Allochronic taxa as an alternative model to explain circumantarctic disjunctions

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

The importance of looking at small-scale patterns when inferring Gondwanan biogeography: a case study of the centipede Paralamyctes (Chilopoda, Lithobiomorpha, Henicopidae)

Gondwanan biogeography has fascinated zoologists and botanists for over a century, but most biogeographical work has used continent-scale areas as analytical units. More finely resolved patterns, as can be obtained from small invertebrates with limited dispersal abilities, will be obscured in those studies. A common case is treating Australia as a single biogeographical region. In the present study, the necessity of splitting Australia into multiple microareas is demonstrated using centipedes as an example. The lithobiomorph centipede Paralamyctes is distributed on fragments of Gondwana, with species in southern Africa, Madagascar, southern India, Patagonia, eastern Australia, and New Zealand. A cladogram for Paralamyctes is based on morphology and sequences for four molecular markers for 30 terminals that sample 20 of 26 known ingroup species and four outgroups. Analysis with direct optimization across a range of indel costs and transversion : transition cost ratios identifies two main clades: Paralamyctes ( Paralamyctes ) unites species from southern Africa, Madagascar, tropical and warm temperate Australia, and New Zealand. The other group includes the temperate Australian/New Zealand Paralamyctes ( Haasiella ) and Paralamyctes ( Thingathinga ) and a Chilean clade. Subtree analysis finds that different parts of Australia have closest affinities to other Gondwanan fragments, and some of these relationships (such as that between north Queensland and New Zealand) are based on taxonomically stable clades. Area delimitation for large continental fragments should use sufficiently fine resolution to test the 'monophyly' of those fragments and attempt to eliminate spurious geographical paralogy.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 65–78.     

Biogeography of limno-terrestrial Tardigrada, with particular reference to the Antarctic fauna

The Tardigrada is a cosmopolitan phylum of pre-Pangaean origin, yet tardigrade families and genera show distinct biogeographic components isolated by two major geological events. Separate Laurasian and Gondwanan familial clusters correlate with the Triassic disintegration of Pangaea, while discrete Antarctic, Australian and New Zealand familial/generic clusters relate to the subsequent Jurassic/Cretaceous disintegration of Gondwana.     

An asymmetry in niche conservatism contributes to the latitudinal species diversity gradient in New World vertebrates

The Tropical Niche Conservatism hypothesis is a leading explanation for why biodiversity increases towards the equator. The model suggests that most lineages have tropical origins, with few dispersing into temperate regions. However, biotas are comprised of lineages with differing geographical origins, thus it is unclear whether lineages that originated on different continents will exhibit similar patterns of niche conservatism. Here, we summarised biogeographical patterns of New World vertebrates and compared species diversity patterns between families that originated in North and South America. Overall, families with southern origins exhibit niche conservatism with many lineages restricted to the Neotropics, whereas many northern‐origin families are distributed across the Neotropics and the Nearctic. Consequently, northern lineages have contributed to high tropical biodiversity, but southern lineages have contributed relatively little to temperate biodiversity in North America. The asymmetry in niche conservatism between northern and southern lineages is an important contributor to the biodiversity gradient.     

A new global palaeobiogeographical model for the late Mesozoic and early Tertiary

Late Mesozoic palaeobiogeography has been characterized by a distinction between the northern territories of Laurasia and the southern landmasses of Gondwana. The repeated discovery of Gondwanan lineages in Laurasia has led to the proposal of alternative scenarios to explain these anomalous occurrences. A new biogeographical model for late Mesozoic terrestrial ecosystems is here proposed in which Europe and "Gondwanan" territories possessed a common Eurogondwanan fauna during the earliest Cretaceous. Subsequently, following the Hauterivian, the European territories severed from Africa and then connected to Asiamerica resulting in a faunal interchange. This model explains the presence of Gondwanan taxa in Laurasia and the absence of Laurasian forms in the southern territories during the Cretaceous. In order to test this new palaeobiogeographical model, tree reconciliation analyses (TRAs) were performed based on biogeographical signals provided by a supertree of late Mesozoic archosaurs. The TRAs found significant evidence for the presence of an earliest Cretaceous Eurogondwanan fauna followed by a relatively short-term Gondwana-Laurasia dichotomy. The analysis recovered evidence for a biogeographical reconnection of the European territories with Africa and South America-Antarctica during the Campanian to Maastrichtian time-slice. This biogeographical scenario appears to continue through the early Tertiary and sheds light on the trans-Atlantic disjunct distributions of several extant plant and animal groups.     

A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous.     

Biogeography of the Monimiaceae (Laurales): a role for East Gondwana and long‐distance dispersal,but not West Gondwana

Aim The biogeography of the tropical plant family Monimiaceae has long been thought to reflect the break‐up of West and East Gondwana, followed by limited transoceanic dispersal. Location Southern Hemisphere, with fossils in East and West Gondwana. Methods We use phylogenetic analysis of DNA sequences from 67 of the c. 200 species, representing 26 of the 28 genera of Monimiaceae, and a Bayesian relaxed clock model with fossil prior constraints to estimate species relationships and divergence times. Likelihood optimization is used to infer switches between biogeographical regions on the highest likelihood tree. Results Peumus from Chile, Monimia from the Mascarenes and Palmeria from eastern Australia/New Guinea form a clade that is sister to all other Monimiaceae. The next‐deepest split is between the Sri Lankan Hortonia and the remaining genera. The African Monimiaceae, Xymalos monospora, then forms the sister clade to a polytomy of five clades: (I) Mollinedia and allies from South America; (II) Tambourissa and allies from Madagascar and the Mascarenes; (III) Hedycarya, Kibariopsis and Leviera from New Zealand, New Caledonia and Australia; (IV) Wilkiea, Kibara, Kairoa; and (V) Steganthera and allies, all from tropical Australasia. Main conclusions Tree topology, fossils, inferred divergence times and ances‐tral area reconstruction fit with the break‐up of East Gondwana having left a still discernible signature consisting of sister clades in Chile and Australia. There is no support for previous hypotheses that the break‐up of West Gondwana (Africa/South America) explains disjunctions in the Monimiaceae. The South American Mollinedia clade is only 28–16 Myr old, and appears to have arrived via trans‐Pacific dispersal from Australasia. The clade apparently spread in southern South America prior to the Andean orogeny, fitting with its first‐diverging lineage (Hennecartia) having a southern‐temperate range. The crown ages of the other major clades (II–V) range from 20 to 29 Ma, implying over‐water dispersal between Australia, New Caledonia, New Zealand, and across the Indian Ocean to Madagascar and the Mascarenes. The endemic genus Monimia on the Mascarenes provides an interesting example of an island lineage being much older than the islands on which it presently occurs.     

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

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

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

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

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 new model Gondwanan taxon: systematics and biogeography of the harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi), with a taxonomic revision of genera from Australia and New Zealand

The phylogeny of the temperate Gondwanan harvestman family Pettalidae is investigated by means of a new morphological matrix of 45 characters, and DNA sequence data from five markers, including two nuclear ribosomal genes (18S rRNA and 28S rRNA), one nuclear protein coding gene (histone H3), and two mitochondrial genes–one protein coding (cytochrome c oxidase subunit I) and one ribosomal (16S rRNA). Phylogenetic analyses using an array of homology schemes (dynamic and static), criteria (parsimony and maximum likelihood), and sampling strategies (optimal trees versus Bayesian phylogenetics) all agree on the monophyly of Pettalidae as well as several of its subclades, each of which is restricted to a modern landmass. While most genera as traditionally defined are monophyletic, Rakaia and Neopurcellia, distributed across Queensland (Australia) and New Zealand, are not. Instead, the species from Queensland, previously described under three genera, constitute a well‐supported clade, suggesting that in this case biogeography prevails over traditional taxonomy. A taxonomic emendation of the genera from Queensland and New Zealand is presented, and the new genus Aoraki is erected to include the species of the New Zealand denticulata group. A biogeographical hypothesis of the relationships of the former temperate Gondwana landmasses (with the exception of Madagascar) is presented, although ambiguity in the deep nodes of the pettalid tree renders such inference provisional. The data suggest that neither the South African fauna, the New Zealand fauna nor the Australian fauna is monophyletic but instead monophyly is found at smaller geographic scales (e.g., Western Australia, Queensland, NE South Africa). © The Willi Hennig Society 2007.     

On the edge of Bantu expansions: mtDNA, Y chromosome and lactase persistence genetic variation in southwestern Angola

Background

Ariids or sea catfishes are one of the two otophysan fish families (out of about 67 families in four orders) that inhabit mainly marine and brackish waters (although some species occur strictly in fresh waters). The group includes over 150 species placed in ~29 genera and two subfamilies (Galeichthyinae and Ariinae). Despite their global distribution, ariids are largely restricted to the continental shelves due in part to their specialized reproductive behavior (i.e., oral incubation). Thus, among marine fishes, ariids offer an excellent opportunity for inferring historical biogeographic scenarios. Phylogenetic hypotheses available for ariids have focused on restricted geographic areas and comprehensive phylogenies are still missing. This study inferred phylogenetic hypotheses for 123 ariid species in 28 genera from different biogeographic provinces using both mitochondrial and nuclear sequences (up to ~4 kb).

Results

While the topologies obtained support the monophyly of basal groups, up to ten genera validated in previous morphological studies were incongruent with the molecular topologies. New World ariines were recovered as paraphyletic and Old World ariines were grouped into a well-supported clade that was further divided into subclades mainly restricted to major Gondwanan landmasses. A general area cladogram derived from the area cladograms of ariines and three other fish groups was largely congruent with the geological area cladogram of Gondwana. Nonetheless, molecular clock estimations provided variable results on the timing of ariine diversification (~105-41 mya).

Conclusion

This study provides the most comprehensive phylogeny of sea catfishes to date and highlights the need for re-assessment of their classification. While from a topological standpoint the evolutionary history of ariines is mostly congruent with vicariance associated with the sequence of events during Gondwanan fragmentation, ambiguous divergence time estimations hinders assessing the vicariant hypothesis on a temporal framework. Further examination of ariid fossils might provide the basis for more accurate inferences on the timing of ariine diversification.     

Historical transoceanic dispersal of a freshwater shrimp: the colonization of the South Pacific by the genus Paratya (Atyidae)

Aim To infer the phylogenetic relationships within the freshwater shrimp genus Paratya Miers, 1882 (Atyidae) and to use these data to answer biogeographical questions about the location, timing and form of evolution of this genus in the South Pacific. Location Paratya are spread throughout various freshwater habitats in the western Pacific, with a disjunct northern range in the North Pacific (Japan, Korea, Ryukyu Islands, Siberia) and South Pacific (Australia, New Zealand, New Caledonia, Lord Howe, Norfolk Island). Methods Specimens were obtained from throughout its range. Mitochondrial sequences of cytochrome oxidase subunit I and 16S ribosomal DNA were analysed using phylogenetic techniques to identify whether landmasses are monophyletic and what the relationships are between landmasses. Molecular clock dating methods were used to date divergences between taxa. Results Each landmass was recovered as monophyletic. Japan/Ryukyu Islands is the most basal group, followed by New Zealand. Australian specimens form a sister group to a clade made up of two groups (New Caledonia and Lord Howe/Norfolk Island). The oldest divergence within the genus (between North and South Pacific) took place 12–19 Ma. Main conclusions The geographical origin of the genus (either Gondwana or Laurasia) is unclear. Dispersal occurred between the North and South Pacific long after the split up of Gondwana. Dispersal likely explains the presence of Paratya on each landmass in the South Pacific, from continent to isolated oceanic island. This dispersal is conjectured to have taken place through oceanic currents because of the amphidromous life cycle of some taxa of Paratya, given that amphyidromy is plesiomorphic in atyid shrimp.     

Process and pattern in the biogeography of New Zealand – a global microcosm?

Aim  To describe New Zealand's historical terrestrial biogeography and place this history in a wider Southern Hemisphere context.
Location  New Zealand.
Methods  The analysis is based primarily on literature on the distributions and relationships of New Zealand's terrestrial flora and fauna.
Results  New Zealand is shown to have a biota that has broad relationships, primarily around the cool Southern Hemisphere, as well as with New Caledonia to the north. There are hints of ancient Gondwanan taxa, although the long-argued predominance of taxa derived by vicariant processes, driven by plate tectonics and the fragmentation of Gondwana, is no longer accepted as a principal explanation of the biota's origins and relationships.
Main conclusions  Most of the terrestrial New Zealand flora and fauna has clearly arrived in New Zealand much more recently than the postulated separation of New Zealand from Gondwana, dated at c. 80 Ma. There is a view that New Zealand may have disappeared completely beneath the sea in the early Cenozoic, and acceptance of this would mean derivation of the entire biota by transoceanic dispersal. However, there are elements in the biota that seem to have broad distributions that date back to Gondwanan times, and also some that are thought unlikely to have been able to disperse to New Zealand across ocean gaps, especially freshwater organisms. Very strong connections to the biota of Australia, rather than to South America, are inconsistent with the timing of New Zealand's ancient and early separation from Gondwana and seem likely to have resulted from dispersal.     

Biogeographical affinities of the New Caledonian biota: a puzzle with 24 pieces

Aim The distributions of many New Caledonian taxa were reviewed in order to ascertain the main biogeographical connections with other areas. Location Global. Methods Panbiogeographical analysis. Results Twenty‐four areas of endemism (tracks) involving New Caledonia and different areas of Gondwana, Tethys and the central Pacific were retrieved. Most are supported by taxa of lower and higher plants, and lower and higher animals. Main conclusions Although parts of New Caledonia were attached to Gondwana for some time in the mid‐Cretaceous, most of the New Caledonian terranes formed as oceanic island arcs and sections of sea floor bearing seamounts. The flora and fauna have evolved and survived for tens of millions of years as metapopulations on ephemeral islands. Later, the biotas were juxtaposed and fused during terrane accretion. This process, together with the rifting of Gondwana, explains the biogeographical affinities of New Caledonia with parts of Gondwana, Tethys and the Pacific.     

Burmese amber: evidence of Gondwanan origin and Cretaceous dispersion

Abstract

Burmese amber is an extremely important source of mid-Cretaceous plant and animal remains with over 870 species of organisms, ranging from protozoa to vertebrates, described from this source. The amber mines are located on the West Burma Block that according to geologists was originally part of Gondwana. The present study introduces some angiosperms and insects in Burmese amber whose closest extant relatives have a Gondwanan distribution and there is no previous evidence of a Laurasian distribution. Based on this evidence, it is proposed that organisms in Burmese amber represent a selection of tropical to subtropical life forms that inhabited the interconnected continents of Gondwana in the Early Cretaceous. Based on the fossil record of angiosperms and their diversity in Burmese amber, the West Burma Block could not have rafted from Gondwana to SE Asia before the Early Cretaceous.     

Phylogeny and historical biogeography of Gondwanan moss-bugs (Insecta: Hemiptera: Coleorrhyncha: Peloridiidae)

The moss bugs of the Peloridiidae, a small group of cryptic and mostly flightless insects, is the only living family in Coleorrhyncha (Insecta: Hemiptera). Today 37 species in 17 genera are known from eastern Australia, New Zealand, New Caledonia and Patagonia, and the peloridiids are thereby a group with a classical southern Gondwanan distribution. To explicitly test whether the present-day distribution of the Peloridiidae actually results from the sequential breakup of southern Gondwana, we provide the first total-evidence phylogenetic study based on morphological and molecular characters sampled from about 75% of recognized species representing 13 genera. The results largely confirm the established morphological phylogenetic context except that South American Peloridium hammoniorum constitutes the sister group to the remaining peloridiids. A timescale analysis indicates that the Peloridiidae began to diversify in the land mass that is today's Patagonia in the late Jurassic (153 Ma, 95% highest posterior density: 78–231 Ma), and that splitting into the three extant well-supported biogeographical clades (i.e. Australia, Patagonia and New Zealand/New Caledonia) is consistent with the sequential breakup of southern Gondwana in the late Cretaceous, indicating that the current transoceanic disjunct distributions of the Peloridiidae are best explained by a Gondwanan vicariance hypothesis.     

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

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

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Nothofagus Biogeography Revisited with Special Emphasis on the Enigmatic Distribution of Subgenus Brassospora in New Caledonia

Dispersals versus vicariance events and the presence of subgenus Brassospora in New Caledonia are two riddles of Nothofagus biogeography, a genus also distributed in New Guinea, New Zealand, South America, Southeast Australia, and Tasmania. Within a cladistic framework using the software COMPONENT 2.0, we demonstrate that most parsimonious area cladograms (areagrams) sensu cladistic biogeography need not always be the most plausible explanation nor reflect alternative geological hypotheses. The most parsimonious Nothofagus history sensu historical biogeography is reconstructed where a minimum of dispersed taxa is hypothesized and vicariance events are identified. A fully resolved well-established Nothofagus phylogeny was reconciled with three geological hypotheses (geograms) of East Gondwana break-up: (a) the conventional view, (b) an Australian—New Caledonian relationship, and (c) a biotic interchange between New Guinea and New Caledonia. Fossils determined to subgenus were optimized to the predicted lineages in the reconciled tree. Due to extensive extinctions, a maximum of three vicariance events are inferred, all being basal in the subgenera, an indication of subgeneric diversification prior to the break-up of Gondwana. Two taxa, N. gunnii and N. menziesii, are hypothesized as being long-distance dispersed. The most parsimonious solution suggests a close relationship between New Guinea and New Caledonia, supporting a Brassospora colonization route, but this hypothesis fails to predict numerous extinct lineages observed in the fossil record and thus must be rejected. The traditional break-up sequence of Gondwana is not the most parsimonious solution, indicating one incongruent node, but causes no overall incongruence with the fossil record. Considering all parameters, the occurrence of Brassospora in New Caledonia is most parsimoniously explained as a single colonization event from New Zealand where the subgenus subsequently went extinct in the Pliocene.