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The separation of sexes in dioecious plants enables males and females to adopt different strategies to balance reproduction and growth, but can also lead to female susceptibility due to their high reproductive burden. Understanding if a dioecious species is susceptible or adaptable in the face of worsening abiotic conditions would be useful for revegetating habitats under climate change. Our study compared four populations of the Australian native shrub, Pimelea microcephala subsp. microcephala (n = 885) across an annual rainfall gradient of ∼250–400 mm to understand the impact of decreasing rainfall on size classes, growth metrics, sex ratio, the proportion of juveniles and spatial distributions. We found that irrespective of site rainfall, male and female plants achieved similar sizes. The populations exhibited four size classes, defined by height, diameter and sex, but not site rainfall (unpaired group method with arithmetic mean cluster analysis, p <.05). Spatially, populations reflected the clumped distribution of overlying canopy cover, and did not demonstrate niche partitioning between sexes. The lack of population variation with rainfall indicates that the species may be suitable for arid zone revegetation in arid regions with declining rainfall. Conservation management of the species should include maintaining canopy tree cover to encourage seed dispersal. [ABSTRACT FROM AUTHOR]

Context: The proportion of dioecious species can vary considerably among climates and habitats. However, studies often involve isolated communities or large diverse areas and fail to capture how proportions vary across diverse landscapes. Aims: To identify (1) life-history associations of terrestrial dioecious plant species in central southern Australia, (2) whether proportion of dioecy varies spatially across central southern Australia, and (3) whether proportion of dioecy is correlated with life-history and/or climate factors. Methods: Species growth form, pollination mechanisms and seed-dispersal features were extracted from herbarium databases to determine potential dioecy-linked traits. Distribution data for native terrestrial species in 66 Interim Biogeographical Regionalisation of Australia subregions were extracted from the Australasian Virtual Herbarium to calculate the proportion of total native species richness that are dioecious. Climate data for each subregion were also obtained from Terrestrial Ecology Research Network databases to investigate relationships among climate, life-history traits and dioecy. Key results: Woodiness, abiotic pollination and endozoochory were more prevalent in dioecious than non-dioecious taxa. Proportion of dioecy ranged from 1.7% to 8.5% among subregions and correlated negatively with annual temperature range, January to March rainfall and precipitation seasonality and with average annual daily mean, minimum, maximum and average annual minimum temperature. The highest-ranked models of dioecy incorporated the additive effects of the relative proportion of woody species and either annual temperature ranges, January to March rainfall or average annual daily maximum temperature. Conclusions: Dioecy was associated with woodiness, abiotic pollination and endozoochory, in line with studies of other flora, with the model of stable temperature range and woodiness being the highest-ranked model of dioecy. Implications: Areas with higher proportions of dioecy can be targeted for future investigations into dioecious plant ecology to aid conservation and ecosystem management. Dioecious plants comprise 6% of Angiosperm species, yet the proportion of dioecious species varies considerably among the native floras of the world. Higher proportions appear to be linked to life history and habitat climate conditions; however, the variation of proportions across larger, climatically diverse landmasses is rarely studied. We compared the proportion of dioecious plants of total native species richness across the climatically diverse southern Australia, to identify dioecious 'hotspots' and climate and life-history conditions associated with higher proportions of dioecy. [ABSTRACT FROM AUTHOR]

Incidental bycatch in fishing nets is a global cause of incidental mortality of marine mammals. Two classes of approaches attempt to mitigate this impact: (1) approaches that change the behaviour of the fisher (e.g. closures and gear modifications), (2) approaches that attempt to change the behaviour of the bycatch species (e.g. acoustic alarms or pingers). Even though the effectiveness of pingers has been established for very few bycatch species, pingers are now mandatory in many fisheries throughout the world. Pingers are being trialled in commercial gill net fisheries in tropical Australia to reduce the bycatch of the dugong and three species of coastal dolphins, despite an absence of robust assessments of: (1) their effectiveness in reducing bycatch, (2) the likelihood of alienating bycatch species from critical habitats. We conducted replicate experiments to test the behavioural responses of dugongs to 4 and 10 kHz pingers in an array simulating a net. Each experiment comprised three sequential 10-min treatments in which two pingers were: (1) inactive, (2) active, (3) inactive. The rate of decline of the number of dugongs within the focal arena did not change significantly while pingers were activated. Dugongs passed between the pingers (where a net would be located) irrespective of whether the alarms were active or inactive, fed throughout the experiments and did not change their orientation to investigate pinger noise, or their likelihood of vocalizing. We conclude that: (1) pingers are unlikely to alienate dugongs from critical habitats or reduce dugong mortalities in fishing nets, (2) bycatch mitigation strategies such as pingers that rely on changing animal behaviour should only be used after rigorous testing on all likely bycatch species. [ABSTRACT FROM AUTHOR]