Hannah Buckley

Although treeline elevations are limited globally by growing season temperature, at regional scales treelines frequently deviate below their climatic limit. The cause of these deviations relate to a host of climatic, disturbance, and geomorphic factors that operate at multiple scales. The ability to disentangle the relative effects of these factors is currently hampered by the lack of reliable topoclimatic data, which describe how regional climatic characteristics are modified by topographic effects in mountain areas. In this study we present an analysis of the combined effects of local- and regional-scale factors on southern beech treeline elevation variability at 28 study areas across New Zealand. We apply a mesoscale atmospheric model to generate local-scale (200 m) meteorological data at these treelines and, from these data, we derive a set of topoclimatic indices that reflect possible detrimental and ameliorative influences on tree physiological functioning. Principal component...

ABSTRACT Microhabitat variation at a tree level results in the patchy distribution of epiphytic lichens. Our study examined how this microhabitat variation affects the biomass of all Usnea species on the main trunk of a tree up to 2 m in height. Total Usnea biomass and microhabitat data were collected from 48 mountain beech (Nothofagus solandri var. cliffortioides) trees from four different sites in the Nina Valley, South Island, New Zealand. Variation in total Usnea biomass was related to tree-level microenvironmental variables using a linear mixed-effects model. Biomass was positively related to minimum bark depth and negatively to canopy cover, but was unrelated to tree diameter, distance to nearest occupied tree and the per cent cover of sooty mould and bryophytes. These results suggest that epiphytic Usnea on mountain beech trees prefer thicker, textured bark in high-light environments.

ABSTRACT Aims Studies integrating phylogenetic history and large-scale community assembly are few, and many questions remain unanswered. Here, we use a global coastal dune plant data set to uncover the important factors in community assembly across scales from the local filtering processes to the global long-term diversification and dispersal dynamics. Coastal dune plant communities occur worldwide under a wide range of climatic and geologic conditions as well as in all biogeographic regions. However, global patterns in the phylogenetic composition of coastal dune plant communities have not previously been studied. Methods The data set comprised vegetation data from 18 463 plots in New Zealand, South Africa, South America, North America and Europe. The phylogenetic tree comprised 2241 plant species from 149 families. We calculated phylogenetic clustering (Net Relatedness Index, NRI, and Nearest Taxon Index, NTI) of regional dune floras to estimate the amount of in situ diversification relative to the global dune species pool and evaluated the relative importance of land and climate barriers for these diversification patterns by geographic analyses of phylogenetic similarity. We then tested whether dune plant communities exhibit similar patterns of phylogenetic structure within regions. Finally, we calculated NRI for local communities relative to the regional species pool and tested for an association with functional traits (plant height and seed mass) thought to vary along sea–inland gradients. Important Findings Regional species pools were phylogenetically clustered relative to the global pool, indicating regional diversification. NTI showed stronger clustering than NRI pointing to the importance of especially recent diversifications within regions. The species pools grouped phylogenetically into two clusters on either side of the tropics suggesting greater dispersal rates within hemispheres than between hemispheres. Local NRI plot values confirmed that most communities were also phylogenetically clustered within regions. NRI values decreased with increasing plant height and seed mass, indicating greater phylogenetic clustering in communities with short maximum height and good dispersers prone to wind and tidal disturbance as well as salt spray, consistent with environmental filtering along sea–inland gradients. Height and seed mass both showed significant phylogenetic signal, and NRI tended to correlate negatively with both at the plot level. Low NRI plots tended to represent coastal scrub and forest, whereas high NRI plots tended to represent herb-dominated vegetation. We conclude that regional diversification processes play a role in dune plant community assembly, with convergence in local phylogenetic community structure and local variation in community structure probably reflecting consistent coastal-inland gradients. Our study contributes to a better understanding of the globally distributed dynamic coastal ecosystems and the structuring factors working on dune plant communities across spatial scales and regions.

ABSTRACT Aim The extent to which bacterial communities exhibit biogeographic patterns in their distribution remains unclear. We examined the relative influence of factors including geographic distance, latitude, elevation and catchment land use on the distribution and taxon richness of stream bacterial communities across New Zealand. Location Bacterial communities were collected from biofilm growing on submerged rocks in 244 streams. Sample sites spanned a north–south gradient of over 970 km, an elevational gradient of c. 750 m and were collected from a variety of catchment types across New Zealand. Methods We used automated ribosomal intergenic spacer analysis, a DNA fingerprinting technique, to characterize the structure and taxon richness of each bacterial community. Key attributes relating to sample location, upstream catchment land use and a suite of additional environmental parameters were collected for every site using GIS procedures. Univariate correlations between measures of bacterial community structure and latitude, elevation and distance were examined. Variance partitioning was then used to assess the relative importance of purely spatial factors versus catchment land use and environmental attributes for determining bacterial community structure and taxon richness. Results Bacterial taxon richness was related to the geographic location of the sample site, being significantly greater at latitudes closer to the equator and reduced at higher elevations. We observed distance decay patterns in bacterial community similarity related to geographic distance and latitudinal distance, but not to elevational distance. Overall, however, bacterial community similarity and taxon richness was more closely related to variability in catchment land use than to climatic variability or geographic location. Main conclusion Our data suggest that stream biofilm communities across New Zealand are more influenced by catchment land use attributes than by dispersal limitation.

Page 1. Two decades of vegetation change across tussock grasslands of New Zealand's South Island October 2007 Nicola Day and Dr. Hannah L. Buckley * Bio-Protection & Ecology Division Lincoln University * Author for contact: buckleyh@lincoln.ac.nz Page 2. ...

Question: Is epiphytic lichen community structure significantly affected by isolation from source community?

Location: Foothills of the Southern Alps, South Island, New Zealand.

Methods: Epiphytic lichen richness and environmental variables were measured on 382, young Nothofagus solandri var. cliffortioides (Hook. f.) Poole (mountain beech) trees that had recently colonized grassland adjacent to a forest remnant. Richness and the presence of individual lichen taxa were modelled as a function of isolation from the forest fragment, tree size and other habitat conditions.

Results: Richness of epiphytic lichen communities was negatively related to tree isolation, although this effect was much smaller than the effects of tree size and other local (tree-scale) habitat conditions. Different lichen taxa responded in different ways to isolation, area effects and local habitat conditions.

Conclusions: This study shows that many epiphytic lichens on mountain beech are limited in their ability to colonize new substrate, even over distances of less than 1 km, which may be due to limitation in dispersal and/or establishment. Lichens are greatly influenced by local habitat conditions, such as tree size, and in this particular environment their negative interaction with sooty moulds is an important driver of community structure.

Aim  We investigated patterns of species richness and composition of the aquatic food web found in the liquid-filled leaves of the North American purple pitcher plant, Sarracenia purpurea (Sarraceniaceae), from local to continental scales.Location  We sampled 20 pitcher-plant communities at each of 39 sites spanning the geographic range of S. purpurea– from northern Florida to Newfoundland and westward to eastern British Columbia.Methods  Environmental predictors of variation in species composition and species richness were measured at two different spatial scales: among pitchers within sites and among sites. Hierarchical Bayesian models were used to examine correlates and similarities of species richness and abundance within and among sites.Results  Ninety-two taxa of arthropods, protozoa and bacteria were identified in the 780 pitcher samples. The variation in the species composition of this multi-trophic level community across the broad geographic range of the host plant was lower than the variation among pitchers within host-plant populations. Variation among food webs in richness and composition was related to climate, pore-water chemistry, pitcher-plant morphology and leaf age. Variation in the abundance of the five most common invertebrates was also strongly related to pitcher morphology and site-specific climatic and other environmental variables.Main conclusions  The surprising result that these communities are more variable within their host-plant populations than across North America suggests that the food web in S. purpurea leaves consists of two groups of species: (1) a core group of mostly obligate pitcher-plant residents that have evolved strong requirements for the host plant and that co-occur consistently across North America, and (2) a larger set of relatively uncommon, generalist taxa that co-occur patchily.

Within-community species-area relationships were examined for vascular plants and epiphytic lichens on Populus spp within 100 treed patches in an area of less than 4km2 in the aspen parkland of south-central Alberta, Canada. Both plants and lichens were sampled on three scales (patch-scale and two within-patch scales). This study is one of the few to demonstrate scale-dependent species-area relationships at a small scale and highlights the importance of multi-scale sampling in ecology. At the larger patch scale, the relationship between plant species richness and area was positive for both the full plant datasets and the forest habitat specialist subset. For lichens, the species-area relationships were positive at all scales. However, for plants, at small scales, the species-area relationship was negative for all plants, but non-significant for forest habitat specialist species when considered separately. This difference reflects the different mechanisms behind the species-area relationships for the two taxa. For vascular plants, small-scale species richness decreased with patch size due to an edge effect within patches. The species-area relationships for the forest habitat specialist species were unaffected by this edge effect because these species were more common in larger patches. The distribution of lichens within patches was not significantly different from random. Therefore, the positive species-area relationships observed for this taxon reflect a passive sampling effect; where there are more individuals, there are more species.

Important predictors of the species richness of vascular plants and epiphytic lichens on Populus spp in the Canadian aspen parkland were determined. Plants and lichens were sampled on three scales within 100 treed patches within an area of less than 4km2 (patch-scale and two within-patch scales). Small-scale species richness within patches was positively related to the number of species in the surrounding patch and a few measured environmental variables. This suggests that, at this scale, the species richness of these communities is limited by the availability of species in addition to local environmental conditions and species habitat preferences. For plant species richness, environmental variables that were related to light availability were most important, whereas for epiphytic lichens, variables that were related to moisture availability on trees were most important. This study adds to a growing body of literature showing that both small-scale and larger-scale processes affect species richness within communities.

ABSTRACT A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Dept. of Biological Sciences, University of Alberta. Thesis (Ph. D.)--University of Alberta, 2001. Includes bibliographical references.