Cenozoic Dispersal Research Articles

Evolution and biogeography of acidocerine water scavenger beetles (Coleoptera: Hydrophilidae) shaped by Gondwanan vicariance and Cenozoic isolation of South America

AbstractThe water scavenger beetle subfamily Acidocerinae is a cosmopolitan, ecologically diverse lineage with more than 500 described species whose morphology and classification are poorly understood. We present the first phylogenetic analyses of the subfamily inferred from five loci (18S, 28S, H3, CAD, COI). We used secondary calibrations to estimate divergence times and employ this phylogeny to revise the classification and examine the historical biogeography of this lineage. Most genera are resolved as reciprocally monophyletic, with several exceptions: Horelophopsis syn. n. is recovered as a derived lineage of and placed in synonymy with Agraphydrus. The large genus Helochares, as well as its primary constituent subgenera Helochares (s. str.) and Hydrobaticus are found to be polyphyletic. Batochares stat. n. and Sindolus stat. rev. are elevated from subgenera of Helochares to generic rank. Crephelochares stat. rev. is removed from synonymy with Chasmogenus. We found that the crown Acidocerinae date to the mid‐Jurassic in South America + Africa (West Gondwana). South America and Africa remain important areas of endemism throughout the evolution of the lineage and are resolved either individually or in combination as the ancestral area for all but one clade that is older than 90 million years ago. Six of the seven lineages occurring in South America diverged more than 100 million years ago and are endemic to the region, suggesting the Neotropical acidocerine fauna became isolated following the breakup of West Gondwana. Conversely, lineages found on other Gondwanan fragments (India, Madagascar, Australia) are comparatively young and derived, with all being Cenozoic in age. The few taxa that occur in North America today are all the result of recent Cenozoic dispersal from South America, although North America may have played an important role as an ancestral area in the Mesozoic.

Biogeographical and co-evolutionary origins of scarabaeine dung beetles: Mesozoic vicarianceversusCenozoic dispersal and dinosaurversusmammal dung

The subfamily Scarabaeinae (Coleoptera: Scarabaeidae) may have originated in Gondwanaland, through Mesozoic vicariance or dispersal in association with dinosaur dung, or through Cenozoic dispersal in association with mammal dung. We review evidence from age-calibrated phylogenies, fossil records, biogeographical patterns, and ecological associations. Fossil calibrated phylogenies for Scarabaeoidea predict a Cretaceous origin for Scarabaeinae, although age estimates would rely on other scarabaeoid groups given the doubtful validity of Mesozoic ‘scarabaeine’ fossils. Molecular clock calibrated phylogenies for Scarabaeinae predict an early Cenozoic origin coeval with modern mammal diversification. Trace fossil evidence suggests the exploitation of dinosaur dung by fossorial insects, although scarabaeine fossils are only validated for the Cenozoic. Although we discuss fossil evidence for dinosaur dung as a faunal resource, the origin of modern scarabaeines from an earlier Mesozoic vicariant or dispersal fauna remains unsupported. Although clock-constrained, phylogram topography is consistent with early Cenozoic palaeoclimatic and palaeoecological events, Eocene marine barriers would demand dispersal to explain the distributional origins of Scarabaeinae. Inconsistencies between classification and phylogeny complicate biogeographical analysis, although earlier southern radiation of basally-derived tribes has probably been followed by later diversification and the global dispersal of both basally and terminally-derived taxa, primarily via restored land links.

India-Madagascar vicariance explains cascade beetle biogeography

India and Madagascar drifted apart more than 80 Mya, yet few taxonomic groups currently found in these regions bear any signature of this split. When drifting in isolation, extensive volcanic activity covered almost half of India in lava flows, likely triggering widespread extinction on the island. Consequently, most of India's rich extant flora and fauna are considered to be the result of recent Cenozoic dispersal, and no lineages are conclusively a result of ancient vicariance. Many of Madagascar's lineages also stem from either Cenozoic diversification or dispersal events, with the latter being a result of the close proximity of the island with mainland Africa. In the present study, we focus on two remarkable lineages of cascade beetles in the genera Scoliopsis and Tritonus (Coleoptera, Hydrophilidae), respectively, dwelling in the mountains of south India and Sri Lanka, as well as in Madagascar. Based on a molecular phylogeny of the family Hydrophilidae dated with eight fossils, we show that these two lineages are sister taxa, and diverged when Madagascar and Greater India (India, Sri Lanka, Seychelles) separated, suggesting a pattern of Gondwanean vicariance. The results of the present study show that, despite geological upheaval, the present-day fauna of India still retains traces of its Gondwanan past.

Intricate patterns of phylogenetic relationships in the olive family as inferred from multi-locus plastid and nuclear DNA sequence analyses: A close-up on Chionanthus and Noronhia (Oleaceae)

Noronhia represents the most successful radiation of the olive family (Oleaceae) in Madagascar with more than 40 named endemic species distributed in all ecoregions from sea level to high mountains. Its position within the subtribe Oleinae has, however, been largely unresolved and its evolutionary history has remained unexplored. In this study, we generated a dataset of plastid (trnL-F, trnT-L, trnS-G, trnK-matK) and nuclear (internal transcribed spacer [ITS]) DNA sequences to infer phylogenetic relationships within Oleinae and to examine evolutionary patterns within Noronhia. Our sample included most species of Noronhia and representatives of the ten other extant genera within the subtribe with an emphasis on Chionanthus. Bayesian inferences and maximum likelihood analyses of plastid and nuclear data indicated several instances of paraphyly and polyphyly within Oleinae, with some geographic signal. Both plastid and ITS data showed a polyphyletic Noronhia that included Indian Ocean species of Chionanthus. They also found close relationships between Noronhia and African Chionanthus. However, the plastid data showed little clear differentiation between Noronhia and the African Chionanthus whereas relationships suggested by the nuclear ITS data were more consistent with taxonomy and geography. We used molecular dating to discriminate between hybridization and lineage sorting/gene duplication as alternative explanations for these topological discordances and to infer the biogeographic history of Noronhia. Hybridization between African Chionanthus and Noronhia could not be ruled out. However, Noronhia has long been established in Madagascar after a likely Cenozoic dispersal from Africa, suggesting any hybridization between representatives of African and Malagasy taxa was ancient. In any case, the African and Indian Ocean Chionanthus and Noronhia together formed a strongly supported monophyletic clade distinct and distant from other Chionanthus, which calls for a revised and more conservative taxonomy for this group.

Phylogeography of a successful aerial disperser: the golden orb spider Nephila on Indian Ocean islands

BackgroundThe origin and diversification patterns of lineages across the Indian Ocean islands are varied due to the interplay of the complex geographic and geologic island histories, the varying dispersal abilities of biotas, and the proximity to major continental landmasses. Our aim was to reconstruct phylogeographic history of the giant orbweaving spider (Nephila) on western Indian Ocean islands (Madagascar, Mayotte, Réunion, Mauritius, Rodrigues), to test its origin and route of dispersal, and to examine the consequences of good dispersal abilities for colonization and diversification, in comparison with related spiders (Nephilengys) inhabiting the same islands, and with other organisms known for over water dispersal. We used mitochondrial (COI) and nuclear (ITS2) markers to examine phylogenetic and population genetic patterns in Nephila populations and species. We employed Bayesian and parsimony methods to reconstruct phylogenies and haplotype networks, respectively, and calculated genetic distances, fixation indices, and estimated clade ages under a relaxed clock model.ResultsOur results suggest an African origin of Madagascar Nephila inaurata populations via Cenozoic dispersal, and the colonization of the Mascarene islands from Madagascar. We find evidence of gene flow across Madagascar and Comoros. The Mascarene islands share a common 'ancestral' COI haplotype closely related to those found on Madagascar, but itself absent, or as yet unsampled, from Madagascar. Each island has one or more unique haplotypes related to the ancestral Mascarene haplotype. The Indian Ocean N. inaurata are genetically distinct from the African populations.ConclusionsNephila spiders colonized Madagascar from Africa about 2.5 (0.6-5.3) Ma. Our results are consistent with subsequent, recent and rapid, colonization of all three Mascarene islands. On each island, however, we detected unique haplotypes, consistent with a limited gene flow among the islands subsequent to colonization, a scenario that might be referred to as speciation in progress. However, due to relatively small sample sizes, we cannot rule out that we simply failed to collect Mascarene haplotypes on Madagascar, a scenario that might imply human mediated dispersal. Nonetheless, the former interpretation better fits the available data and results in a pattern similar to the related Nephilengys. Nephilengys, however, shows higher genetic divergences with diversification on more remote islands. That the better disperser of the two lineages, Nephila, has colonized more islands but failed to diversify, demonstrates how dispersal ability can shape both the patterns of colonization and formation of species across archipelagos.

Biogeography and diversification of hermit spiders on Indian Ocean islands (Nephilidae: Nephilengys)

The origin of the terrestrial biota of Madagascar and, especially, the smaller island chains of the western Indian Ocean is relatively poorly understood. Madagascar represents a mixture of Gondwanan vicariant lineages and more recent colonizers arriving via Cenozoic dispersal, mostly from Africa. Dispersal must explain the biota of the smaller islands such as the Comoros and the chain of Mascarene islands, but relatively few studies have pinpointed the source of colonizers, which may include mainland Africa, Asia, Australasia, and Madagascar. The pantropical hermit spiders (genus Nephilengys) seem to have colonized the Indian Ocean island arc stretching from Comoros through Madagascar and onto Mascarenes, and thus offer one opportunity to reveal biogeographical patterns in the Indian Ocean. We test alternative hypotheses on the colonization route of Nephilengys spiders in the Indian Ocean and simultaneously test the current taxonomical hypothesis using genetic and morphological data. We used mitochondrial (COI) and nuclear (ITS2) markers to examine Nephilengys phylogenetic structure with samples from Africa, southeast Asia, and the Indian Ocean islands of Madagascar, Mayotte, Réunion and Mauritius. We used Bayesian and parsimony methods to reconstruct phylogenies and haplotype networks, and calculated genetic distances and fixation indices. Our results suggest an African origin of Madagascar Nephilengys via Cenozoic dispersal, and subsequent colonization of the Mascarene islands from Madagascar. We find strong evidence of gene flow across Madagascar and through the neighboring islands north of it, while phylogenetic trees, haplotype networks, and fixation indices all reveal genetically isolated and divergent lineages on Mauritius and Réunion, consistent with female color morphs. These results, and the discovery of the first males from Réunion and Mauritius, in turn falsify the existing taxonomic hypothesis of a single widespread species, Nephilengys borbonica, throughout the archipelago. Instead, we diagnose three Nephilengys species: Nephilengys livida ( Vinson, 1863) from Madagascar and Comoros, N. borbonica ( Vinson, 1863) from Réunion, and Nephilengys dodo new species from Mauritius. Nephilengys followed a colonization route to Madagascar from Africa, and on through to the Mascarenes, where it speciated on isolated islands. The related golden orb-weaving spiders, genus Nephila, have followed the same colonization route, but Nephila shows shallower divergencies, implying recent colonization, or a moderate level of gene flow across the archipelago preventing speciation. Unlike their synanthropic congeners, N. borbonica and N. dodo are confined to pristine island forests and their discovery calls for evaluation of their conservation status.

Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae)

Agnarsson, I., Kuntner, M., Coddington, J. A. & Blackledge, T. A. (2009). Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae). —Zoologica Scripta, 39, 75–87.Madagascar is a biodiversity hotspot, thought to be colonized mostly via Cenozoic dispersal from Africa, followed by endemic radiation of multiple lineages. Anelosimus spiders are diverse in Madagascar, and, like their congeners in the Americas, are most diverse in wet montane forests. Most Anelosimus species are social in that they cooperate in web building and prey capture either during a part of their life cycles (subsocial), including hitherto studied Malagasy species, or permanently (quasisocial). One Central American coastal species, Anelosimus pacificus, has secondarily switched to solitary living, and available evidence suggests that its closest relatives from S. America and Europe are likely also solitary. Here, we show that the only known coastal Anelosimus species in Madagascar and Comoros –Anelosimus decaryi and Anelosimus amelie sp. n. – are also solitary. Using a phylogenetic approach, we test two competing hypotheses: (i) that Malagasy Anelosimus are monophyletic and thus represent a second example of reversal to solitary living in a littoral habitat or (ii) that solitary and subsocial lineages independently colonized Madagascar. We find that solitary Malagasy Anelosimus are closely related to their solitary counterparts from Europe and the Americas, while subsocial Malagasy species nest sister to Anelosimus nelsoni from S. Africa. This finding suggests that (i) the two Anelosimus lineages colonized Madagascar independently and (ii) a reversal to solitary behaviour has occurred only once in Anelosimus. Thus, solitary littoral Malagasy species did not descend from Malagasy mountains, but arrived from much further afar. African and possibly American origin of the two lineages is implied by our findings. To restore natural classification of Anelosimus, Seycellocesa Koçak & Kemal is synonymized with it.

Galaxias fossils from Miocene lake deposits, Otago, New Zealand: The earliest records of the Southern Hemisphere family Galaxiidae (Teleostei)

Galaxiid fishes are commonly assumed to exhibit a Gondwanan distribution, but little fossil evidence has been available to support or refute this assumption until now. Here we report on three species of fossil Galaxias, represented by exquisitely preserved, almost entire skeletons, together with jaw and skull fragments, from several Miocene lacustrine deposits in Otago, South Island, New Zealand. These are the only certain Galaxias fossils, and provide unequivocal evidence that the genus was abundant, and taxonomically and ecologically diverse in the New Zealand region before 23 million years ago. One new species, Galaxias effusus, from an Early Miocene diatomite deposit near Middlemarch is described on the basis of low vertebral count, short caudal peduncle, expansive dorsal, caudal and anal fins, rounded to truncate caudal fin, with 15 principal caudal fin rays. The intact skeletons of G. effusus confirm that they inhabited a deep, stratified maar lake with cool, anoxic bottom water. The maar lake was completely landlocked, from sedimentological evidence, and this species must have been non‐migratory. Disarticulated fish jaws and skull fragments from Early Miocene mudstones near Bannockburn are likely to be from a second large species of Galaxias on the basis of dentary, premaxilla and parasphenoid size and morphology. These disarticulated fish remains from a regionally extensive inland lake system indicate decomposition and/or predation in shallow nearshore environments, but we have no evidence yet of migratory behaviour. New specimens of G. kaikorai Whitley from Late Miocene diatomite deposits near Dunedin confirm its morphological similarity to the living G. brevipinnis. The occurrence and diversity of galaxiids in lakes of early and Late Miocene age in southern New Zealand can be explained by either oceanic dispersal across the Southern Hemisphere at any time during the Cenozoic, relict Gondwanan distributions or, most likely, an ancient Gondwanan origin overprinted by Cenozoic dispersal.

Has Vicariance or Dispersal Been the Predominant Biogeographic Force in Madagascar? Only Time Will Tell

Madagascar is one of the world's hottest biodiversity hot spots due to its diverse, endemic, and highly threatened biota. This biota shows a distinct signature of evolution in isolation, both in the high levels of diversity within lineages and in the imbalance of lineages that are represented. For example, chameleon diversity is the highest of any place on Earth, yet there are no salamanders. These biotic enigmas have inspired centuries of speculation relating to the mechanisms by which Madagascar's biota came to reside there. The two most probable causal factors are Gondwanan vicariance and/or Cenozoic dispersal. By reviewing a comprehensive sample of phylogenetic studies of Malagasy biota, we find that the predominant pattern is one of sister group relationships to African taxa. For those studies that include divergence time analysis, we find an overwhelming indication of Cenozoic origins for most Malagasy clades. We conclude that most of the present-day biota of Madagascar is comprised of the descendents of Cenozoic dispersers, predominantly with African origins.

Latitudinal and longitudinal barriers in global biogeography

Due to changes in climate and continental arrangement, plant and animal assemblages faced different dispersal barriers at different moments in Earth's history. It is generally accepted that groups which diversified during times of Gondwanan-Laurasian separation show different distribution patterns from those of more recent origin. Here I present principal component-derived maps for two globally distributed groups, with ca 1000 species each. Gymnosperm assemblages perfectly illustrate the existence of southern and northern components, corresponding to the Gondwanan and Laurasian temperate floras at the time when angiosperms started becoming dominant in the tropics, thus imposing a latitudinal barrier. Bat (chiropteran) assemblages indicate that the major biogeographical barrier in their Cenozoic dispersal was the longitudinal separation between the Old and New World.

A Cordilleran model for the evolution of Avalonia

Striking similarities between the late Mesoproterozoic–Early Paleozoic record of Avalonia and the Late Paleozoic–Cenozoic history of western North America suggest that the North American Cordillera provides a modern analogue for the evolution of Avalonia and other peri-Gondwanan terranes during the late Precambrian. Thus: (1) The evolution of primitive Avalonian arcs (proto-Avalonia) at 1.2–1.0 Ga coincides with the amalgamation of Rodinia, just as the evolution of primitive Cordilleran arcs in Panthalassa coincided with the Late Paleozoic amalgamation of Pangea. (2) The development of mature oceanic arcs at 750–650 Ma (early Avalonian magmatism), their accretion to Gondwana at ca. 650 Ma, and continental margin arc development at 635–570 Ma (main Avalonian magmatism) followed the breakup of Rodinia at ca. 755 Ma in the same way that the accretion of mature Cordilleran arcs to western North America and the development of the main phase of Cordilleran arc magmatism followed the Early Mesozoic breakup of Pangea. (3) In the absence of evidence for continental collision, the diachronous termination of subduction and its transition to an intracontinental wrench regime at 590–540 Ma is interpreted to record ridge–trench collision in the same way that North America's collision with the East Pacific Rise in the Oligocene led to the diachronous initiation of a transform margin. (4) The separation of Avalonia from Gondwana in the Early Ordovician resembles that brought about in Baja California by the Pliocene propagation of the East Pacific Rise into the continental margin. (5) The Late Ordovician–Early Silurian sinistral accretion of Avalonia to eastern Laurentia emulates the Cenozoic dispersal of Cordilleran terranes and may mimic the paths of future terranes transferred to the Pacific plate. This close similarity in tectonothermal histories suggests that a geodynamic coupling like that linking the evolution of the Cordillera with the assembly and breakup of Pangea, may have existed between Avalonia and the late Precambrian supercontinent Rodinia. Hence, the North American Cordillera is considered to provide an actualistic model for the evolution of Avalonia and other peri-Gondwanan terranes, the histories of which afford a proxy record of supercontinent assembly and breakup in the late Precambrian.

Phylogeny of South American and Malagasy Boine Snakes: Molecular Evidence for the Validity of Sanzinia and Acrantophis and Biogeographic Implications

A total of 1981 bp of the mitochondrial 16S rRNA, 12S rRNA and cytochrome b genes were analyzed in five boine and one pythonine snake species to determine phylogenetic relationships between Malagasy and Neotropical taxa included in the genus Boa. The obtained cladograms significantly grouped Boa constrictor with the Neotropical genera Eunectes and Epicrates, whereas the Malagasy species were the sister group of the clade of the three Neotropical taxa. Based on these results, Sanzinia and Acrantophis should be considered as valid generic names for the Malagasy boas. Their origin may be a result of a Cenozoic dispersal from Africa or Asia.

Reconciling fossils and molecules: Cenozoic divergence of cichlid fishes and the biogeography of Madagascar

AimThe biogeographical origins of the extant vertebrates endemic to Madagascar are largely unsolved, but have often been related to vicariance in the context of fragmentation of the supercontinent Gondwana in the Mesozoic. Such hypotheses are especially appealing in the case of cichlid fishes, which show phylogenetic relationships reflecting the temporal successions of the breakup of Gondwana. We used molecular clock data to test this assumption.LocationFragments of the 16S rRNA gene and of the nuclear Tmo‐4C4 locus, partly obtained from Genbank from South American, African, Malagasy and Indian cichlids were analysed.MethodsBased on monophyletic cichlid radiations in African lakes, we calibrated a molecular clock. The obtained rates were used to estimate the age of divergence of the major cichlid clades.ResultsThe results agreed better with a Cenozoic than with a Mesozoic divergence, and were in accordance with the fossil record. Sequence divergences of the 16S and 12S rRNA genes of most lineages of Malagasy terrestrial and freshwater vertebrates from their non‐Malagasy sister groups were below saturation and many were relatively similar to those of cichlids.Main conclusionsA Cenozoic dispersal from continental landmasses may explain the origin of most extant Malagasy vertebrate groups better than a Jurassic/Cretaceous vicariance.