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Summary Understanding the mechanisms causing phenotypic differences between females and males has long fascinated evolutionary biologists. An extensive literature exists on animal sexual dimorphism but less information is known about sex differences in plants, particularly the extent of geographical variation in sexual dimorphism and its life‐cycle dynamics.Here, we investigated patterns of genetically based sexual dimorphism in vegetative and reproductive traits of a wind‐pollinated dioecious plant, Rumex hastatulus, across three life‐cycle stages using open‐pollinated families from 30 populations spanning the geographic range and chromosomal variation (XY and XY1Y2) of the species.The direction and degree of sexual dimorphism was highly variable among populations and life‐cycle stages. Sex‐specific differences in reproductive function explained a significant amount of temporal change in sexual dimorphism. For several traits, geographical variation in sexual dimorphism was associated with bioclimatic parameters, likely due to the differential responses of the sexes to climate. We found no systematic differences in sexual dimorphism between chromosome races.Sex‐specific trait differences in dioecious plants largely result from a balance between sexual and natural selection on resource allocation. Our results indicate that abiotic factors associated with geographical context also play a role in modifying sexual dimorphism during the plant life‐cycle.

Sexual dimorphism in resource allocation is expected to change during the life cycle of dioecious plants because of temporal differences between the sexes in reproductive investment. Given the potential for sex-specific differences in reproductive costs, resource availability may contribute to variation in reproductive allocation in females and males. Here, we used Rumex hastatulus, a dioecious, wind-pollinated annual plant, to investigate whether sexual dimorphism varies with life-history stage and nutrient availability, and determine whether allocation patterns differ depending on reproductive commitment. To examine if the costs of reproduction varied between the sexes, reproduction was either allowed or prevented through bud removal, and biomass allocation was measured at maturity. In a second experiment to assess variation in sexual dimorphism across the life cycle, and whether this varied with resource availability, plants were grown in high and low nutrients and allocation to roots, aboveground vegetative growth and reproduction were measured at three developmental stages. Males prevented from reproducing compensated with increased above- and belowground allocation to a much larger degree than females, suggesting that male reproductive costs reduce vegetative growth. The proportional allocation to roots, reproductive structures and aboveground vegetative growth varied between the sexes and among life-cycle stages, but not with nutrient treatment. Females allocated proportionally more resources to roots than males at peak flowering, but this pattern was reversed at reproductive maturity under low-nutrient conditions. Our study illustrates the importance of temporal dynamics in sex-specific resource allocation and provides support for high male reproductive costs in wind-pollinated plants.

Dioecious plant species commonly exhibit deviations from the equilibrium expectation of 1:1 sex ratio, but the mechanisms governing this variation are poorly understood. Here, we use comparative analyses of 243 species, representing 123 genera and 61 families to investigate ecological and genetic correlates of variation in the operational (flowering) sex ratio. After controlling for phylogenetic nonindependence, we examined the influence of growth form, clonality, fleshy fruits, pollen and seed dispersal vector, and the possession of sex chromosomes on sex-ratio variation. Male-biased flowering sex ratios were twice as common as female-biased ratios. Male bias was associated with long-lived growth forms (e.g., trees) and biotic seed dispersal and fleshy fruits, whereas female bias was associated with clonality, especially for herbaceous species, and abiotic pollen dispersal. Female bias occurred in species with sex chromosomes and there was some evidence for a greater degree of bias in those with heteromorphic sex chromosomes. Although the role of interactions among these correlates require further study, our results indicate that sex-based differences in costs of reproduction, pollen and seed dispersal mechanisms and sex chromosomes can each play important roles in affecting flowering sex ratios in dioecious plants.

The primary goal of restoration is to create self-sustaining ecological communities that are resilient to periodic disturbance. Currently, little is known about how restored communities respond to disturbance events such as fire and how this response compares to remnant vegetation. Following the 2003 fires in south-eastern Australia we examined the post-fire response of revegetation plantings and compared this to remnant vegetation. Ten burnt and 10 unburnt (control) sites were assessed for each of three types of vegetation (direct seeding revegetation, revegetation using nursery seedlings (tubestock) and remnant woodland). Sixty sampling sites were surveyed 6 months after fire to quantify the initial survival of mid- and overstorey plant species in each type of vegetation. Three and 5 years after fire all sites were resurveyed to assess vegetation structure, species diversity and vigour, as well as indicators of soil function. Overall, revegetation showed high (>60%) post-fire survival, but this varied among species depending on regeneration strategy (obligate seeder or resprouter). The native ground cover, mid- and overstorey in both types of plantings showed rapid recovery of vegetation structure and cover within 3 years of fire. This recovery was similar to the burnt remnant woodlands. Non-native (exotic) ground cover initially increased after fire, but was no different in burnt and unburnt sites 5 years after fire. Fire had no effect on species richness, but burnt direct seeding sites had reduced species diversity (Simpson's Diversity Index) while diversity was higher in burnt remnant woodlands. Indices of soil function in all types of vegetation had recovered to levels found in unburnt sites 5 years after fire. These results indicate that even young revegetation (stands

Summary 1. The role of genetic factors in species decline and extinction is the subject of a long-running controversy, with demographical factors often seen as more important for the immediate persistence of populations and species. One gene system that directly links genetic diversity with reproduction, through its influence on fertilization success, is the self-incompatibility (SI) locus in angiosperm plants. Despite the potential importance of SI allele diversity for demographical function, there are few direct measures of S-allele numbers in multiple populations, and no studies have simultaneously measured reproductive output, mate availability, S-allele diversity and pollinator service. 2. We used diallel crosses to estimate S-allele number and mate availability in seven populations of the forb Rutidosis leptorrhynchoides ranging in size from 5 to 100 000 plants. Seed set and correlated paternity were assessed from open-pollinated inflorescences to examine reproductive output and variance in female and male fitness. To assess whether populations were receiving adequate pollinator service, the amount of pollen deposited on open-pollinated stigmas was quantified. 3. We found that small populations ( 1000 plants) with higher numbers of S-alleles, despite the maintenance of pollinator service. Greater variance in seed set among plants and higher correlated paternity in small populations suggest that low S-allele numbers are directly limiting mate availability and causing the observed reproductive failure. 4. Synthesis and applications. Our work demonstrates that the loss of genetic diversity at the SI locus can have immediate detrimental effects on reproductive performance, despite the maintenance of pollinator service. These results highlight the importance of genetic factors in determining demographical outcomes when clear links between genotype and individual fitness exist, even when populations are not ecologically constrained. This result is important for the conservation and management of many plant species as approximately half of all angiosperm families contain species with genetically controlled SI and the loss of genetic diversity through habitat loss and fragmentation is an ever-increasing reality for plant species worldwide.

Through identifying and understanding ecologically important dimensions of plant trait variation we gain insight into why particular trait combinations are favoured and into the implications of trait differences among species. Here, we describe relationships among several poorly understood leaf and stem traits across species from several Australian vegetation types. Species with lower wood density (WD) consistently deployed more leaf area per unit shoot mass (LA/SM), as did the larger-leaved species within forested sites. Higher LA/SM is likely to lead to faster growth rates, implying a previously unrecognized implication to interspecific variation in leaf size and WD. Leaf : sapwood area ratio is one of several important traits contributing to a plant's water-use strategy, yet, we still only poorly understand how plants vary in the extent to which hydraulic properties and traits such as leaf size, WD and LM/SM are coordinated, and what the implications of this variation may be.

Summary 1The leaf size–twig size spectrum is an important spectrum of variation between species, although the costs and benefits of larger vs smaller leaf size are poorly understood. This study quantified the dry mass costs of deploying leaf area in relation to leaf size, across 70 species from four sites contrasted on the basis of rainfall and soil nutrients in east-temperate Australia. 2Leaf mass fraction beyond 10 mm2 of conductive cross-section (LMF10) varied threefold and was strongly positively correlated with leaf size, both across all species and within each habitat. This and other key correlations were significant both across species and as evolutionary divergences. 3An LMF10 advantage for larger-leaved species should translate into a proportional advantage in dry mass acquisition, yet species with small leaves persist and sustain populations. This raises the question as to what factors might counterbalance an LMF advantage associated with larger leaf size. 4Within some sites, specific leaf area (SLA) decreased with leaf size, which counterbalanced the LMF10 advantage. Within other sites, and across all sites, SLA did not decline with leaf size. In these comparisons other factors, such as avoidance of overheating, must counterbalance the LMF10 advantage to larger-leaved species. 5Wood density was negatively correlated with leaf size. However, the relationship was weaker within sites in the lower rainfall zone, and species in these sites had generally higher wood density. Sapwood cross-sectional area per unit leaf area (Huber value) varied approximately ninefold across all species, and was correlated with both leaf size and SLA across all species, but not within sites.

Seed germination is dependent on the interaction between the dormancy state of a seed and the presence of favourable environmental conditions. Thus, the spectacular pulse of seedling recruitment in many Australian vegetation communities following disturbances such as fire can be attributed to changes in microsite conditions and/ or the dormancy-breaking effect of the disturbance on accumulated seed banks. Grevillea rivularis is a threatened species endemic to the area immediately above Carrington Falls in the NSW Southern Highlands. Most of the population is confined to the riparian vegetation zone in woodland and heath, and is therefore subject to periodic disturbance from fire and flood. For this species, a pulse of seedling recruitment has been recorded after fire, flood and mechanical soil disturbance. The aims of this study were to examine the density and vertical distribution of the soil-stored seed bank and to investigate the role of heat and scarification as cues for germination of fresh and soil-stored seed. There was a large seed bank under the canopies of established individuals (194 ± 73 seeds m -2 ) and most seeds were found in the 0-2 cm and leaf-litter layers of the soil profile. The germination response of soil-stored and fresh seed was examined using a hierarchical series of laboratory experiments. Seeds of G. rivularis showed marked dormancy polymorphism. Thirty-six percent of soil-stored seed germinated without treatment, whereas no untreated fresh seeds germinated. Scarification or heating caused significant germination of dormant soil-stored seed, but only scarification resulted in germination of dormant fresh seeds. These results highlight important differences in the dormancy state of soil-stored and fresh seed. Thus, being a riparian species in a fire-prone environment, the dormancy mechanisms in seeds of G. rivularis suit this species to disturbance by both fire and flood.