Diversity patterns of herbivores have been related to climate, host plant traits, host plant distribution and evolutionary relationships individually. However, few studies have assessed the relative contributions of a range of variables to explain these diversity patterns across large geographical and host plant species gradients. Here we assess the relative influence that climate and host plant traits have on endophagous species (leaf miners and plant gallers) diversity across a suite of host species from a genus that is widely distributed and morphologically variable. Forty-six species of Acacia were sampled to encapsulate the diversity of species across four taxonomic sections and a range of habitats along a 950 km climatic gradient: from subtropical forest habitats to semi-arid habitats. Plant traits, climatic variables, leaf miner and plant galler diversity were all quantified on each plant species. In total, 97 leaf mining species and 84 plant galling species were recorded from all host plants. Factors that best explained leaf miner richness across the climatic gradient (using AIC model selection) included specific leaf area (SLA), foliage thickness and mean annual rainfall. The factor that best explained plant galler richness across the climatic gradient was C:N ratio. In terms of the influence of plant and climatic traits on species composition, leaf miner assemblages were best explained by SLA, foliage thickness, mean minimum temperature and mean annual rainfall, whilst plant gall assemblages were explained by C:N ratio, %P, foliage thickness, mean minimum temperature and mean annual rainfall. This work is the first to assess diversity and structure across a broad environmental gradient and a wide range of potential key climatic and plant trait determinants simultaneously. Such methods provide key insights into endophage diversity and provide a solid basis for assessing their responses to a changing climate.

Although the underlying phylogeny determines the qualitative wood structure, climate has a significant influence on the functional wood anatomy of Acacia s.s. , which is an ideal genus to study the effect of these factors.

The floral morphology and embryology of two species of Australian Citrus L. occurring in the most southerly range of the genus, C. australasica F.Muell. and C. australis (Mudie) Planchon, have been studied. Cytokinesis in the microsporocytes was simultaneous resulting in tetrahedral tetrads. Tapetal cells were bi- to multinucleate and unevenly one- or two-layered. Microspore development was frequently asynchronous. Anther wall consisted of a layer of endothecium, three to five middle layers and one or two layers of Secretory tapetum. The ovules were anatropous, bitegmic and crassinucellate. Although multiple sporogenous cells that grew into multiple megasporocytes were common, occurrence of twin or multiple gametophytes was rare. Development of the female gametophyte was of the Polygonum type, with antipodal cells frequently persisting until after fertilisation. Endosperm was of the Nuclear type while embryogeny was of the Onagrad type. Both integuments contributed to the seed coat. Cells of the outer layer of the testa developed fibrous thickenings and secreted mucilage. Seeds were monoembryonate and seed germination was hypogeal. The recent move incorporating Australian native citrus species in to the genus Citrus was supported on the grounds of close embryological similarities.

This study examined the water relations of sclerophyllous evergreen vegetation (wallum) on coastal sand barriers in eastern Australia. Many wallum species may be groundwater dependent, although the extent of this dependency is largely unknown. Twenty-six perennial tree, shrub and herb species were investigated in three groundwater habitats (ridge, open depression, closed depression). Pre-dawn and midday shoot xylem water potentials (ψx) were measured monthly between late autumn 2010 and late summer 2011. Pressure–volume curve traits were determined in mid- to late spring 2009, including the osmotic potential at full (π100) and zero (π0) turgor, and bulk modulus of elasticity (ε). Carbon isotope ratios (δ13C) were also determined in mid- to late spring 2009, to measure water-use efficiency (WUE). The species displayed a range of physiological strategies in response to water relations, and these strategies overlapped among contrasting growth forms and habitats. Linear relationships between osmotic and elastic adjustment were significant. A strong correlation between δ13C and distribution along the hydrological gradient was not apparent. Banksia ericifolia subsp. macrantha (A.S.George) A.S.George, Eucalyptus racemosa Cav. subsp. racemosa and Eucalyptus robusta Sm. displayed little seasonal variation in ψx and maintained a comparatively high pre-dawn ψx, and are therefore likely to be phreatophytic. Wetland vegetation in the lowest part of the landscape appeared to tolerate extreme fluctuations in water availability linked to a prevailing climatic pattern of variable and unreliable seasonal rainfall.

Acacia s.s. comprises approximately 1020 species (i.e. just under one-third of all mimosoid legumes) and is almost entirely restricted to, although widespread, on the Australian continent. We investigated variation in the wood anatomy of 12 species from temperate New South Wales in a study concentrating on four recognised taxonomic sections (Botrycephalae, Juliflorae, Phyllodineae and Plurinerves), to elucidate which characteristics are consistent within the sections, having removed climatic effect as much as possible. The sections had great utility in species identification, whereas none of the wood characters reflected the hypothesised phylogeny of the genus. The main consistent difference among species was in ray width (uniseriate versus 1–3 cells wide). All species had distinct growth rings. The vessels had alternate vestured pitting and simple perforation plates. Fibres were generally thick-walled, and many fibres had a gelatinous inner wall (tension wood fibres) and were inconsistently distributed. Axial parenchyma was mainly paratracheal, ranging from vasicentric to confluent and varied greatly in abundance. Prismatic crystals were usually present in chambered fibres and axial parenchyma strands, and also varied in abundance. The variation in these qualitative characters obscures taxonomic differences, but may allow inferences to be made about environmental adaptation.