Transoceanic Dispersal Research Articles

Diversification in an Afro-Asian songbird clade (Erythropygia–Copsychus) reveals founder-event speciation via trans-oceanic dispersals and a southern to northern colonization pattern in Africa

Erythropygia scrub-robins and their allies are distributed throughout Africa, Europe, Southeast Asia, India, Madagascar and the Seychelles. This broad distribution, as well as the distribution of Erythropygia taxa across Africa, presents an interesting opportunity to explore the mechanisms by which this biogeographic distribution was achieved. Multilocus sequence data (3310 base pairs from two mitochondrial and two nuclear genes) were generated for all species of Erythropygia and Cercotrichas scrub-robins, as well as from genera previously shown to render Erythropygia paraphyletic. Using model-based phylogenetic methods and molecular clock dating, we constructed a time-calibrated molecular phylogenetic hypothesis for the lineage. Ancestral area reconstructions were performed on the phylogeny using probabilistic approaches implemented in LaGrange and BioGeoBEARS. Our results confirm that Erythropygia is not monophyletic, and that one of the two Erythropygia clades is more closely related to a clade of Asian and Indian Ocean islands distributed species. Overall, the Erythropygia and allies clade originated in Africa in the late Miocene c. 6.9 Ma. Subsequently, a number of overwater dispersals occurred to include an initial colonization of Southeast Asia, and an ensuing progression of colonizations from Southeast Asia to the Seychelles, from there to Madagascar, and from these Indian Ocean islands back to Southeast Asia. Within the two clades of Erythropygia, ancestral area reconstructions within Africa indicate a Southern Africa origin, with subsequent lineage divergence in each clade indicating northward colonization. Overall, this clade of non-migratory songbirds shows a remarkable number of trans-oceanic colonization events, that were possibly facilitated by wind-driven dispersal; repeated Africa to Asia colonizations, two of which occur in this clade, are exceptionally rare in birds. Also rare is our finding that colonization patterns in Africa indicate a southern to northern progression.

A living fossil tale of Pangaean biogeography.

The current distributions of widespread groups of terrestrial animals and plants are supposedly the result of a mixture of either vicariance owing to continental split or more recent trans-oceanic dispersal. For organisms exhibiting a vicariant biogeographic pattern-achieving their current distribution by riding on the plates of former supercontinents-this view is largely inspired by the belief that Pangaea lacked geographical or ecological barriers, or that extinctions and dispersal would have erased any biogeographic signal since the early Mesozoic. We here present a time-calibrated molecular phylogeny of Onychophora (velvet worms), an ancient and exclusively terrestrial panarthropod group distributed throughout former Pangaean landmasses. Our data not only demonstrate that trans-oceanic dispersal does not need be invoked to explain contemporary distributions, but also reveal that the early diversification of the group pre-dates the break-up of Pangaea, maintaining regionalization even in landmasses that have remained contiguous throughout the history of the group. These results corroborate a growing body of evidence from palaeontology, palaeogeography and palaeoclimatic modelling depicting ancient biogeographic regionalization over the continuous landmass of Pangaea.

Species diversity and distribution of Ruppia in China: Potential roles of long‐distance dispersal and environmental factors

AbstractRuppia is a cosmopolitan genus and the species identity within the genus has been often confusing due to high plasticity in morphology. We used nuclear ribosomal DNA internal transcribed spacer and seven chloroplast DNA fragments combined with morphological traits to distinguish Ruppia species along the coastline of China, and to infer the potential mechanisms shaping their distribution patterns. Molecular and morphological data distinguished three congruent clades corresponding with three species: R. cirrhosa (Petagna) Grande, R. maritima L., and R. megacarpa Mason. The geographical ranges of R. cirrhosa and R. maritima coincided closely with coastal current breaks by the Taiwan Strait; R. cirrhosa was found in 17 locations mainly in the north, whereas R. maritima was common in the south, most likely to be the result of differentiated adaptation to optimal temperatures of growth and/or seed germination. Ruppia megacarpa, usually considered as an endemic species of Australia and New Zealand, was first reported in China at two bird stopover sites, Qingdao and Yancheng. The transoceanic dispersal by migratory birds may contribute to the presence and distribution of R. megacarpa in China.

Radiation and repeated transoceanic dispersal of Schoeneae (Cyperaceae) through the southern hemisphere

The broad austral distribution of Schoeneae is almost certainly a product of long-distance dispersal. Owing to the inadequacies of existing phylogenetic data and a lack of rigorous biogeographic analysis, relationships within the tribe remain poorly resolved and its pattern of radiation and dispersal uncertain. We employed an expanded sampling of taxa and markers and a rigorous analytic approach to address these limitations. We evaluated the roles of geography and ecology in stimulating the initial radiation of the group and its subsequent dispersal across the southern hemisphere. A dated tree was reconstructed using reversible-jump Markov chain Monte Carlo (MCMC) with a polytomy prior and molecular dating, applied to data from two nuclear and three cpDNA regions. Ancestral areas and habitats were inferred using dispersal-extinction-cladogenesis models. Schoeneae originated in Australia in the Paleocene. The existence of a "hard" polytomy at the base of the clade reflects the rapid divergence of six principal lineages ca. 50 Ma, within Australia. From this ancestral area, Schoeneae have traversed the austral oceans with remarkable frequency, a total of 29 distinct dispersal events being reported here. Dispersal rates between landmasses are not explicable in terms of the geographical distances separating them. Transoceanic dispersal generally involved habitat stasis. Although the role of dispersal in explaining global distribution patterns is now widely accepted, the apparent ease with which such dispersal may occur has perhaps been under-appreciated. In Schoeneae, transoceanic dispersal has been remarkably frequent, with ecological opportunity, rather than geography, being most important in dictating dispersal patterns.

Global biogeography of scaly tree ferns (Cyatheaceae): evidence for Gondwanan vicariance and limited transoceanic dispersal.

AimScaly tree ferns, Cyatheaceae, are a well-supported group of mostly tree-forming ferns found throughout the tropics, the subtropics and the south-temperate zone. Fossil evidence shows that the lineage originated in the Late Jurassic period. We reconstructed large-scale historical biogeographical patterns of Cyatheaceae and tested the hypothesis that some of the observed distribution patterns are in fact compatible, in time and space, with a vicariance scenario related to the break-up of Gondwana.LocationTropics, subtropics and south-temperate areas of the world.MethodsThe historical biogeography of Cyatheaceae was analysed in a maximum likelihood framework using Lagrange. The 78 ingroup taxa are representative of the geographical distribution of the entire family. The phylogenies that served as a basis for the analyses were obtained by Bayesian inference analyses of mainly previously published DNA sequence data using MrBayes. Lineage divergence dates were estimated in a Bayesian Markov chain Monte Carlo framework using beast.ResultsCyatheaceae originated in the Late Jurassic in either South America or Australasia. Following a range expansion, the ancestral distribution of the marginate-scaled clade included both these areas, whereas Sphaeropteris is reconstructed as having its origin only in Australasia. Within the marginate-scaled clade, reconstructions of early divergences are hampered by the unresolved relationships among the Alsophila, Cyathea and Gymnosphaera lineages. Nevertheless, it is clear that the occurrence of the Cyathea and Sphaeropteris lineages in South America may be related to vicariance, whereas transoceanic dispersal needs to be inferred for the range shifts seen in Alsophila and Gymnosphaera.Main conclusionsThe evolutionary history of Cyatheaceae involves both Gondwanan vicariance scenarios as well as long-distance dispersal events. The number of transoceanic dispersals reconstructed for the family is rather few when compared with other fern lineages. We suggest that a causal relationship between reproductive mode (outcrossing) and dispersal limitations is the most plausible explanation for the pattern observed.

“Terror Birds” (Phorusrhacidae) from the Eocene of Europe Imply Trans-Tethys Dispersal

BackgroundPhorusrhacidae was a clade including middle-sized to giant terrestrial carnivorous birds, known mainly from the Cenozoic of South America, but also occurring in the Plio-Pleistocene of North America and the Eocene of Africa. Previous reports of small phorusrhacids in the Paleogene of Europe have been dismissed as based on non-phorusrhacid material.Methodologywe have re-examined specimens of large terrestrial birds from the Eocene (late Lutetian) of France and Switzerland previously referred to gastornithids and ratites and have identified them as belonging to a phorusrhacid for which the name Eleutherornis cotei should be used.Conclusions/SignificanceThe occurrence of a phorusrhacid in the late Lutetian of Europe indicates that these flightless birds had a wider geographical distribution than previously recognized. The likeliest interpretation is that they dispersed from Africa, where the group is known in the Eocene, which implies crossing the Tethys Sea. The Early Tertiary distribution of phorusrhacids can be best explained by transoceanic dispersal, across both the South Atlantic and the Tethys.

How Was the Australian Flora Assembled Over the Last 65 Million Years? A Molecular Phylogenetic Perspective

Australia has a mostly dry, open, fire-shaped landscape of sclerophyllous and xeromorphic flora dominated by eucalypt and acacia trees, with diverse shrubs from a few families such as Myrtaceae, Proteaceae, and Fabaceae. Using molecular phylogenies to test hypotheses derived from the fossil record, we review the principal forces that transformed the ancestral Gondwanan rainforest through the Cenozoic. Today's vegetation is a mix of ancient radiations that have persisted in Australia through dramatic climate change since before the breakup of Gondwana, and more recent lineages whose ancestors arrived by trans-oceanic dispersal. Signatures in the fossil record of lineage turnover and trait evolutionary change are detected in phylogenies, but often at earlier dates. The Australian biota is a sample of the wider region, with extinction of some taxa and radiation of others (due to chance and opportunity), but biotic and abiotic interactions have resulted in a unique flora and fauna.

The phylogeography of trypanosomes from South American alligatorids and African crocodilids is consistent with the geological history of South American river basins and the transoceanic dispersal of Crocodylus at the Miocene

BackgroundLittle is known about the diversity, phylogenetic relationships, and biogeography of trypanosomes infecting non-mammalian hosts. In this study, we investigated the influence of host species and biogeography on shaping the genetic diversity, phylogenetic relationship, and distribution of trypanosomes from South American alligatorids and African crocodilids.MethodsSmall Subunit rRNA (SSU rRNA) and glycosomal Glyceraldehyde Phosphate Dehydrogenase (gGAPDH) genes were employed for phylogenetic inferences. Trypanosomes from crocodilians were obtained by haemoculturing. Growth behaviour, morphology, and ultrastructural features complement the molecular description of two new species strongly supported by phylogenetic analyses.ResultsThe inferred phylogenies disclosed a strongly supported crocodilian-restricted clade comprising three subclades. The subclade T. grayi comprised the African Trypanosoma grayi from Crocodylus niloticus and tsetse flies. The subclade T. ralphi comprised alligatorid trypanosomes represented by Trypanosoma ralphi n. sp. from Melanosuchus niger, Caiman crocodilus and Caiman yacare from Brazilian river basins. T. grayi and T. ralphi were sister subclades. The basal subclade T. terena comprised alligatorid trypanosomes represented by Trypanosoma terena n. sp. from Ca. yacare sharing hosts and basins with the distantly genetic related T. ralphi. This subclade also included the trypanosome from Ca. crocodilus from the Orinoco basin in Venezuela and, unexpectedly, a trypanosome from the African crocodilian Osteolaemus tetraspis.ConclusionThe close relationship between South American and African trypanosomes is consistent with paleontological evidence of recent transoceanic dispersal of Crocodylus at the Miocene/Pliocene boundaries (4–5 mya), and host-switching of trypanosomes throughout the geological configuration of South American hydrographical basins shaping the evolutionary histories of the crocodilians and their trypanosomes.

Phylogeny and divergence times of Australian Sphenomorphus group skinks (Scincidae, Squamata)

The Australian Sphenomorphus group is a diverse clade (c. 250 species) of scincid lizards (skinks) incorporating more than half of the Australian scincid fauna. Previous phylogenetic analyses of mitochondrial and nuclear gene sequence data for selected Australian Sphenomorphus group scincids have provided support for several morphologically- and ecologically-distinct clades; however, the relationships among these clades are only incompletely resolved. This paper presents a new phylogenetic analysis of the Australian Sphenomorphus group, based on nucleotide sequences for three regions of the mitochondrial genome and four nuclear genes (5645 aligned sites in total). Phylogenies generated using standard concatenation and multi-species coalescent approaches are generally similar, and nearly all conflicting nodes are weakly supported. Monophyly of a number of genera and other (informal) supra-specific taxa, including Calyptotis, Ctenotus, Eremiascincus, Hemiergis, Lerista, Notoscincus, the ‘Eulamprus’ quoyii group, and the ‘Glaphyromorphus’ crassicaudis group is well supported in all analyses. There is significant support for a clade including the ‘Eulamprus’ tenuis group, Gnypetoscincus, and Nangura, and a clade comprising Coeranoscincus, Coggeria, Ophioscincus, and Saiphos receives at least marginal support (posterior probabilities above 0.93). All analyses indicate that Anomalopus is polyphyletic, although topology tests suggest that support for this result is equivocal. Divergence times inferred using relaxed molecular clock methods are consistent with an Oligocene origin of the Australian Sphenomorphus group following trans-oceanic dispersal from Asia. Age estimates for clades distributed primarily in arid habitats (c. 9–17million years) are generally younger than those for clades occurring in mesic environments (c. 15–22million years); however, arid-zone clades are substantially more diverse, including nearly 80% of all Australian Sphenomorphus group scincids. This pattern conforms well with reconstructions of Australian palaeo-environments during the Cenozoic, which indicate a progressive shift from widespread mesic habitats in the Early Miocene (prior to 16Mya) to predominantly arid environments 4–2Mya.

Strong genetic structure over the American continents and transoceanic dispersal in the mangrove genus Rhizophora (Rhizophoraceae) revealed by broad‐scale nuclear and chloroplast DNA analysis

The global distribution of mangroves is attributed to interactions between long-distance propagule dispersal and geographical barriers, which are manifest in genetic structuring. Uncovering this genetic structure thus provides a window into the ecological, evolutionary, and phylogeographic history of mangroves. We used cpDNA and nuclear microsatellites to evaluate transbarrier (transoceanic and transisthmian) linkages in the genus Rhizophora in the Atlantic East Pacific (AEP) and South Pacific region. • Leaf samples of 756 individuals of Rhizophora mangle, R. racemosa, R. ×harrisonii, and R. samoensis from 36 populations across the AEP supplied material from which we used the cpDNA haplotypes and nine microsatellite markers for population analyses. • Clear genetic differentiation of cpDNA haplotypes was found between the Pacific and Atlantic populations in R. mangle and R. racemosa, supporting the hypothesis of the Central American Isthmus as a barrier to gene flow. Both cpDNA and microsatellite analyses support the hypothesis of recent and frequent transatlantic propagule dispersal for R. mangle. Finally, we provide strong evidence for genetic similarity of Pacific R. mangle and R. samoensis suggesting trans-Pacific dispersal of R. mangle. • The American continents are strong geographical barriers to dispersal of Rhizophora, to the point where the Pacific and Atlantic populations are distinct genealogical units, supporting the recommendation to treat the populations as separate conservation and management units. Trans-Pacific propagule dispersal of Rhizophora has occurred; R. mangle and R. samoensis might be the same species and this question should be resolved with further taxonomic study.

An invasive Mimosa in India does not adopt the symbionts of its native relatives.

The large monophyletic genus Mimosa comprises approx. 500 species, most of which are native to the New World, with Central Brazil being the main centre of radiation. All Brazilian Mimosa spp. so far examined are nodulated by rhizobia in the betaproteobacterial genus Burkholderia. Approximately 10 Mya, transoceanic dispersal resulted in the Indian subcontinent hosting up to six endemic Mimosa spp. The nodulation ability and rhizobial symbionts of two of these, M. hamata and M. himalayana, both from north-west India, are here examined, and compared with those of M. pudica, an invasive species. Nodules were collected from several locations, and examined by light and electron microscopy. Rhizobia isolated from them were characterized in terms of their abilities to nodulate the three Mimosa hosts. The molecular phylogenetic relationships of the rhizobia were determined by analysis of 16S rRNA, nifH and nodA gene sequences. Both native Indian Mimosa spp. nodulated effectively in their respective rhizosphere soils. Based on 16S rRNA, nifH and nodA sequences, their symbionts were identified as belonging to the alphaproteobacterial genus Ensifer, and were closest to the 'Old World' Ensifer saheli, E. kostiensis and E. arboris. In contrast, the invasive M. pudica was predominantly nodulated by Betaproteobacteria in the genera Cupriavidus and Burkholderia. All rhizobial strains tested effectively nodulated their original hosts, but the symbionts of the native species could not nodulate M. pudica. The native Mimosa spp. in India are not nodulated by the Burkholderia symbionts of their South American relatives, but by a unique group of alpha-rhizobial microsymbionts that are closely related to the 'local' Old World Ensifer symbionts of other mimosoid legumes in north-west India. They appear not to share symbionts with the invasive M. pudica, symbionts of which are mostly beta-rhizobial.

Sertularella mutsuensis Stechow, 1931 (Cnidaria: Hydrozoa: Sertulariidae) from Japanese tsunami debris: systematics and evidence for transoceanic dispersal

The leptothecate hydroid Sertularella mutsuensis Stechow, 1931 is reported on debris from the 2011 Japanese tsunami that came ashore on 5 June 2012 at Agate Beach north of Newport, Oregon. Its discovery on a barnacle (Semibalanus cariosus) from a derelict floating dock originating at Misawa, Honshu, confirms the capability of successful transoceanic dispersal for this species. We compare our specimens to Stechow’s syntype material of S. mutsuensis in collections at the Zoologische Staatssammlung Munchen, and designate a lectotype and paralectotype of the species.

Stable phylogenetic patterns in scutigeromorph centipedes (Myriapoda : Chilopoda : Scutigeromorpha): dating the diversification of an ancient lineage of terrestrial arthropods

Although stable and well-supported relationships are in place for the three main clades (families) of Scutigeromorpha, the interrelationships of particular taxa within the most diverse family, Scutigeridae, are less clearly resolved. Novel molecular data for taxa from Mesoamerica, the Caribbean, southern Africa, New Guinea and previously unsampled parts of the Pacific are incorporated into phylogenetic analyses. Relationships across the tree are stable under variable analytical conditions, whether these are homology-based (multiple sequence alignment versus implied alignment; untrimmed versus trimmed datasets) or method-based (parsimony versus maximum likelihood). Hypervariable regions, contrary to common belief, add phylogenetic structure to the data, as measured by the increased support for many nodes when compared with the same alignments trimmed with Gblocks. Our analyses show that a Yule-3-rate model best explained the diversification of Scutigeromorpha during their 400 million years of history. More complete molecular data for the New Guinea genus Ballonema stabilise its position as sister group to Thereuoneminae. To reconcile scutigeromorph systematics with the phylogeny, the monotypic genus Madagassophora Verhoeff, 1936, is placed in synonymy with Scutigerina Silvestri, 1901 (n. syn.), its type species M. hova becoming Scutigerina hova (de Saussure & Zehntner, 1902) new comb. (from Scutigera), and Lassophora Verhoeff, 1905, is re-established for an Afro-Malagasy clade containing Lassophora nossibei (de Saussure & Zehntner, 1902) new comb. (from Scutigera) and a newly sequenced species from Mozambique that diverged at the base of the lineage to Thereuoneminae. The dated phylogeny of Scutigeromorpha is more consistent with ancient vicariant splits between Madagascar–southern Africa and Australia–New Caledonia than with younger dispersal scenarios, though some geologically young Pacific islands that harbour lineages dating to the Cretaceous demonstrate the potential for trans-oceanic dispersal.

No gene flow across the Eastern Pacific Barrier in the reef‐building coral Porites lobata

The expanse of deep water between the central Pacific islands and the continental shelf of the Eastern Tropical Pacific is regarded as the world's most potent marine biogeographic barrier. During recurrent climatic fluctuations (ENSO, El Niño Southern Oscillation), however, changes in water temperature and the speed and direction of currents become favourable for trans-oceanic dispersal of larvae from central Pacific to marginal eastern Pacific reefs. Here, we investigate the population connectivity of the reef-building coral Porites lobata across the Eastern Pacific Barrier (EPB). Patterns of recent gene flow in samples (n = 1173) from the central Pacific and the Eastern Tropical Pacific (ETP) were analysed with 12 microsatellite loci. Results indicated that P. lobata from the ETP are strongly isolated from those in the central Pacific and Hawaii (F(ct) ' = 0.509; P < 0.001). However, samples from Clipperton Atoll, an oceanic island on the eastern side of the EPB, grouped with the central Pacific. Within the central Pacific, Hawaiian populations were strongly isolated from three co-occurring clusters found throughout the remainder of the central Pacific. No further substructure was evident in the ETP. Changes in oceanographic conditions during ENSO over the past several thousand years thus appear insufficient to support larval deliveries from the central Pacific to the ETP or strong postsettlement selection acts on ETP settlers from the central Pacific. Recovery of P. lobata populations in the frequently disturbed ETP thus must depend on local larval sources.

Population genetics of Australian white sharks reveals fine-scale spatial structure, transoceanic dispersal events and low effective population sizes

Despite international protection of white sharks Carcharodon carcharias, important conservation parameters such as abundance, population structure and genetic diversity are largely unknown. The tissue of 97 predominately juvenile white sharks sampled from spatially distant eastern and southwestern Australian coastlines was sequenced for the mitochondrial DNA (mtDNA) control region and genotyped with 6 nuclear-encoded microsatellite loci. MtDNA population structure was found between the eastern and southwestern coasts (F-ST = 0.142, p < 0.0001), implying female reproductive philopatry. This concurs with recent satellite and acoustic tracking findings which suggest the sustained presence of discrete east coast nursery areas. Furthermore, population subdivision was found between the same regions with biparentally inherited micro satellite markers (F-ST = 0.009, p < 0.05), suggesting that males may also exhibit some degree of reproductive philopatry; 5 sharks captured along the east coast had mtDNA haplotypes that resembled western Indian Ocean sharks more closely than Australian/New Zealand sharks, suggesting that transoceanic dispersal, or migration resulting in breeding, may occur sporadically. Our most robust estimate of contemporary genetic effective population size was low and close to thresholds at which adaptive potential may be lost. For a variety of reasons, these contemporary estimates were at least 1, possibly 2, orders of magnitude below our historical effective size estimates. Population decline could expose these genetically isolated populations to detrimental genetic effects. Regional Australian white shark conservation management units should be implemented until genetic population structure, size and diversity can be investigated in more detail.

Update: Updated DIVA program

ISSN 1948-6596 news and update update Updated DIVA program Botanists have long been stuck on the flora agenda, collecting and cataloging plants, and eventually producing narrative explanations of distributions. With increased data access and new analytic tools, the approach is now rapidly chang- ing towards synthesis of more general character. A recent paper in PNAS, by Alexandre An- tonelli and colleagues improves the standard set of tools for biogeographic reconstruction. The core of this paper is a molecular phylogeny of the coffee family (Rubiaceae), with broad taxon sam- pling but main focus on the Neotropics. The in- credible biodiversity of this region is often ex- plained from the extent and geological age of its rainforests, and from niche conservatism, whereby the once-widespread tropical biomes became restricted to low latitudes after the global cooling at the Eocene-Oligocene transition. The Andes is often assumed to have played a big role in South America, although it is poorly under- stood, first of all because the orogeny was often considered as a single, time-limited event. Little attention has been given to the fact that discrete geological structures were uplifted at different times, and to how the mountains affected the cli- mate of adjacent lowlands and constrained disper- sal within the lowlands. Montane biotas are often assumed to be young, recruited from adjacent lowlands, but mountains also seem to play a role as crates of biodiversity and dispersal centers. The study presents standard parsimony and Bayesian phylogenetic analysis and a likelihood estimation of evolutionary time. Building on Ron- quist’s DIVA program, Johan Nylander developed a new tool for biogeographic reconstruction, which uses a Bayesian sample of highly probable trees, thereby generating credibility support val- ues for alternative relationships. Thus, even with partially resolved trees and incomplete taxon sampling, the method provides very stable recon- structions of ancestral areas for the different phy- logenetic nodes. The combined chronogram and bio- geographic analysis demonstrates: (1) an old world origin of the Rubiaceae with dispersal to North America, before the opening of the North Atlantic in the Eocene, and (2) then to South America (which rejects the former view of Gond- wanic origin). (3) During late Oligocene to early Miocene, when the Amazon drained west through a Western Andean Portal, radiation took place in what is now the northern Andes and Amazonia, while the southern Andean region was out of reach. (4) From the mid-Miocene the Andes was connected as a continuous dispersal avenue, but at the same time it was isolated from the eastern Amazonian lowlands by marine incursions from the north and enormous wetlands. (5) Finally, when the present Amazonian drainage pattern to the Atlantic was established in the upper Mio- cene, there was a strong flora exchange through- out the tropical South American lowlands. Alto- gether, the study reveals a clear sequence of events of dispersal and diversification in distinct areas. The analytic approach has been used also in two recent studies of transoceanic dispersal in birds, and we must expect many further examples to follow. Antonelli, A., Nylander, J.A.A., Persson, C. & Sanmartin, I. (2009) Tracing the impact of the Andean uplift on Neotropical plant evolution. Proceedings of the National Academy of Sciences USA, 106, Jon Fjeldsa Natural History Museum of Denmark, Univer- sity of Copenhagen, Denmark e-mail: jfjeldsaa@snm.ku.dk http://snm.ku.dk/english/staffsnm/staff/profile/? id=75192 Edited by Camilla Flojgaard © 2009 the authors; journal compilation © 2009 The International Biogeography Society — frontiers of biogeography 1.1, 2009

Spatial and temporal arrival patterns of Madagascar's vertebrate fauna explained by distance, ocean currents, and ancestor type

How, when, and from where Madagascar's vertebrates arrived on the island is poorly known, and a comprehensive explanation for the distribution of its organisms has yet to emerge. We begin to break that impasse by analyzing vertebrate arrival patterns implied by currently existing taxa. For each of 81 clades, we compiled arrival date, source, and ancestor type (obligate freshwater, terrestrial, facultative swimmer, or volant). We analyzed changes in arrival rates, with and without adjusting for clade extinction. Probability of successful transoceanic dispersal is negatively correlated with distance traveled and influenced by ocean currents and ancestor type. Obligate rafters show a decrease in probability of successful transoceanic dispersal from the Paleocene onward, reaching the lowest levels after the mid-Miocene. This finding is consistent with a paleoceanographic model [Ali JR, Huber M (2010) Nature 463:653-656] that predicts Early Cenozoic surface currents periodically conducive to rafting or swimming from Africa, followed by a reconfiguration to present-day flow 15-20 million years ago that significantly diminished the ability for transoceanic dispersal to Madagascar from the adjacent mainland.

What is natural? The scale of cryptogenesis in the North Atlantic Ocean

AbstractAim Cryptogenic species may include those taxa that were historically introduced and are now falsely viewed as native. Investigated here is the scale of cryptogenesis in the North Atlantic Ocean by examining disjunct distributions, defined as temperate species occurring only on both sides of the North Atlantic. Disjunct distributions can be explained by four scenarios: glacial relicts, taxonomic artefacts, natural trans‐oceanic dispersal and human‐mediated introduction.Location North Atlantic Ocean.Methods Model taxa included ascidians, bivalves and hydrozoans. Biogeographic status (native, introduced or cryptogenic) was assigned to all species exhibiting a disjunct distribution, based upon multiple criteria.Results Of 1030 species, 60 have a strictly disjunct distribution. Of these disjunct species, for five species there is no reason to doubt their native status, and 55 species are cryptogenic or introduced. Groups with high relative dispersal capacities do not have disjunct distributions more often. Infaunal bivalves have the lowest relative number of disjunct species; none are cryptogenic or naturally disjunct. This supports the concept that glaciations are unlikely to cause disjunct distributions: there are no studies that provide conclusive evidence for the glacial relict model. Hydrozoa have the highest relative number of disjunct species, which, while historically explained by undocumented rafting, may more likely be the result of dispersal by ships, which travel relatively fast, are independent of currents and provide greater surface area.Main conclusions This reanalysis of the historical biogeography of the North Atlantic marine biota reveals that far more species may have been introduced than previously recognized, potentially significantly altering our fundamental understanding of community evolution and ecology. Species that have been present for centuries and can be important ecological engineers who have shaped contemporary communities are possibly falsely viewed as native: they may in fact be the unrecognized introductions of historical times.

‘Out‐of‐Africa’ dispersal of tropical floras during the Miocene climatic optimum: evidence fromUvaria(Annonaceae)

AbstractAim African–Asian disjunctions are common in palaeotropical taxa, and are typically explained by reference to three competing hypotheses: (1) ‘rafting’ on the Indian tectonic plate, enabling Africa‐to‐Asia dispersal; (2) migration via Eocene boreotropical forests; and (3) transoceanic long‐distance dispersal. These hypotheses are tested usingUvaria(Annonaceae), which is distributed in tropical regions of Africa, Asia and Australasia. Recent phylogenetic reconstructions of the genus show a clear correlation with geographical provenance, indicating a probable origin in Africa and subsequent dispersal to Asia and then Australasia. Ancestral areas and migration routes are inferred and compared with estimates of divergence times in order to distinguish between the prevailing dispersal hypotheses.Location Palaeotropics.Methods Divergence times inUvariaare estimated by analysing the sequences of four DNA regions (matK,psbA–trnH spacer,rbcL andtrnL–F) from 59Uvariaspecies and 77 outgroup species, using a Bayesian uncorrelated lognormal (UCLD) relaxed molecular clock. The ancestral area ofUvariaand subsequent dispersal routes are inferred using statistical dispersal–vicariance analysis (s‐diva).Results Uvariais estimated to have originated in continental Africa 31.6 Ma [95% highest posterior density (HPD): 38.4–25.1 Ma] between the Middle Eocene and Late Oligocene. Two main migration events during the Miocene are identified: dispersal into Madagascar around 17.0 Ma (95% HPD: 22.3–12.3 Ma); and dispersal into Asia between 21.4 Ma (95% HPD: 26.7–16.7 Ma) and 16.1 Ma (95% HPD: 20.1–12.1 Ma).Main conclusions Uvariafruits are widely reported to be consumed by primates, and are therefore unlikely candidates for successful long‐distance transoceanic dispersal. The other biogeographical hypotheses, involving rafting on the Indian tectonic plate, and dispersal via the European boreotropical forests associated with the Eocene thermal maximum, can be discounted due to incongruence with the divergence time estimates. An alternative scenario is suggested, involving dispersal across Arabia and central Asia via the tropical forests that developed during the late Middle Miocene thermal maximum (17–15 Ma), associated with the ‘out‐of‐Africa’ dispersal of primates. The probable route and mechanism of overland dispersal between Africa and Asia for tropical plant groups during the Miocene climatic optimum are clarified based on theUvariadata.

Novel alpine algae for New Zealand: Klebsormidiales

The alpine zone of Mt Philistine, Arthur's Pass National Park, is home to at least three species of algae in the Klebsormidiales. Klebsormidium dissectum was described from the site previously. A distinctive filamentous species, Klebsormidium crenulatum, has now been found that is larger than other New Zealand strains and is a new record for New Zealand. A unicellular species, Interfilum terricola, is also described as another new record for New Zealand. Phylogenetic analyses of the rbcL gene and the ITS-1-5.8S-ITS2 region show that New Zealand Klebsormidium is not monophyletic. The very close relationship between New Zealand and Belgian I. terricola illustrates the readiness with which transoceanic dispersal must occur in this genus. Our analyses of individual and concatenated genes suggest the paraphyly of the genus Klebsormidium, that the ancestral condition of the genus may have been the larger form, and that the incorporation of Klebsormidium into Interfilum is likely in the future, when more knowledge of diversity and relationships has accumulated.