Hyliota as a lost lineage in the Oscine songbird tree: Molecular support for an African origin of the Passerida

The African genus Hyliota includes three or four species of warbler-like birds of uncertain phylogenetic affinities, as it has historically been placed in different avian families that are now known to represent unrelated lineages: Malaconotidae (bush-shrikes), Platysteiridae (batises and wattle-eyes), Muscicapidae (Old World flycatchers) and Sylviidae (Old-World Warblers). To assess the affinities of Hyliota we sequenced a mitochondrial protein-coding gene (ND2, 1018bp) and a nuclear intron (myoglobin intron-2, 685bp). Our analyses suggest that all previous hypotheses concerning the affinities of Hyliota are erroneous. Instead, Hyliota represents a basal branch in the Passerida radiation with no close relatives. Our results, which also include analyses of relationships among other of other atypical songbird genera, lend support to an African origin of the Passerida songbird radiation.

Phylogenetic relationships of the African bush-shrikes and helmet-shrikes (Passeriformes: Malaconotidae)

The African bush-shrikes and helmet-shrikes (Malaconotidae sensu [A Complete Checklist of the Birds of the World, third ed., Helm Editions, London, 2003]) include 10 genera and 52 species of predatory passerine birds for which monophyly, sister-group, and inter-generic relationships are disputed. To resolve their relationships, we analyzed 2313 bp of sequence data obtained from two nuclear introns (myoglobin intron-2, beta-fibrinogen intron-5) and a mitochondrial protein-coding gene (ND2) using parsimony, maximum likelihood, and Bayesian inference. A strongly supported clade that included representatives of the Malaconotidae, Platysteiridae, and Vangidae was found in all analyses. Three main groups emerged within this clade but relationships between these three groups were always poorly supported. The first group included the helmet-shrikes (Prionops), flycatcher-shrikes (Bias and Megabyas), and vangas (Cyanolanius and Pseudobias), currently placed in the families Malaconotidae, Platysteiridae, and Vangidae, respectively. The second group consisted of four Platysteiridae genera (Lanioturdus, Batis, Platysteira, and Dyaphorophyia), with the remaining Malaconotidae genera ('core malaconotids') forming the last group. Two main clades emerged within the 'core malaconotids,' with the position of the genus Nilaus being variable. The first clade included Malaconotus, Dryoscopus, Bocagia, and Tchagra and the second Chlorophoneus, Laniarius, Rhodophoneus, and Telophorus. Monophyly of the genus Chlorophoneus was never recovered, a result that is consistent with morphological data.

What are African monarchs (Aves, Passeriformes)? A phylogenetic analysis of mitochondrial genes

We address the phylogenetic relationships of ten passerine bird species representing the five presently supposed monarchine (family Monarchidae) genera (Terpsiphone, Hypothymis, Elminia, Trochocercus, Erythrocercus) from Asia and Africa, as well as three monarchs from Australasia, three representatives of the related genera Rhipidura and Dicrurus, and 20 representatives of 11 other oscine groups (including two Culicicapa flycatchers) and one sub-oscine, using two partial mitochondrial genes (cytochrome b and large sub-unit ribosomal 16S RNA). Molecular data corroborate ecological, ethological and morphological observations on the probable heterogeneity of Trochocercus and indicate that this genus is polyphyletic; two of its species are members of Monarchidae allied to Terpsiphone and Hypothymis; the others are more closely related to Elminia. Elminia is not a member of Monarchidae and is not related to any other sampled species, except Culicicapa. Erythrocercus is also outside the Monarchidae but inside a Sylvii-Pycnonotidae group. These results point once more to the need of a fully revised phylogeny of passerine birds.

An endemic radiation of Malagasy songbirds is revealed by mitochondrial DNA sequence data

The bird fauna of Madagascar includes a high proportion of endemic species, particularly among passerine birds (Aves: Passeriformes). The endemic genera of Malagasy songbirds are not allied obviously with any African or Asiatic taxa, and their affinities have been debated since the birds first were described. We used mitochondrial sequence data to estimate the relationships of 13 species of endemic Malagasy songbirds, 17 additional songbird species, and one species of suboscine passerine. In our optimal trees, nine of the 13 Malagasy species form a clade. although these birds currently are classified in three different families. In all optimal trees, the sister to this endemic clade is a group of Old World warblers including both African and Malagasy birds. The endemic Malagasy songbird clade rivals other island radiations, including the vangas of Madagascar and the finches of the Galapagos, in ecological diversity.

Phylogenetic relationships in the Ranidae. Independent origin of direct development in the genera Philautus and Taylorana

Phylogenetic relationships within a group of Ranidae were studied, particularly between the genera Philautus and Taylorana, to determine whether their original reproductive mode (direct development) appeared independently. To study these relationships, we used the DNA sequences of the 5' end of the gene coding for mitochondrial ribosome small subunit in 28 species. Parsimony analysis resulted in two equiparsimonious trees, 867 steps long (CI = 0.382; RI = 0.429). Data saturation was studied and we applied weighting (weight of 5 for transversions and 1 for transitions) to enhance the phylogenetic information. The tree we obtained (2,212 steps long, CI = 0.408; RI = 0.482) is best supported and allows us to determine clearly that direct development has appeared independently in Philautus and Taylorana. In addition, it is confirmed that the genus Rana sensu lato is heterogeneous. The genera Occidozyga and Phrynoglossus form a clade basal to all the group but this position is not supported. The inclusion of the Rhacophorinae in the Ranidae is confirmed. Finally, this study confirms that the relationships within the group Tomopterna sensu Boulenger, 1918 should be re-evaluated.

Molecular systematics of the Malagasy babblers (Passeriformes: timaliidae) and warblers (Passeriformes: sylviidae), based on cytochrome b and 16S rRNA sequences

The phylogenetic relationships of the Timaliidae (babblers) and Sylviidae (warblers) have long challenged ornithologists. We focus here on three Malagasy genera currently assigned to the Timaliidae, Mystacornis, Oxylabes, and Neomixis, and on their relationships with other babblers and warblers using the sequences of two mitochondrial genes (cytochrome b and 16S rRNA). Maximum parsimony analyses show that the Malagasy "babblers" are not related to any of the other African and Asian babblers. The genus Mystacornis is neither a babbler nor a warbler. The other Malagasy "babblers" are members of warbler groups (the monophyly of the Sylviidae is not demonstrated). Oxylabes madagascariensis and Hartertula flavoviridis (we recognize Hartertula as a genus for the species flavoviridis, previously Neomixis flavoviridis) constitute, with two presumed sylviine taxa, Thamnornis chloropetoides and Cryptosylvicola randrianasoloi, a warbler radiation endemic to the island of Madagascar. The other Neomixis species (tenella, striatigula, and viridis) belong to another warbler group comprising cisticoline taxa. These results show that the Timaliidae did not disperse to Madagascar. Rather, the island has been colonized, independently, by at least two clades of warblers, probably originating from Africa, where the Sylviidae radiation has been the most extensive.