Aim
To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and ...hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser‐availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource‐availability hypothesis).
Time period
Tree‐inventory plots established between 1934 and 2019.
Major taxa studied
Trees with a diameter at breast height (DBH) ≥ 9.55 cm.
Location
Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield.
Methods
We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree‐inventory plots across terra‐firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance‐weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes.
Results
Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra‐firme forests (excluding podzols) compared to flooded forests.
Main conclusions
The disperser‐availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.
Aim
Understanding how the landscape influences gene flow is important in explaining biodiversity, especially when co‐distributed taxa across heterogeneous landscapes exhibit species‐specific habitat ...associations. Here, we test predictions about the effects of forest‐type on population connectivity in two sympatric species of spiny rats that differ in their forest associations. Specifically, we evaluate the hypothesis that seasonal floodplain forests (várzea) provide linear connectivity, facilitating gene flow among individuals, while non‐flooded forests (terra‐firme) may diminish the functional connectivity.
Location
Western Amazon, South America.
Taxon
Proechimys simonsi (non‐flooded forests, terra‐firme) and Proechimys steerei (seasonal floodplain forests, várzea).
Methods
We analyse about 13,000 single nucleotide polymorphisms along with characterizations of landscape heterogeneity for two forest types to test for differences in the functional connectivity. Influence of the landscape and environmental variables are quantified using maximum‐likelihood population effect models to identify the relative importance of variables in explaining the gene flow.
Results
There are significant differences in functional connectivity between species. However, the genomic data does not support the conventional hypotheses of higher connectivity for inhabitants of várzea than those of terra‐firme. Stronger genetic structure in P. steerei than P. simonsi based on isolation by distance models suggests reduced gene flow in species associated with várzea forests. Isolation by resistance reinforces that wetland habitats inhibit and promote the functional connectivity in P. simonsi and P. steerei, respectively, although large distances along the rivers can prevent gene flow in P. steerei.
Main conclusion
Interpreting differences between connectivity in taxa apparent from genetic analyses through the lens of a single dimension of Amazonian heterogeneity—that is, forest type—may be an oversimplification. Our statistical modelling and fit of the data to different models points to specific environmental and habitat differences between the ecological divergent spiny rat species that may contribute to differences in the genetic structure of these sympatric taxa.
Abstract
Major historical landscape changes have left significant signatures on species diversification. However, how these changes have affected the build-up and maintenance of Amazonia’s ...megadiversity continues to be debated. Here, we addressed this issue by focusing on the evolutionary history of a pan-Amazonian toad genus that has diversified throughout the Neogene (Amazophrynella). Based on a comprehensive spatial and taxonomic sampling (286 samples, all nominal species), we delimited operational taxonomic units (OTUs) from mitochondrial DNA sequences. We delimited 35 OTUs, among which 13 correspond to nominal species, suggesting a vast underestimation of species richness. Next, we inferred time-calibrated phylogenetic relationships among OTUs based on complete mitogenomic data, which confirmed an ancient divergence between two major clades distributed in eastern and western Amazonia, respectively. Ancestral area reconstruction analyses suggest that the Andean foothills and the Brazilian Shield region represent the ancient core areas for their diversification. These two clades, probably isolated from one other by lacustrine ecosystems in western Amazonia during the Miocene, display a pattern of northward and eastward dispersals throughout the Miocene‒Pliocene. Given the ecological association of Amazophrynella with non-flooded forests, our results reinforce the perception that ancient Amazonian landscape changes had a major impact on the diversification of terrestrial vertebrates.
The Tierra Firme Fleet was one of the main naval systems of the Carrera de Indias. After several previous trials, it was finally established in 1550 and its structure remained unchanged until 1647. ...From the study of practically its first hundred years of life (1550-1647), this article examines the organization of the Tierra Firme Fleet, its means of financing, the ships that made it up, the crew that carried each ship, the artillery that mounted its vessels, the route it used to cross the Atlantic and the cargoes that were kept in the ship’s holds
La Flota de Tierra Firme fue uno de los principales sistemas navales de la Carrera de Indias. Tras varios ensayos previos, se estableció definitivamente en 1550 ysu estructura se mantuvo inaltera-ble hasta 1647A partir del estudio de prácticamente sus primeros cien años de vida (1550-1647), en este artículo se examina la organización de la Flota de Tierra Firme, sus medios de financiación, los navíos que la integraban, la tripulación que llevaba cada barco, la artillería que montaban sus bajeles, la ruta que empleaba para cruzar el Atlántico y los cargamentos que se guardaban en las bodegas de la nave.
A Frota da Terra Firme foi um dos principais sistemas navais da Carrera de Indias. Depois de várias tentativas anteriores, foi definitivamente estabelecido em 1550 e a sua estructura permaneceu inalteradaaté 1647. A partir do estudo de praticamente seus primeiros cem anos de vida (1550-1647), este artigo examina a organização da Frota da Terra Firme, seus meios de financiamento, os navios que o compunham, a tripulação que transportava cada navio, a artilharia que montou seus barcos, rota que utilizou para cruzar o Atlântico e os cargamentos que ficaram nos porões do navio
•Emergent trees are an important component of the Amazonian terra firme because of their high transpiration rates.•Thus a relatively small number of trees per hectare are responsible for the majority ...of the stand transpiration.•During dry months tree transpiration is responsible for almost all the evapotranspiration.•The forest mediates a high amount of rain water back to the atmosphere, what supports the rainfall recycling theory.
The Amazon forest is integral to the global climate system in part because of the high rate of rainfall recycling through tree transpiration and biodiversity (size and species composition). However, the partitioning of precipitation into evaporation, transpiration and runoff, has been quantified at only a few sites. At our study site in the central Amazon, annual rainfall in 2013 was 2302mm and latent heat flux measurements made using eddy covariance revealed that 1360mm (59%) was returned to the atmosphere through evaporation and transpiration. Runoff accounted for 41% of the net ecosystem water loss. Combining annual xylem sap flux estimates with total stand sap wood area, we estimated annual stand transpiration rate to be 851mm (36% of annual rainfall). Emergent canopy trees (diameter >30cm; average height of 28m) were responsible for the majority (71%) of the transpired water flux, recycling potentially 26% of the rainfall back to the atmosphere. By difference, we estimate that 510mm of intercepted rainwater (22% of rainfall) was evaporated directly back to atmosphere from the canopy. Highest stand transpiration rates occurred during the dryer months due to both increased water vapor pressure deficit and the onset of new leaf flush. This study provides further evidence for convergent water use characteristics of tropical trees and highlights the importance of large trees in tropical moist forests. Large trees have been demonstrated to be vulnerable to drought-related mortality, and thus potentially will make up a critical component of the response of tropical forests to climate change.
Silicon Valley technology is transforming the way we work, and Uber is leading the charge. An American startup that promised to deliver entrepreneurship for the masses through its technology, Uber ...instead built a new template for employment using algorithms and Internet platforms. Upending our understanding of work in the digital age,Uberlandpaints a future where any of us might be managed by a faceless boss.The neutral language of technology masks the powerful influence algorithms have across the New Economy.Uberlandchronicles the stories of drivers in more than twenty-five cities in the United States and Canada over four years, shedding light on their working conditions and providing a window into how they feel behind the wheel. The book also explores Uber's outsized influence around the world: the billion-dollar company is now influencing everything from debates about sexual harassment and transportation regulations to racial equality campaigns and labor rights initiatives.Based on award-winning technology ethnographer Alex Rosenblat's firsthand experience of riding over 5,000 miles with Uber drivers, daily visits to online forums, and face-to-face discussions with senior Uber employees,Uberlandgoes beyond the headlines to reveal the complicated politics of popular technologies that are manipulating both workers and consumers.
In order to investigate how familial biodiversity structures forests in the critically important Amazon, I combined past plot samplings to investigate the contributions of tree families in those ...samplings to the structure of common Amazon forest types. I found that the families Arecaceae, Fabaceae, Clusiaceae, and Malvaceae had the most stems; Staphyleaceae, Caricaceae, and Anacardiaceae had the largest stems; Arecaceae, Fabaceae, Lecythidaceae, and Malvaceae had the largest basal area; Fabaceae, Malvaceae, and Sapotaceae had the most genera; Annonaceae, Euphorbiaceae, Fabaceae, Lauraceae, Malvaceae, Moraceae, and Sapotaceae had the most species, and the maximum Fisher’s α diversity index was found for many families. Together, results suggest that Fabaceae and Malvaceae are the most important families structuring these forests, but also that Arecaceae and Sapotaceae may be important. Thus, conservationists and managers may help sustain structure in these forests by propagating and maintaining species in these families. Finally, correlations between total number of stems and basal area, and between total number of genera and total number of species, suggest a causal relationship between them as they structure these forests, but the lack of correlations with Fisher’s α suggest it has little structural utility for these forests.
•Palm communities on the banks of the Madeira River differ among forest formations.•Extreme floods in 2014 affected the populations of 61.3% of the palm species.•Six palm species had populations ...severely affected by the reservoir in Madeira River.•The loss of habitat was more impactful for species in riparian environments.
Mega hydroelectric dams cause loss of habitat for many species and lead to local or regional extinction. Despite these dire facts, little is known about the impact of these mega-dams on Amazonia. Using palms as a model, we investigated this question by sampling 26 1-ha plots distributed in the influence areas of the Jirau mega-dam in southwestern Brazilian Amazonia. We examined palm community patterns and species distributions as a function of environmental variables, as well as the effect of this large dam on plant survival. Palm communities on the banks of the Madeira River differ among three main habitats sampled (campinarana, terra-firme and várzea forests), and these differences are associated with the gradient of C, pH, N, P, soil texture, slope, and depth to the water-table. The level of the Madeira River raised after the construction of the Jirau mega-dam, directly affecting the populations of 61.3% of the palm species, particularly those species associated to areas with silty soils, low slope, and low depth to the water-table. Várzea and terra-firme forests near the river, as well as low-lying plots, even those distant from the river, were affected by the filling of the reservoir. Várzea forests and campinaranas had a greater proportion of palm species flooded by the reservoir and the reduction of water-table depth. Várzea forests and campinaranas harbor distinct palm communities from the terra-firme forests and require priority in conservation policies and management to mitigate harmful environmental impacts in the Amazon.
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