Propagating uncertainty from catchment experiments to estimates of streamflow reduction by invasive alien plants in southwestern South Africa

Abstract Long-term catchment experiments from South Africa have demonstrated that afforestation of grasslands and shrublands significantly reduces surface-water runoff. These results have guided the country’s forestry policy and the implementation of a national Invasive Alien Plant (IAP) control programme for the past few decades. Unfortunately, woody IAP densities continue to increase, compounding existing threats to water security from population growth and climatic change. Decision makers need defensible estimates of the impacts of afforestation or invasions on runoff to weigh up alternative land use options, or guide investment of limited resources into ecosystem restoration through IAP clearing versus engineering-based water-augmentation schemes. Existing attempts to extrapolate the impacts observed in catchment afforestation experiments to broad-scale IAP impacts give no indication of uncertainty. Globally, the uncertainty inherent in the results from paired-catchment experiments is seldom propagated into subsequent analyses making use of these data. We present a fully reproducible Bayesian model that propagates uncertainty from input data to final estimates of changes in streamflow when extrapolating from catchment experiments to broader landscapes. We apply our model to South Africa’s catchment experiment data, estimating streamflow losses to plantations and analogous plant invasions in the catchments of southwestern South Africa, including uncertainty. We estimate that regional streamflow is reduced by 304 million m3 or 4.14% annually as a result of IAPs, with an upper estimate of 408 million m3 (5.54%) and a lower estimate of 267 million m3 (3.63%). Our model quantifies uncertainty associated with all parameters and their contribution to overall uncertainty, helping guide future research needs. Acknowledging and quantifying inherent uncertainty enables more defensible decisions regarding water resource management. This article is protected by copyright. All rights reserved

Terminal regions confer plasticity to the tetrameric assembly of human HspB2 and HspB3

Heterogeneity in small heat shock proteins (sHsps) spans multiple spatiotemporal regimes – from fast fluctuations of part of the protein, to conformational variability of tertiary structure, plasticity of the interfaces, and polydispersity of the inter-converting, and co-assembling oligomers. This heterogeneity and dynamic nature of sHsps has significantly hindered their structural characterisation. Atomic-coordinates are particularly lacking for vertebrate sHsps, where most available structures are of extensively truncated homomers. sHsps play important roles in maintaining protein levels in the cell and therefore in organismal health and disease. HspB2 and HspB3 are vertebrate sHsps that are found co-assembled in neuromuscular cells, and variants thereof are associated with disease. Here, we present the structure of human HspB2/B3, which crystallised as a hetero-tetramer in a 3:1 ratio. In the HspB2/B3 tetramer, the four a-crystallin domains (ACDs) assemble into a flattened tetrahedron which is pierced by two non-intersecting approximate dyads. Assembly is mediated by flexible “nuts and bolts” involving IXI/V motifs from terminal regions filling ACD pockets. Parts of the N-terminal region bind in an unfolded conformation into the anti-parallel shared ACD dimer grooves. Tracts of the terminal regions are not resolved, most likely due to their disorder in the crystal lattice. This first structure of a full-length human sHsp heteromer reveals the heterogeneous interactions of the terminal regions and suggests a plasticity that is important for the cytoprotective functions of sHsps

Priority questions for biodiversity conservation in the Mediterranean biome: Heterogeneous perspectives across continents and stakeholders

The identification of research questions with high relevance for biodiversity conservation is an important step towards designing more effective policies and management actions, and to better allocate funding among alternative conservation options. However, the identification of priority questions may be influenced by regional differences in biodiversity threats and social contexts, and to variations in the perceptions and interests of different stakeholders. Here we describe the results of a prioritization exercise involving six types of stakeholders from the Mediterranean biome, which includes several biodiversity hotspots spread across five regions of the planet (Europe, Africa, North and South America, and Australia). We found great heterogeneity across regions and stakeholder types in the priority topics identified and disagreement among the priorities of research scientists and other stakeholders. However, governance, climate change, and public participation issues were key topics in most regions. We conclude that the identification of research priorities should be targeted in a way that integrates the spectrum of stakeholder interests, potential funding sources and regional needs, and that further development of interdisciplinary studies is required. The key questions identified here provide a basis to identify priorities for research funding aligned with biodiversity conservation needs in this biome

Range-wide population viability analyses reveal high sensitivity to wildflower harvesting in extreme environments Range-wide population viability analyses reveal high sensitivity to wildflower harvesting in extreme environments

Abstract 1. The ecological effects of harvesting from wild populations are often uncertain, especially since the sensitivity of populations to harvesting can vary across species’ geographical ranges. In the Cape Floristic Region (CFR, South Africa) biodiversity hotspot, wildflower harvesting is widespread and economically important, providing an income to many rural communities. However, with very few species studied to date, and without considering range-wide sensitivity to harvesting, there is limited information available to ensure the sustainability of wildflower harvesting. 2. We studied geographical variation in sensitivity to wildflower harvesting for 26 Proteaceae shrubs with fire-driven life cycles using population viability analyses. We developed stochastic, density-dependent population models that were parameterized from individual demographic rates (adult fecundity, seedling recruitment and adult fire survival) and local environmental conditions across the geographical ranges of the study species. We then simulated the effects of harvesting on populations in different environments across species ranges. Our model simulations predicted extinction risk per population, and we derived extinction probabilities over 100 years in response to different harvesting regimes. We used these population-level extinction probabilities to quantify inter- and intraspecific variation in sensitivity to wildflower harvesting, and to explore how geographical variation in sensitivity depends on environmental conditions (climate, soil fertility and fire disturbance). 3. We detected considerable inter- and intraspecific variation in sensitivity to wildflower harvesting for the 26 study species. This held for both ‘nonsprouters’ and ‘resprouters’ (species with low and high fire persistence ability, respectively). Intraspecific variation in sensitivity to harvesting showed varying geographical patterns and associated with environmental variation. Notably, sensitivity was high towards range edges and at the climatic extremes of species ranges, respectively. 4. Synthesis and applications: We show the importance of combining spatial demographic data, density-dependent population dynamics and environmental variation when assessing sensitivity to harvesting across species geographical ranges. Our findings caution against the application of general harvesting guidelines irrespective of species, geographical location or local environmental conditions. Our range-wide population viability analyses provide insights for developing species-specific, spatially nuanced guidelines for conservation management. Our approach also identifies species and areas to prioritise for monitoring to prevent the overexploitation of harvested species. Abstract 1. The ecological effects of harvesting from wild populations are often uncertain, especially since the sensitivity of populations to harvesting can vary across species’ geographical ranges. In the Cape Floristic Region (CFR, South Africa) biodiversity hotspot, wildflower harvesting is widespread and economically important, providing an income to many rural communities. However, with very few species studied to date, and without considering range-wide sensitivity to harvesting, there is limited information available to ensure the sustainability of wildflower harvesting. 2. We studied geographical variation in sensitivity to wildflower harvesting for 26 Proteaceae shrubs with fire-driven life cycles using population viability analyses. We developed stochastic, density-dependent population models that were parameterized from individual demographic rates (adult fecundity, seedling recruitment and adult fire survival) and local environmental conditions across the geographical ranges of the study species. We then simulated the effects of harvesting on populations in different environments across species ranges. Our model simulations predicted extinction risk per population, and we derived extinction probabilities over 100 years in response to different harvesting regimes. We used these population-level extinction probabilities to quantify inter- and intraspecific variation in sensitivity to wildflower harvesting, and to explore how geographical variation in sensitivity depends on environmental conditions (climate, soil fertility and fire disturbance). 3. We detected considerable inter- and intraspecific variation in sensitivity to wildflower harvesting for the 26 study species. This held for both ‘nonsprouters’ and ‘resprouters’ (species with low and high fire persistence ability, respectively). Intraspecific variation in sensitivity to harvesting showed varying geographical patterns and associated with environmental variation. Notably, sensitivity was high towards range edges and at the climatic extremes of species ranges, respectively. 4. Synthesis and applications: We show the importance of combining spatial demographic data, density-dependent population dynamics and environmental variation when assessing sensitivity to harvesting across species geographical ranges. Our findings caution against the application of general harvesting guidelines irrespective of species, geographical location or local environmental conditions. Our range-wide population viability analyses provide insights for developing species-specific, spatially nuanced guidelines for conservation management. Our approach also identifies species and areas to prioritise for monitoring to prevent the overexploitation of harvested species

Functional traits explain the Hutchinsonian niches of plant species

Aim: The Hutchinsonian niche is a foundational concept in ecology and evolutionary biology that describes fundamental characteristics of any species: the global maximum population growth rate (rmax); the niche optimum (the environment for which rmax is reached); and the niche width (the environmental range for which intrinsic population growth rates are positive). We examine whether these characteristics are related to inter- and intraspecific variation in functional traits. Location: Cape Floristic Region, South Africa. Time period: Present day. Major taxa studied: Twenty-six plant species (Proteaceae). Methods: We measured leaf, plant-architectural and seed traits across species geographical ranges. We then examined how species-mean traits are related to demographically derived niche characteristics of rmax, in addition to niche optima and widths in five environmental dimensions, and how intraspecific trait variation is related to niche widths. Results: Interspecific trait variation generally exceeded range-wide intraspecific trait variation. Species-mean trait values were associated with variation in rmax (R-2 = 0.27) but were more strongly related to niche optima (mean R-2 = 0.56). These relationships generally matched trait-environment associations described in the literature. Both species-mean traits and intraspecific trait variability were strongly related to niche widths (R-2 = 0.66 and 0.59, respectively). Moreover, niche widths increased with intraspecific trait variability. Overall, the different niche characteristics were associated with few, largely non-overlapping sets of traits. Main conclusions: Our study relating functional traits to Hutchinsonian niches demonstrates that key demographic properties of species relate to few traits with relatively strong effects. Our results further support the hypothesis that intraspecific trait variation increases species niche widths. Given that niche characteristics were related to distinct sets of traits, different aspects of environmental change might affect axes of trait variation independently. Trait-based studies of Hutchinsonian niches thus yield important insights into the mechanisms shaping functional biodiversity, which should reinforce the role of traits in functional biogeography

Global patterns in the phylogenetic structure of island mammal assemblages

Assemblage-level phylogenies carry the signature of ecological and evolutionary processes, which may provide useful information on modes of assemblage formation. We present a global-scale analysis of the emergent phylogenetic properties of mammal assemblages on islands, in which we compared the structure of 595 island assemblages with null models constructed under four alternative definitions of regional source pools. Although most assemblages had a structure indistinguishable from random samples, for some mammal taxa, up to 40% of island assemblages were phylogenetically overdispersed. This suggests that in at least some cases, the processes that shape island faunas are not independent of phylogeny. Furthermore, measures of phylogenetic structure were associated in some cases with island geographical features (size, maximum elevation and habitat diversity). Our results suggest that part of the signal of assemblage formation processes is detectable in the phylogenies of contemporary island mammal faunas, though much is obscured by the complexity of these processes