We assessed the effects of environmental variables on the distribution and feeding behaviour of adult Little Terns Sternula albifrons in Ria Formosa Natural Park, Algarve, southern Portugal, in ...different foraging habitats (main lagoon, salinas and sea) during the breeding seasons, April-July, of 2003-05. Foraging density was higher in the lagoon than in the sea, and at low tide. The number of foraging individuals at sea was independent of tide. Individual Little Terns foraged further from the nearest breeding colony in April and May (courtship feeding and incubation) than in June and July (chick-rearing). During intermediate tidal phases, individuals foraged further from the nearest colony, and followed main lagoon channels, perhaps because stronger currents increased prey availability. Diving activity and foraging success were higher in 2003 than 2004 or 2005, perhaps because of greater availability of marine prey in 2003. Diving rate was higher in July (when independent juveniles began learning how to forage) but diving success was higher in June (chick-rearing) than in other months. The variables selected by the final logistic models reflected four basic needs for the selection of feeding habitats by Little Terns: (1) association between foraging individuals, (2) areas with abundant feeding resources, (3) entrance channels and main lagoon channels with strong currents, and (4) the proximity to areas with alternative feeding resources, the salinas. Areas subjected to strong human pressure were avoided by foraging Little Terns.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Radical carbene transfer reactions promoted by macrocyclic CoII–porphyrinates bearing nitrogen‐based axial ligands were used to assemble asymmetrical 2rotaxanes through the active‐metal‐template ...technique. Careful control of the reaction conditions and proper choice of axial ligands enable formation of rotaxanes in up to 95% yield, while precluding formation of non‐interlocked byproducts and total suppression of radical proton ion and carbene dimerization side reactions. The present study provides a detailed investigation on how to control the redox cooperative mechanism between the CoII ion in the porphyrin core and the radical carbene species to favor rotaxane formation. More information can be found in the Full Paper by J. D. Megiatto et al. on page 7808.
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Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using ...LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.
Editor’s summary
Indigenous societies have lived in the Amazon for at least 12,000 years. Finding evidence of these societies, however, has been greatly hampered by the density of the forest in Amazonia. Peripato
et al
. used LIDAR (light detection and ranging) surveys to identify more than 20 previously unidentified developments and then modeled the occurrence of others across the Amazon. The authors predict that between 10,000 and 24,000 ancient earthworks are waiting to be discovered. Sampling of some of the LIDAR transects revealed a consistent set of domesticated tree species associated with the developments, suggesting active forestry practices among these societies. —Sacha Vignieri
Amazon-wide LIDAR surveys and predictive models suggest thousands of undocumented archaeological sites across the basin.
Aim
Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized ...multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.
Location
Amazonia.
Taxon
Angiosperms (Magnoliids; Monocots; Eudicots).
Methods
Data for the abundance of 5082 tree species in 1989 plots were combined with a mega‐phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.
Results
In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white‐sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.
Main Conclusion
Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long‐standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
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We used pellets and prey dropped near nests to study the diet and feeding ecology of Little Tern (Sterna albifrons) adults and chicks in northern and southern Portugal during 2000–2004. We compared ...diets among study areas, years, and birds breeding in two main habitat types: sandy beaches and salinas (man-made salt-pans). We also sampled prey fish in one study area and used published data from another area to examine whether the diet of Little Tern adults and chicks corresponded with the abundance of prey found in primary foraging habitats. Adult Little Terns fed mainly on sand-smelts (Atherina spp.) and gobies (Pomatoschistus spp.), which were the most abundant fish species in our estuarine and lagoon study areas. Despite some differences among colonies we did not find clear differences in adult diets among study areas and habitat types. Little Tern chicks also ate primarily Atherina spp., but their diet was more diverse than that of the adults, and characterized by a significantly higher proportion of prey with a high energetic value such as sardines (Sardina pilchardus), garfish (Belone belone), and killifish (Fundulus spp.). Chick diets differed significantly between habitat types, which may be a consequence of the limited foraging range of adult breeding birds. Both adult and chick diets matched the abundance of the main prey in our study areas, confirming the opportunistic foraging character of this species. We suggest that annual variation in prey availability may be the most important factor explaining annual variation in adult diets.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained ...maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Seabirds breeding at tropical latitudes suffer an increased pressure to forage efficiently, because oligotrophic waters have less abundant and more patchily distributed prey. In related species ...living in sympatry, trophic or spatial niche partitioning may emerge as a strategy to mitigate increased competition. However, studies using molecular methodologies such as high-throughput sequencing (HTS) to test for these strategies are still scarce. In this study we used HTS to assess prey diversity partitioning on two sulid species living sympatrically in the tropical Raso Islet (Cabo Verde). Brown boobies (Sula leucogaster) breed in Raso Islet throughout the year while Red-footed boobies (Sula sula) occur during molt, from June to October. We compared Brown boobies diet prey diversity between the two periods (non-coexistence vs. coexistence with Red-footed booby), as well as between both sulids while in coexistence. Overall, the diets of all groups were clearly dominated by a small number of Molecular Operational Taxonomic Units (MOTUs), with a predominance of flying fish. The diet composition of Brown boobies was significantly different between the two time periods, most likely due to temporal differences in prey availability or possible competition with other seabird species. Brown boobies exploited a wider taxonomic range of prey, while Red-footed boobies used a subset of Brown boobies' prey diversity. Furthermore, we did not find intersexual differences in the diet composition of both species. Overall, we did not find evidence that prey diversity partitioning occurred, probably due to the parallel occurrence of spatial niche partitioning.
•DNA metabarcoding assess diet of seabirds in distinct breeding stages.•High diet overlap between the two sulids when in coexistence.•Sula leucogaster shift their diet from non-coexistence to coexistence period.•Diet overlap has conservation implications due to Sula sula increasing numbers.•Commercial interest prey may have fisheries management implications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study evaluated the influence of human disturbance in nesting success of little tern (
Sterna albifrons) and its interaction with the intrinsic seasonal variation in the birds’ breeding biology. ...During 2003–2005 we studied little tern nesting ecology in southern Portugal in two different types of habitat: their natural habitat (sandy beaches) and a man-made habitat (salinas). In both habitat types, annual variations were found in the distribution of nest initiation over the breeding season and in the size of the clutches. The percentage of nests producing hatched chicks varied between 26.7% and 66.4% in different years and habitats. The main causes of hatching failure varied between years and habitats, but predation, flooding and human activities were very common. No consistent differences in breeding parameters or nesting success were found between habitats. On sandy beaches, the effect of protective measures (warning signs and wardening) on nesting success, together with differences between years and within each breeding season, were assessed using a logistic regression model. The presence/absence of protective measures was the most important predictor of nesting success, with birds being up to 34 times more likely to succeed with protective measures. Seasonal declines were found for clutch size and egg volume, and season was also an important predictor of nesting success, with nests more likely to succeed earlier in the season. Hence, earlier breeders will be those that benefit more from protective measures, suggesting that conservation efforts for little tern can be maximised if concentrated earlier in the season.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and ...investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution.
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