Demystifying the convergent ecological specialization of desiccation-tolerant vascular plants for water deficit.

BACKGROUND AND AIMS: Desiccation-tolerant vascular plants (DT plants) are able to tolerate the desiccation of their vegetative tissues; as a result, two untested paradigms can be found in the literature, despite contradictions to theoretical premises and empirical findings. First, it is widely accepted that DT plants form a convergent group of specialist plants to water deficit conditions. A derived paradigm is that DT plants are placed at the extreme end of stress tolerance. Here, we tested the hypotheses that DT plants (1) are in fact convergent specialists for water deficit conditions and (2) exhibit ecological strategies related to stress tolerance, conservative resource-use and survival. METHODS: We used biogeographical and functional-traits approaches to address the mentioned paradigms and assess the species' ecological strategies. For this, 27 DT plants were used and compared to 27 phylogenetically related desiccation-sensitive vascular plants (DS plants). KEY RESULTS: We could not confirm either of the two hypotheses. We found that despite converging in desiccation tolerance, DT plants differ in relation to the conditions in which they occur and the ecological strategies they use to deal with water deficit. We found that some DT plants exhibit advantageous responses for higher growth and resource acquisition, which are suitable responses to cope with more productive conditions or with higher disturbance. We discuss that the ability to tolerate desiccation could compensate for a drought vulnerability promoted by higher investment in growth and bring advantages to deal with quick and pronounced variation of water, rather than to drought solely. CONCLUSIONS: DT plants are not only selected by drought as an environmental constraint. The alternative functional designs could promote the diversity of ecological strategies, which preclude their convergence to the same resources and conditions. Thus, DT plants are a heterogeneous group of plants in how they deal with drought, despite their desiccation tolerance ability.

People-Centered and Ecosystem-Based Knowledge Co-Production to Promote Proactive Biodiversity Conservation and Sustainable Development in Namibia.

Growing levels of uncertainty and vulnerability generated by land use conversion and climate change set demands on local communities and national institutions to build synergies between the diverse array of knowledge systems in order to provide policy makers and practitioners with the best available information to decide what urgent actions must be taken. Science policy arenas and agreements such as the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) and the Convention on Biological Diversity (CBD) recognize the importance of different types of knowledge and the need for broad stakeholder involvement, yet the use of indigenous and local knowledge (ILK) in environmental decision-making processes is still underdeveloped. This study involved working with local stakeholders, using the MARISCO method (adaptive MAnagement of vulnerability and RISks at COnservation sites) to carry out a systematic situation analysis of the existing socioenvironmental conditions. The assessments were conducted in the Kavango East Region in northern Namibia with the participation of inhabitants of the Khaudum North Complex, a protected area network covering wooded savannahs belonging to the Northern Kalahari sandveld. General outcomes of the assessments and evaluations made by the local stakeholders concerning the most critical drivers of degradation of the ecosystems appeared to support existing scientific knowledge of the study area, demonstrating that community-based assessments can provide valuable information about socioecological systems where scientific data are scarce. The findings of this study also highlight the importance of power dynamics for the implementation of participatory processes and the interpretation of their outcomes.

Plant communities on inselbergs in Burkina Faso.

The safeguarding and sustainable management of natural resources, particularly plant resources, requires the implementation of conservation strategies. The study of plant communities is an essential tool for monitoring the development of plant formations. The aim of this study was to identify the plant communities on inselbergs of Burkina Faso in West Africa, to provide a database to supporting the sustainable management of the plant resources withing these fragile ecosystems. Stratified and random sampling was carried out on selected inselbergs in different parts of Burkina Faso along a climatic gradient. In the different phytogeographical sectors, inselbergs consist of granite or sandstone. Plant surveys were conducted using 900 m2 plots for the woody stratum and 100 m2 plots for the herbaceous stratum. An exhaustive list of plant species was compiled and an abundance-dominance coefficient for each species was determined. A DCA, through PCord.6, was used to obtain preliminary groups. Indicator species were determined by a Monte Carlo test with p < 0.05 and calculation of the fidelity index (Phi). Diversity indices through the Shannon index and equitability of Pielou were calculated using Pcord.6 to compare plant communities. A total of 12 plant communities were identified for the inselbergs of Burkina Faso, including 9 communities for savannah and 3 communities for monocotyledonous-mats and ephemeral flush vegetation. The main ecological factors governing the distribution of these inselberg plant communities were found to be were found to be climate, soil depth, soil moisture and altitude. In savannah plant communities, the Terminalia laxiflora and Tephrosia nana communities (unit 6) had the highest number (13) of diagnostic species and the highest fidelity (Phi = 0.97) was for Cleome viscosa species in the Acacia tortilis and Aristida kerstingii communities (unit 1). Diagnostic species numbers vary from 6 to 4 in monocotyledonous-mats and ephemeral flush vegetation and the Dopatrium longidens (Phi = 0.76) and Cyperus podocarpus (Phi = 0.75) have the highest fidelity to unit 3. The Shannon diversity index of deep soil plant communities was highest and significantly different from that of the other savannah communities. Concerning the Piélou equitability index, high values were found in all plant groups, reflecting the absence of species dominance and a balance of the different plant groups. Floristically, Afrotrilepis pilosa infestation of inselbergs is common in West Africa. In Burkina Faso, in addition to Afrotrilepis pilosa, 10 other plant species are found specifically on inselbergs. Given the fragility of the ecosystems in which they live, these inselberg species should be protected.

The ecological and evolutionary dynamics of inselbergs.

Islands are fundamental model systems in ecology, biogeography, and evolutionary biology. However, terrestrial islands, unlike their aquatic counterparts, have received comparatively less attention. Among these land islands, inselbergs (i.e. isolated rock outcrops with diverse lithologies and a modest topographical prominence) stand out as iconic examples distributed worldwide across global biomes. Due to their durable lithology, inselbergs change slowly, persisting for tens of millions of years. In this review, we propose a biological definition for inselbergs that captures three fundamental characteristics of inselbergs from the perspective of biota. These are old age, isolation and the presence of unique microhabitats that are rare or absent in the surrounding matrix, fostering distinct communities often with unique and endemic biota. We synthesise the state of the art and formulate a set of testable hypotheses to deepen our understanding of the origins and maintenance of diversity on inselbergs, which are increasingly exposed to anthropogenic threats. By offering different habitats compared to the surrounding habitat matrix (e.g. moist microhabitats in dryland landscapes and xeric environments in humid tropical landscapes), inselbergs may allow specific lineages to thrive beyond their typical geographical limits. Particularly in drylands and degraded landscapes, inselbergs may not just provide different habitats but also act as ecological refuges or evolutionary refugia by providing a wider range of potential microhabitats than the surrounding matrix, enhancing resilience and promoting regional biodiversity. The central role of the matrix ensures that the ecological and evolutionary dynamics of inselbergs differ from those of true islands such as oceanic islands. Given that inselberg biota coexist within a terrestrial matrix, interactions between inselberg and matrix populations impact each other significantly. Over evolutionary timescales, matrix species may contract to inselberg refugia, preserving lineages while cycles of isolation and reconnection may drive speciation via a species pump. Although inselberg biodiversity has been studied predominantly from an island biogeography perspective, we argue that depending on the spatial scale, habitat specificity and mobility of the organisms considered, a range of different theories and paradigms can help explain the biogeography and local distribution patterns of different taxonomic and functional groups of inselberg species.

Variation in the reproductive performance of the Trollius-Chiastocheta mutualism at the edge of its range in north-east Germany.

Empirical studies into obligate pollination mutualisms which elucidate the variation in reproductive performance of shrinking populations within human-altered environments are rare. This study focuses on the obligate pollination mutualism between Trollius europaeus (Ranunculaceae) and fly species of the genus Chiastocheta which act both as the plant's main pollinators and as predators in that their larvae eat a fraction of the developing seeds. The study area is situated in the lowlands of north-east Germany. Many populations of T. europaeus have become comparatively small and scattered in this region as a consequence of agricultural land use intensification. We studied the plant's reproductive fitness in populations ranging in size from 7 to 12,000 flowers. In a field experiment, we applied four pollination treatments and also recorded fly density in 28 natural T. europaeus populations. The fitness of the offspring from 19 populations was studied in a common garden experiment. In both approaches, a reduction in the fitness of small host plant populations could be demonstrated. Fitness loss can be put down to the quantitative and qualitative limitation of pollen caused by inbreeding and the negative feedback on relative seed set caused by the reduced ability of small plant populations to support a sufficiently large fly population. Although increases in fly density are associated with rising predation costs, the plant species' net benefit is a positive function of its population size. Our study highlights the reproductive variability of the Trollius-Chiastocheta interaction along a population size gradient in a marginal region of its range, thus contributing to the understanding of the overall variability of this mutualism.

The BIOTA Biodiversity Observatories in Africa--a standardized framework for large-scale environmental monitoring.

The international, interdisciplinary biodiversity research project BIOTA AFRICA initiated a standardized biodiversity monitoring network along climatic gradients across the African continent. Due to an identified lack of adequate monitoring designs, BIOTA AFRICA developed and implemented the standardized BIOTA Biodiversity Observatories, that meet the following criteria (a) enable long-term monitoring of biodiversity, potential driving factors, and relevant indicators with adequate spatial and temporal resolution, (b) facilitate comparability of data generated within different ecosystems, (c) allow integration of many disciplines, (d) allow spatial up-scaling, and (e) be applicable within a network approach. A BIOTA Observatory encompasses an area of 1 km(2) and is subdivided into 100 1-ha plots. For meeting the needs of sampling of different organism groups, the hectare plot is again subdivided into standardized subplots, whose sizes follow a geometric series. To allow for different sampling intensities but at the same time to characterize the whole square kilometer, the number of hectare plots to be sampled depends on the requirements of the respective discipline. A hierarchical ranking of the hectare plots ensures that all disciplines monitor as many hectare plots jointly as possible. The BIOTA Observatory design assures repeated, multidisciplinary standardized inventories of biodiversity and its environmental drivers, including options for spatial up- and downscaling and different sampling intensities. BIOTA Observatories have been installed along climatic and landscape gradients in Morocco, West Africa, and southern Africa. In regions with varying land use, several BIOTA Observatories are situated close to each other to analyze management effects.

Local perception of ecosystem services and their conservation in Sudanian savannas of Burkina Faso (West Africa).

CONTEXT: In Burkina Faso, Sudanian savannas are important ecosystems for conservation of plant diversity. Due to desertification and insecurity, population migration from the North has increased human density and anthropogenic pressure on southern savannas. This study aims to investigate knowledge of local populations on ecosystem services (ES) and perception of their conservation. METHOD: Individual semi-structured interviews about knowledge on ES and ecosystem conservation issues were conducted. Informants were selected according to sociocultural groups and sex in three areas of different land use intensity: the communal area of Dano (CAD), the Total Wildlife Reserve of Bontioli (TWRB) and the Game Ranch of Nazinga (GRN). The use value and vulnerability index of each plant species were determined. A cluster analysis and a principal component analysis were carried out to identify the particular knowledge of different ethnic groups. RESULTS: Overall, 163 plant species were cited for fifteen ES. Provisioning services were most frequently cited (100%), regulating services second most frequently (92.47%). Entire plants were exclusively used for ES with non-material benefits (protection against wind, for shading, soil fertility, erosion prevention, tourism and religion). The ten species contributing most to ES provision were Vitellaria paradoxa, Parkia biglobosa, Diospyros mespiliformis, Adansonia digitata, Lannea microcarpa, Faidherbia albida, Khaya senegalensis, Afzelia africana, Ficus sycomorus, Pterocarpus erinaceus. Seven of them were identified as highly vulnerable. Around GRN, migrants and natives shared the same knowledge, while migrants in TWRB used the ES only to a small extent due to restricted contact with the native population. Migrants and natives of GRN had more knowledge on tourism and crafts services while the natives of CAD and TWRB made use of the services that sustain the quality of the agricultural land and meet their primary needs. To reduce further degradation, different communities suggested unanimously raising awareness of the importance of biodiversity and ecosystem conservation. The most quoted motivations to preserve ecosystems were vegetation sustainability and village development. CONCLUSION: This study documented important local knowledge-based information to guide cultivation of local multipurpose species and initiation of communities to practice best management strategies for sustainable conservation of biodiversity.

Sugarloaf Land in south-eastern Brazil: a tropical hotspot of lowland inselberg plant diversity.

BACKGROUND: Isolated monoliths of granitic and/or gneissic rock rising abruptly from the surrounding landscape are known as inselbergs. Dome-shaped inselbergs are common throughout the Atlantic Forest in south-eastern Brazil, a region known as Sugarloaf Land (SLL). This study aimed to create the first checklist of vascular plant species occurring on lowland inselbergs in SLL, with a focus on vegetation islands. We used information from online databases, our own field sampling and data from previously-published studies. We found 548 vascular plant species (505 angiosperms; 43 ferns and lycophytes) belonging to 69 families and 212 genera. Of all identified species, 536 are native and 12 are naturalised. NEW INFORMATION: We updated the information currently available in Flora do Brasil 2020, as 59% of the angiosperms and 63% of the ferns and lycophytes on our checklist were not previously characterised as occurring on rock outcrops. As a first step towards generating a Virtual Herbarium of lowland inselberg vascular plants, we added barcode vouchers with images available online for 75% of the total number of vascular species. In the official lists of endangered species, 115 angiosperms and five ferns and lycophytes are mentioned. However, the conservation status of many species have not yet been evaluated (77% angiosperms; 88% ferns and lycophytes), thus this list is an important step towards their conservation. The information provided herein is essential for management programmes related to rock outcrops in Brazil as they are facing serious threats to conservation.

New microsatellite markers for Xerophyta dasylirioides (Velloziaceae), an endemic species on Malagasy inselbergs.

PREMISE: Microsatellite markers were developed for Xerophyta dasylirioides (Velloziaceae), a species endemic to the Malagasy inselbergs, to explore the impact of its island-like distribution on genetic diversity and gene flow. METHODS AND RESULTS: A total of 7110 perfect microsatellite loci were recovered by shotgun sequencing on an Illumina MiSeq platform. Primer pairs were designed for 40 arbitrarily selected loci. Fifteen primer pairs that generated distinct PCR products were used to genotype 80 individuals of X. dasylirioides from three inselberg populations. All markers were polymorphic, revealing two to 17 alleles in the overall sampling. Levels of observed and expected heterozygosity per locus ranged from zero to 1.000 and from zero to 0.850, respectively. Success rates of cross-amplification in 10 additional species of Xerophyta (X. croatii, X. decaryi, X. isaloensis, X. labatii, X. lewisiae, X. pinifolia, X. retinervis, X. setosa, X. spekei, X. tulearensis) ranged from zero to 70%. CONCLUSIONS: Fifteen newly developed microsatellite markers provide a toolkit for assessing population genetic parameters of X. dasylirioides in its unique island-like habitats.

Impact of human disturbance on bee pollinator communities in savanna and agricultural sites in Burkina Faso, West Africa.

All over the world, pollinators are threatened by land-use change involving degradation of seminatural habitats or conversion into agricultural land. Such disturbance often leads to lowered pollinator abundance and/or diversity, which might reduce crop yield in adjacent agricultural areas. For West Africa, changes in bee communities across disturbance gradients from savanna to agricultural land are mainly unknown. In this study, we monitored for the impact of human disturbance on bee communities in savanna and crop fields. We chose three savanna areas of varying disturbance intensity (low, medium, and high) in the South Sudanian zone of Burkina Faso, based on land-use/land cover data via Landsat images, and selected nearby cotton and sesame fields. During 21 months covering two rainy and two dry seasons in 2014 and 2015, we captured bees using pan traps. Spatial and temporal patterns of bee species abundance, richness, evenness and community structure were assessed. In total, 35,469 bee specimens were caught on 12 savanna sites and 22 fields, comprising 97 species of 32 genera. Bee abundance was highest at intermediate disturbance in the rainy season. Species richness and evenness did not differ significantly. Bee communities at medium and highly disturbed savanna sites comprised only subsets of those at low disturbed sites. An across-habitat spillover of bees (mostly abundant social bee species) from savanna into crop fields was observed during the rainy season when crops are mass-flowering, whereas most savanna plants are not in bloom. Despite disturbance intensification, our findings suggest that wild bee communities can persist in anthropogenic landscapes and that some species even benefitted disproportionally. West African areas of crop production such as for cotton and sesame may serve as important food resources for bee species in times when resources in the savanna are scarce and receive at the same time considerable pollination service.

Bee pollination increases yield quantity and quality of cash crops in Burkina Faso, West Africa.

Mutualistic biotic interactions as among flowering plants and their animal pollinators are a key component of biodiversity. Pollination, especially by insects, is a key element in ecosystem functioning, and hence constitutes an ecosystem service of global importance. Not only sexual reproduction of plants is ensured, but also yields are stabilized and genetic variability of crops is maintained, counteracting inbreeding depression and facilitating system resilience. While experiencing rapid environmental change, there is an increased demand for food and income security, especially in sub-Saharan communities, which are highly dependent on small scale agriculture. By combining exclusion experiments, pollinator surveys and field manipulations, this study for the first time quantifies the contribution of bee pollinators to smallholders' production of the major cash crops, cotton and sesame, in Burkina Faso. Pollination by honeybees and wild bees significantly increased yield quantity and quality on average up to 62%, while exclusion of pollinators caused an average yield gap of 37% in cotton and 59% in sesame. Self-pollination revealed inbreeding depression effects on fruit set and low germination rates in the F1-generation. Our results highlight potential negative consequences of any pollinator decline, provoking risks to agriculture and compromising crop yields in sub-Saharan West Africa.

Spatially explicit multi-threat assessment of food tree species in Burkina Faso: A fine-scale approach.

Over the last decades agroforestry parklands in Burkina Faso have come under increasing demographic as well as climatic pressures, which are threatening indigenous tree species that contribute substantially to income generation and nutrition in rural households. Analyzing the threats as well as the species vulnerability to them is fundamental for priority setting in conservation planning. Guided by literature and local experts we selected 16 important food tree species (Acacia macrostachya, Acacia senegal, Adansonia digitata, Annona senegalensis, Balanites aegyptiaca, Bombax costatum, Boscia senegalensis, Detarium microcarpum, Lannea microcarpa, Parkia biglobosa, Sclerocarya birrea, Strychnos spinosa, Tamarindus indica, Vitellaria paradoxa, Ximenia americana, Ziziphus mauritiana) and six key threats to them (overexploitation, overgrazing, fire, cotton production, mining and climate change). We developed a species-specific and spatially explicit approach combining freely accessible datasets, species distribution models (SDMs), climate models and expert survey results to predict, at fine scale, where these threats are likely to have the greatest impact. We find that all species face serious threats throughout much of their distribution in Burkina Faso and that climate change is predicted to be the most prevalent threat in the long term, whereas overexploitation and cotton production are the most important short-term threats. Tree populations growing in areas designated as 'highly threatened' due to climate change should be used as seed sources for ex situ conservation and planting in areas where future climate is predicting suitable habitats. Assisted regeneration is suggested for populations in areas where suitable habitat under future climate conditions coincides with high threat levels due to short-term threats. In the case of Vitellaria paradoxa, we suggest collecting seed along the northern margins of its distribution and considering assisted regeneration in the central part where the current threat level is high due to overexploitation. In the same way, population-specific recommendations can be derived from the individual and combined threat maps of the other 15 food tree species. The approach can be easily transferred to other countries and can be used to analyze general and species specific threats at finer and more local as well as at broader (continental) scales in order to plan more selective and efficient conservation actions in time. The concept can be applied anywhere as long as appropriate spatial data are available as well as knowledgeable experts.

Anatomical analysis of turgescent and semi-dry resurrection plants: the effect of sample preparation on the sample, resolution, and image quality of X-ray micro-computed tomography (µCT).

Computer tomography has been used frequently for the 3-D visualization of plant anatomical traits but sample preparation has been widely neglected. Without any preparation smaller (i.e., up to 1 × 1 cm(2) ) turgescent or semi-dry plant samples (especially leaf samples) diminish the image quality of a scan due to gradual water loss and therefore constant movement. A suitable preparation for scans of turgescent and semi-dry plant samples with a high resolution µCT (<1-5 µm) has to be very thin, heat-resistant (up to 35°C), have a low attenuation coefficient, and should not alter the water content and structure of the sample. Several agents have been tested, but only a coating with vaseline conserved the water content of a plant sample efficiently. However, water molecules and vaseline both attenuate the X-ray beam, which decreases the image quality of scans of turgescent or semi-dry plant samples. Therefore, trade-offs between the spatial resolution, sample water content, sample size, and image quality have to be considered: larger samples have to be placed further away from the X-ray tube, which leads to a lower spatial resolution; water and preparation agents attenuate the X-ray beam, causing low-quality images which may be accompanied by motion artifacts compared to a scan of a dry sample, where no preparation is necessary.