Functional Traits and Grain Size in Species Assemblages of a Neotropical Dry Forest

A long-standing question in ecology is how so many tree species can coexist. New insight into assembly processes has been gained through functional traits that influence fitness. Such traits include the maximum height and diameter of a species as these describe the plant’s ability to compete for light. Additionally, specific leaf area (SLA) describes the amount of leaf area for light capture per unit of biomass invested. SLA is one of the easiest traits to measure, but it depends on access to fresh leaf material which is not possible for samples from remote areas or historical collections e.g. herbaria. The study examined community assembly patterns based on species functional tratis in a species-rich tropical dry forest at the Madidi National Park (MNP) of Bolivia. In my first chapter, a protocol to predict SLA for fresh leaves from dry leaves was developed. On the same leaf, area was repeatedly measured for fresh and dried leaves to generate four general mixed effects models, varying in their inclusion of the position in the crown where the leaf develops. The accuracy of the models was tested on leaves from an oak-hickory forest in USA. Both models performed well and are readily applicable to other datasets. A protocol for studies predicting SLA from dry leaves was developed. In my second chapter, I investigated the distribution of trait values at plots of different sizes to understand processes that lead to different species assemblages. Deterministic (habitat filtering and competitive exclusion) and stochastic processes are potential drivers of species coexistence in assemblages. The importance of these non-exclusive processes in structuring assemblages at different scales remains unclear. I compared the trait dispersion of SLA (using models from chapter 1), maximum height, and maximum diameter of observed versus null species assemblages with metrics sensitive to deterministic processes. I found evidence for deterministic processes structuring species assemblages in the MNP. Competitive exclusion had greater importance at small grain sizes. Habitat filtering had greater importance at large grain sizes. Ecologically, the results indicate that stabilizing processes promote patterns of species diversity and co-existence in a species-rich tropical dry forest in Bolivia

Elevational gradients in β-diversity reflect variation in the strength of local community assembly mechanisms across spatial scales

Despite long-standing interest in elevational-diversity gradients, little is known about the processes that cause changes in the compositional variation of communities (β-diversity) across elevations. Recent studies have suggested that β-diversity gradients are driven by variation in species pools, rather than by variation in the strength of local community assembly mechanisms such as dispersal limitation, environmental filtering, or local biotic interactions. However, tests of this hypothesis have been limited to very small spatial scales that limit inferences about how the relative importance of assembly mechanisms may change across spatial scales. Here, we test the hypothesis that scale-dependent community assembly mechanisms shape biogeographic β-diversity gradients using one of the most well-characterized elevational gradients of tropical plant diversity. Using an extensive dataset on woody plant distributions along a 4,000-m elevational gradient in the Bolivian Andes, we compared observed patterns of β-diversity to null-model expectations. β-deviations (standardized differences from null values) were used to measure the relative effects of local community assembly mechanisms after removing sampling effects caused by variation in species pools. To test for scale-dependency, we compared elevational gradients at two contrasting spatial scales that differed in the size of local assemblages and regions by at least an order of magnitude. Elevational gradients in β-diversity persisted after accounting for regional variation in species pools. Moreover, the elevational gradient in β-deviations changed with spatial scale. At small scales, local assembly mechanisms were detectable, but variation in species pools accounted for most of the elevational gradient in β-diversity. At large spatial scales, in contrast, local assembly mechanisms were a dominant force driving changes in β-diversity. In contrast to the hypothesis that variation in species pools alone drives β-diversity gradients, we show that local community assembly mechanisms contribute strongly to systematic changes in β-diversity across elevations.We conclude that scale-dependent variation in community assembly mechanisms underlies these iconic gradients in global biodiversityThe Madidi Project has been funded by the National Science Foundation (DEB-0101775 and DEB-0743457), the Comunidad de Madrid, the National Geographic Society (NGS 7754-04 and NGS 8047-06), the Taylor Fund for Ecological Research, the Andrew W. Mellon Foundation, the Centro de Estudios de América Latina, Universidad Autónoma de Madrid, and Christopher Davidson and Sharon Christoph. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

Molecular detection and parasite load of Trypanosoma cruzi in digestive tract tissue of Chagas disease patients affected by megacolon

Chagas disease, caused by the Trypanosoma cruzi parasite in the Americas affects similar to 7 million people, 30% with cardiac tissue damage and 10-15% with digestive disorders. In this study, we have developed a protocol to detect the presence of the parasite and estimate its load in resected dysfunctional tissue segments of chronically infected patients with digestive megacolon. We have included samples from 43 individuals, 38/5 with positive/negative serology for Chagas disease and digestive syndromes. Samples of 1.5 to 2.0 cm(2) were taken from different points of the dysfunctional digestive tract in specialized centres in Cochabamba, Bolivia. T. cruzi cultures were performed by inoculation with NNN-LIT culture medium, and genomic material was obtained from the samples for multiplex qPCR with TaqMan probes targeting satellite nuclear DNA. Cultures failed to isolate T. cruzi but qPCR reached a sensitivity of 42.1% (16/38) with all three spots and in triplicate. A new quantification methodology using synthetic satellite DNA as quantitation standard revealed parasite loads ranging from 2.2 x 10(2) to 1.0 x 10(6) satellite DNA copies/mu l. Positive samples from the distal end showed a higher parasite load. The results of the present study strengthen and add further evidence to previous findings in an experimental mouse model of chronic T. cruzi infection, providing a valuable tool to improve scientific knowledge on the relevance of the digestive tract in parasite persistence, and underline the need of a better understanding of host-pathogen interaction in digestive tissues, considering pathophysiology, disease immunology and response to treatment

Mycorrhizas in South American Anthropic Environments

The agricultural expansion has leaded to increase the irrigated cropland area and the use of fertilizers, resulting in water degradation, increased energy use, and common pollution. Of particular concern is the increased interest to reduce the environmental impacts of high quantities of water dedicated to irrigation by agricultural activities We are now truly recognizing the importance of sustainable measures in agriculture such as conservation of the vegetation cover and management approach to understand surface and deep soil responses to global change. The agroecology management based on key processes from natural ecosystems can help to solve some agricultural difficulties. Increasing studies on the Arbuscular mycorrhizal fungi (AMF) has showed their importance for soil ecology and studies on their biodiversity have spread in some agro-ecosystems such as corn and soybean monocultures. Therefore, it is needed to deeply study the mycorrhizal functions under global change. In this chapter, we examine the major developments and advances on mycorrhizal fungi based on recent research from South American countries. New reports on the occurrence of mycorrhizas in Amazonian dark earth, as well as the inoculum production of arbuscular mycorrhizal fungi native of soils under native forest covers, have resulted in a more detailed understanding of the soil biology from South America. Reports from Amazonian dark earth or “Terra preta do índio” soil has stimulated the use of biochar worldwide as a soil conditioner that can add value to non-harvested agricultural products and promote plant growth. Few reports from Brazil showed that the addition of inorganic fertilizer, compost and chicken manure resulted in increases in plant cover and plant species richness. In this sense, the biochar/mycorrhizae interactions also can be prioritized for sequestration of carbon in soils to contribute to climate change mitigation

Enhancing the ecological restoration of semi-natural grasslands following topsoil removal through AMF-inoculation and manipulating plant species arrival order

SUMMARY Many restoration projects across Europe have attempted to mitigate plant species loss in semi-natural grasslands. However, the success of these restoration projects is currently rather limited, mainly due to constraints imposed by high soil nutrient levels and seed dispersal limitation. One common restoration practice to deal with soil nutrient enrichment is topsoil removal. At the same time there is currently increasing evidence that plant community restoration is constrained by degraded or absent soil microbial communities. Therefore, it has been proposed that more integrated aboveground-belowground biodiversity approaches should be considered during the restoration of semi-natural grasslands. In an attempt to contribute to a better understanding of how to successfully restore nutrient-poor grasslands following topsoil removal, through integrating aboveground and belowground restoration, we firstly aimed to study the potential role of adding arbuscular mycorrhizal fungi (AMF) which form a mutualistic relationship with most of the land plants. This symbiosis entails a reciprocal exchange of benefits between the host plant and the fungus; the fungus provides nutrients to the host and in return receives photosynthetic carbon. AMF presence may therefore be vital for the establishment of colonizing species during grassland restoration. To restores AMF communities on topsoil stripped soils, we produced a custom-made AMF inoculum consisting of the roots of AMF-dependent species from nutrient-poor grasslands. Prior to experimentally inoculating the restoration sites, we tested the efficacy of the developed AMF-inoculum in a greenhouse experiment where it proved to be effective in enhancing spore production and the colonization of plant species typical of nutrient-poor grasslands. Furthermore, the inoculum significantly improved biomass production of the grassland species during the first weeks of establishment. In a following in situ experiment on a topsoil removed site where intact remnant grassland (IRG) patches were kept, we inoculated some sites and left others without inoculation to evaluate the effects of the AMF inoculum on both plant species and AMF re-colonization. We found that AMF spore diversity, plant species richness and plant species diversity was enhanced by the AMF inoculum. Inoculated and non-inoculated sites also showed strong differences in plant community composition and AMF community composition. Owing to the presence of IRG patches at the restoration site, we could also evaluate the spontaneous colonization rates of AMF spores and seeds. The spontaneous re-colonization of AMF spores benefited from the presence of IRG patches, and there was no evidence of AMF spore dispersal limitation. However, AMF spore density, species richness and diversity were lower at spontaneously colonized sites when compared to AMF inoculated sites. These results suggest that AMF inoculation is a desirable management tool to speed up AMF re-colonization. On the other hand, many plant species were found to be dispersal limited. More specifically, the positive effect of inoculum addition on richness and/or diversity of all plant species, AMF-dependent plant species and specialist plant species of nutrient-poor grasslands decreased with increasing distance from the IRG patches to the plots, likely indicating priority effects. This indicates that the presence of IRG patches at restoration sites may not completely help to overcome dispersal plant limitation, which may suggest that seed addition could be useful to improve restoration success. In order to test whether manipulating the order of plant species arrival is a valuable restoration practice, we finally evaluated the effects of the early arrival of plant species that (i) can grow fast and reach high cover (dominants) and (ii) occur at low density (subordinates), on the establishment of both target species and unwanted species, such as ruderal and/or pioneer species. The early arrival of dominants successfully suppressed colonization of unwanted plant species and this improved the establishment success of target species. Similarly, the early arrival of subordinates successfully suppressed unwanted early colonizing plant species. However, subordinates also suppressed the establishment of target species, likely due to the fact that these species compete for the same niches. Therefore, our results suggest that restoration practitioners may early sow species that can grow fast and reach high cover to suppress and control unwanted species, and to enhance the establishment of target species for ecological restoration.status: publishe

Styloceras connatum (Buxaceae), una Nueva Especie de Bolivia

Volume: 20Start Page: 363End Page: 36

Specific leaf area : a predictive model using dried samples

Specific leaf area (SLA; fresh-leaf area/dry mass) describes the amount of leaf area for light capture per unit of biomass invested. The standard protocol is simple; however, it requires recently collected sun-exposed leaves to determine fresh-leaf area, limiting where and which samples can be studied. A protocol to predict SLA for fresh leaves from herbarium-dried leaves was developed from samples collected in a dry forest in Bolivia. Leaf area was measured both fresh and dried on the same leaf samples to generate two general mixed-effects models, varying in their inclusion of the position in the crown where the leaf developed. As a test of the potential generality of the models for other systems, we applied them to samples collected in an oak–hickory forest in Missouri, USA. Both models performed well. A recommended protocol for studies predicting SLA from dry leaves was developed. These predictive models and protocols can extend the temporal, geographic, ecological and taxonomic scope of SLA studies.8 page(s

Ecological quality as a coffee quality enhancer. A review.

As both coffee quality and sustainability become increasingly important, there is growing interest in understanding how ecological quality affects coffee quality. Here we analyze, for the first time, the state of evidence that ecological quality, in terms of biodiversity and ecosystem functions, impacts the quality of Coffea arabica and C. canephora, based on 78 studies. The following ecosystem functions were included: pollination; weed, disease, and pest control; water and soil fertility regulation. Biodiversity was described by the presence, percentage, and diversity of shade trees. Coffee quality was described by the green bean physical characteristics, biochemical compounds, and organoleptic characteristics. The presence and diversity of shade trees positively impacted bean size and weight and reduced the percentage of rejected beans, but these observations were not consistent over different altitudes. In fact, little is known about the diversity of shade trees and their influence on biochemical compounds. All biochemical compounds varied with the presence of shade, percentage of shade, and elevation. Coffee beans from more diverse tree shade plantations obtained higher scores for final total organoleptic quality than simplified tree shade and unshaded plantations. Decreasing ecological quality diminished ecosystem functions such as pollination, which in turn negatively affected bean quality. Shade affected pests and diseases in different ways, but weeds were reduced. High soil quality positively affected coffee quality. Shade improved the water use efficiency, such that coffee plants were not water stressed and coffee quality was improved. While knowledge on the influence of shade trees on overall coffee quality remains scarce, there is evidence that agroecosystem simplification is negatively correlated with coffee quality. Given global concerns about biodiversity and habitat loss, we recommend that the overall definition of coffee quality include measures of ecological quality, although these aspects are not always detectable in certain coffee quality characteristics or the final cup

Phylogenetic Patterns of Rarity in a Regional Species Pool of Tropical Woody Plants

AimRarity, which is believed to influence extinction risk, can be defined in terms of local abundance, geographical range size and habitat breadth. Phylogenetic patterns in these attributes provide insight into the extent to which rarity and extinction risk are conserved during evolution and the potential for species‐level heritability. We evaluated phylogenetic signal (i.e., related species resembling each other more than species drawn at random) and evolutionary conservatism (similarity among related species exceeding that expected from a Brownian model of evolution) in three axes of rarity (local abundance, geographical range size and habitat breadth) among species in a regional pool of tropical woody plants.LocationThe Madidi region in Bolivia.Time period2001–2010.Major taxa studiedLignophyta clade.MethodsWe used a network of 48 1‐ha forest plots and 442 0.1‐ha forest plots to measure local abundance and habitat breadth of 1,700+ woody plant species (from 100+ plant families). We estimated geographical range size from occurrence records of individual species across the Neotropics. We characterized overall phylogenetic patterns of rarity using Blomberg\u27s K and applied variance partitioning among taxonomic levels, as well as disparity analysis, to describe patterns of trait distribution at different depths in the phylogeny.ResultsWe found phylogenetic signal, but not evolutionary conservatism, in the three axes of rarity. The variance in rarity among supra‐specific taxa, particularly families and genera, exceeded that calculated from random draws of species from the Madidi region. Phylogenetic signal, estimated by the proportion of variance among supra‐specific taxonomic levels, varied between 23 and 36% for local abundance and geographical range size, and between 9 and 10% for habitat breadth.Main conclusionsThe regional pool of woody plant species in Madidi exhibits phylogenetic signal in rarity that is consistent with biologically significant species‐level heritability

Phylogenetic patterns of rarity in a regional species pool of tropical woody plants

AimRarity, which is believed to influence extinction risk, can be defined in terms of local abundance, geographical range size and habitat breadth. Phylogenetic patterns in these attributes provide insight into the extent to which rarity and extinction risk are conserved during evolution and the potential for species‐level heritability. We evaluated phylogenetic signal (i.e., related species resembling each other more than species drawn at random) and evolutionary conservatism (similarity among related species exceeding that expected from a Brownian model of evolution) in three axes of rarity (local abundance, geographical range size and habitat breadth) among species in a regional pool of tropical woody plants.LocationThe Madidi region in Bolivia.Time period2001–2010.Major taxa studiedLignophyta clade.MethodsWe used a network of 48 1‐ha forest plots and 442 0.1‐ha forest plots to measure local abundance and habitat breadth of 1,700+ woody plant species (from 100+ plant families). We estimated geographical range size from occurrence records of individual species across the Neotropics. We characterized overall phylogenetic patterns of rarity using Blomberg\u27s K and applied variance partitioning among taxonomic levels, as well as disparity analysis, to describe patterns of trait distribution at different depths in the phylogeny.ResultsWe found phylogenetic signal, but not evolutionary conservatism, in the three axes of rarity. The variance in rarity among supra‐specific taxa, particularly families and genera, exceeded that calculated from random draws of species from the Madidi region. Phylogenetic signal, estimated by the proportion of variance among supra‐specific taxonomic levels, varied between 23 and 36% for local abundance and geographical range size, and between 9 and 10% for habitat breadth.Main conclusionsThe regional pool of woody plant species in Madidi exhibits phylogenetic signal in rarity that is consistent with biologically significant species‐level heritability