Mitonuclear discordance results from incomplete lineage sorting, with no detectable evidence for gene flow, in a rapid radiation of Todiramphus kingfishers.

Many organisms possess multiple discrete genomes (i.e. nuclear and organellar), which are inherited separately and may have unique and even conflicting evolutionary histories. Phylogenetic reconstructions from these discrete genomes can yield different patterns of relatedness, a phenomenon known as cytonuclear discordance. In many animals, mitonuclear discordance (i.e. discordant evolutionary histories between the nuclear and mitochondrial genomes) has been widely documented, but its causes are often considered idiosyncratic and inscrutable. We show that a case of mitonuclear discordance in Todiramphus kingfishers can be explained by extensive genome-wide incomplete lineage sorting (ILS), likely a result of the explosive diversification history of this genus. For these kingfishers, quartet frequencies reveal that the nuclear genome is dominated by discordant topologies, with none of the internal branches in our consensus nuclear tree recovered in >50% of genome-wide gene trees. Meanwhile, a lack of inter-species shared ancestry, non-significant pairwise tests for gene flow, and little evidence for meaningful migration edges between species, leads to the conclusion that gene flow cannot explain the mitonuclear discordance we observe. This lack of evidence for gene flow combined with evidence for extensive genome-wide gene tree discordance, a hallmark of ILS, leads us to conclude that the mitonuclear discordance we observe likely results from ILS, specifically deep coalescence of the mitochondrial genome. Based on this case study, we hypothesize that similar demographic histories in other 'great speciator' taxa across the Indo-Pacific likely predispose these groups to high levels of ILS and high likelihoods of mitonuclear discordance.

Wallacean and Melanesian Islands Promote Higher Rates of Diversification within the Global Passerine Radiation Corvides.

The complex island archipelagoes of Wallacea and Melanesia have provided empirical data behind integral theories in evolutionary biology, including allopatric speciation and island biogeography. Yet, questions regarding the relative impact of the layered biogeographic barriers, such as deep-water trenches and isolated island systems, on faunal diversification remain underexplored. One such barrier is Wallace's Line, a significant biogeographic boundary that largely separates Australian and Asian biodiversity. To assess the relative roles of biogeographic barriers-specifically isolated island systems and Wallace's Line-we investigated the tempo and mode of diversification in a diverse avian radiation, Corvides (Crows and Jays, Birds-of-paradise, Vangas, and allies). We combined a genus-level data set of thousands of ultraconserved elements (UCEs) and a species-level, 12-gene Sanger sequence matrix to produce a well-resolved supermatrix tree that we leveraged to explore the group's historical biogeography and the effects of the biogeographic barriers on their macroevolutionary dynamics. The tree is well resolved and differs substantially from what has been used extensively for past comparative analyses within this group. We confirmed that Corvides, and its major constituent clades, arose in Australia and that a burst of dispersals west across Wallace's Line occurred after the uplift of Wallacea during the mid-Miocene. We found that dispersal across this biogeographic barrier was generally rare, though westward dispersals were two times more frequent than eastward dispersals. Wallacea's central position between Sundaland and Sahul no doubt acted as a bridge for island-hopping dispersal out of Australia, across Wallace's Line, to colonize the rest of Earth. In addition, we found that the complex island archipelagoes east of Wallace's Line harbor the highest rates of net diversification and are a substantial source of colonists to continental systems on both sides of this biogeographic barrier. Our results support emerging evidence that island systems, particularly the geologically complex archipelagoes of the Indo-pacific, are drivers of species diversification. [Historical biogeography; island biogeography; Melanesia; molecular phylogenetics; state-dependent diversification and extinction.].

Gene flow and rapid differentiation characterize a rapid insular radiation in the southwest Pacific (Aves: Zosterops).

As a dispersive lineage expands its distribution across a heterogeneous landscape, it leaves behind allopatric populations with varying degrees of geographic isolation that often differentiate rapidly. In the case of oceanic islands, even narrowly separated populations often differentiate, which seems contrary to the highly dispersive nature of the founding lineage. This pattern of highly dispersive lineages differentiating across narrow sea barriers has perplexed biologists for more than a century. We used two reduced-representation genomic datasets to examine the diversification of a recent, rapid geographic radiation, the white-eyes (Aves: Zosterops) of the Solomon Islands. We incorporated methods that targeted phylogenetic structure, population structure, and explicit tests for gene flow. Both datasets showed evidence of gene flow among species, but not involving the closely spaced islands in the New Georgia Group. Instead, gene flow has occurred among the larger islands in the archipelago, including those recently connected by land bridges as well as those isolated by large expanses of deep ocean. Populations separated by shallow seas, and connected by land bridges during glacial cycles, ranged from no differentiation to both phenotypic and genomic differentiation. These complex patterns of gene flow and divergence support a model of rapid geographic radiation in which lineages differentially evolve dispersal disparity and phenotypic differences.

Parachute geckos free fall into synonymy: Gekko phylogeny, and a new subgeneric classification, inferred from thousands of ultraconserved elements.

Recent phylogenetic studies of gekkonid lizards have revealed unexpected, widespread paraphyly and polyphyly among genera, unclear generic boundaries, and a tendency towards the nesting of taxa exhibiting specialized, apomorphic morphologies within geographically widespread "generalist" clades. This is especially true in Australasia, where monophyly of Gekko proper has been questioned with respect to phenotypically ornate flap-legged geckos of the genus Luperosaurus, the Philippine false geckos of the genus Pseudogekko, and even the elaborately "derived" parachute geckos of the genus Ptychozoon. Here we employ sequence capture targeting 5060 ultraconserved elements (UCEs) to infer phylogenomic relationships among 42 representative ingroup gekkonine lizard taxa. We analyze multiple datasets of varying degrees of completeness (10, 50, 75, 95, and 100 percent complete with 4715, 4051, 3376, 2366, and 772 UCEs, respectively) using concatenated maximum likelihood and multispecies coalescent methods. Our sampling scheme addresses four persistent systematic questions in this group: (1) Are Luperosaurus and Ptychozoon monophyletic, and are any of these named species truly nested within Gekko? (2) Are prior phylogenetic estimates of Sulawesi's L. iskandari as the sister taxon to Melanesian G. vittatus supported by our genome-scale dataset? (3) Is the high-elevation L. gulat of Palawan Island correctly placed within Gekko? (4) And, finally, where do the enigmatic taxa P. rhacophorus and L. browni fall in a higher-level gekkonid phylogeny? We resolve these issues; confirm with strong support some previously inferred findings (placement of Ptychozoon taxa within Gekko; the sister taxon relationship between L. iskandari and G. vittatus); resolve the systematic position of unplaced taxa (L. gulat, and L. browni); and transfer L. iskandari, L. gulat, L. browni, and all members of the genus Ptychozoon to the genus Gekko. Our unexpected and novel systematic inference of the placement of Ptychozoon rhacophorus suggests that this species is not grouped with Ptychozoon or even Luperosaurus (as previously expected) but may, in fact, be most closely related to several Indochinese species of Gekko. With our resolved and strongly supported phylogeny, we present a new classification emphasizing the most inclusive, original generic name (Gekko) for these ~60 taxa, arranged into seven subgenera.

A Laurasian origin for a pantropical bird radiation is supported by genomic and fossil data (Aves: Coraciiformes).

The evolution of pantropically distributed clades has puzzled palaeo- and neontologists for decades regarding the different hypotheses about where they originated. In this study, we explored how a pantropical distribution arose in a diverse clade with a rich fossil history: the avian order Coraciiformes. This group has played a central role in the debate of the biogeographical history of Neoaves. However, the order lacked a coherent species tree to inform study of its evolutionary dynamics. Here, we present the first complete species tree of Coraciiformes, produced with 4858 ultraconserved elements, which supports two clades: (1) Old World-restricted bee-eaters, rollers and ground-rollers; and (2) New World todies and motmots, and cosmopolitan kingfishers. Our results indicated two pulses of diversification: (1) major lineages of Coraciiformes arose in Laurasia approximately 57 Ma, followed by independent dispersals into equatorial regions, possibly due to tracking tropical habitat into the lower latitudes-the Coracii (Coraciidae + Brachypteraciidae) into the Afrotropics, bee-eaters throughout the Old World tropics, and kingfishers into the Australasian tropics; and (2) diversification of genera in the tropics during the Miocene and Pliocene. Our study supports the important role of Laurasia as the geographical origin of a major pantropical lineage and provides a new framework for comparative analyses in this charismatic bird radiation.

Tectonic collision and uplift of Wallacea triggered the global songbird radiation.

Songbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity. Songbirds originated in Australia, but the evolutionary trajectory from a single species in an isolated continent to worldwide proliferation is poorly understood. Here, we combine the first comprehensive genome-scale DNA sequence data set for songbirds, fossil-based time calibrations, and geologically informed biogeographic reconstructions to provide a well-supported evolutionary hypothesis for the group. We show that songbird diversification began in the Oligocene, but accelerated in the early Miocene, at approximately half the age of most previous estimates. This burst of diversification occurred coincident with extensive island formation in Wallacea, which provided the first dispersal corridor out of Australia, and resulted in independent waves of songbird expansion through Asia to the rest of the globe. Our results reconcile songbird evolution with Earth history and link a major radiation of terrestrial biodiversity to early diversification within an isolated Australian continent.

Phylogeny of the monarch flycatchers reveals extensive paraphyly and novel relationships within a major Australo-Pacific radiation.

Monarch flycatchers are a major component of Australo-Pacific and Wallacean avifaunas. To date, the family has received incomplete attention by molecular systematists who focused on subclades with minimal character and/or taxon sampling. As a result, Monarchidae taxonomy is still out-of-date, and biogeographic reconstructions have been based on poorly-resolved phylogenies, limiting their interpretation. Here, we produced a comprehensive, molecular phylogeny of the Monarchidae inferred from mitochondrial and nuclear loci using both concatenated and multilocus coalescent frameworks. We sampled 92% of the 99 recognized monarchid biological species and included deeper sampling within several phylogenetic species complexes, including Monarcha castaneiventris, Symposiachrus barbatus, and Terpsiphone rufiventer. Melampitta is identified as sister to the monarch flycatchers, which themselves comprise four major lineages. The first lineage comprises Terpsiphone and allies, the second lineage is Grallina, the third is Arses and Myiagra, and the fourth lineage comprises a diverse assemblage of genera including the "core monarchs" and the most geographically isolated groups like Chasiempis (Hawaii) and Pomarea (eastern Polynesia). Gene tree discordance was evident in Myiagra, which has implications for basal lineages in the genus (e.g., M. azureocapilla, M. hebetior, and M. alecto). Numerous genera within the core monarchs are paraphyletic, including Mayrornis and Pomarea, whereas the validity of others such as Metabolus are questionable. We recognize polytypic taxa as multiple species, including Lamprolia victoriae and Myiagra azureocapilla. In general, the topology of species complexes included short internodes that were not well resolved, owing to their rapid diversification across island archipelagos. Terpsiphone rufiventer comprises multiple lineages, including a heretofore-unappreciated West African lineage, but relationships within these rapid radiations will require extensive genomic sampling for further resolution. This study establishes a new benchmark for Monarchidae systematics and it provides an excellent framework for future work on biogeography and character evolution in a diverse Australo-Papuan radiation.

A molecular phylogeny of Pacific honeyeaters (Aves: Meliphagidae) reveals extensive paraphyly and an isolated Polynesian radiation.

We investigated the molecular phylogenetic placement of 14 species of Pacific island honeyeaters (Aves: Meliphagidae) in the broader context of an existing family-level phylogeny. We examined the evolutionary history of Pacific honeyeater lineages to assess the accuracy of current taxonomies and to evaluate their biogeographic history. We compare these biogeographic patterns to other Pacific birds to identify emergent patterns across lineages. We found strong support for a previously unknown endemic radiation in central Polynesia, which comprises five genera: Meliarchus, Guadalcanaria, Gymnomyza, Xanthotis, and Foulehaio. Conversely, other Pacific lineages were found to be strongly allied with continental radiations (e.g., Philemon eichhorni, P. cockerelli, and Lichmera incana). Our results necessitated taxonomic changes, both at the generic level (e.g., Xanthotis, Melidectes/Vosea, and Glycifohia/Gliciphila) and regarding species limits within polytypic species. Here, we discuss species limits in Foulehaio and Gymnomyza and recommend elevating three nominal subspecies of Foulehaio to species status, each of which forms well-differentiated clades.