Molecular evidence for long distance dispersal across the Southern Hemisphere in the Ganoderma applanatum-australe species complex (Basidiomycota)

We examined phylogeographic relationships in the cosmopolitan polypore fungus Ganoderma applanatum and allies, and conservatively infer a possible age of origin for these fungi. Results indicate that it is very unlikely that members of this species complex diversified before the break-up of Gondwana from Laurasia ca 120 M years ago, and also before the final separation of the Gondwanan landmasses from each other that was achieved about 66 M years ago. An earliest possible age of origin of 30 M years was estimated from nucleotide substitution rates in the 18S rDNA gene. Phylogenetic reconstruction of a worldwide sampling of ITS rDNA sequences reveals at least eight distinct clades that are strongly correlated with the geographic origin of the strains, and also correspond to mating groups. These include one Southern Hemisphere clade, one Southern Hemisphere–Eastern Asia clade, two temperate Northern Hemisphere clades, three Asian clades, and one neotropical clade. Geographically distant collections from the Southern Hemisphere shared identical ITS haplotypes, and an ITS recombinant was noted. Nested clade analysis of a parsimony network among isolates of the Southern Hemisphere clade indicated restricted gene flow with isolation-by-distance among the New Zealand, Australia–Tasmania, Chile–Argentine, and South Africa populations, suggesting episodic events of long-distance dispersal within the Southern Hemisphere. This study indicates that dispersal bias plays a more important role than generally admitted to explain the Southern Hemisphere distribution of many taxa, at least for saprobic fungi.     

Phylogenetic analysis of Russian Permian dicynodonts (Therapsida: Anomodontia): implications for Permian biostratigraphy and Pangaean biogeography

Dicynodont therapsids have been known from the Upper Permian of Eastern Europe since the beginning of the twentieth century, but the phylogenetic relationships of these taxa have not been examined cladistically. Here we present the results of a phylogenetic analysis that includes eight Permian dicynodonts from Russia as well as 18 taxa best known from southern Africa. Our results do not conflict with much of the established picture of Permian dicynodont phylogeny, but are consistent with several novel hypotheses. Most importantly, our analysis suggests that the genus Dicynodon is paraphyletic, and we question its use in correlating widely separated basins. However, we cannot strongly reject a monophyletic Dicynodon . Our results also indicate that the closest Permian relatives of Kannemeyeria lived in Russia, suggesting a Laurasian origin for the lineage that includes this important Triassic taxon. The phylogeny presented here also suggests a Laurasian origin for several other dicynodont clades, but a Gondwanan origin is equally likely given the data at hand. Regardless of where these groups originated, there appears to be some endemism among Late Permian dicynodont faunas. Although our understanding of dicynodont phylogeny is improving, this study emphasizes the disparity in sampling of the dicynodont record between Gondwana and Laurasia and the need for a large scale phylogenetic analysis of Permian and Triassic dicynodonts.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society, 2003, 139 , 157−212.     

5. Biogeography of desmids

Compared with other groups of unicellular freshwater algae, desmids lend themselves well to biogeographical studies since, at species level, identification is often relatively easy, whereas high ecological demands use to curtain their geographical distribution. Considering some ten desmid floral regions as distinguished in the beginning of this century, Indo-Malaysia/Northern Australia, tropical America, and equatorial Africa come to the fore as most pronounced. Also well typified are Eastern Asia, New Zealand/Southern Australia, and North America. Less endemic species are met with in Southern Africa and extratropical South America, whereas temperate Eurasia, with respect to the other continents, is mainly negatively characterized. The so-called arctic-alpine desmid flora may be encountered on all continents, provided that adequate minimum temperatures occur. Its distribution seems to be determined microclimatologically rather than macroclimatologically. Arguments for a tropical origin of the desmids as an algal group are adduced.     

On the Distribution and Origin of Salix in the World

1. The distribution of Salix species among the continents. There are about 526 species of Salix in the world, most of which are distributed in the Northern Hemisphere with only a few species in the Southern Hemisphere. In Asia, there are about 375 species, making up 71.29 percent of the total in the world, including 328 endemics; in Europe, about 114 species, 21.67 percent with 73 endemics; in North America, about 91 species, 17.3 percent with 71 endemics; in Africa, about 8 species, 1.5 percent, with 6 endemics. Only one species occurs in South America. Asia, Europe and North America have 8 species in common (excluding 4 cultivated species). There are 34 common species between Asia and Europe, 14 both between Europe and North America and between Asia and North America, 2 between Asia and Africa. Acording to the Continental Drift Theory, the natural circumstances which promoted speciation and protected newly originated and old species were created by the orogenic movement of the Himalayas in the middle and late Tertiary. Besides, the air temperature was a little higher in Asia than in Europe and North America (except its west part) and the dominant glaciers were mountainous in Asia during the glacial epoch in the Quaternary Period. Then willows of Europe moved southwards to Asia. During the interglacial period they moved in opposite direction. Such a to-and-fro willow migration between Asia and Europe and between and North America occurred so often that it resulted in the diversity of willow species in Asia. Those species of willows common among the continents belong to the Arctic flora. 2. The multistaminal willows are of the primitive group in Salix. Asia has 28 species of multistaminal willows, but Europe has only one which is also found in Asia. These 28 species are divided into two groups, “northern type” and “southern type”, according to morphology of the ovary. The boundary between the two forms in distribution is at 40°N. The multistaminal willows from south Asia, Africa and South America are very similar to each other and may have mutually communicated between these continents in the Middle or Late Cretaceous Period. The southern type willows in south Asia are similar to the North American multistaminal willows but a few species. The Asian southern type willows spreaded all over the continents of Europe, Asia and North America through the communication between them before the Quaternany Period. Nevertheless, it is possible that the willows growing in North America immigranted through the middle America from South America. The Asian northern type multistaminal willows may have originated during the ice period. The multistaminal willows are more closed to populars in features of sexual organs. They are more primitive than the willows with 1-3 stamens and the most primitive ones in the genus. 3. The center of origin and development of willows Based on the above discussion it is reasonable to say that the region between 20°-40°N in East Asia is the center of the origin and differentiation of multistaminal willows. It covers Southern and Southwestern China and northern Indo-China Pennisula.     

Novel methods reveal shifts in migration phenology of barn swallows in South Africa

Many migratory bird species, including the barn swallow (Hirundo rustica), have advanced their arrival date at Northern Hemisphere breeding grounds, showing a clear biotic response to recent climate change. Earlier arrival helps maintain their synchrony with earlier springs, but little is known about the associated changes in phenology at their non-breeding grounds. Here, we examine the phenology of barn swallows in South Africa, where a large proportion of the northern European breeding population spends its non-breeding season. Using novel analytical methods based on bird atlas data, we show that swallows first arrive in the northern parts of the country and gradually appear further south. On their north-bound journey, they leave South Africa rapidly, resulting in mean stopover durations of 140 days in the south and 180 days in the north. We found that swallows are now leaving northern parts of South Africa 8 days earlier than they did 20 years ago, and so shortened their stay in areas where they previously stayed the longest. By contrast, they did not shorten their stopover in other parts of South Africa, leading to a more synchronized departure across the country. Departure was related to environmental variability, measured through the Southern Oscillation Index. Our results suggest that these birds gain their extended breeding season in Europe partly by leaving South Africa earlier, and thus add to scarce evidence for phenology shifts in the Southern Hemisphere.     

ITS sequence data support a single origin for North American Astereae (Asteraceae) and reflect deep geographic divisions in Aster s.l

The Astereae is the largest tribe of Asteraceae in North America. Morphological diversity suggests that the North American assemblage is polyphyletic as 12 endemic genera, as well as lineages of the genus Erigeron and Conyza (Conyzinae), have been hypothesized to represent at least five separate invasions of North America from Africa, Australia, Eurasia, and South America. This hypothesis was tested with a phylogenetic analysis of nucleotide sequence data from the internal transcribed spacers (ITS) of nuclear ribosomal DNA. Sequences for 62 taxa represent seven outgroup taxa and all major Northern and Southern Hemisphere groups of Astereae, including broad taxonomic and geographic sampling of Conyzinae and Aster s.l. (sensu lato). Parsimony analyses indicate that all North American Astereae are members of a strongly supported clade, and that a diverse group of predominantly woody taxa from Africa, Australia, and South America, are basal Astereae. Furthermore, Aster s.l. is deeply polyphyletic as Eurasian taxa, including Aster s.s. (sensu stricto), appear more closely related to Southern Hemisphere taxa than to North American Aster segregates. There is only low to moderate agreement between proposed higher level Astereae relationships based on ITS and those based either on morphology or chloroplast restriction site data.     

Biogeography of ‘tropical Anagallis’ (Myrsinaceae) inferred from nuclear and plastid DNA sequence data

Aim ‘Tropical Anagallis’ corresponds to one of two evolutionary lineages within the genus Anagallis L. Generally, species within this lineage have a limited distribution in (sub‐)tropical regions in Africa or Madagascar. Two species, however, are endemic to South America, and exhibit a trans‐Atlantic disjunction with the rest of the species within the lineage. To investigate this disjunct distribution, as well as other dispersal events, the distribution of extant taxa was used to hypothesize the ancestral area(s) of distribution. Location Africa, Madagascar, Europe and South America. Methods Dispersal–vicariance analysis (DIVA) was used to optimize distribution areas onto parsimony and Bayesian phylogenies based on sequence data from four chloroplast loci and the nuclear internal transcribed spacers (ITS). Results Parsimony analysis gave one most parsimonious tree while Bayesian analysis resulted in a collapsed node due to alternative placements of Anagallis nummularifolia Baker, endemic to Madagascar. Optimization of the present distribution using DIVA, and the most parsimonious tree and six alternative topologies of the Bayesian analysis, show an origin of the lineage in Europe as most likely, although one topology indicates a broader ancestral distribution area. Dispersal to Africa appears to have been a single event, while two parallel dispersal events seem to have resulted in the American as well as Madagascan distributions. Main conclusions The lineage ‘tropical Anagallis’ evolved in Europe and may have been present in the Eocene boreotropical forests, although scarcity of fossils makes assessment of age difficult. Dispersal to South America is proposed to have been via the North Atlantic land bridge, or, more likely, through transport by the North Equatorial Current. Dispersal from Europe to Africa represents a single event, while dispersal to Madagascar from mainland Africa has occurred twice.     

The most basal anomodont therapsid and the primacy of Gondwana in the evolution of the anomodonts

A new specimen from the base of the Beaufort Group, Upper Permian of South Africa, represents a new therapsid (''mammal-like reptile'') which has been identified as the most basal (''primitive'') member of the Anomodontia. Anomocephalus africanus gen. et sp. nov. is based upon a partial skull that exhibits several characteristic anomodont synapomorphies including the presence of isodont marginal teeth and a dorsally bowed zygoma, but is distinguished from other anomodonts by the possession of peg-like marginal dentition with oblique wear facets on the tips of the teeth. Anomocephalus is excluded from a clade comprised of all other anomodonts as (i) the snout is relatively long, (ii) the vertically aligned zygomatic process of the squamosal is blade-like, and (iii) the squamosal does not contact the ventral tip of the postorbital. The basal position of Anomocephalus, together with its South African occurrence, strongly supports the postulate that a Gondwanan distribution was ancestral for anomodonts.     

A new basal dicynodont from the Upper Permian of South Africa

The skull of a small anomodont therapsid, from the Tapinocephalus Assemblage Zone (Abrahamskraal Formation, Beaufort Group, Upper Permian) in Northern Cape Province, South Africa, represents a new basal dicynodont and is described in detail. Colobodectes cluveri gen. et sp. nov. is distinguished from other dicynodonts by an anteroposteriorly extensive caniniform process, parietals that were broadly overlapped posterolaterally by posterodorsal processes of the postorbitals, diverging anterior palatal ridges, and a dorsoventrally low foramen magnum. A phylogenetic analysis indicates that Colobodectes is the basalmost member of a dicynodont clade that excludes Eodicynodon . This position is not particularly strong, as two additional steps are needed to make Colobodectes and Eodicynodon oosthuizeni exchange places on the most parsimonious tree. Another discovery of the phylogenetic analysis is that there is little basis for recognizing Eodicynodon oelofseni as the closest relative of E. oosthuizeni . The former species is identified as the sister taxon of a clade that includes the latter and all other dicynodonts.     

Phylogeny of the sundews, Drosera (Droseraceae), based on chloroplast rbcL and nuclear 18S ribosomal DNA Sequences

The sundew genus Drosera consists of carnivorous plants with active flypaper traps and includes nearly 150 species distributed mainly in Australia, Africa, and South America, with some Northern Hemisphere species. In addition to confused intrageneric classification of Drosera, the intergeneric relationships among the Drosera and two other genera in the Droseraceae with snap traps, Dionaea and Aldrovanda, are problematic. We conducted phylogenetic analyses of DNA sequences of the chloroplast rbcL gene for 59 species of Drosera, covering all sections except one. These analyses revealed that five of 11 sections, including three monotypic sections, are polyphyletic. Combined rbcL and 18S rDNA sequence data were used to infer phylogenetic relationships among Drosera, Dionaea, and Aldrovanda. This analysis revealed that all Drosera species form a clade sister to a clade including Dionaea and Aldrovanda, suggesting that the snap traps of Aldrovanda and Dionaea are homologous despite their morphological differences. MacClade reconstructions indicated that multiple episodes of aneuploidy occurred in a clade that includes mainly Australian species, while the chromosome numbers in the other clades are not as variable. Drosera regia, which is native to South Africa, and most species native to Australia, were clustered basally, suggesting that Drosera originated in Africa or Australia. The rbcL tree indicates that Australian species expanded their distribution to South America and then to Africa. Expansion of distribution to the Northern Hemisphere from the Southern Hemispere occurred in a few different lineages.     

Population structure and diversity of an invasive pine needle pathogen reflects anthropogenic activity

Dothistroma septosporum is a haploid fungal pathogen that causes a serious needle blight disease of pines, particularly as an invasive alien species on Pinus radiata in the Southern Hemisphere. During the course of the last two decades, the pathogen has also incited unexpected epidemics on native and non‐native pine hosts in the Northern Hemisphere. Although the biology and ecology of the pathogen has been well documented, there is a distinct lack of knowledge regarding its movement or genetic diversity in many of the countries where it is found. In this study we determined the global population diversity and structure of 458 isolates of D. septosporum from 14 countries on six continents using microsatellite markers. Populations of the pathogen in the Northern Hemisphere, where pines are native, displayed high genetic diversities and included both mating types. Most of the populations from Europe showed evidence for random mating, little population differentiation and gene flow between countries. Populations in North America (USA) and Asia (Bhutan) were genetically distinct but migration between these continents and Europe was evident. In the Southern Hemisphere, the population structure and diversity of D. septosporum reflected the anthropogenic history of the introduction and establishment of plantation forestry, particularly with Pinus radiata. Three introductory lineages in the Southern Hemisphere were observed. Countries in Africa, that have had the longest history of pine introductions, displayed the greatest diversity in the pathogen population, indicating multiple introductions. More recent introductions have occurred separately in South America and Australasia where the pathogen population is currently reproducing clonally due to the presence of only one mating type.     

Late Permian dicynodonts of Eastern Europe

The data on morphology and systematics of Late Permian dicynodonts of Eastern Europe are considered. The taxonomic position of dicynodonts and probable evolutionary trends in their development are discussed.     

A remarkable assemblage of terrestrial tetrapods from the Zechstein (Upper Permian: Tatarian) near Korbach (northwestern Hesse)

We present a preliminary report on the first diverse central European assemblage of Late Permian terrestrial tetrapods from a fissure-filling in marine sediments of the lower Zechstein near Korbach (northwestern Hesse, Germany). It includes therapsids (cynodonts and dicynodonts), archosauromorph diapsids, and pareiasaurs. Similar assemblages were previously known only from the Upper Permian of Russia, Scotland, and South and East Africa. The occurrence of the basal cynodontProcynosuchus is paleobiogeographically significant because this taxon was previously known only from theDicynodon lacerticeps-Whaitsia assemblage zone of South Africa and the Madumabisa Mudstone of Zambia. The geological context of the Korbach site permits a rather precise chronostratigraphic placement of the tetrapod assemblage in the interval between Zechstein 1 and 3. The Korbach tetrapod assemblage is late Tatarian in age.     

The first records of Stylodrilus heringianus (Oligochaeta: Lumbriculidae) from the Southern Hemisphere

Abstract

The oligochaete family Lumbriculidae is well represented in the Northern Hemisphere, but for the Southern Hemisphere only Lumbriculus variegatus (Müller) is recorded, from Africa, Australia, and New Zealand; no species are known from South America (Brinkhurst & Jamieson 1971). According to Brinkhurst (1971), L. variegatus may be a recent introduction to New Zealand, where it is now widely distributed in a range of inland waters.     

Amphitropic amphiantarctic disjunctions in Apiaceae subfamily Apioideae

Aim Four genera of the plant family Apiaceae subfamily Apioideae –Apium, Chaerophyllum, Daucus and Lilaeopsis– are characterized by amphitropic and amphiantarctic distribution patterns, and in Australasia the subfamily is also represented by the tribe Aciphylleae. We infer the molecular ages of achieving amphitropic distribution for these lineages, reconstruct the biogeographical histories of Apium, Chaerophyllum, Daucus and Lilaeopsis, and identify the sister group of Aciphylleae. Location Worldwide, with an emphasis on South America and Australasia. Methods Divergence times were estimated employing a Bayesian approach (beast ) with fossil pollen of basal apioids as calibration points and using a data set of nuclear ribosomal DNA internal transcribed spacer (nrDNA ITS) sequences from 284 accessions of Apioideae. Additionally, maximum‐likelihood analyses were performed for data subsets comprising Apium, Daucus and Lilaeopsis. For Chaerophyllum, maximum‐likelihood and beast analyses were carried out using combined chloroplast DNA and ITS data. Biogeographical scenarios were inferred using diva and lagrange . Results The sister group to Aciphylleae is the Sino‐Himalayan Acronema clade and the divergence between these two lineages is dated at 34.8 Ma, whereas the radiation of Aciphylleae started 11.0 Ma. A Northern Hemispheric origin was inferred for Apium, Chaerophyllum and Daucus, whereas Lilaeopsis probably originated in South America following a dispersal of its ancestor from North America. Chaerophyllum, Daucus and Lilaeopsis dispersed to the Southern Hemisphere at 5.3, 7.0 and 27.9 Ma, respectively. For Apium, two dispersals from Europe were inferred: to South America at 6.3 Ma, and to southern Africa at 3.9 Ma. The taxa migrated along the land masses of North and South America (Daucus, Lilaeopsis) and Africa (Apium) or by direct transoceanic dispersals through the Atlantic (Apium) or the Pacific (Chaerophyllum). Within the Southern Hemisphere they dispersed both westwards (Apium, Daucus, Lilaeopsis) and eastwards (Chaerophyllum, Lilaeopsis). For Chaerophyllum and Lilaeopsis, subsequent dispersal events to the Northern Hemisphere were also inferred. Main conclusions Similar timing, contrasted with the diversity of migration routes, suggests that the dispersal events of these umbellifer taxa (and many other amphitropic amphiantarctic genera) were facilitated by favourable ecological conditions in the Southern Hemisphere (climatic cooling of the late Palaeogene/early Neogene) rather than by increased dispersal opportunities.     

A molecular investigation of the genus Ecklonia (Phaeophyceae,Laminariales) with special focus on the Southern Hemisphere

Brown algae of the order Laminariales, commonly referred to as kelps, are the largest and most productive primary producers in the coastal inshore environment. The genus Ecklonia (Lessoniaceae, Phaeophyceae) consists of seven species with four species in the Northern Hemisphere and three in the Southern Hemisphere. It was recently transferred to the family Lessoniaceae based on phylogenetic analyses of nuclear and chloroplastic markers, though the type of the genus was not included and its relationship with allied genera Eckloniopsis and Eisenia remained unresolved. The present study is the first to produce a phylogeny focussed on the genus Ecklonia. It included sequences from nuclear, mitochondrial, and chloroplastic DNA, for most of the distribution range of the three current Southern Hemisphere species (Ecklonia radiata, Ecklonia maxima, and a sample of a putative Ecklonia brevipes specimen), sequences for East Asiatic species (Ecklonia cava, Ecklonia kurome, and Ecklonia stolonifera), as well as the closely related genera Eckloniopsis and Eisenia. Results confirmed E. radiata and E. maxima as two distinct species in South Africa, E. radiata as a single species throughout the Southern Hemisphere (in South Africa, Australia, and New Zealand) and East Asiatic species as a distinct lineage from the Southern Hemisphere clade. Results further pointed out a close sister relationship between Eckloniopsis radicosa and two Eisenia species (including the type species: Eisenia arborea) to the genus Ecklonia suggesting that the genera Eckloniopsis and Eisenia are superfluous.     

Phylogeny and biogeography of Caltha (Ranunculaceae) based on chloroplast and nuclear DNA sequences

The genus Caltha (Ranunculaceae) consists of 10 species of low-growing, perennial herbs distributed throughout the moist temperate and cold regions of both the Northern and Southern Hemispheres. Traditionally, the species have been divided into two sections: section Psychrophila in the Southern Hemisphere with diplophyllous leaves and section Caltha in the Northern Hemisphere with leaves lacking inflexed appendages. This study uses chloroplast and nuclear DNA sequences to determine the relationships among the 10 species, test the monophyly of sections Psychrophila and Caltha, trace the evolutionary history of diplophylly, and explore biogeographical hypotheses for the genus. Analysis of these data resulted in a well-resolved and well-supported phylogeny. Section Psychrophila (C. sagittata, C. appendiculata, C. dionaeifolia, C. obtusa, C. introloba, and C. novae-zelandiae) was resolved as monophyletic, indicating a single origin of diplophylly. The species of section Caltha (C. natans, C. scaposa, C. palustris, and C. leptosepala) formed a paraphyletic grade. The resulting phylogeny strongly supports a Northern Hemisphere origin for Caltha, followed by dispersal to the Southern Hemisphere (Gondwanaland). A vicariance model is invoked to explain present-day distributions in South America, Australia, and New Zealand.     

Invasive blue mussels threaten regional scale genetic diversity in mainland and remote offshore locations: the need for baseline data and enhanced protection in the Southern Ocean

Human‐mediated biological transfers of species have substantially modified many ecosystems with profound environmental and economic consequences. However, in many cases, invasion events are very hard to identify because of the absence of an appropriate baseline of information for receiving sites/regions. In this study, use of high‐resolution genetic markers (single nucleotide polymorphisms – SNPs) highlights the threat of introduced Northern Hemisphere blue mussels (Mytilus galloprovincialis) at a regional scale to Southern Hemisphere lineages of blue mussels via hybridization and introgression. Analysis of a multispecies SNP dataset reveals hotspots of invasive Northern Hemisphere blue mussels in some mainland New Zealand locations, as well as the existence of unique native lineages of blue mussels on remote oceanic islands in the Southern Ocean that are now threatened by invasive mussels. Samples collected from an oil rig that has moved between South Africa, Australia, and New Zealand were identified as invasive Northern Hemisphere mussels, revealing the relative ease with which such non‐native species may be moved from region to region. In combination, our results highlight the existence of unique lineages of mussels (and by extension, presumably of other taxa) on remote offshore islands in the Southern Ocean, the need for more baseline data to help identify bioinvasion events, the ongoing threat of hybridization and introgression posed by invasive species, and the need for greater protection of some of the world's last great remote areas.     

DNA bar-coding reveals source and patterns of <Emphasis Type="Italic">Thaumastocoris peregrinus</Emphasis> invasions in South Africa and South America

Thaumastocoris peregrinus is a recently introduced invertebrate pest of non-native Eucalyptus plantations in the Southern Hemisphere. It was first reported from South Africa in 2003 and in Argentina in 2005. Since then, populations have grown explosively and it has attained an almost ubiquitous distribution over several regions in South Africa on 26 Eucalyptus species. Here we address three key questions regarding this invasion, namely whether only one species has been introduced, whether there were single or multiple introductions into South Africa and South America and what the source of the introduction might have been. To answer these questions, bar-coding using mitochondrial DNA (COI) sequence diversity was used to characterise the populations of this insect from Australia, Argentina, Brazil, South Africa and Uruguay. Analyses revealed three cryptic species in Australia, of which only T. peregrinus is represented in South Africa and South America. Thaumastocoris peregrinus populations contained eight haplotypes, with a pairwise nucleotide distance of 0.2–0.9% from seventeen locations in Australia. Three of these haplotypes are shared with populations in South America and South Africa, but the latter regions do not share haplotypes. These data, together with the current distribution of the haplotypes and the known direction of original spread in these regions, suggest that at least three distinct introductions of the insect occurred in South Africa and South America before 2005. The two most common haplotypes in Sydney, one of which was also found in Brisbane, are shared with the non-native regions. Sydney populations of T. peregrinus, which have regularly reached outbreak levels in recent years, might thus have served as source of these three distinct introductions into other regions of the Southern Hemisphere.     

Do extraordinarily high growth rates in Permo‐Triassic dicynodonts (Therapsida,Anomodontia) explain their success before and after the end‐Permian extinction?

Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo‐Triassic. They include Lystrosaurus, one of the few taxa known to survive the end‐Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end‐Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end‐Permian extinction and its dominance during the postextinction recovery period. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 341–365.