Generally, species with broad niches also show large range sizes. We investigated the relationship between hydrological niche breadth and geographic range size for Amazonian tree species seeking to ...understand the role of habitat specialization to Amazonian wetlands and upland forests on the current distribution of tree species. We obtained 571,092 valid occurrence points from GBIF and SpeciesLink to estimate the range size and the niche breadth of 76% of all known Amazonian tree species (5150 tree species). Hydrological niche breadth was measured on different unidimensional axes defined by (1) total annual precipitation; (2) precipitation seasonality; (3) actual evapotranspiration; and (4) water table depth. Geographic range sizes were estimated using alpha‐hull adjustments. General linear models were used to relate niche breadth to range size while contrasting tree species occurring and not occurring in wetlands. The hydrological niche breadth of Amazonian tree species varied mostly along the water table depth axis. The average range size for an Amazonian tree species was 751,000 km2 (median of 154,000 km2 and standard deviation of 1,550,000 km2). Niche breadth–range size relationships for Amazonian tree species were positive for all models, and the explanatory power of the models improved when including whether a species occurred in wetlands or in terrestrial uplands. Wetland species had steeper positive slopes for the niche breadth–range size relationship, and consistently larger range sizes for a given niche breadth. Amazonian tree species varied strongly in hydrological niche breadth and range size, but most species had narrow niche breadths and range sizes. Our results suggest that the South American riverscape may have been acting as a corridor for species dispersal in the Neotropical lowlands.
The general ecological pattern for a positive range size‐niche breadth association holds for Amazonian tree species. Furthermore, those wetland‐adapted tree species have broader niche breadth and large range sizes compared with tree species only occurring in upland forests.
Aim
The centre‐periphery hypothesis (CPH) explains the decline of species abundance towards range limits and how this is driven by increasing ecological marginality. So far, most studies testing the ...CPH have focused on abiotic factors contributing to marginality, while the role of biotic interactions in limiting species distribution has been neglected. Here, we investigate both drivers' roles in restricting an orchid's range along a broad environmental gradient.
Location
Atlantic Forest and Pampas grasslands (south and southeastern Brazil).
Taxa
Sand dune orchid Epidendrum fulgens (Orchidaceae).
Methods
We integrated empirical data on geographical distribution, pollinator richness and genetic diversity along the entire range of the species to investigate whether range limits match niche limits and whether habitat suitability declines towards low‐ and high‐latitude species ranges. We performed niche models to predict niche limits and used polynomial and linear regression models to investigate the associations between ecological niche and species range as well as to test the relationship between genetic‐derived metrics and the geographical and ecological distances.
Results
Ecological conditions become more marginal towards the edges of the E. fulgens range, with an abrupt variation in precipitation. While pollinator richness increases habitat suitability of E. fulgens in the low‐latitude edge range, climate has primarily shaped the species' high‐latitude limit. Genetic diversity within populations decreases, while genetic differentiation increases towards both margins, although with a more consistent pattern for the low‐latitudinal component.
Main Conclusions
This study corroborates the predictions of CPH regarding ecological and genetic patterns of variation in space and highlights distinct factors limiting geographical distribution at the opposite margins of a latitudinal and narrowly distributed species. This improves our understanding on how biotic and abiotic variables limit species distribution ranges along latitudinal gradients in an extremely diverse and vulnerable tropical ecosystem, with potential for informing conservation practices.
We determined the filtered tree species pool of Amazonian wetland forests, based on confirmed occurrence records, to better understand how tree diversity in wetland environments compares to tree ...diversity in the entire Amazon region. The tree species pool was determined using data from two main sources: 1) a compilation of published tree species lists plus one unpublished list of our own, derived from tree plot inventories and floristic surveys; 2) queries on botanical collections that include Amazonian flora, curated by herbaria and available through the SpeciesLink digital biodiversity database. We applied taxonomic name resolution and determined sample-based species accumulation curves for both datasets, to estimate sampling effort and predict the expected species richness using Chao's analytical estimators. We report a total of 3 615 valid tree species occurring in Amazonian wetland forests. After surveying almost 70 years of research efforts to inventory the diversity of Amazonian wetland trees, we found that 74% these records were registered in published species lists (2 688 tree species). Tree species richness estimates predicted from either single dataset underestimated the total pooled species richness recorded as occurring in Amazonian wetlands, with only 41% of the species shared by both datasets. The filtered tree species pool of Amazonian wetland forests comprises 53% of the 6 727 tree species taxonomically confirmed for the Amazonian tree flora to date. This large proportion is likely to be the result of significant species interchange among forest habitats within the Amazon region, as well as in situ speciation processes due to strong ecological filtering. The provided tree species pool raises the number of tree species previously reported as occurring in Amazonian wetlands by a factor of 3.2.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Patterns in substrate, canopy openness, tree species composition and structure were studied in a swamp forest in southeastern Brazil (Itirapina, SP), using a fine spatial scale (∼0.05
km
2). Sixty ...quadrats of 10
m
×
10
m were divided into three sample plots, located in the centre and at both ends of the forest remnant (upstream and downstream), encompassing different environmental conditions. In each quadrat we quantified and identified individuals with CBH (circumference at breast height)
≥
10
cm, the chemical properties of the soil, the drainage (flooded area) and the percentage of canopy openness. We keep 5124 individuals distributed over 37 species and 25 families. The downstream site presented a lower frequency of flooding, canopy openness, species richness (15 species) and density of individuals. In the central site we found different patterns of drainage and light incidence, the greatest species richness (31 species) and density of individuals, but smaller trees both in height and in diameter. The upstream site was subject to higher frequency of flooding, with intermediate values for density and species richness (27 species). Floristic and structural variation between and within sites reflects the different environmental conditions related to substrate and canopy openness. However, a larger number of species were correlated with drainage pattern (21 species) rather than with canopy openness (14 species), suggesting that the main factor responsible for the spatial organization of the plant community in swamp forests is soil drainage.
•Our results demonstrate high levels of beta-diversity in Amazonian floodplain forests.•The number of species restricted to a single forest site was high, with only few species occurring in all ...forests surveyed.•The floodplain forests inventoried were dominated by a few very abundant species.•Several species were recorded on the Amazonian floodplains for the first time.
Floodplain forests cover extensive areas of the Amazon basin, but the number of tree inventories is low. Vast floodplain regions therefore remain floristically unknown. We present a quantitative inventory of floodplain forests from four Amazon river basins (Jutaí, Juruá, Tefé and Purus), investigate within- and between-basin floristic similarity, and examine patterns of tree species dominance and distribution. Twelve hectares with all trees ≥10cm dbh were inventoried; three hectares in each river basin. Rarefaction curves were used to compare species richness across study areas. GNMDS was used to investigate within- and between-basin floristic similarity, combined with an analysis of similarity (ANOSIM) to test for significant differences. In total, 7722 stems representing 518 species were recorded. Inventory plots from the same river basin were clearly clustered in the GNMDS ordination and the ANOSIM showed that floristic composition differed significantly both between and within study areas. Fabaceae was the most abundant family and Eschweilera albiflora the most abundant species. Only nine species were highly abundant in more than one study area, whereas 220 species were recorded in only one sample plot. Our results demonstrate high levels of beta-diversity in Amazonian floodplain forests. The high number of uncommon species is consistent with other studies.
Pseudogymnoascus destructans is the causative agent of white-nose syndrome, a disease that has caused the deaths of millions of bats in North America. This psychrophilic fungus proliferates at low ...temperatures and targets hibernating bats, resulting in their premature arousal from stupor with catastrophic consequences. Despite the impact of white-nose syndrome, little is known about the fungus itself or how it infects its mammalian host. P. destructans is not amenable to genetic manipulation, and therefore understanding the proteins involved in infection requires alternative approaches. Here, we identify hydrolytic enzymes secreted by P. destructans, and use a novel and unbiased substrate profiling technique to define active peptidases. These experiments revealed that endopeptidases are the major proteolytic activities secreted by P. destructans, and that collagen, the major structural protein in mammals, is actively degraded by the secretome. A serine endopeptidase, hereby-named Destructin-1, was subsequently identified, and a recombinant form overexpressed and purified. Biochemical analysis of Destructin-1 showed that it mediated collagen degradation, and a potent inhibitor of peptidase activity was identified. Treatment of P. destructans-conditioned media with this antagonist blocked collagen degradation and facilitated the detection of additional secreted proteolytic activities, including aminopeptidases and carboxypeptidases. These results provide molecular insights into the secretome of P. destructans, and identify serine endopeptidases that have the clear potential to facilitate tissue invasion and pathogenesis in the mammalian host.
Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes ...conspecific spatial aggregation to an extended database of forest plots with up-to-date taxonomy. We show that the species abundance distribution of Amazonia is best approximated by a logseries with aggregated individuals, where aggregation increases with rarity. By averaging several methods to estimate total richness, we confirm that over 15,000 tree species are expected to occur in Amazonia. We also show that using ten times the number of plots would result in an increase to just ~50% of those 15,000 estimated species. To get a more complete sample of all tree species, rigorous field campaigns may be needed but the number of trees in Amazonia will remain an estimate for years to come.
Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and ...how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
The Amazonian floodplains harbor highly diverse wetland forests, with angiosperms adapted to survive extreme floods and droughts. About 14% of the Amazon Basin is covered by floodplains, which are ...fundamental to river productivity, biogeochemical cycling and trophic flow, and have been subject to human occupation since Pre-Colombian times. The botanical knowledge about these forests is still incomplete, and current forest degradation rates are much higher than the rate of new botanical surveys. Herein we report the results of three years of botanical surveys in floodplain forests of the Central Amazon. This checklist contains 432 tree species comprising 193 genera and 57 families. The most represented families are Fabaceae, Myrtaceae, Lauraceae, Sapotaceae, Annonaceae, and Moraceae representing 53% of the identified species. This checklist also documents the occurrence of approximately 236 species that have been rarely recorded as occurring in white-water floodplain forests.
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