Extent and timing of floristic exchange between Australian and Asian rain forests

Aim We tested an entrenched concept – that the Australian rain forest flora is essentially a Gondwanan relict. We also assessed the role of regional‐level source–sink dynamics in the assembly of this flora. Location Eastern Australia. Methods To avoid potential biases inherent in selective studies undertaken to date, we used an analytical, whole‐of‐flora approach integrated with the fossil record. We identified disjunctions between woody Australian rain forest plant taxa and relatives on other land masses. To test the strength of the fossil evidence for the regional antiquity of this flora, we evaluated the proportion of these disjunct clades represented in the Australian fossil record, and to minimize the effects of biases in this record, we compared late Quaternary (i.e. late Pleistocene and Holocene, 126–0 ka), Pliocene and late Oligocene–early Miocene Australian pollen records interpreted as tropical rain forest. Using within‐species disjunctions as a proxy, we assessed the role of recent immigration from Asia into Australia. To assess the role of source–sink dynamics, we performed comparative analyses of disjunctions in major rain forest categories representing a north–south/climatic gradient. Results Southern Australian, cool temperate (microthermal) rain forests contain many floristic disjunctions with Gondwanan fragments and most of these clades have Gondwanan fossils. Disjunct clades in Australian mesothermal rain forest mostly occur in Asia/Malesia and a low proportion of these clades show pre‐Neogene records. Many clades in lowland tropical and ‘dry’ rain forest show disjunctions with Asia/Malesia and few have Australian fossil records. Rates of recent immigration from Asia/Malesia are high in these northern forests, and outweigh rates of recent emigration approximately nine‐fold. The late Quaternary fossil record has many more rain forest angiosperms than Oligocene–Miocene and Pliocene floras, consistent with extensive late Cenozoic immigration. Main conclusions The microthermal rain forests are largely Gondwanan relicts, but there is progressively greater, and more recent contribution from Asia/Malesia into more northern, and more lowland tropical rain forests. This variation reflects a strong gradient in geographic and ecological proximity between these forests and source floras in Asia/Malesia, and is consistent with a source–sink size model of immigration driven by late Cenozoic contractions and expansions of Australian rain forest.     

Phylogenetic relationships within the aplocheiloid fish genus Rivulus (Cyprinodontiformes, Rivulidae): implications for Caribbean and Central American biogeography

We examined the phylogenetic relationships of 16 northern species of the aplocheiloid genus Rivulus inhabiting the Caribbean, Central America, and South America. A total of 714 base pairs per taxon were sequenced from two segments of the mitochondrial genome, 12S rRNA and cytochrome b. Both parsimony and neighbor-joining analyses suggest an ancient vicariant origin of the Greater Antillean taxa, in addition to a quite recent dispersal of species into the Lesser Antilles from the South American mainland. Combined analyses support the monophyly of the northern South American assemblage as the sister group of a Central American/Columbian biota. However, the monophyly of the Central American biota remains uncertain. Divergence estimates for the Central American taxa are calibrated from the Last Cretaceous separation of the proto-Antilles from the Americas. These data suggest that the extant Central American taxa represent the descendants of at least two separate invasions during the Cenozoic, prior to the closing of the Panamanian isthmus. Times are consistent with the extensive evidence for reptilian and mammalian exchange throughout the Cenozoic.      

Systematics and historical biogeography of Greater Antillean Cichlidae

A molecular phylogenetic analysis recovers a pattern consistent with a drift vicariance scenario for the origin of Greater Antillean cichlids. This phylogeny, based on mitochondrial and nuclear genes, reveals that clades on different geographic regions diverged concurrently with the geological separation of these areas. Middle America was initially colonized by South American cichlids in the Cretaceous, most probably through the Cretaceous Island Arc. The separation of Greater Antillean cichlids and their mainland Middle American relatives was caused by a drift vicariance event that took place when the islands became separated from Yucatan in the Eocene. Greater Antillean cichlids are monophyletic and do not have close South American relatives. Therefore, the alternative hypothesis that these cichlids migrated via an Oligocene landbridge from South America is falsified. A marine dispersal hypothesis is not employed because the drift vicariance hypothesis is better able to explain the biogeographic patterns, both temporal and phylogenetic.     

A new species of Caracolus (Pulmonata: Camaenidae) from the Oligocene of Nebraska and the biotic history of the American camaenid land snails

A fossil land snail from the Oligocene White River Group of Nebraska is described as Caracolus aquilonaris sp nov. Living members of the genus Caracolus occur in tropical forest on the islands of the Greater Antilles. It is likely that C. aquilonaris occupied a similar habitat and that the present restricted occurrence of the genus Caracolus is a fragment of a previously wider range. The American carnaenid genera Pleurodonte, Polydontes and Zachrysia form a well defined monophyletic group, but there is an unresolved trichotomy involving this group, Labyrinthus and Caracolus . Well characterized fossil camaenids assigned to Pleurodonte (Jamaica, Carriacou) and the related Pleurodontites (Florida) occur in the Miocene. Antecedents to Labyrinthus were isolated in South America and to Caracolus and Pleurodonte in North America, possibly in the late Cretaceous. The latter genera reached the Antilles where Caracolus has persisted relatively unchanged. Ancestral Pleurodonte has diversified producing the distinctive subgenera Eurycratera and Thelidomus on Jamaica and the genus Polydontes on the other Greater Antilles. Drier conditions on Cuba have resulted in the divergence of Zachysia from Polydontes .     

Cenozoic environmental change in South America as indicated by mammalian body size distributions (cenograms)

A cenogram is a rank‐ordered body size distribution of non‐predatory terrestrial mammal species within a community. Studies of cenograms for modern faunas have shown that certain quantifiable attributes of cenograms are correlated with environmental variables such as rainfall and vegetation structure. Based on these correlations, cenograms of fossil communities have been used to infer palaeoenvironments and palaeoenvironmental variables. The present study uses cenogram statistics to interpret palaeoenvironmental conditions for eight Cenozoic South American mammal faunas, ranging from Eocene to Pleistocene in age. Body sizes for fossil taxa were taken either from the literature or were estimated using regressions of body size on molar length (or femoral bicondylar width) for modern mammals. Cenogram statistics are calculated for the eight fossil faunas and compared to similar statistics calculated for 16 modern South American mammal faunas, allowing palaeoenvironmental interpretations to be made. The palaeoenvironmental interpretations based on cenogram analyses sometimes support and sometimes contradict interpretations based on herbivore craniodental morphology (e.g. levels of hypsodonty). Simulations of expected errors in body size estimates for fossil taxa suggest that the discrepancies do not result primarily from erroneous body size estimates. It is possible that some of the incongruity in interpretations results from certain non‐analogue attributes of South American faunas during much of the Cenozoic (e.g. the relatively depauperate mammalian predator diversity prior to the Great American Biotic Interchange).     

Deglaciation explains bat extinction in the Caribbean

Ecological factors such as changing climate on land and interspecific competition have been debated as possible causes of postglacial Caribbean extinction. These hypotheses, however, have not been tested against a null model of climate‐driven postglacial area loss. Here, we use a new Quaternary mammal database and deep‐sea bathymetry to estimate species–area relationships (SARs) at present and during the Last Glacial Maximum (LGM) for bats of the Caribbean, and to model species loss as a function of area loss from rising sea level. Island area was a significant predictor of species richness in the Bahamas, Greater Antilles, and Lesser Antilles at all time periods, except for the Lesser Antilles during the LGM. Parameters of LGM and current SARs were similar in the Bahamas and Greater Antilles, but not the Lesser Antilles, which had fewer estimated species during the LGM than expected given their size. Estimated postglacial species losses in the Bahamas and Greater Antilles were largely explained by inferred area loss from rising sea level in the Holocene. However, there were more species in the Bahamas at present, and fewer species in the smaller Greater Antilles, than expected given island size and the end‐Pleistocene/early Holocene SARs. Poor fossil sampling and ecological factors may explain these departures from the null. Our analyses illustrate the importance of changes in area in explaining patterns of species richness through time and emphasize the role of the SAR as a null hypothesis in explorations of the impact of novel ecological interactions on extinction.     

Adaptive radiation versus intraspecific differentiation: morphological variation in Caribbean Anolis lizards

Lizards in the genus Anolis have experienced adaptive radiation in the Greater Antilles, producing a suite of species morphologically adapted to use different parts of the environment. In the Lesser Antilles, adaptive radiation has not occurred, but on some islands, interpopulational variation is high and represents adaptation to different habitats. We compared the extent of morphological differentiation among Greater Antillean habitat specialists with that exhibited among populations of two species, Anolis marmoratus and A. oculatus, from the Lesser Antillean islands of Guadeloupe and Dominica. Although extensive, intraspecific divergence in the Lesser Antilles is substantially less in magnitude than the differences among habitat specialists in the Greater Antilles. All populations of A. marmoratus are most similar to Greater Antillean trunk‐crown habitat specialists, but populations of A. oculatus differ in their affinities: some are similar to trunk‐crown anoles, but others are more similar to trunk‐ground habitat specialists.     

Unexpected evolutionary diversity in a recently extinct Caribbean mammal radiation

Identifying general patterns of colonization and radiation in island faunas is often hindered by past human-caused extinctions. The insular Caribbean is one of the only complex oceanic-type island systems colonized by land mammals, but has witnessed the globally highest level of mammalian extinction during the Holocene. Using ancient DNA analysis, we reconstruct the evolutionary history of one of the Caribbean''s now-extinct major mammal groups, the insular radiation of oryzomyine rice rats. Despite the significant problems of recovering DNA from prehistoric tropical archaeological material, it was possible to identify two discrete Late Miocene colonizations of the main Lesser Antillean island chain from mainland South America by oryzomyine lineages that were only distantly related. A high level of phylogenetic diversification was observed within oryzomyines across the Lesser Antilles, even between allopatric populations on the same island bank. The timing of oryzomyine colonization is closely similar to the age of several other Caribbean vertebrate taxa, suggesting that geomorphological conditions during the Late Miocene facilitated broadly simultaneous overwater waif dispersal of many South American lineages to the Lesser Antilles. These data provide an important baseline by which to further develop the Caribbean as a unique workshop for studying island evolution.     

Paleobiogeographic relationships of angiosperms from the Cretaceous and early Tertiary of the North American area

The biogeographic affinities of the Cretaceous and early Tertiary angiosperm floras of the North American area (which includes Meso-America, and the Greater Antilles) have been the subject of considerable interest. Although recent treatments of isolated taxa have shown affinities between North American, European, east Asian and Neotropic floras, the relationships have not been quantified. This study compiles the records of fossils whose familial relationships seem secure. This provides a carefully culled, and uniformly presented review of the Cretaceous and Paleogene record from 1950 to 1989 and supplements LaMotte (1950). A subset of these records, which showed compelling evidence of subfamilial relationships, was analyzed to quantify the relationships of the Cretaceous, Paleocene, Eocene and Oligocene floras to other regions. The analysis suggests that for the entire period 24% of the fossil species had affinities with extant taxa from the Northern Hemisphere; 10% with taxa from the Northern Hemisphere that have a few species in South America; 17% with taxa from Eurasia; 3% with taxa with a disjunct Eurasian-South American pattern; 19% with taxa from South America and/or Africa; 8% with taxa from South America and/or Africa that have an important sister group in southeast Asia; 5% with taxa from the Old World; and 13% with taxa having other distribution patterns. Those fossils with affinities to Laurasian taxa are mostly found in the northern and western portions of the North American area. The fossils with affinities to South American and/or African taxa are found in the southern portions of North America, Meso-America, and the Greater Antilles. The taxa with disjunct distributions show both patterns. These patterns suggest that during this time there were wide-spread temperate elements, found throughout Laurasia; Boreotropical flora elements, distributed in North America, Europe and along the Tethys seaway to southeast Asia; and West Gondwana elements which show dispersion from South America across the proto-Caribbean. The paleobotanical data are compatible with current geological, paleontological and biogeographical studies.     

Evolutionary consequences of ecological release in Caribbean Anolis lizards

On the large islands of the Greater Antilles, multi-species communities of Anolis lizards are composed of species specialized to use particular habitats; similar sets of specialized species have evolved independently on each island. We studied species of anoles found on small Caribbean islands. Because these islands contain at most only one other species of anole, we predicted that species on these islands should not be as specialized as Greater Antillean species; rather, they might be expected to exhibit a generalized morphology and a greater breadth of habitat use. Our findings, however, do not confirm these predictions. Lesser Antillean species do not exhibit greater breadth of habitat use than Greater Antillean species, nor do they exhibit a generalized morphology. Most species are ecologically and morphologically similar to specialized trunk-crown anoles of the Greater Antilles, although some species exhibit morphologies unlike those seen in Greater Antillean species. Among descendants of specialized Greater Antillean species occurring on one-or two-species islands, most descendants of trunk-crown species have diverged relatively little, whereas several descendants of trunk-ground anoles have diverged considerably. Consequently, we propose that ancestral species in the Greater Antilles may have been trunk-crown anoles.     

The profound influence of the Late Pliocene Panamanian uplift on the exchange,diversification, and distribution of New World birds

Separated throughout most of the Cenozoic era, North and South America were joined during the mid‐Pliocene when the uplift of Panama formed a land bridge between these two continents. The fossil record indicates that this connection allowed an unprecedented degree of inter‐continental exchange to occur between unique, previously isolated biotic assemblages, a phenomenon now recognized as the “Great American Biotic Interchange”. However, a relatively poor avian fossil record has prevented our understanding the role of the land bridge in shaping New World avian communities. To address the question of avian participation in the GABI, we compiled 64 avian phylogenetic studies and applied a relaxed molecular clock to estimate the timing of trans‐isthmus diversification events. Here, we show that a significant pulse of avian interchange occurred in concert with the isthmus uplift. The avian exchange was temporally consistent with the well understood mammalian interchange, despite the presumed greater vagility of birds. Birds inhabiting a variety of habitats and elevational zones responded to the newly available corridor. Within the tropics, exchange was equal in both directions although between extratropical and tropical regions it was not. Avian lineages with Nearctic origins have repeatedly invaded the tropics and radiated throughout South America; whereas, lineages with South American tropical origins remain largely restricted to the confines of the Neotropical region. This previously unrecognized pattern of asymmetric niche conservatism may represent an important and underappreciated contributor to the latitude diversity gradient.     

Extinction of South American sparassodontans (Metatheria): environmental fluctuations or complex ecological processes?

Sparassodontans are a diverse but now extinct group of metatherians that were apex predators in South America during most of the Cenozoic. Studying their decline has been controversial mainly due to the scarcity of the fossil record, and different methodological approaches have led to contradictory hypotheses. In an effort to explore questions about their extinction, we developed a novel multi‐model statistical approach to analyse all of the currently available data at a continental scale. Using multiple regression analysis and new advances in beta diversity analysis, we used all currently available fossil data at a continental scale to test four competing hypotheses to account for the decline of sparassodontans: competition with placental carnivorans, competition with avian phorusrhacids, non‐competitive ecological interactions, and environmental fluctuations. Our results show that the sparassodontan extinction was a gradual process with species disappearing throughout the Cenozoic. Multiple regression analysis supported non‐competitive ecological interactions as the best extinction model. Native South American ungulates, African migrants (caviomorph rodents and platyrrhine primates) and didelphimorphians were the groups with the highest statistical significance. Sparassodontan beta diversity increased between South American Land Mammal Ages after the Paleocene–Eocene boundary. Our results demonstrate that ecological modelling techniques illuminate aspects of extinction processes whilst mitigating the limitations of the fossil record. Our study suggests that non‐competitive ecological interactions could have been the main driver for sparassodontan extinction rather than, as commonly assumed, a result of competition and/or abiotic fluctuations.     

Exploring the phylogenetic history of mammal species richness

Aim At broad geographical scales, species richness is a product of three basic processes: speciation, extinction and migration. However, determining which of these processes predominates is a major challenge. Whilst palaeontological studies can provide information on speciation and extinction rates, data are frequently lacking. Here we use a recent dated phylogenetic tree of mammals to explore the relative importance of these three processes in structuring present‐day richness gradients. Location The global terrestrial biosphere. Methods We combine macroecological data with phylogenetic methods more typically used in community ecology to describe the phylogenetic history of regional faunas. Using simulations, we explore two simple phylogenetic metrics, the mean and variance in the pairwise distances between taxa, and describe their relationship to phylogenetic tree topology. We then use these two metrics to characterize the evolutionary relationships among mammal species assemblages across the terrestrial biome. Results We show that the mean and variance in the pairwise distances describe phylogenetic tree topology well, but are less sensitive to phylogenetic uncertainty than more direct measures of tree shape. We find the phylogeny for South American mammals is imbalanced and ‘stemmy’ (long branches towards the root), consistent with recent diversification within evolutionarily disparate lineages. In contrast, the phylogeny for African mammals is balanced and ‘tippy’ (long branches towards the tips), more consistent with the slow accumulation of diversity over long times, reflecting the Old World origin of many mammal clades. Main conclusions We show that phylogeny can accurately capture biogeographical processes operating at broad spatial scales and over long time periods. Our results support inferences from the fossil record – that the New World tropics are a diversity cradle whereas the Old World tropics are a museum of old diversity.     

That awkward age for butterflies: insights from the age of the butterfly subfamily Nymphalinae (Lepidoptera: Nymphalidae)

The study of the historical biogeography of butterflies has been hampered by a lack of well-resolved phylogenies and a good estimate of the temporal span over which butterflies have evolved. Recently there has been surge of phylogenetic hypotheses for various butterfly groups, but estimating ages of divergence is still in its infancy for this group of insects. The main problem has been the sparse fossil record for butterflies. In this study I have used a surprisingly good fossil record for the subfamily Nymphalinae (Lepidoptera: Nymphalidae) to estimate the ages of diversification of major lineages using Bayesian relaxed clock methods. I have investigated the effects of varying priors on posterior estimates in the analyses. For this data set, it is clear that the prior of the rate of molecular evolution at the ingroup node had the largest effect on the results. Taking this into account, I have been able to arrive at a plausible history of lineage splits, which appears to be correlated with known paleogeological events. The subfamily appears to have diversified soon after the K/T event about 65 million years ago. Several splits are coincident with major paleogeological events, such as the connection of the African and Asian continents about 21 million years ago and the presence of a peninsula of land connecting the current Greater Antilles to the South American continent 35 to 33 million years ago. My results suggest that the age of Nymphalidae is older than the 70 million years speculated to be the age of butterflies as a whole.     

Historical phytogeography of the Greater Antilles

An understanding of the phytogeographic history of a region depends upon an adequate fossil record to reveal migrational histories and the timing and directions(s) of introductions and extinctions, and to augment or circumvent undue reliance on molecular clocks. It further depends upon an accurate phylogeny of the taxa to establish real patterns of geographic affinities (phylogeography), and a relatively detailed geologic history to assess the relative roles of dispersal and vicariance in populating the islands. For the Greater Antilles new information is slowly emerging on the plant fossil record through study of new floras such as the Eocene Saramaguacán palynoflora from Cuba, and more is potentially available from the middle Oligocene San Sebastian megafossil flora of Puerto Rico that has not been revised since the early 1900s. Phylogeographic studies and area cladograms are still meager for plants, but data from various animal groups are providing a context for the general biotic history of the Antilles. Perhaps the area of greatest advance is being made in achieving an adequate plate tectonic model for the Caribbean region. There is now some convergence toward a mobilist model that depicts a Cretaceous volcanic island arc that extended from the Mexico/Chortis block in the north to Ecuador in the south, and gradually moved through the developing portal between North and South America to collide with the Bahamas Platform in the middle Eocene. Throughout this 70-million-year history there was an immensely complex pattern of collision/separation and submergence/emergence that provided opportunity both for vicariance and dispersal in the migration, evolution, and speciation of the flora of the Greater Antilles.     

Major issues in the origins of ray‐finned fish (Actinopterygii) biodiversity

Ray‐finned fishes (Actinopterygii) dominate modern aquatic ecosystems and are represented by over 32000 extant species. The vast majority of living actinopterygians are teleosts; their success is often attributed to a genome duplication event or morphological novelties. The remainder are ‘living fossils’ belonging to a few depauperate lineages with long‐retained ecomorphologies: Polypteriformes (bichirs), Holostei (bowfin and gar) and Chondrostei (paddlefish and sturgeon). Despite over a century of systematic work, the circumstances surrounding the origins of these clades, as well as their basic interrelationships and diagnoses, have been largely mired in uncertainty. Here, I review the systematics and characteristics of these major ray‐finned fish clades, and the early fossil record of Actinopterygii, in order to gauge the sources of doubt. Recent relaxed molecular clock studies have pushed the origins of actinopterygian crown clades to the mid‐late Palaeozoic [Silurian–Carboniferous; 420 to 298 million years ago (Ma)], despite a diagnostic body fossil record extending only to the later Mesozoic (251 to 66 Ma). This disjunct, recently termed the ‘Teleost Gap’ (although it affects all crown lineages), is based partly on calibrations from potential Palaeozoic stem‐taxa and thus has been attributed to poor fossil sampling. Actinopterygian fossils of appropriate ages are usually abundant and well preserved, yet long‐term neglect of this record in both taxonomic and systematic studies has exacerbated the gaps and obscured potential synapomorphies. At the moment, it is possible that later Palaeozoic‐age teleost, holostean, chondrostean and/or polypteriform crown taxa sit unrecognized in museum drawers. However, it is equally likely that the ‘Teleost Gap’ is an artifact of incorrect attributions to extant lineages, overwriting both a post‐Palaeozoic crown actinopterygian radiation and the ecomorphological diversity of stem‐taxa.     

Phylogeny and biogeography of tropical carnivorous land‐snails (Pulmonata: Streptaxoidea) with particular reference to East Africa and the Indian Ocean

Rowson, B., Tattersfield, P. & Symondson, W. O. C. (2010). Phylogeny and biogeography of tropical carnivorous land‐snails (Pulmonata: Streptaxoidea) with particular reference to East Africa and the Indian Ocean. —Zoologica Scripta, 40, 85–98. A phylogeny is presented for the speciose, near pan‐tropical, carnivorous achatinoid land‐snail superfamily Streptaxoidea inferred from DNA sequences (two nuclear and two mitochondrial regions) from 114 taxa from Africa, the Indian Ocean, Asia, South America and Europe. In all analyses, Streptaxidae are monophyletic, while the (two to six) previously recognised subfamilies are polyphyletic, as are several genus‐level taxa including the most speciose genus Gulella, necessitating major taxonomic review. The Asian Diapheridae are sister to Streptaxidae, which forms several well‐supported clades originating in a persistent basal polytomy. Divergence dating estimates, historical biogeography, and the fossil context suggest a Cretaceous origin of these families, but suggest Gondwanan vicariance predated most radiation. The basal polytomy dates to the Paleogene and may correspond to a rapid radiation in Africa. There is evidence for multiple Cenozoic dispersals followed by radiation, including at least two from Africa to South America, at least two from Africa to Asia and at least two from Africa to Madagascar, indicating Cenozoic turnover in tropical snail faunas. The endemic Seychelles and Mascarene streptaxid faunas each are composites of early Cenozoic lineages and more recent dispersals from Africa, with no direct evidence for an Asian origin as currently proposed. Peak streptaxid diversity in East Africa is explained by Neogene speciation among a large number of coexisting ancient lineages, a phenomenon most pronounced in the Eastern Arc‐Coastal Forests centre of endemism. This includes Miocene diversification in Gulella, a primarily East and South‐East African group which remains strikingly diverse even after unrelated ‘Gulella’ species are reclassified.     

History and the species-area relationship in Lesser Antillean birds

We examined the species-area relationship for three historically distinct subsets of Lesser Antillean birds identified by molecular phylogenetic analysis of island and continental populations. The groups comprised recent colonists from continental or Greater Antillean source populations, old taxa having recently expanded distributions within the Lesser Antilles, and old endemic taxa lacking evidence of recent dispersal between islands. The number of young taxa was primarily related to distance from the source of colonists in South America. In a multiple regression, the logarithmic slope of the species-area relationship for this group was shallow (0.066+/-0.016). Old endemic taxa were restricted to islands with high elevation, and within this subset, species richness was related primarily to island area, with a steep slope (0.719+/-0.110). The number of recently spread endemic taxa was related primarily to island elevation, apparently reflecting the persistence of such populations on islands with large areas of forested and montane habitats. Historical analysis of the Lesser Antillean avifauna supports the dynamic concept of island biogeography of MacArthur and Wilson, rather than the more static view of David Lack, in that colonists exhibit dispersal limitation and extinction plays a role in shaping patterns of diversity. However, the avifauna of the Lesser Antilles is probably not in equilibrium at present, and the overall species-area relationship might reflect changing proportions of historically distinguishable subsets of species.     

Diversity and biogeography of the Antarctic flora

Aim To establish how well the terrestrial flora of the Antarctic has been sampled, how well the flora is known, and to determine the major patterns in diversity and biogeography. Location Antarctica south of 60° S, together with the South Sandwich Islands, but excluding South Georgia, Bouvetøya and the periantarctic islands. Methods Plant occurrence data were collated from herbarium specimens and literature records, and assembled into the Antarctic Plant Database. Distributional patterns were analysed using a geographic information system. Biogeographical patterns were determined with a variety of multivariate statistics. Results Plants have been recorded from throughout the Antarctic, including all latitudes between 60° S and 86° S. Species richness declines with latitude along the Antarctic Peninsula, but there was no evidence for a similar cline in Victoria Land and the Transantarctic mountains. Multi‐dimensional scaling ordinations showed that the species compositions of the South Orkney, South Shetland Islands and the north‐western Antarctic Peninsula are very similar to each other, as are the floras of different regions in continental Antarctica. They also suggest, however, that the eastern Antarctic Peninsula flora is more similar to the flora of the southern Antarctic Peninsula than to the continental flora (with which it has traditionally been linked). The South Sandwich Islands have a flora that is very dissimilar to that in all Antarctic regions, probably because of their isolation and volcanic nature. Main conclusions The Antarctic flora has been reasonably well sampled, but certain areas require further floristic surveys. Available data do, however, allow for a number of robust conclusions. A diversity gradient exists along the Antarctic Peninsula, with fewer species (but not fewer higher taxa) at higher latitudes. Multi‐dimensional scaling ordination suggests three major floral provinces within Antarctica: northern maritime, southern maritime, and continental. Patterns of endemism suggest that a proportion of the lichen flora may have an ancient vicariant distribution, while most bryophytes are more recent colonists.     

Molecular dating and diversification of the South American lizard genus Liolaemus (subgenus Eulaemus) based on nuclear and mitochondrial DNA sequences

The temperate South American lizard genus Liolaemus is the one of the most widely distributed and species‐rich genera of lizards on earth. The genus is divided into two subgenera, Liolaemus sensu stricto (the ‘Chilean group’) and Eulaemus (the ‘Argentino group’), a division that is supported by recent molecular and morphological data. Owing to a lack of reliable fossil data, previous studies have been forced to use either global molecular clocks, a standardized mutation rate adopted from previous studies, or the use of geological events as calibration points. However, simulations indicate that these types of assumptions may result in less accurate estimates of divergence times when clock‐like models or mutation rates are violated. We used a multilocus data set combined with a newly described fossil to provide the first calibrated phylogeny for the crown groups of the clade Eulaemus, and derive new fossil‐calibrated substitution rates (with error) of both nuclear and mtDNA gene regions for Eulaemus specifically. Divergence date estimates for each of the crown groups and appropriate rate estimates will provide the foundation for understanding rates of speciation, historical biogeography, and phylogeographical history for various clades in one of the most diverse lizard genera in the poorly studied Patagonian region. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 825–835.