Steven A. Trewick

The Waipounamu Erosion Surface: questioning the antiquity of the New Zealand land surface and terrestrial fauna and flora

The Waipounamu Erosion Surface is a time-transgressive, nearly planar, wave-cut surface. It is not a peneplain. Formation of the Waipounamu Erosion Surface began in Late Cretaceous time following break-up of Gondwanaland, and continued until earliest Miocene time, during a 60millionyearperiodofwidespreadtectonicquiescence,thermalsubsidenceandmarinetransgression. Sedimentary facies and geomorphological evidence suggest that the erosion surface may have eventually covered the New Zealand subcontinent (Zealandia). We can find no geological evidence to indicate that land areas were continuously present throughout the middle Cenozoic. Important implications of this conclusion are: (1) the New Zealand subcontinent was largely, or entirely, submerged and (2) New Zealands present terrestrial fauna and flora evolved largely from fortuitous arrivals during the past 22 million years. Thus the modern terrestrial biota may not be descended from archaic ancestors residing on Zealandia when it broke away from Gondwanaland in the Cretaceous, since the terrestrial biota would have been extinguished if this landmass was submerged in Oligocene- Early Miocene time. We conclude that there is insufficient geological basis for assuming that land was continuously present in the New Zealand region through Oligocene to Early Miocene time, and we therefore contemplate the alternative possibility, complete submergence of Zealandia.

The age and origin of the Pacific islands: a geological overview

The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were initially one plate, produced to the east of the original spreading centre before becoming split into three. The islands of the Pacific have originated as: linear chains of volcanic islands on the above plates either by mantle plume or propagating fracture origin, atolls, uplifted coralline reefs, fragments of continental crust, obducted portions of adjoining lithospheric plates and islands resulting from subduction along convergent plate margins. Out of the 11 linear volcanic chains identified, each is briefly described and its history summarized. The geology of 10 exemplar archipelagos (Japan, Izu-Bonin, Palau, Solomons, Fiji, New Caledonia, New Zealand, Society, Galápagos and Hawaii) is then discussed in detail.

New Zealand phylogeography: evolution on a small continent.

New Zealand has long been a conundrum to biogeographers, possessing as it does geophysical and biotic features characteristic of both an island and a continent. This schism is reflected in provocative debate among dispersalist, vicariance biogeographic and panbiogeographic schools. A strong history in biogeography has spawned many hypotheses, which have begun to be addressed by a flood of molecular analyses. The time is now ripe to synthesize these findings on a background of geological and ecological knowledge. It has become increasingly apparent that most of the biota of New Zealand has links with other southern lands (particularly Australia) that are much more recent than the breakup of Gondwana. A compilation of molecular phylogenetic analyses of ca 100 plant and animal groups reveals that only 10% of these are even plausibly of archaic origin dating to the vicariant splitting of Zealandia from Gondwana. Effects of lineage extinction and lack of good calibrations in many cases strongly suggest that the actual proportion is even lower, in keeping with extensive Oligocene inundation of Zealandia. A wide compilation of papers covering phylogeographic structuring of terrestrial, freshwater and marine species shows some patterns emerging. These include: east–west splits across the Southern Alps, east–west splits across North Island, north–south splits across South Island, star phylogenies of southern mountain isolates, spread from northern, central and southern areas of high endemism, and recent recolonization (postvolcanic and anthropogenic). Excepting the last of these, most of these patterns seem to date to late Pliocene, coinciding with the rapid uplift of the Southern Alps. The diversity of New Zealand geological processes (sinking, uplift, tilting, sea level change, erosion, volcanism, glaciation) has produced numerous patterns, making generalizations difficult. Many species maintain pre‐Pleistocene lineages, with phylogeographic structuring more similar to the Mediterranean region than northern Europe. This structure reflects the fact that glaciation was far from ubiquitous, despite the topography. Intriguingly, then, origins of the flora and fauna are island‐like, whereas phylogeographic structure often reflects continental geological processes.

Polyploidy, phylogeography and Pleistocene refugia of the rockfern Asplenium ceterach : evidence from chloroplast DNA

Chloroplast DNA sequences were obtained from 331 Asplenium ceterach plants representing 143 populations from throughout the range of the complex in Europe, plus outlying sites in North Africa and the near East. We identified nine distinct haplotypes from a 900 bp fragment of trnL‐trnF gene. Tetraploid populations were encountered throughout Europe and further afield, whereas diploid populations were scarcer and predominated in the Pannonian‐Balkan region. Hexaploids were encountered only in southern Mediterranean populations. Four haplotypes were found among diploid populations of the Pannonian‐Balkans indicating that this region formed a northern Pleistocene refugium. A separate polyploid complex centred on Greece, comprises diploid, tetraploid and hexaploid populations with two endemic haplotypes and suggests long‐term persistence of populations in the southern Mediterranean. Three chloroplast DNA (cpDNA) haplotypes were common among tetraploids in Spain and Italy, with diversity reducing northwards suggesting expansion from the south after the Pleistocene. Our cpDNA and ploidy data indicate at least six independent origins of polyploids.

BRIDGING THE “BEECH-GAP”: NEW ZEALAND INVERTEBRATE PHYLOGEOGRAPHY IMPLICATES PLEISTOCENE GLACIATION AND PLIOCENE ISOLATION

Abstract The existence of areas of lower endemism and disjunction of New Zealand biota is typified by Nothofagus beech trees (hence “beech‐gap”) and have been attributed to a variety of causes ranging from ancient fault‐mediated displacement (20–25 million years ago) to Pleistocene glacial extirpation (<1.8 million years ago). We used cytochrome oxidase I and 12S mtDNA sequence data from a suite of endemic invertebrates to explore phylogeographic depth and patterns in South Island, New Zealand, where the “beech‐gap” occurs. Phylogeographic structure and genetic distance data are not consistent with ancient vicariant processes as a source of observed pattern. However, we also find that phylogeographic patterns are not entirely congruent and appear to reflect disparate responses to fragmentation, which we term “gap,”“colonization,” and “regional.” Radiations among congenerics, and in at least one instance within a species, probably took place in the Pliocene (2–7 million years ago), possibly under the influence of the onset of mountain building. This orogenic phase may have had a considerable impact on the development of the biota generally. Some of the taxa that we studied do not appear to have suffered range reduction during Pleistocene glaciation, consistent with their survival throughout that epoch in alpine habitats to which they are adapted. Other taxa have colonized the beech‐gap recently (i.e., after glaciation), whereas few among our sample retain evidence of extirpation in the most heavily glaciated zone.

Phylogeographical pattern correlates with pliocene mountain building in the alpine scree weta (Orthoptera, anostostomatidae).

Most research on the biological effects of Pleistocene glaciation and refugia has been undertaken in the northern hemisphere and focuses on lowland taxa. Using single‐strand conformation polymorphism (SSCP) analysis and sequencing of mitochondrial cytochrome oxidase I, we explored the intraspecific phylogeography of a flightless orthopteran (the alpine scree weta, Deinacrida connectens) that is adapted to the alpine zone of South Island, New Zealand. We found that several mountain ranges and regions had their own reciprocally monophyletic, deeply differentiated lineages. Corrected genetic distance among lineages was 8.4% (Kimura 2‐parameter [K2P]) / 13% (GTR + I + Γ), whereas within‐lineage distances were only 2.8% (K2P) / 3.2% (GTR + I + Γ). We propose a model to explain this phylogeographical structure, which links the radiation of D. connectens to Pliocene mountain building, and maintenance of this structure through the combined effects of mountain‐top isolation during Pleistocene interglacials and ice barriers to dispersal during glacials.

Evolution of New Zealand's terrestrial fauna: a review of molecular evidence

New Zealand biogeography has been dominated by the knowledge that its geophysical history is continental in nature. The continental crust (Zealandia) from which New Zealand is formed broke from Gondwanaland ca 80 Ma, and there has existed a pervading view that the native biota is primarily a product of this long isolation. However, molecular studies of terrestrial animals and plants in New Zealand indicate that many taxa arrived since isolation of the land, and that diversification in most groups is relatively recent. This is consistent with evidence for species turnover from the fossil record, taxonomic affinity, tectonic evidence and observations of biological composition and interactions. Extinction, colonization and speciation have yielded a biota in New Zealand which is, in most respects, more like that of an oceanic archipelago than a continent.

DNA Barcoding is not enough: mismatch of taxonomy and genealogy in New Zealand grasshoppers (Orthoptera: Acrididae).

DNA barcoding has been touted as a program that will efficiently and relatively cheaply inform on biological diversity; yet many exemplars purporting to demonstrate the efficacy of the method have been undertaken by its principal proponents. Critics of DNA barcoding identify insufficient within‐taxon sampling coupled with the knowledge that levels of haplotypic paraphyly are rather high as key reasons to be sceptical of the value of an exclusively DNA‐based taxonomic. Here I applied a DNA barcoding approach using mtDNA sequences from the cytochrome oxidase I gene to examine diversity in a group of endemic New Zealand grasshoppers belonging to the genus Sigaus. The mtDNA data revealed high genetic distances among individuals of a single morpho‐species, but this diversity was geographically partitioned. Phylogenetic analysis supported at least four haplogroups within one species (Sigaus australis) but paraphyly of this species with respect to several others. In some instances two morphologically and ecologically distinct species shared identical mtDNA haplotypes. The mismatch of genealogy and taxonomy revealed in the Sigaus australis complex indicates that, if used in isolation, DNA barcoding data can be highly misleading about biodiversity. Furthermore, failure to take into account evidence from natural history and morphology when utilizing DNA barcoding will tend to conceal the underlying evolutionary processes associated with speciation.

Mitochondrial DNA sequences support allozyme evidence for cryptic radiation of New Zealand Peripatoides (Onychophora)

A combination of single‐strand conformation polymorphism analysis (SSCP) and sequencing were used to survey cytochrome oxidase I (COI) mitochondrial DNA (mtDNA) diversity among New Zealand ovoviviparous Onychophora. Most of the sites and individuals had previously been analysed using allozyme electrophoresis. A total of 157 peripatus collected at 54 sites throughout New Zealand were screened yielding 62 different haplotypes. Comparison of 540‐bp COI sequences from Peripatoides revealed mean among‐clade genetic distances of up to 11.4% using Kimura 2‐parameter (K2P) analysis or 17.5% using general time‐reversible (GTR + I + Γ) analysis. Phylogenetic analysis revealed eight well‐supported clades that were consistent with the allozyme analysis. Five of the six cryptic peripatus species distinguished by allozymes were confirmed by mtDNA analysis. The sixth taxon appeared to be paraphyletic, but genetic and geographical evidence suggested recent speciation. Two additional taxa were evident from the mtDNA data but neither occurred within the areas surveyed using allozymes. Among the peripatus surveyed with both mtDNA and allozymes, only one clear instance of recent introgression was evident, even though several taxa occurred in sympatry. This suggests well‐developed mate recognition despite minimal morphological variation and low overall genetic diversity.

Chromosome races with Pliocene origins: evidence from mtDNA

There are eight distinct chromosomal races of the New Zealand weta Hemideina thoracica. We used mtDNA sequence data to test the hypothesis that these races originated on islands during the early Pliocene (7–4 million years ago). Nine major mitochondrial lineages were identified from 65 cytochrome oxidase I sequences. Phylogenetic analysis of these lineages suggests that they arose at approximately the same time. The geographical distribution of some lineages coincides with areas that were islands during the Pliocene. Overall, hierarchical AMOVA analysis shows that chromosomal races and Pliocene islands describe only 28% and 24%, respectively, of the total current mtDNA variation. However, removing one widespread (A) and one putatively introgressed (F) lineage increases these estimates to 65% and 80%, respectively. Intraspecific sequence divergence was very high, reaching a maximum of 9.5% (uncorrected distance) and GC content was high compared to other insect mtDNA sequences. Average corrected distance among mtDNA lineages supports the Pliocene origins of this level of genetic diversity. In the southern part of the species range there is reduced mtDNA variation, probably related to local extinction of H. thoracica populations from recent volcanic activity and subsequent re-colonization from a leading edge. In contrast, in this southern part there are five chromosome races, suggesting that chromosome races here may be younger than those in the north.