Sky Islands of the Cameroon Volcanic Line: a diversification hot spot for puddle frogs (Phrynobatrachidae: Phrynobatrachus)

The continental highlands of the Cameroon Volcanic Line (CVL) represent biological ‘sky islands’ with high levels of species richness and endemism, providing the ideal opportunity to understand how orogenesis and historical climate change influenced species diversity and distribution in these isolated African highlands. Relationships of puddle frogs (Phrynobatrachus) endemic to the CVL are reconstructed to examine the patterns and timing of puddle frog diversification. Historical distributions were reconstructed using both elevation and geography data. Puddle frogs diversified in the CVL via several dispersal and vicariance events, with most of the locally endemic species distributed across the northern part of the montane forest area in the Bamenda‐Banso Highlands (Bamboutos Mts., Mt. Lefo, Mt. Mbam, Mt. Oku and medium elevation areas connecting these mountains). Two new species, P. jimzimkusi sp. n. and P. njiomock sp. n., are also described based on molecular analyses and morphological examination. We find that these new species are most closely related to one another and P. steindachneri with the ranges of all three species overlapping at Mt. Oku. Phrynobatrachus jimzimkusi sp. n. is distributed in the southern portion of the continental CVL, P. njiomock sp. n. is endemic to Mt. Oku, and P. steindachneri is present in the northeastern part of the montane forest area. Both new species can be distinguished from all other puddle frogs by a combination of morphological characters, including their large size, ventral coloration and secondary sexual characteristics present in males. These results highlight the Bamenda‐Banso Highlands, and specifically emphasize Mt. Oku, as a centre of diversification for puddle frogs, supporting the conservation importance of this region. Our results also provide new insights into the evolutionary processes shaping the CVL ‘sky islands’, demonstrating that lineage diversification in these montane amphibians is significantly older than expected with most species diverging from their closest relative in the Miocene. Whereas climatic changes during the Pliocene and Pleistocene shaped intraspecific diversification, most speciation events were significantly older and cannot be linked to Africa's aridification in response to Pleistocene climate fluctuations.     

Timing and tempo of early and successive adaptive radiations in Macaronesia

The flora of Macaronesia, which encompasses five Atlantic archipelagos (Azores, Canaries, Madeira, Cape Verde, and Salvage), is exceptionally rich and diverse. Spectacular radiation of numerous endemic plant groups has made the Macaronesian islands an outstanding area for studies of evolution and speciation. Despite intensive investigation in the last 15 years, absolute age and rate of diversification are poorly known for the flora of Macaronesia. Here we report molecular divergence estimates and rates of diversification for five representative, putative rapid radiations of monophyletic endemic plant lineages across the core eudicot clade of flowering plants. Three discrete windows of colonization during the Miocene and early Pliocene are suggested for these lineages, all of which are inferred to have had a single colonization event followed by rapid radiation. Subsequent inter-archipelago dispersal events into Madeira and the Cape Verdes took place very recently during the late Pliocene and Pleistocene after initial diversification on the Canary Islands. The tempo of adaptive radiations differs among the groups, but is relatively rapid compared to continental and other island radiations. Our results demonstrate that opportunity for island colonization and successful radiation may have been constrained to discrete time periods of profound climatic and geological changes in northern African and the Mediterranean.     

Evolutionary diversification of cryophilic <Emphasis Type="Italic">Grylloblatta</Emphasis>species (Grylloblattodea: Grylloblattidae) in alpine habitats of California

Background  

Climate in alpine habitats has undergone extreme variation during Pliocene and Pleistocene epochs, resulting in repeated expansion and contraction of alpine glaciers. Many cold-adapted alpine species have responded to these climatic changes with long-distance range shifts. These species typically exhibit shallow genetic differentiation over a large geographical area. In contrast, poorly dispersing organisms often form species complexes within mountain ranges, such as the California endemic ice-crawlers (Grylloblattodea: Grylloblattidae: Grylloblatta). The diversification pattern of poorly dispersing species might provide more information on the localized effects of historical climate change, the importance of particular climatic events, as well as the history of dispersal. Here we use multi-locus genetic data to examine the phylogenetic relationships and geographic pattern of diversification in California Grylloblatta.     

Out of Cuba: overwater dispersal and speciation among lizards in the Anolis carolinensis subgroup

Overwater dispersal and subsequent allopatric speciation contribute importantly to the species diversity of West Indian Anolis lizards and many other island radiations. Here we use molecular phylogenetic analyses to assess the contribution of overwater dispersal to diversification of the Anolis carolinensis subgroup, a clade comprising nine canopy-dwelling species distributed across the northern Caribbean. Although this clade includes some of the most successful dispersers and colonists in the anole radiation, the taxonomic status and origin of many endemic populations have been ambiguous. New mitochondrial and nuclear DNA sequences from four species occurring on small islands or island banks (Anolis brunneus, Anolis longiceps, Anolis maynardi, Anolis smaragdinus) and one species from the continental United States (A. carolinensis) are presented and analysed with homologous sequences sampled from related species on Cuba (Anolis allisoni and Anolis porcatus). Our analyses confirm that all five non-Cuban species included in our study represent distinct, independently evolving lineages that warrant continued species recognition. Moreover, our results support Ernest Williams's hypothesis that all of these species originated by overseas colonization from Cuban source populations. However, contrary to Williams's hypothesis of Pleistocene dispersal, most colonization events leading to speciation apparently occurred earlier, in the late Miocene-Pliocene. These patterns suggest that overwater dispersal among geologically distinct islands and island banks is relatively infrequent in anoles and has contributed to allopatric speciation. Finally, our results suggest that large Greater Antillean islands serve as centres of origin for regional species diversity.     

Local endemism and within‐island diversification of shrews illustrate the importance of speciation in building Sundaland mammal diversity

Island systems are important models for evolutionary biology because they provide convenient, discrete biogeographic units of study. Continental islands with a history of intermittent dry land connections confound the discrete definitions of islands and have led zoologists to predict (i) little differentiation of terrestrial organisms among continental shelf islands and (ii) extinction, rather than speciation, to be the main cause of differences in community composition among islands. However, few continental island systems have been subjected to well‐sampled phylogeographic studies, leaving these biogeographic assumptions of connectivity largely untested. We analysed nine unlinked loci from shrews of the genus Crocidura from seven mountains and two lowland localities on the Sundaic continental shelf islands of Sumatra and Java. Coalescent species delimitation strongly supported all currently recognized Crocidura species from Sumatra (six species) and Java (five species), as well as one undescribed species endemic to each island. We find that nearly all species of Crocidura in the region are endemic to a single island and several of these have their closest relative(s) on the same island. Intra‐island genetic divergence among allopatric, conspecific populations is often substantial, perhaps indicating species‐level diversity remains underestimated. One recent (Pleistocene) speciation event generated two morphologically distinct, syntopic species on Java, further highlighting the prevalence of within‐island diversification. Our results suggest that both between‐ and within‐island speciation processes generated local endemism in Sundaland, supplementing the traditional view that the region's fauna is relictual and primarily governed by extinction.     

Island-like radiation of Saussurea (Asteraceae: Cardueae) triggered by uplifts of the Qinghai–Tibetan Plateau

Increasing evidence suggests that geological or climatic events in the past triggered the radiative diversification of both animals and plants on islands as well as continents. The Qinghai–Tibetan Plateau (QTP) has been extensively uplifted since the Miocene, but there is little information on possible links between these events and biological diversification in this and adjacent regions. Partly to explore such links, we have examined the diversification of Saussurea (Asteraceae: Cardueae), a species-rich genus that is mostly endemic to QTP, but also occurs in arid highlands elsewhere in the Northern Hemisphere. The phylogenetic analyses were conducted on the basis of the nuclear (internal transcribed spacer, ITS) and plastid ( trnL-F and psbA-trnH ) sequences from 55 species, representing 19 sections from all six subgenera of Saussurea , and species from 15 genera of the Cardueae. The results suggest that the currently circumscribed genus Saussurea ( s.l. ) is a polyphyletic group and that five sections should be excluded from the genus. Samples from the other 14 sections (representing five subgenera) clustered as a monophyletic group (here designated the Saussurea s.s. lineage, SSSL) with high statistical support. However, none of the analyses (nuclear, plastid or combined) resolved SSSL's infrageneric phylogeny, and the parallel clades of the lineage indicate that island-like adaptive radiation occurred. Furthermore, this radiation appears to have occurred 14–7 Mya, during the period of the major uplift events of QTP. Thus, our results support the hypothesis that geological events may play important roles in driving biological diversification through continental radiation.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 893–903.     

Diversification of montane species via elevation shifts: the case of the Kaçkar cricket Phonochorion (Orthoptera)

Localized up‐down altitudinal shifts and subsequent isolation–admixture of montane species in response to glacial cycles has been proposed as a mechanism for the high diversity along Anatolian mountains. However, specific predictions of the proposed mechanism (the elevation shift model) have yet to be tested. Here, we provide a first assessment of this model for promoting inter‐ and intraspecific genetic diversity in the bush‐cricket genus Phonochorion endemic to the West Lesser Caucasus hotspot. Mitochondrial genes were analysed by Bayesian Markov Chain Monte Carlo inferences and coalescent simulations. Timing of diversification was estimated using a multispecies coalescent model. Divergence with gene flow was tested using an isolation with migration model. Population genetic parameters and genetic structuring were determined using Bayesian coalescent methods and spatial analysis. Demographic history was assessed using mismatch distributions and extended Bayesian skyline plots. Speciation events corresponded both to the Miocene and Pleistocene while intraspecific divergence was Pleistocene based. There was evidence for moderate levels of gene flow between species during diversification; however, incomplete lineage sorting could explain the data as well as gene flow. Overall diversification patterns within the genus Phonochorion agree with the predictions of the elevations shift model. Genetic patterns of diversification were driven mainly by Pleistocene glacial cycles and reflected the nature and distribution of sky islands. There was also some albeit weak evidence of demographic expansions coinciding with glacial cooling. However, evidence for divergence with gene flow was inconclusive.     

Islands: stability, diversity, conservation

Islands present both a diversity and a stability paradox. They are often highly species-poor but have considerable biological interest in terms of extraordinary endemic genera and taxonomically isolated groups. They appear to be stable, as in some cases these organisms have persisted for many millions of years, and having an oceanic climate, extreme climatic events may be comparatively rare. However, when subject to extrinsic (anthropogenic) disturbance they do not appear to be stable, but often suffer catastrophic ecological change. These apparent paradoxes are resolved when it is realized that all these features are consequences of the same island characteristics: biotic isolation and oceanicity. As a result of these two characteristics, far oceanic islands are quantitatively different from continental systems in the nature of their ecological processes, which appear to give rise to an extreme punctuated equilibrium model of evolutionary change. Endemics may be ancient relict endemics displaying prolonged stasis and persistence, or products of adaptive radiation representing rapid punctuational events. A process-based definition of a relict endemic (palaeoendemic) is one whose founding lineage (i.e. the original continental source taxon) has not left any descendents. A corollary of this definition is that the time of divergence between an endemic and its continental sister-group should predate the colonization of the island by the now endemic lineage. An example is Dicksonia arborescens which has been on St Helena for at least 9 Myrs and no longer occurs in the likely source area of Africa. These relict endemics, frequent on islands, are important as the last remnants of tranches of biodiversity that have vanished elsewhere. Island conservation strategies require an integrated understanding of both sides of the diversity and stability paradox so that both island processes and island organisms can be conserved.     

Vicariance and marine migration in continental island populations of a frog endemic to the Atlantic Coastal forest

The theory of island biogeography is most often studied in the context of oceanic islands where all island inhabitants are descendants from founding events involving migration from mainland source populations. Far fewer studies have considered predictions of island biogeography in the case of continental islands, where island formation typically splits continuous populations and thus vicariance also contributes to the diversity of island populations. We examined one such case on continental islands in southeastern Brazil, to determine how classic island biogeography predictions and past vicariance explain the population genetic diversity of Thoropa taophora, a frog endemic to the Atlantic Coastal Forest. We used nuclear microsatellite markers to examine the genetic diversity of coastal and island populations of this species. We found that island isolation has a role in shaping the genetic diversity of continental island species, with island populations being significantly less diverse than coastal populations. However, area of the island and distance from coast had no significant effect on genetic diversity. We also found no significant differences between migration among coastal populations and migration to and from islands. We discuss how vicariance and the effects of continued migration between coastal and island populations interact to shape evolutionary patterns on continental islands.     

Multiple levels of allopatric divergence in the endemic Philippine fruit bat Haplonycteris fischeri (Pteropodidae)

As part of a larger comparative phylogeographical study of Philippine fruit bats, I used fragments of the mitochondrial genes cytochrome  b and ND2 to investigate phylogeography and diversification in Haplonycteris fischeri , a pteropodid bat endemic to the Philippines but widespread within the archipelago. Genetic diversity in H. fischeri was extremely high in these commonly studied genes, with 101 unique haplotypes in 123 sequenced individuals, although small, continuously isolated islands had less diversity than had large island complexes. Seven monophyletic groups and one paraphyletic group were restricted to individual islands, groups of islands, or parts of islands. Each Pleistocene island complex had a single resident monophyletic lineage; these five groups were separated by approximately 6–8% sequence divergence and apparently have been diverging for 4–6 Myr. Within island groups, monophyletic lineages on some individual islands suggest that current ocean channels have also been barriers to gene flow; in some cases, multiple allopatric clades were present on single islands. Basal divergence dates were estimated to be in the early Pliocene, and most diversification was apparently connected to the ongoing geological evolution of the Philippines. Geological history and current geography interact with ecology to cause substantial genetic differentiation within this primary forest-specialist species.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 329–349.     

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.     

Phylogeographic patterns of Hawaiian Megalagrion damselflies (Odonata: Coenagrionidae) correlate with Pleistocene island boundaries

The Pleistocene geological history of the Hawaiian Islands is becoming well understood. Numerous predictions about the influence of this history on the genetic diversity of Hawaiian organisms have been made, including the idea that changing sea levels would lead to the genetic differentiation of populations isolated on individual volcanoes during high sea stands. Here, we analyse DNA sequence data from two closely related, endemic Hawaiian damselfly species in order to test these predictions, and generate novel insights into the effects of Pleistocene glaciation and climate change on island organisms. Megalagrion xanthomelas and Megalagrion pacificum are currently restricted to five islands, including three islands of the Maui Nui super-island complex (Molokai, Lanai, and Maui) that were connected during periods of Pleistocene glaciation, and Hawaii island, which has never been subdivided. Maui Nui and Hawaii are effectively a controlled, natural experiment on the genetic effects of Pleistocene sea level change. We confirm well-defined morphological species boundaries using data from the nuclear EF-1alpha gene and show that the species are reciprocally monophyletic. We perform phylogeographic analyses of 663 base pairs (bp) of cytochrome oxidase subunit II (COII) gene sequence data from 157 individuals representing 25 populations. Our results point to the importance of Pleistocene land bridges and historical island habitat availability in maintaining inter-island gene flow. We also propose that repeated bottlenecks on Maui Nui caused by sea level change and restricted habitat availability are likely responsible for low genetic diversity there. An island analogue to northern genetic purity and southern diversity is proposed, whereby islands with little suitable habitat exhibit genetic purity while islands with more exhibit genetic diversity.     

Systematics and evolution of the Pan‐Alcidae (Aves,Charadriiformes)

Puffins, auks and their allies in the wing‐propelled diving seabird clade Pan‐Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (～ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan‐alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (～ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan‐Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan‐alcid cladogenesis.     

Speciation and phylogeography of Hawaiian terrestrial arthropods

The Hawaiian archipelago is arguably the world's finest natural laboratory for the study of evolution and patterns of speciation. Arthropods comprise over 75% of the endemic biota of the Hawaiian Islands and a large proportion belongs to species radiations. We classify patterns of speciation within Hawaiian arthropod lineages into three categories: (i) single representatives of a lineage throughout the islands; (ii) species radiations with either (a) single endemic species on different volcanoes or islands, or (b) multiple species on each volcano or island; and (iii) single widespread species within a radiation of species that exhibits local endemism. A common pattern of phylogeography is that of repeated colonization of new island groups, such that lineages progress down the island chain, with the most ancestral groups (populations or species) on the oldest islands. While great dispersal ability and its subsequent loss are features of many of these taxa, there are a number of mechanisms that underlie diversification. These mechanisms may be genetic, including repeated founder events, hybridization, and sexual selection, or ecological, including shifts in habitat and/or host affiliation. The majority of studies reviewed suggest that natural selection is a primary force of change during the initial diversification of taxa.     

Mitochondrial DNA diversification, molecular phylogeny, and biogeography of the primitive rhacophorid genus Buergeria in East Asia

In this study we sought to clarify the evolutionary relationships and biogeographic history of the bell-ring frog, Buergeria buergeri (family Rhacophoridae), and two congeneric species Buergeria japonica and Buergeria robusta, by analyzing three mitochondrial (mt) genes: 12S rRNA, Cytb, and ND5. Phylogenetic analyses based on gene data showed the mt clades corresponding to the Buergeria species and three major haplogroups within B. buergeri. Each haplogroup corresponded clearly to the area in which it was distributed, namely eastern Japan (excluding Hokkaido; Hg I), central Japan (Hg II), and western Japan (including the Shikoku and Kyushu regions; Hg III). The estimated divergence time suggested that the lineage splits of the Buergeria species occurred before the formation of the island of Taiwan and the Japan Archipelago (including the Ryukyu islands). The differentiation among the genealogical lineages of B. buergeri seems to have begun in the Late Miocene (approx. 7-5Mya), and the formation of their present distribution pattern might have been influenced by climatic changes and geographical events such as the formation of a wide peneplane and expansions of certain basins.     

Evolution of Cryptocephalus leaf beetles related to C. sericeus (Coleoptera: Chrysomelidae) and the role of hybridization in generating species mtDNA paraphyly

Gómez‐Zurita, J., Sassi, D., Cardoso, A. & Balke, M. (2011). Evolution of Cryptocephalus leaf beetles related to C. sericeus (Coleoptera: Chrysomelidae) and the role of hybridization in generating species mtDNA paraphyly. —Zoologica Scripta, 41, 47–67. Autochthonous European insect diversity is the result of the very complex geological, geographic and climatic history of the Mediterranean area. The leaf beetle genus Cryptocephalus has over 250 species in this area. Among them stands out a group nearly endemic from this region consisting of conspicuous metallic green or blue beetles which can be found visiting yellow Asteraceae flowers in most mid‐ to high‐altitude European grasslands: the Linnaean species C. hypochaeridis, C. sericeus, and all their relatives. In all, these are 32 species forming several taxonomically complex groups across Europe. We sampled all morphological diversity in this lineage and characterized it for two mitochondrial DNA genes. The mtDNA phylogeny of this assemblage was inferred, as well as the timing of its diversification using standard mtDNA substitution rates and a hypothetical Messinian vicariant split. The origin of the group can be traced back to western continental Eurasia in the Lower Miocene. Its subsequent taxonomic splits can be linked to specific periods in the formation of Europe, with a marked trend to east–west phylogenetic divides throughout time and space, and a nearly constant rate of diversification. Only during the Pleistocene, a significant increase in diversification rate can be associated with species formation in the C. hypochaeridis and C. sericeus species complexes. Within these latter groups, most taxa show some degree of mtDNA paraphyly as a result of their recent separation and remarkably by episodes of gene flow in areas of secondary contact among recently diverged species, possibly driven by climatic change.     

Lineage diversification and historical demography of a sky island salamander,Plethodon ouachitae,from the Interior Highlands

Sky islands provide ideal opportunities for understanding how climatic changes associated with Pleistocene glacial cycles influenced species distributions, genetic diversification, and demography. The salamander Plethodon ouachitae is largely restricted to high‐elevation, mesic forest on six major mountains in the Ouachita Mountains. Because these mountains are separated by more xeric, low‐elevation valleys, the salamanders appear to be isolated on sky islands where gene flow among populations on different mountains may be restricted. We used DNA sequence data along with ecological niche modelling and coalescent simulations to test several hypotheses related to diversifications in sky island habitats. Our results revealed that P. ouachitae is composed of seven well‐supported lineages structured across six major mountains. The species originated during the Late Pliocene, and lineage diversification occurred during the Middle Pleistocene in a stepping stone fashion with a cyclical pattern of dispersal to a new mountain followed by isolation and divergence. Diversification occurred primarily on an east–west axis, which is likely related to the east–west orientation of the Ouachita Mountains and the more favourable cooler and wetter environmental conditions on north slopes compared to south‐facing slopes and valleys. All non‐genealogical coalescent methods failed to detect significant population expansion in any lineages. Bayesian skyline plots showed relatively stable population sizes over time, but indicated a slight to moderate amount of population growth in all lineages starting approximately 10 000–12 000 years ago. Our results provide new insight into sky island diversifications from a previously unstudied region, and further demonstrate that climatic changes during the Pleistocene had profound effects on lineage diversification and demography, especially in species from environmentally sensitive habitats in montane regions.     

In and out of Madagascar: Dispersal to Peripheral Islands, Insular Speciation and Diversification of Indian Ocean Daisy Trees (Psiadia, Asteraceae)

Madagascar is surrounded by archipelagos varying widely in origin, age and structure. Although small and geologically young, these archipelagos have accumulated disproportionate numbers of unique lineages in comparison to Madagascar, highlighting the role of waif-dispersal and rapid in situ diversification processes in generating endemic biodiversity. We reconstruct the evolutionary and biogeographical history of the genus Psiadia (Asteraceae), a plant genus with near equal numbers of species in Madagascar and surrounding islands. Analyzing patterns and processes of diversification, we explain species accumulation on peripheral islands and aim to offer new insights on the origin and potential causes for diversification in the Madagascar and Indian Ocean Islands biodiversity hotspot. Our results provide support for an African origin of the group, with strong support for non-monophyly. Colonization of the Mascarenes took place by two evolutionary distinct lineages from Madagascar, via two independent dispersal events, each unique for their spatial and temporal properties. Significant shifts in diversification rate followed regional expansion, resulting in co-occurring and phenotypically convergent species on high-elevation volcanic slopes. Like other endemic island lineages, Psiadia have been highly successful in dispersing to and radiating on isolated oceanic islands, typified by high habitat diversity and dynamic ecosystems fuelled by continued geological activity. Results stress the important biogeographical role for Rodrigues in serving as an outlying stepping stone from which regional colonization took place. We discuss how isolated volcanic islands contribute to regional diversity by generating substantial numbers of endemic species on short temporal scales. Factors pertaining to the mode and tempo of archipelago formation and its geographical isolation strongly govern evolutionary pathways available for species diversification, and the potential for successful diversification of dispersed lineages, therefore, appears highly dependent on the timing of arrival, as habitat and resource properties change dramatically over the course of oceanic island evolution.     

Sequential colonization and diversification of Galapágos endemic land snail genus Bulimulus (Gastropoda, Stylommatophora)

Species richness on island or islandlike systems is a function of colonization, within-island speciation, and extinction. Here we evaluate the relative importance of the first two of these processes as a function of the biogeographical and ecological attributes of islands using the Galápagos endemic land snails of the genus Bulimulus, the most species-rich radiation of these islands. Species in this clade have colonized almost all major islands and are found in five of the six described vegetation zones. We use molecular phylogenetics (based on COI and ITS 1 sequence data) to infer the diversification patterns of extant species of Bulimulus, and multiple regression to investigate the causes of variation among islands in species richness. Maximum-likelihood, Bayesian, and maximum-parsimony analyses yield well-resolved trees with similar topologies. The phylogeny obtained supports the progression rule hypothesis, with species found on older emerged islands connecting at deeper nodes. For all but two island species assemblages we find support for only one or two colonization events, indicating that within-island speciation has an important role in the formation of species on these islands. Even though speciation through colonization is not common, island insularity (distance to nearest major island) is a significant predictor of species richness resulting from interisland colonization alone. However, island insularity has no effect on the overall bulimulid species richness per island. Habitat diversity (measured as plant species diversity), island elevation, and island area, all of which are indirect measures of niche space, are strong predictors of overall bulimulid land snail species richness. Island age is also an important independent predictor of overall species richness, with older islands harboring more species than younger islands. Taken together, our results demonstrate that the diversification of Galápagos bulimulid land snails has been driven by a combination of geographic factors (island age, size, and location), which affect colonization patterns, and ecological factors, such as plant species diversity, that foster within-island speciation.     

Stop and Go – Waves of Tarsier Dispersal Mirror the Genesis of Sulawesi Island

The Indonesian island of Sulawesi harbors a highly endemic and diverse fauna sparking fascination since long before Wallace’s contemplation of biogeographical patterns in the region. Allopatric diversification driven by geological or climatic processes has been identified as the main mechanism shaping present faunal distribution on the island. There is both consensus and conflict among range patterns of terrestrial species pointing to the different effects of vicariant events on once co-distributed taxa. Tarsiers, small nocturnal primates with possible evidence of an Eocene fossil record on the Asian mainland, are at present exclusively found in insular Southeast Asia. Sulawesi is hotspot of tarsier diversity, whereby island colonization and subsequent radiation of this old endemic primate lineage remained largely enigmatic. To resolve the phylogeographic history of Sulawesi tarsiers we analyzed an island-wide sample for a set of five approved autosomal phylogenetic markers (ABCA1, ADORA3, AXIN1, RAG1, and TTR) and the paternally inherited SRY gene. We constructed ML and Bayesian phylogenetic trees and estimated divergence times between tarsier populations. We found that their arrival at the Proto-Sulawesi archipelago coincided with initial Miocene tectonic uplift and hypothesize that tarsiers dispersed over the region in distinct waves. Intra-island diversification was spurred by land emergence and a rapid succession of glacial cycles during the Plio-Pleistocene. Some tarsier range boundaries concur with spatial limits in other taxa backing the notion of centers of faunal endemism on Sulawesi. This congruence, however, has partially been superimposed by taxon-specific dispersal patterns.