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The size of fleshy fruits spans several orders of magnitude. However, the evolution of fruit size diversity is poorly understood. Fruit size diversity is hypothesised to result from several potential processes. The frugivore hypothesis postulates that different-sized animal fruit consumers select for different-sized fruits. The correlated selection hypothesis postulates that fruit size is allometrically related to other plant traits (e.g. leaf size, plant height); therefore differences in fruit size result from correlated evolution with other plant traits. We tested the frugivore and correlated selection hypotheses as potential explanations for fruit size diversity in two New Zealand study sites. We observed birds foraging for fruits over two fruiting seasons at each site and measured fruit size, leaf size and plant height in a total of 32 plant species. Relationships between average fruit size, leaf size, plant size and the average size of birds consuming each fruit species were then evaluated using phylogenetically independent contrasts. Similar results were obtained in both study sites. Fruit size was correlated with the size of avian fruit consumers, but was unrelated to leaf size or plant height. Therefore, results falsified the correlated selection hypothesis but failed to falsify the frugivore hypothesis. Although results suggest that frugivores may have influenced the evolution of fruit size in New Zealand, further study is needed to generate a mechanistic understanding of how frugivores may have selected for interspecific variation in fruit size. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Seed size and shape predict seed persistence in the soil for British and Argentinian herbaceous plant species. Those species with small, rounded seeds tend to have persistent seeds while those with larger, more elongate or flattened seeds usually lack persistence. It has been suggested that the mechanism underlying this pattern may be ease of burial, as small, rounded seeds are incorporated into the soil more easily than large, elongate or flattened seeds and are therefore less likely to be eaten by seed predators. We tested whether seed size and shape were related to persistence in the soil for 47 species native to New Zealand forests. There was a tendency for species with persistent seeds to have smaller seeds than species with transient seeds. However, species with large and/or elongate or flattened persistent seeds were relatively common. This indicates that seed size and shape are not related to persistence in New Zealand in the same way as in Britain and Argentina. A similar negative result has been found in Australia. The underlying cause of the patterns observed is unlikely to be ease of burial, since incorporation of seeds into the soil is likely to operate in all countries in a similar manner on seeds without specialised seed burial mechanisms. Data from all four floras studied to date also suggest that species with small, rounded seeds that do not germinate immediately must have the ability to survive periods of burial.. [ABSTRACT FROM AUTHOR]

Correlations between environment and tree alpha-diversity in New Zealand's primary forests were examined using an extensive quantitative dataset (14 540 plots). Generalised additive models were used to examine relationships between species richness and temperature, solar radiation, root-zone moisture deficit, relative humidity, lithology, drainage, and plot size for all trees (112 species), and separately for broadleaved trees (88 species), conifers (17), and the genus Nothofagus (4). Diversity both for all tree species and for broadleaved treeswas predicted to be highest on sites with high temperatures, high solar radiation, and high soil and atmospheric moisture, and on sedimentary and basaltic substrates. Highest conifer diversity was predictedon sites with intermediate temperatures, low solar radiation, high root-zone and atmospheric moisture, and rhyolitic and Quaternary substrates, particularly where drainage was impeded. Highest Nothofagus diversity was predicted for sites combining low temperatures, high solar radiation, high root-zone moisture but low atmospheric moisture, and on granitic substrates. Differences in diversity between the species groups on different lithologies are interpreted as reflecting both the effects of variation in large-scale disturbance histories, and the effects of confounding environmental factors associated with particular substrates. There were also significant interactions between species groups: both broadleaved tree and conifer richness were predicted to be lower on sites where one or more Nothofagus spp. - all of which have marked patchiness in their distribution - are present. Although these results are consistent with the hypothesis that tree diversity is highest on sites conducive to high productivity, history is also indicated as an important determinant of tree diversity in New Zealand. [ABSTRACT FROM AUTHOR]

Helical thickenings were observed on the vessel walls of ninety woods indigenous to New Zealand. They were not observed in a further eighty-eight species. Four types of thickenings are described: faint striations, light helical thickenings sometimes merging with the vessel wall, prominent helical thickenings and very prominent close helical thickenings. These types are illustrated with scanning electron micrographs. Although the helical winding orientation was predominantly in the S-direction, considerable variation was observed in the helical winding angle both between adjacent vessel members of similar dimensions, and also within individual cells. Vestures were observed adhering to the helical thickenings in three species. [ABSTRACT FROM AUTHOR]