Establishing a perimeter position: speciation around the Indian Ocean Basin

Historical biological interactions among peripheral landmasses on the periphery of the Indian Ocean Basin (IOB) are generally poorly understood. While interactions based on early Gondwanan vicariance have been used to explain present day lineage distributions, several recent studies have instead inferred dispersal across the IOB. This inference is often advanced because lineages under study have species inhabiting IOB islands. Here we examine the roles of continental vicariance vs. trans-IOB dispersal in the distribution of an avian genus found around the perimeter of the IOB. A molecular phylogeny does reveal evidence of a relationship that would require the inference of trans-IOB dispersal between eastern Africa and Sri Lanka. However, molecular clock data, ancestral area analyses and paleoclimatic reconstructions suggest that vicariance related to tropical forest expansion and retraction is more likely to have facilitated African-Asian interchange, with an initial colonization of Africa from Asia quickly followed by a recolonization of Asia. Subsequent dispersal from Asia to Sri Lanka and islands east of the Sunda Shelf are inferred; these latter islands were colonized in a stepping-stone fashion that culminated in colonization of the Sunda Shelf, and a recolonization of mainland Asia. We propose that circum-IOB distributions, which post-date early Gondwanan breakup, are most likely the result of continent-based vicariant events, particularly those events related to large-scale habitat alterations, and not trans-IOB dispersals.     

Marine dispersal as a pre‐requisite for Gondwanan vicariance among elements of the galaxiid fish fauna

Aim The aim of this study was to determine the contributions of Gondwanan vicariance and marine dispersal to the contemporary distribution of galaxiid fishes. This group has been central in arguments concerning the roles of dispersal and vicariance in the Southern Hemisphere, as some taxa have marine life history stages through which transoceanic dispersal may have been facilitated, yet other galaxiids are entirely restricted to freshwaters. Location Southern Hemisphere land masses of Gondwanan derivation. Methods Biogeographic hypotheses of Gondwanan vicariance and marine dispersal were tested using four lines of evidence: (1) concordance of species–area phylogenetic relationships, (2) molecular estimates of lineage divergence times with a priori expectations based on plate tectonics, (3) reconstructions of ancestral dispersal capabilities, and (4) reconstructions of distribution inheritance scenarios (using the dispersal–extinction–cladogenesis model to infer historical ranges and dispersal and extinction events). Results Phylogenetic relationships were reconstructed from 4531 mitochondrial and nuclear nucleotide characters, and 181 morphological characters, across 53 of the 56 presently recognized species. Phylogenetic relationships were generally well resolved and supported among galaxiids using the combined dataset, and conflicting relationships between molecular and morphological datasets typically received low topological support from either or both datasets. Transoceanic disjunctions were exhibited at 16 nodes, but only three pre‐dated relevant continental fragmentation events; furthermore, ancestral distribution inheritance scenarios for two of these nodes reflected cladogenesis within, rather than between, Gondwanan land masses, and ancestral marine dispersal capability could not be rejected for all three. Instead, the four lines of evidence surveyed suggest that Gondwanan vicariance occurred twice, but in both instances was preceded by marine dispersal between land masses, and in at least one instance was initiated by the cessation of marine dispersal subsequent to continental fragmentation. Main conclusions Gondwanan vicariance appears to have been preceded by marine dispersal in the few instances where it may explain contemporary galaxiid distribution, such that these biogeographic mechanisms may sometimes have a synergistic relationship.     

Biogeographic mirages? Molecular evidence for dispersal‐driven evolution in Hydrobiusini water scavenger beetles

Water beetles of the tribe Hydrobiusini are globally distributed in the northern hemisphere and all austral continents except Antarctica. A remarkable clade also occurs in the Hawaiian Islands. The phylogenetic relationships among genera were recently investigated using a combination of molecules and morphology. Here, we use this phylogenetic framework to address the biogeographic evolution of this group using Bayesian fossil‐based divergence times, and model‐based maximum likelihood ancestral range estimations. We recover an origin of the tribe in the Cretaceous ca. 100 Ma. Our biogeographic analyses support an origin of the tribe in Laurasia followed by the colonization of Australia. However, a Gondwanan origin of the group cannot be ruled out when considering the fossil record. The timeframe of the tribe's evolution as well as the model‐based approach of ancestral range estimation favour a scenario invoking multiple transoceanic dispersal events over a Gondwana vicariance hypothesis. The Hawaiian radiation originated from long‐distance dispersal to now‐submerged islands, paired with dispersal to new islands as they formed.     

Molecular dating of the 'Gondwanan' plant family Proteaceae is only partially congruent with the timing of the break-up of Gondwana

Aim  The flowering plant family Proteaceae is putatively of Gondwanan age, with modern and fossil lineages found on all southern continents. Here we test whether the present distribution of Proteaceae can be explained by vicariance caused by the break-up of Gondwana.
Location  Africa, especially southern Africa, Australia, New Zealand, South America, New Caledonia, New Guinea, Southeast Asia, Sulawesi, Tasmania.
Methods  We obtained chloroplast DNA sequence data from the rbc L gene, the rbc L- atp B spacer, and the atp B gene from leaf samples of forty-five genera collected from the field and from living collections. We analysed these data using Bayesian phylogenetic and molecular dating methods, with five carefully selected fossil calibration points to obtain age estimates for the nodes within the family.
Results  Four of eight trans-continental disjunctions of sister groups within our sample of the Proteaceae post-date the break-up of Gondwana. These involve independent lineages, two with an Africa-Australia disjunction, one with an Africa–South America disjunction, and one with a New Zealand–Australasia disjunction. The date of the radiation of the bird-pollinated Embothriinae corresponds approximately to the hypothesized date of origin of nectar-feeding birds in Australia.
Main conclusions  The findings suggest that disjunct distributions in Proteaceae result from both Gondwanan vicariance and transoceanic dispersal. Our results imply that ancestors of some taxa dispersed across oceans rather than rafting with Gondwanan fragments as previously thought. This finding agrees with other studies of Gondwanan plants in dating the divergence of Australian, New Zealand and New Caledonian taxa in the Eocene, consistent with the existence of a shared, ancestral Eocene flora but contrary to a vicariance scenario based on accepted geological knowledge.     

Evolutionary Diversification of New Caledonian Araucaria

New Caledonia is a global biodiversity hotspot. Hypotheses for its biotic richness suggest either that the island is a ‘museum’ for an old Gondwana biota or alternatively it has developed following relatively recent long distance dispersal and in situ radiation. The conifer genus Araucaria (Araucariaceae) comprises 19 species globally with 13 endemic to this island. With a typically Gondwanan distribution, Araucaria is particularly well suited to testing alternative biogeographic hypotheses concerning the origins of New Caledonian biota. We derived phylogenetic estimates using 11 plastid and rDNA ITS2 sequence data for a complete sampling of Araucaria (including multiple accessions of each of the 13 New Caledonian Araucaria species). In addition, we developed a dataset comprising 4 plastid regions for a wider taxon sample to facilitate fossil based molecular dating. Following statistical analyses to identify a credible and internally consistent set of fossil constraints, divergence times estimated using a Bayesian relaxed clock approach were contrasted with geological scenarios to explore the biogeographic history of Araucaria. The phylogenetic data resolve relationships within Araucariaceae and among the main lineages in Araucaria, but provide limited resolution within the monophyletic New Caledonian species group. Divergence time estimates suggest a Late Cretaceous-Cenozoic radiation of extant Araucaria and a Neogene radiation of the New Caledonian lineage. A molecular timescale for the evolution of Araucariaceae supports a relatively recent radiation, and suggests that earlier (pre-Cenozoic) fossil types assigned to Araucaria may have affinities elsewhere in Araucariaceae. While additional data will be required to adequately resolve relationships among the New Caledonian species, their recent origin is consistent with overwater dispersal following Eocene emersion of New Caledonia but is too old to support a single dispersal from Australia to Norfolk Island for the radiation of the Pacific Araucaria sect. Eutacta clade.     

Molecular clocks keep dispersal hypotheses afloat: evidence for trans‐Atlantic rafting by rodents

Aim In order to resolve disputed biogeographical histories of biota with Gondwanan continental distributions, and to assess the null hypothesis of vicariance, it is imperative that a robust geological time‐frame be established. As an example, the sudden and coincident appearance of hystricognath rodents (Rodentia: Hystricognathi) on both the African and South American continents has been an irreconcilable controversy for evolutionary biologists, presenting enigmas for both Gondwanan vicariance and Late Eocene dispersal hypotheses. In an attempt to resolve this discordance, we aim to provide a more robust phylogenetic hypothesis and improve divergence‐date estimates, which are essential to assessing the null hypothesis of vicariance biogeography. Location The primary centres of distribution are in Africa and South America. Methods We implemented parsimony, maximum‐likelihood and Bayesian methods to generate a phylogeny of 37 hystricognath taxa, the most comprehensive taxonomic sampling of this group to date, on the basis of two nuclear gene regions. To increase phylogenetic resolution at the basal nodes, these data were combined with previously published data for six additional nuclear gene regions. Divergence dates were estimated using two relaxed‐molecular‐clock methods, Bayesian multidivtime and nonparametric rate smoothing. Results Our data do not support reciprocal monophyly of African and South American lineages. Indeed, Old World porcupines (i.e. Hystricomorpha) appear to be more closely related to New World lineages (i.e. Caviomorpha) than to other Old World families (i.e. Bathyergidae, Petromuridae and Thryonomyidae). The divergence between the monophyletic assemblage of South American lineages and its Old World ancestor was estimated to have occurred c. 50 Ma. Main conclusions Our phylogenetic hypothesis and divergence‐date estimates are strongly at odds with Gondwanan‐vicariance isolating mechanisms. In contrast, our data suggest that transoceanic dispersal has played a significant role in governing the contemporary distribution of hystricognath rodents. Molecular‐clock analyses imply a trans‐Tethys dispersal event, broadly confined to the Late Cretaceous, and trans‐Atlantic dispersal within the Early Eocene. Our analyses also imply that the use of the oldest known South American rodent fossil as a calibration point has biased molecular‐clock inferences.     

Pliocene climatic change in insular Southeast Asia as an engine of diversification in Ficedula flycatchers

Aims Insular Southeast Asia and adjacent regions are geographically complex, and were dramatically affected by both Pliocene and Pleistocene changes in climate, sea level and geology. These circumstances allow the testing of several biogeographical hypotheses regarding species distribution patterns and phylogeny. Avian species in this area present a challenge to biogeographers, as many are less hindered by barriers that may block the movements of other species. Widely distributed Southeast Asian avian lineages, of which there are many, have been generally neglected. Ficedula flycatchers are distributed across Eurasia, but are most diverse within southern Asia and Southeast Asian and Indo‐Australian islands. We tested the roles of vicariance, dispersal and the evolution of migratory behaviours as mechanisms of speciation within the Ficedula flycatchers, with a focus on species distributed in insular Southeast Asia. Methods Using a published molecular phylogeny of Ficedula flycatchers, we reconstructed ancestral geographical areas using dispersal vicariance analysis, weighted ancestral area analysis, and a maximum likelihood method. We evaluated the evolution of migratory behaviours using maximum likelihood ancestral character state reconstruction. Speciation timing estimates were calculated via local molecular clock methods. Results Ficedula originated in southern mainland Asia, c. 6.5 Ma. Our analyses indicate that two lineages within Ficedula independently and contemporaneously colonized insular Southeast Asia and Indo‐Australia, c. 5 Ma. The potential impact of vicariance due to rising sea levels is difficult to assess in these early colonization events because the ancestral areas to these clades are reconstructed as oceanic islands. Within each of these clades, inter‐island dispersal was critical to species’ diversification across oceanic and continental islands. Furthermore, Pliocene and Pleistocene climatic change may have caused the disjunct island distributions between several pairs of sister taxa. Both vicariance and dispersal shaped the distributions of continental species. Main conclusions This study presents the first evaluation, for Ficedula, of the importance of vicariance and dispersal in shaping distributions, particularly across insular Southeast Asia and Indo‐Australia. Although vicariant speciation may have initially separated the island clades from mainland ancestors, speciation within these clades was driven primarily by dispersal. Our results contribute to the emerging body of literature concluding that dynamic geological processes and climatic change throughout the Pliocene and Pleistocene have been important factors in faunal diversification across continental and oceanic islands.     

Evidence for Gondwanan vicariance in an ancient clade of gecko lizards

Aim Geckos (Reptilia: Squamata), due to their great age and global distribution, are excellent candidates to test hypotheses of Gondwanan vicariance against post‐Gondwanan dispersal. Our aims are: to generate a phylogeny of the sphaerodactyl geckos and their closest relatives; evaluate previous phylogenetic hypotheses of the sphaerodactyl geckos with regard to the other major gecko lineages; and to use divergence date estimates to inform a biogeographical scenario regarding Gondwanan relationships and assess the roles of vicariance and dispersal in shaping the current distributions of the New World sphaerodactyl geckos and their closest Old World relatives. Location Africa, Asia, Europe, South America, Atlantic Ocean. Methods We used parsimony and partitioned Bayesian methods to analyse data from five nuclear genes to generate a phylogeny for the New World sphaerodactyl geckos and their close Old World relatives. We used dispersal–vicariance analysis to determine ancestral area relationships among clades, and divergence times were estimated from the phylogeny using nonparametric rate smoothing. Results We recovered a monophyletic group containing the New World sphaerodactyl genera, Coleodactylus, Gonatodes, Lepidoblepharis, Pseudogonatodes and Sphaerodactylus, and the Old World Gekkotan genera Aristelliger, Euleptes, Quedenfeldtia, Pristurus, Saurodactylus and Teratoscincus. The dispersal–vicariance analysis indicated that the ancestral area for this clade was North Africa and surrounding regions. The divergence between the New World spaherodactyl geckos and their closest Old World relative was estimated to have occurred c. 96 Myr bp . Main conclusions Here we provide the first molecular genetic phylogenetic hypothesis of the New World sphaerodactyl geckos and their closest Old World relatives. A combination of divergence date estimates and dispersal–vicariance analysis informed a biogeographical scenario indicating that the split between the sphaerodactyl geckos and their African relatives coincided with the Africa/South America split and the opening of the Atlantic Ocean. We resurrect the family name Sphaerodactylidae to represent the expanded sphaerodactyl clade.     

Older than New Caledonia emergence? A molecular phylogenetic study of the eneopterine crickets (Orthoptera: Grylloidea)

Aim A New Caledonian insect group was studied in a world‐wide phylogenetic context to test: (1) whether local or regional island clades are older than 37 Ma, the postulated re‐emergence time of New Caledonia; (2) whether these clades show evidence for local radiations or multiple colonizations; and (3) whether there is evidence for relict taxa with long branches in phylogenetic trees that relate New Caledonian species to geographically distant taxa. Location New Caledonia, south‐west Pacific. Methods We sampled 43 cricket species representing all tribes of the subfamily Eneopterinae and 15 of the 17 described genera, focusing on taxa distributed in the South Pacific and around New Caledonia. One nuclear and three mitochondrial genes were analysed using Bayesian and parsimony methods. Phylogenetic divergence times were estimated using a relaxed clock method and several calibration criteria. Results The analyses indicate that, under the most conservative dating scenario, New Caledonian eneopterines are 5–16 million years old. The largest group in the Pacific region dates to 18–29 Ma. New Caledonia has been colonized in two phases: the first around 10.6 Ma, with the subsequent diversification of the endemic genus Agnotecous, and the second with more recent events around 1–4 Ma. The distribution of the sister group of Agnotecous and the lack of phylogenetic long branches in the genus refute an assumption of major extinction events in this clade and the hypothesis of local relicts. Main conclusions Our phylogenetic studies invalidate a simple scenario of local persistence of this group in New Caledonia since 80 Ma, either by survival on the New Caledonian island since its rift from Australia, or, if one accepts the submergence of New Caledonia, by local island‐hopping among other subaerial islands, now drowned, in the region during periods of New Caledonian submergence.     

New Caledonia: a very old Darwinian island?

New Caledonia has generally been considered a continental island, the biota of which largely dates back to Gondwanan times owing to its geological origin and the presence of phylogenetic relicts. This view is contradicted by geological evidence indicating long Palaeocene and Eocene submersions and by recent biogeographic and phylogenetic studies, with molecular or geophysical dating placing the biota no older than the Oligocene. Phylogenetic relicts do not provide conclusive information in this respect, as their presence cannot be explained by simple hypotheses but requires assumption of many ad hoc extinction events. The implication of this new scenario is that all the New Caledonian biota colonized the island since 37 Ma Local richness can be explained by local radiation and adaptation after colonization but also by many dispersal events, often repeated within the same groups of organisms. Local microendemism is another remarkable feature of the biota. It seems to be related to recent speciation mediated by climate, orography, soil type and perhaps unbalanced biotic interactions created by colonization disharmonies. New Caledonia must be considered as a very old Darwinian island, a concept that offers many more fascinating opportunities of study.     

Out of Africa: Biogeography and diversification of the pantropical pond skater genus Limnogonus Stål, 1868 (Hemiptera: Gerridae)

Gondwanan vicariance, long‐distance dispersal (LDD), and boreotropical migration have been proposed as alternative hypotheses explaining the pantropical distribution pattern of organisms. In this study, the historical biogeography of the pond skater genus Limnogonus was reconstructed to evaluate the impact of biogeographical scenarios in shaping their modern transoceanic disjunction. We sampled almost 65% of recognized Limnogonus species. Four DNA fragments including 69 sequences were used to reconstruct a phylogram. Divergence time was estimated using a Bayesian relaxed clock method and three fossil calibrations. Diversification dynamics and ancestral area reconstruction were investigated by using maximum likelihood and Bayesian approaches. Our results showed the crown group of Limnogonus originated and diversified in Africa in the early Eocene (49 Ma, HPD: 38–60 Ma), subsequently expanding into other regions via dispersal. The colonization of the New World originated from the Oriental Region probably via the Bering Land Bridge in the late Eocene. Two split events between the Old World and New World were identified: one between Neotropics and Oriental region around the middle Oligocene (30 Ma, HPD: 22–38 Ma), and the other between Neotropics and Africa during the middle Miocene (14 Ma, HPD: 8–21 Ma). The evolutionary history of Limnogonus involved two biogeographical processes. Gondwanan vicariance was not supported in our analyses. The diversification of Limnogonus among Africa, Oriental, and Neotropical regions corresponded with the age of land bridge connection and dispersed as a member associated with the broad boreotropical belt before local cooling (34 Ma). The current transoceanic disjunctions in Limnogonus could be better explained by the disruption of “mixed‐mesophytic” forest belt; however, the direct transoceanic LDD between the Neotropics and Africa could not be ruled out. In addition, the “LDD” model coupled with island hopping could be a reasonable explanation for the diversification of the Oriental and Australian regions during the Oligocene.     

Gondwanan radiation of the Southern Hemisphere crayfishes (Decapoda: Parastacidae): evidence from fossils and molecules

Aim The sequential break‐up of Gondwana is thought to be a dominant process in the establishment of shared biota across landmasses of the Southern Hemisphere. Yet similar distributions are shared by taxa whose radiations clearly post‐date the Gondwanan break‐up. Thus, determining the contribution of vicariance versus dispersal to seemingly Gondwanan biota is complex. The southern freshwater crayfishes (family Parastacidae) are distributed on Australia and New Guinea, South America, Madagascar and New Zealand and are unlikely to have dispersed via oceans, owing to strict freshwater limitations. We test the hypotheses that the break‐up of Gondwana has led to (1) a predominately east–west (((Australia, New Zealand: 80 Ma) Madagascar: 160–121 Ma) South America: 165–140 Ma), or (2) a southern (((Australia, South America: 52–35 Ma) New Zealand: 80 Ma) Madagascar: 160–121 Ma) pattern for parastacid crayfish. Further, we examine the evidence for a complete drowning of New Zealand and subsequent colonization by freshwater crayfish. Location Southern Hemisphere. Methods The evolutionary relationships among the 15 genera of Parastacidae were reconstructed using mitochondrial [16S, cytochrome c oxidase subunit I (COI)] and nuclear (18S, 28S) sequence data and maximum likelihood and Bayesian methods of phylogenetic reconstruction. A Bayesian (multidivtime ) molecular dating method using six fossil calibrations and phylogenetic inference was used to estimate divergence time among crayfish clades on Gondwanan landmasses. Results The South American crayfish are monophyletic and a sister group to all other southern crayfish. Australian crayfish are not monophyletic, with two Tasmanian genera, Spinastacoides and Ombrastacoides, forming a clade with New Zealand and Malagasy crayfish (both monophyletic). Divergence of crayfish among southern landmasses is estimated to have occurred around the Late Jurassic to Early Cretaceous (109–178 Ma). Main conclusions The estimated phylogenetic relationships and time of divergence among the Southern Hemisphere crayfishes were consistent with an east–west pattern of Gondwanan divergence. The divergence between Australia and New Zealand (109–160 Ma) pre‐dated the rifting at around 80 Ma, suggesting that these lineages were established prior to the break‐up. Owing to the age of the New Zealand crayfish, we reject the hypothesis that there was a complete drowning of New Zealand crayfish habitat.     

Phylogeny, divergence times, and historical biogeography of New World Dryopteris (Dryopteridaceae)

? Premise of the study: Dryopteris is a large, cosmopolitan fern genus ideal for addressing questions about diversification, biogeography, hybridization, and polyploidy, which have historically been understudied in ferns. We constructed a highly resolved, well-supported phylogeny for New World Dryopteris and used it to investigate biogeographic patterns and divergence times. ? Methods: We analyzed relationships among 97 species of Dryopteris, including taxa from all major biogeographic regions, with analyses based on 5699 aligned nucleotides from seven plastid loci. Phylogenetic analyses used maximum parsimony, maximum likelihood, and Bayesian inference. We conducted divergence time analyses using BEAST and biogeographic analyses using maximum parsimony, maximum likelihood, Bayesian, and S-DIVA approaches. We explored the monophyly of subgenera and sections in the most recent generic classification and of geographic groups of taxa using Templeton tests. ? Key results: The genus Dryopteris arose ca. 42 million years ago (Ma). Most of the Central and South American species form a well-supported clade which arose 32 Ma, but the remaining New World species are the result of multiple, independent dispersal and vicariance events involving Asia, Europe, and Africa over the last 15 Myr. We identified six long-distance dispersal events and three vicariance events in the immediate ancestry of New World species; reconstructions for another four lineages were ambiguous. ? Conclusions: New World Dryopteris are not monophyletic; vicariance has dominated the history of the North American species, while long-distance dispersal prevails in the Central and South American species, a pattern not previously seen in plants.     

THE BIOGEOGRAPHY OF SULAWESI REVISITED: IS THERE EVIDENCE FOR A VICARIANT ORIGIN OF TAXA ON WALLACE'S “ANOMALOUS ISLAND”?

Sulawesi, the largest island in the Indonesian biodiversity hotspot region Wallacea, hosts a diverse endemic fauna whose origin has been debated for more than 150 years. We use a comparative approach based on dated phylogenies and geological constraints to test the role of vicariance versus dispersal in the origin of Sulawesi taxa. Most divergence time estimates for the split of Sulawesi lineages from their sister groups postdate relevant tectonic vicariant events, suggesting that the island was predominantly colonized by dispersal. Vicariance cannot be refuted for 20% of the analyzed taxa, though. Although vicariance across Wallace's Line was only supported for one arthropod taxon, divergence time estimates were consistent with a "tectonic dispersal" vicariance hypothesis from the East in three (invertebrate and vertebrate) taxa. Speciation on Sulawesi did not occur before the Miocene, which is consistent with geological evidence for more extensive land on the island from that time. The Pliocene onset of periodic sea-level changes may have played a role in increasing the potential for dispersal to Sulawesi. A more extensive taxon sampling in Wallacea will be crucial for refining our understanding of the region's biogeography and for testing hypotheses on the origin of taxa on its most important island.     

Orthoglymma wangapeka gen.n., sp.n. (Coleoptera: Carabidae: Broscini): a newly discovered relict from the Buller Terrane,north‐western South Island,New Zealand,corroborates a general pattern of Gondwanan endemism

Orthoglymma Liebherr, Marris, Emberson, Syrett & Roig‐Juñent gen.n. (Coleoptera: Carabidae: Broscini) is described to accommodate the single type species Orthoglymma wangapeka Liebherr, Marris, Emberson, Syrett & Roig‐Juñent sp.n., known from the Wangapeka Track, Kahurangi National Park, north‐western South Island, New Zealand. Orthoglymma wangapeka sp.n. is analysed cladistically along with a comprehensive array of 42 other broscine generic terminals and four out‐group taxa, using information obtained from 73 morphological characters, and placed as adelphotaxon to the remainder of subtribe Nothobroscina, a clade distributed in New Zealand, southern South America and Australia. Based on fossil evidence for Carabidae, the occurrence of Orthoglymma wangapeka sp.n. on the Buller Terrane, a geological feature once situated on the eastern margin of Gondwana, and early cladistic divergence of Orthoglymma from the remaining Nothobroscina, Orthoglymma wangapeka sp.n. is interpreted as a Gondwanan relict. The New Zealand arthropod fauna is reviewed to identify other taxa in existence at the time of Cretaceous vicariance of New Zealand and Australia. These candidate Gondwanan taxa, all of which are specified using fossil data or molecular divergence‐based estimates, are analysed biogeographically. Where phylogenetic hypotheses are available, primordial distributions are optimized using event‐based, dispersal‐vicariance (DIVA) analysis. The hypothesized Gondwanan‐aged taxa demonstrate inordinate fidelity to the Gondwanan‐aged geological terranes that constitute the western portions of New Zealand, especially in the South Island. Persistence of these relicts through a hypothesized ‘Oligocene drowning’ event is the most parsimonious explanation for the concentration of Gondwanan relicts in the Nelson, Buller and Fiordland districts of the South Island. Geographic patterns of Gondwanan‐aged taxa are compared with distributions of taxa hypothesized to have colonized New Zealand across the Tasman Sea from Australia and New Caledonia, subsequent to Cretaceous vicariance. These post‐Gondwanan taxa exhibit very different patterns of distribution and diversification in New Zealand, including: (i) abundant endemism in Northland, and the islands and peninsulas of the North Island; (ii) species geographically restricted to areas underlain by the youngest Rakaia and Pahau geological terranes; and (iii) species exhibiting exceedingly widespread geographic distributions spanning geological terranes of disparate ages.

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Inferring dispersal: a Bayesian approach to phylogeny-based island biogeography, with special reference to the Canary Islands

Aim Oceanic islands represent a special challenge to historical biogeographers because dispersal is typically the dominant process while most existing methods are based on vicariance. Here, we describe a new Bayesian approach to island biogeography that estimates island carrying capacities and dispersal rates based on simple Markov models of biogeographical processes. This is done in the context of simultaneous analysis of phylogenetic and distributional data across groups, accommodating phylogenetic uncertainty and making parameter estimates more robust. We test our models on an empirical data set of published phylogenies of Canary Island organisms to examine overall dispersal rates and correlation of rates with explanatory factors such as geographic proximity and area size. Location Oceanic archipelagos with special reference to the Atlantic Canary Islands. Methods The Canary Islands were divided into three island‐groups, corresponding to the main magmatism periods in the formation of the archipelago, while non‐Canarian distributions were grouped into a fourth ‘mainland‐island’. Dispersal between island groups, which were assumed constant through time, was modelled as a homogeneous, time‐reversible Markov process, analogous to the standard models of DNA evolution. The stationary state frequencies in these models reflect the relative carrying capacity of the islands, while the exchangeability (rate) parameters reflect the relative dispersal rates between islands. We examined models of increasing complexity: Jukes–Cantor (JC), Equal‐in, and General Time Reversible (GTR), with or without the assumption of stepping‐stone dispersal. The data consisted of 13 Canarian phylogenies: 954 individuals representing 393 taxonomic (morphological) entities. Each group was allowed to evolve under its own DNA model, with the island‐model shared across groups. Posterior distributions on island model parameters were estimated using Markov Chain Monte Carlo (MCMC) sampling, as implemented in MrBayes 4.0, and Bayes Factors were used to compare models. Results The Equal‐in step, the GTR, and the GTR step dispersal models showed the best fit to the data. In the Equal‐in and GTR models, the largest carrying capacity was estimated for the mainland, followed by the central islands and the western islands, with the eastern islands having the smallest carrying capacity. The relative dispersal rate was highest between the central and eastern islands, and between the central and western islands. The exchange with the mainland was rare in comparison. Main conclusions Our results confirm those of earlier studies suggesting that inter‐island dispersal within the Canary Island archipelago has been more important in explaining diversification within lineages than dispersal between the continent and the islands, despite the close proximity to North Africa. The low carrying capacity of the eastern islands, uncorrelated with their size or age, fits well with the idea of a historically depauperate biota in these islands but more sophisticated models are needed to address the possible influence of major recent extinction events. The island models explored here can easily be extended to address other problems in historical biogeography, such as dispersal among areas in continental settings or reticulate area relationships.     

Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting

Cichlid fishes are a key model system in the study of adaptive radiation, speciation and evolutionary developmental biology. More than 1600 cichlid species inhabit freshwater and marginal marine environments across several southern landmasses. This distributional pattern, combined with parallels between cichlid phylogeny and sequences of Mesozoic continental rifting, has led to the widely accepted hypothesis that cichlids are an ancient group whose major biogeographic patterns arose from Gondwanan vicariance. Although the Early Cretaceous (ca 135 Ma) divergence of living cichlids demanded by the vicariance model now represents a key calibration for teleost molecular clocks, this putative split pre-dates the oldest cichlid fossils by nearly 90 Myr. Here, we provide independent palaeontological and relaxed-molecular-clock estimates for the time of cichlid origin that collectively reject the antiquity of the group required by the Gondwanan vicariance scenario. The distribution of cichlid fossil horizons, the age of stratigraphically consistent outgroup lineages to cichlids and relaxed-clock analysis of a DNA sequence dataset consisting of 10 nuclear genes all deliver overlapping estimates for crown cichlid origin centred on the Palaeocene (ca 65–57 Ma), substantially post-dating the tectonic fragmentation of Gondwana. Our results provide a revised macroevolutionary time scale for cichlids, imply a role for dispersal in generating the observed geographical distribution of this important model clade and add to a growing debate that questions the dominance of the vicariance paradigm of historical biogeography.     

Molecular phylogenetics of the exoneurine allodapine bees reveal an ancient and puzzling dispersal from Africa to Australia

Previous phylogenetic studies of the bee tribe Allodapini suggested a puzzling biogeographic problem: one of the key basal divergences involved separation of the southern African and southern Australian clades at a very early stage in allodapine evolution, but no taxa occur in the Palaearctic or Asian regions that might suggest a Laurasian dispersal route. However, these studies lacked sufficient sequence data and appropriate maximum likelihood partition models to provide reliable phylogenetic estimates and enable alternative biogeographic hypotheses to be distinguished. Using Bayesian and penalized likelihood approaches and an expanded sequence and taxon set we examine phylogenetic relationships between the Australian, African, and Malagasy groups and estimate divergence times for key nodes. We show that divergence of the three basal Australian clades (known as the exoneurines) occurred at least 25 Mya following a single colonization event, and that this group diverged from the African + Madagascan clade at least 30 Mya, but actual divergence dates are likely to be much older than these very conservative limits. The bifurcation order of the exoneurine clades was not resolved and analyses could not rule out the existence of a hard polytomy, suggesting rapid radiation after colonization of Australia. Their divergence involved major transitions in life history traits and these placed constraints on the kinds of social organization that subsequently evolved in each lineage. Early divergence between the African, Malagasy, and Australian clades presents a major puzzle for historical biogeography: node ages are too recent for Gondwanan vicariance hypotheses, but too early for Laurasian dispersal scenarios. We suggest a scenario involving island hopping across the Indian Ocean via a series of now largely submerged elements of the Kergulen Plateau and Broken Ridge provinces, both of which are known to have had subaerial formations during the Cenozoic. [Bayesian; biogeography; dispersal; Gondwana; Kerguelen Plateau; penalized likelihood.].     

Allochronic taxa as an alternative model to explain circumantarctic disjunctions

Abstract Most biogeographical studies propose that southern temperate faunal disjunctions are either the result of vicariance of taxa originated in Gondwana or the result of transoceanic dispersal of taxa originated after the breakup of Gondwana. The aim of this paper is to show that this is a false dichotomy. Antarctica retained a mild climate until mid‐Cenozoic and had lasting connections, notably with southern South America and Australia. Both taxa originally Gondwanan and taxa secondarily on Gondwanan areas were subjected to tectonic‐induced vicariance, and there is no need to invoke ad hoc transoceanic dispersal, even for post‐Gondwanan taxa. These different elements with circumantarctic distributions are here called ‘allochronic taxa’– taxa presently occupying the same area, but whose presence in that area does not belong to the same time period. This model allows accommodation of conflicting sources of evidence now available for many groups with circumantarctic distributions. The fact that the species from both layers are mixed up in the current biodiversity implies the need to use additional sources of evidence – such as biogeographical, palaeontological, geological and molecular – to discriminate which are the original Gondwanan and which are post‐Gondwanan elements in austral landmasses.