sábado, 25 de maio de 2019
sexta-feira, 24 de maio de 2019
Soil communities threatened by destruction, instability of Amazon forests
Date: May 24, 2019 Source: Colorado State University Summary: A meta-analysis of nearly 300 studies of soil biodiversity in Amazonian forests found that the abundance, biomass, richness and diversity of soil fauna and microbes were reduced following deforestation.
The clearing and subsequent instability of Amazonian forests are among the greatest threats to tropical biodiversity conservation today.
Although the devastating consequences of deforestation to plants and animal species living above the ground are well-documented, scientists and others need to better understand how soil communities respond to this deforestation to create interventions that protect biodiversity and the ecosystem. But that information has been lacking.
A team of researchers led by Colorado State University's André Franco, a research scientist in the Department of Biology, conducted a meta-analysis of nearly 300 studies of soil biodiversity in Amazonian forests and sites in various stages of deforestation and land-use.
The new study, "Amazonian deforestation and soil biodiversity," is published in the June issue of Conservation Biology and is co-authored by CSU Distinguished Professor Diana Wall, Bruno Sobral, professor in the Department of Microbiology, Immunology and Pathology at CSU, and Artur Silva, professor at the Universidade Federal do Pará in Belém, Brazil.
Overall, the researchers found that the abundance, biomass, richness and diversity of soil fauna and microbes were all reduced following deforestation. Soil fauna or animals that were studied include earthworms, millipedes, dung beetles, nematodes, mites, spiders and scorpions.
Franco, who hails from Brazil, said that this is the first time that all of the available scientific data related to soil biodiversity in Amazonian forests has been synthesized.
The research team also found that the way the land is used after the forest is cleared matters to soil biodiversity. Species of invertebrates such as earthworms, ants and termites -- which are described as soil engineers -- were more vulnerable to the displacement of forests with pastures than by crops, while microbes showed the opposite pattern.
Franco said the highest biodiversity losses were found on the side of the Amazon with the highest mean annual precipitation and in areas where the soil was very acidic.
"That means these areas should be higher priorities for conservation efforts," he said.
Scientists also uncovered gaps in existing research.
"Very few studies looked at the impact of disturbances like wildfires and selective logging on these forests," Franco said. "Yet logging is an official management strategy in the Amazon forest."
In addition, the team found a lack of data from seven of the nine countries that the Amazon biome covers parts of, including Bolivia, Peru, Ecuador, Venezuela, Guyana, Suriname and French Guiana.
Sobral noted that biodiversity is a hot topic and was elevated recently with the release of a report from the United Nations, which found that nature is declining globally at unprecedented rates. But most of the scientific knowledge in the world about biodiversity relates to birds and mammals, he said.
The team is continuing this research in the Amazon, working with farmers' associations and two research institutes in Brazil to collect and analyze soil samples with the goal of studying the consequences of this loss of biodiversity.
Zaid Abdo, a bioinformatics expert and associate professor in the Department of Microbiology, Immunology and Pathology, has joined the CSU-based research team.
Sobral said it's extremely important that the scientists work with local farmers and others who are impacted by the deforestation.
"We're very focused on making sure the research isn't disconnected from local communities' needs and aspirations," he said. "Our work is guided by what the farmers want to know and how scientific knowledge could shape their future sustainable development."
Story Source:
Materials provided by Colorado State University. Note: Content may be edited for style and length.
Journal Reference:
André L.C. Franco, Bruno W. Sobral, Artur L.C. Silva, Diana H. Wall. Amazonian deforestation and soil biodiversity. Conservation Biology, 2019; 33 (3): 590 DOI: 10.1111/cobi.13234
Cite This Page:
Colorado State University. "Soil communities threatened by destruction, instability of Amazon forests." ScienceDaily. ScienceDaily, 24 May 2019. <www.sciencedaily.com/releases/2019/05/190524130239.htm>.
quinta-feira, 23 de maio de 2019
How corn's ancient ancestor rejects crossbreeding
Date: May 24, 2019 Source: Carnegie Institution for Science Summary: New research elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.ry:New research elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.
Corn varieties (stock image).
Credit: © cpnjuansanchez / Adobe Stock
Determining how one species becomes distinct from another has been a subject of fascination dating back to Charles Darwin. New research led by Carnegie's Matthew Evans and published in Nature Communications elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.
Speciation requires isolation. Sometimes this isolation is facilitated by geography, such as mountains chains or islands that divide two populations and prevent them from interbreeding until they become different species. But in other instances, the barriers separating species are physiological factors that prevent them from successfully mating, or from producing viable offspring.
"In plants, this genetic isolation can be maintained by features that prevent the 'male' pollen of one species from successfully fertilizing the 'female' pistil of another species," explained Evans.
About 9,000 years ago, maize, or corn, was domesticated from teosinte in the Balsas River Valley of Mexico. Some populations of the two grasses are compatible for breeding. But others grow in the same areas and flower at the same time, but rarely produce hybrids.
It was known that a cluster of genes called Tcb1-s is one of three that confers incompatibility between these rarely hybridizing maize and teosinte populations. Unlike the other two, it is found almost exclusively in wild teosinte. It contains both male and female genes that encode wild teosinte's ability to reject maize pollen.
In sexually compatible plants, the pollen, which is basically a sperm delivery vehicle, lands on the pistil and forms a tube that elongates and burrows down into the ovary, where the egg is fertilized. But that's not what happens when maize pollen lands on the pistil, or silk, of a wild teosinte plant.
Evans and his colleagues -- Carnegie's Yongxian Lu (the first author), Samuel Hokin, and Thomas Hartwig, along with Jerry Kermicle of the University of Wisconsin Madison -- demonstrated that the Tcb1-female gene encodes a protein that is capable of modifying cell walls, likely making maize pollen tubes less elastic and thus preventing them from reaching the teosinte eggs. When these tubes can't stretch all the way to the eggs, fertilization can't occur, and hybrids won't be possible.
What's more, because teosinte pollen can fertilize itself, the researchers think that the Tcb1-male genes encode an ability that allows teosinte pollen to overcome this pollen tube barrier building.
"Most plants that depend on wind and water, not birds or insects, for pollination have low species diversity," said Evans. "But not grasses, which makes their evolutionary history particularly interesting."
This work was supported by the U.S. National Science Foundation and the U.S. Department of Agriculture National Research Initiative.
Story Source:
Materials provided by Carnegie Institution for Science. Note: Content may be edited for style and length.
Journal Reference:
Yongxian Lu, Samuel A. Hokin, Jerry L. Kermicle, Thomas Hartwig, Mathew M. S. Evans. A pistil-expressed pectin methylesterase confers cross-incompatibility between strains of Zea mays. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-10259-0
Cite This Page:
Carnegie Institution for Science. "How corn's ancient ancestor rejects crossbreeding." ScienceDaily. ScienceDaily, 24 May 2019. <www.sciencedaily.com/releases/2019/05/190524113517.htm>.
