Aim To evaluate competing views on the origin and distribution of the New Zealand flora by testing the hypothesis that the geographical distribution of species is unrelated to ecological traits such as habitat requirements and dispersal capabilities. Location The New Zealand archipelago. Methods An analysis of the factors correlated with distribution and endemism for alpine plants within New Zealand, and for the New Zealand biota as a whole. Results Woody plants are highly endemic; nonendemic plants tend to be herbaceous and are concentrated among the highly dispersible ferns and fern allies, orchids and wetland plants. These groups make up 32% of the total flora but contribute 78% of nonendemics. Alpine plants with wide spatial distribution tend to have greater altitudinal ranges, a broader habitat preference and better dispersal ability. Main conclusions Most vascular plants reached New Zealand by long‐distance transoceanic dispersal, probably during the Late Miocene to early Pleistocene period. During the Miocene and Pliocene, similar climates and landscapes to those of Australia and northern island groups, and highly invasible terrain, permitted dispersal of woody plants. Cooling climates and formation of a more mountainous, more compact landscape after that time reduced dispersal of woody plants and favoured herbaceous, wetland and highly dispersible plant groups. The prominence of dispersal has led to intense selective immigration, and is responsible for many characteristic features of the flora. Species selection by glacial–interglacial cycles has restricted acquisition or retention of cool or arid climate adaptations, particularly in the lowland flora. Endemic and range disjunction patterns in the New Zealand mainland are not, in general, directly caused by Pliocene inundations or the faulting and associated horizontal displacement of terrain that has continued since the Miocene. They have arisen mainly through Pleistocene extinctions, speciation and dispersal, and some patterns are strongly linked to repeated glaciation. Endemic centres are associated with differentiated terrain and climates providing isolation, distinctive environments, and habitat continuity conducive to speciation.

Predicting survival and extinction scenarios for climate change requires an understanding of the present day ecological characteristics of species and future available habitats, but also the adaptive potential of species to cope with environmental change. Hybridization is one mechanism that could facilitate this. Here we report statistical evidence that the transfer of genetic information through hybridization is a feature of species from the plant genus Pachycladon that survived the Last Glacial Maximum in geographically separated alpine refugia in New Zealand's South Island. We show that transferred glucosinolate hydrolysis genes also exhibit evidence of intralocus recombination. Such gene exchange and recombination has the potential to alter the chemical defence in the offspring of hybridizing species. We use a mathematical model to show that when hybridization increases the adaptive potential of species, future biodiversity will be best protected by preserving closely related species that hybridize rather than by conserving distantly related species that are genetically isolated. Predicting the response of organisms and estimating loss of genetic diversity are important challenges for evaluating the impact of global climate change on biodiversity 1-3. Although ecological modelling has an important place in understanding this impact 2 , an accurate prediction of range shift and extinction of species also requires determining their adaptive potential, and in particular the frequency with which hybridization facilitates adaptation 4. Determining this is important, because although hybridization can be a maladaptive phenomenon 5 , it might also help species to acquire adaptive traits, respond successfully to environmental change and invade new habitats 1,3,4,6-8. A better understanding of its positive and negative contributions is essential for evaluating biodiversity impacts. Species affected by climate change in the past-the consequences of which are manifested in extant species' ranges and patterns of genetic diversity-provide models to test for signatures of hybridization. Here we studied Pachycladon (Brassicaceae), an allopolyploid genus of 11 species 9 that have radiated in the New Zealand Alps during the Pleistocene period 9,10. Figure 1 shows ice cover at the height of the Last Glacial Maximum (LGM; 21,000-18,000 years ago), the present day distribution of three Pachycladon species, and a chloroplast TCS (statistical parsimony) haplotype network indicating relationships among accessions of the three species. At present, all three species are restricted to greywacke rock in the central and northern regions of the South Island of New

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Aim To report analyses and propose hypotheses of adaptive radiation that explain distributional patterns of the alpine genus Pachycladon Hook.f. – a morphologically diverse genus from New Zealand closely related to Arabidopsis thaliana. Location South Island, New Zealand. Methods Morphological and nrDNA ITS sequence phylogenies were generated for Pachycladon. An analysis is presented of species distributional patterns and attributes. Results Phylogenetic analyses of morphological characters and nrDNA ITS sequence data were found to be congruent in supporting three New Zealand clades for Pachycladon. Monophyletic groups identified within the genus are geographically distinct and are associated with different geological parent materials. Distribution maps, latitude and altitude range, and data on geological parent material are presented for the nine named and one unnamed species of Pachycladon from New Zealand. Main conclusions (a) Panbiogeographic hypotheses accounting for the origin and present‐day distribution of Pachycladon in New Zealand are not supported. 
(b) Species diversity and distributions of Pachycladon are explained by a Late Tertiary–Quaternary adaptive radiation associated with increasing specialization to geological substrates. Pachycladon cheesemanii Heenan & A.D.Mitch. is morphologically similar to the closest overseas relatives. It is a geological generalist and has wide latitudinal and altitudinal ranges, and we suggest it resembles the ancestral form of the genus in New Zealand. Pachycladon novae‐zelandiae (Hook.f.) Hook.f. and P. wallii (Carse) Heenan & A.D.Mitch. are a southern South Island group that predominantly occurs on Haast Schist, are polycarpic, have lobed leaves, and lateral inflorescences. Pachycladon enysii (Cheeseman) Heenan & A.D.Mitch., P. fastigiata (Hook.f.) Heenan & A.D.Mitch., and P. stellata (Allan) Heenan & A.D.Mitch. are restricted to greywacke in the eastern South Island, and are facultatively monocarpic, have serrate leaves, and stout terminal inflorescenes. 
(c) Present distributions of Pachycladon species may relate to Pleistocene climate change. Pachycladon enysii reaches the highest altitude of New Zealand species of Pachycladon and is most common in the Southern Alps in Canterbury. We propose that this species survived on nunataks at the height of the last glaciation. In contrast, P. fastigiata grows at a lower altitude and is absent from the high mountains of the Southern Alps. We suggest it was extirpated from this area during the last glaciation.

The generic taxonomy of the Nothofagaceae is revised. We present a new phylogenetic analysis of morphological characters and map these characters onto a recently published phylogenetic tree obtained from DNA sequence data. Results of these and previous analyses strongly support the monophyly of four clades of Nothofagaceae that are currently treated as subgenera of Nothofagus. The four clades of Nothofagaceae are robust and well-supported, with deep stem divergences, have evolutionary equivalence with other genera of Fagales, and can be circumscribed with morphological characters. We argue that these morphological and molecular differences are sufficient for the four clades of Nothofagaceae to be recognised at the primary rank of genus, and that this classification will be more informative and efficient than the currently circumscribed Nothofagus with four subgenera.        Nothofagus is recircumscribed to include five species from southern South America, Lophozonia and Trisyngyne are reinstated, and the new genus Fuscospora is described. Fuscospora and Lophozonia, with six and seven species respectively, occur in New Zealand, southern South America and Australia. Trisyngyne comprises 25 species from New Caledonia, Papua New Guinea and Indonesia. New combinations are provided where necessary in each of these genera.

AimThe aim is to use DNA sequence data to test between vicariance and long range dispersal (by floating seed-pods) explanations for the origin and range of the Edwardsia species of Sophora (Sophoreae: Papilionoideae: Leguminosae).Location This group is widely distributed around the South Pacific and into the South Atlantic on both continental fragments and oceanic islands.Methods DNA sequences from an intergene region (atpB-rbcL) of the chloroplast were determined for twelve taxa (including outgroups) and used to test these hypotheses. Sophora fossils were used to calibrate the evolutionary tree. ResultsThe Edwardsia group of Sophora appears monophyletic and is well differentiated from other Sophora. However, the genetic difference between species within the South Pacific and to the South Atlantic is very low. Main conclusionsThe results eliminate vicariance explanations for this section of Sophora and strongly support an origin from other (non-Edwardsia) Sophora in the north-west Pacific. Dispersal appears initially to be to Tuvalu, Lord Howe Island, New Zealand, and subsequently across the South Pacific, probably within the last 2-5 million years. Dispersal of buoyant Sophora seeds to oceanic islands is the most likely explanation of its distributions. Fossil pollen dates in New Zealand are consistent with the conclusion.

A taxonomic treatment is provided for the Sophora microphylla complex in New Zealand. Sophora microphyllu sens. str. is endemic to New Zealand, and includes those plants with a distinct divaricating and/or strongly flexuose juvenile Phase, orange-brown to Yellow-brown Juvenile stems, and distant leaflets. S. chathamica is reinstated at species rank, S.fulvida is a new combination provided for the taxon previously known as S. microphylla Var. fulvida, and S. godleyi and S. molloyi are described as new species. S. chathamica, S. fulvida, S. godleyi and S. molloyi lack a divaricating and/or strongly flexuose juvenile phase and are each distinguished by a number of leaf characters. S. fulvida and S. godleyi have distinctive leaf hairs. S. chathamica is a predominantly coastal species in Northland, Auckland, Waikato, Wellington, and the Chatham Islands, S.fulvida occurs in Northland and North Auckland on volcanic rock outcrops S. godleyi Occurs on calcareous mudstone and sandstone in eastem Taranaki King country, Wanganui B99050

Summary Plant radiations are widespread but their influence on community assembly has rarely been investigated. Theory and some evidence suggest that radiations can allow lineages to monopolize niche space when founding species arrive early into new bioclimatic regions and exploit ecological opportunities. These early radiations may subsequently reduce niche availability and dampen diversification of later arrivals. We tested this hypothesis of time‐dependent lineage diversification and community dominance using the alpine flora of New Zealand. We estimated ages of 16 genera from published phylogenies and determined their relative occurrence across climatic and physical gradients in the alpine zone. We used these data to reconstruct occupancy of environmental space through time, integrating palaeoclimatic and palaeogeological changes. Our analysis suggested that earlier‐colonizing lineages encountered a greater availability of environmental space, which promoted greater species diversity and occupancy of niche space. Genera that occupied broader niches were subsequently more dominant in local communities. An earlier time of arrival also contributed to greater diversity independently of its influence in accessing niche space. We suggest that plant radiations influence community assembly when they arise early in the occupancy of environmental space, allowing them to exclude later‐arriving colonists from ecological communities by niche preemption.