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nsf.gov - National Science Foundation - Dirt mounds made by termites in Africa, South America, Asia could prevent spread of deserts .- Montículos de tierra hechos por las termitas en África, América del Sur, Asia podrían prevenir la propagación de los desiertos

Hola amigos: A VUELO DE UN QUINDE EL BLOG., la Fundación Nacional de Ciencias de Los Estados Unidos, nos informa que los montículos de termitas podrían prevenir la propagación de los desiertos en África, América del Sur, Asia;  Las termitas pueden no encabezan la lista de los insectos favoritos de la humanidad, pero una nueva investigación sugiere que los grandes montículos de tierra son cruciales para detener la propagación de los desiertos en los ecosistemas semiáridos.
Los resultados indican que los montículos de termitas podrían hacer que estas áreas sean más resistentes al cambio climático.
Los hallazgos también podrían inspirar un cambio en cómo los científicos a determinar los posibles efectos del cambio climático en los ecosistemas. En los pastizales resecos y sabanas, o tierras secas, de África, América del Sur y Asia, montículos nutrientes  de tienda termitas  y la humedad y a través de túneles internos, deje que el agua penetre mejor el suelo.
Como resultado, la vegetación florece en y cerca de los montículos de termitas en los ecosistemas que son de otra vulnerables a la desertificación.
Los investigadores informan en la edición de esta semana de la revista Science que las termitas frenar la expansión de los desiertos en tierras secas, proporcionando un refugio húmedo para la vegetación en y alrededor de sus montículos.
Las tierras secas con montículos de termitas pueden sobrevivir con mucho menos lluvia que los que no los termiteros.
 
 
Termites create oases of moisture, plant life

tropical grasslands and savanna
Termite mounds are nutrient hotspots in tropical grasslands and savannas, stabilizing ecosystems.
Credit and Larger Version
February 5, 2015
Termites might not top the list of humanity's favorite insects, but new research suggests that their large dirt mounds are crucial to stopping deserts from spreading into semi-arid ecosystems.
The results indicate that termite mounds could make these areas more resilient to climate change.
The findings could also inspire a change in how scientists determine the possible effects of climate change on ecosystems.
In the parched grasslands and savannas, or drylands, of Africa, South America and Asia, termite mounds store nutrients and moisture and via internal tunnels, allow water to better penetrate the soil.
As a result, vegetation flourishes on and near termite mounds in ecosystems that are otherwise vulnerable to desertification.
Researchers report in this week's issue of the journal Science that termites slow the spread of deserts into drylands by providing a moist refuge for vegetation on and around their mounds.
Drylands with termite mounds can survive on significantly less rain than those without termite mounds.
 
Not all termites are pests
 
"This study demonstrates that termite mounds create important refugia for plants and help to protect vast landscapes in Africa from the effects of drought," said Doug Levey, program director in the National Science Foundation's Division of Environmental Biology, which funded the research.
"Clearly," said Levey, "not all termites are pests."
The research was inspired by the fungus-growing termite species, Odontotermes, but the results apply to all types of termites that increase resource availability on or around their mounds.
Corresponding author Corina Tarnita, a Princeton University ecologist and evolutionary biologist, said that termite mounds also preserve seeds and plant life, which helps surrounding areas rebound faster once rainfall resumes.
"Because termites allow water to penetrate the soil better, plants grow on or near the mounds as if there were more rain," said Tarnita. "The vegetation on and around termite mounds persists longer and declines slower.
"Even when you get to harsh conditions where vegetation disappears from the mounds, re-vegetation is still easier. As long as the mounds are there the ecosystem has a better chance to recover."
 
The stages of desertification: Where termites fit in
 
In grasslands and savannas, five stages mark the transition to desert, each having a distinct pattern of plant growth.
The researchers found that these plant growth patterns exist on a much smaller scale than previously thought. Overlaying them is the pattern of termite mounds covered by dense vegetation.
The termite-mound pattern, however, looks deceptively similar to the last and most critical of the five stages that mark the transition of drylands to desert.
Vegetation patterns that might be interpreted as the onset of desertification could mean the opposite: that plants are persevering thanks to termite mounds.
 
Termite mounds help grassland plants persevere
 
Robert Pringle, an ecologist and evolutionary biologist at Princeton and co-author of the paper, said that the unexpected function of termites in savannas and grasslands suggests that ants, prairie dogs, gophers and other mound-building creatures could also have important roles in ecosystem health.
"This phenomenon and these patterned landscape features are common," Pringle said.
"Exactly what each type of animal does for vegetation is hard to know in advance. You'd have to get into a system and determine what is building the mounds and what the properties of the mounds are.
"I like to think of termites as linchpins of the ecosystem in more than one way. They increase the productivity of the system, but they also make it more stable and more resilient."
 
Termites: Linchpins of the ecosystem
 
A mathematical model developed for the work determines how these linchpins affect plant growth.
The scientists applied tools from physics and mathematical and numerical analysis to understand a biological phenomenon, said paper first author Juan Bonachela of Strathclyde University in Scotland.
The model allowed the researchers to apply small-scale data to understand how rainfall influences vegetation growth and persistence in the presence and absence of termites across an entire ecosystem.
"Similar studies would be extremely challenging to perform in the field and would require very long-term experiments," Bonachela said.
"Models such as this allow us to study the system with almost no constraint of time or space and explore a wide range of environmental conditions with a level of detail that can't be attained in the field."
Additional support for the research was provided by a Princeton Environmental Institute Grand Challenges grant, the National Geographic Society, the Andrew W. Mellon Foundation and a John Templeton Foundation Foundational Questions in Evolutionary Biology grant.
-NSF-
Media Contacts Cheryl Dybas, NSF, (703) 292-7734, cdybas@nsf.gov
Morgan Kelly, Princeton University, (609) 258-5729, mgnkelly@princeton.edu
Related WebsitesNSF Grant: Causes and consequences of regular spatial patterning in foundation species: theoretical development and experimental tests in an African savanna:


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Photo of worker termites protected by a soldier.
A study of termites reveals how "worker" insects may have emerged. Shown here, termites painted for the study.

Credit: Barbara L. Thorne, University of Maryland

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Photo of a termite soldier, Zootermopsis nevadensis, with its mandibles open.
A termite soldier, Zootermopsis nevadensis, with its mandibles open.

Credit: Barbara L. Thorne, University of Maryland

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Photo of worker termites protected by a soldier.
Worker termites are protected by a soldier.

Credit: Barbara L. Thorne, University of Maryland

Download the high-resolution JPG version of the image. (407 KB)
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Discovery
Termite Battles May Explain Evolution of Social Insects

Research on why early termite offspring remained home with their parents, instead of leaving to create their own colonies, could provide a missing link to the evolution of sterility among social insects
Photo of worker termites protected by a soldier.
A study of termites reveals how "worker" insects may have emerged.
Credit and Larger Version
February 17, 2010
Natural selection argues for small biological changes that yield greater chances of survival and successful reproduction. Yet, that process does not square well with the evolution of social insects, particularly when their colonies can have over a million non-reproductive members.
A new study of termites may have the answer for such an evolutionary question, first posed by Charles Darwin nearly 150 years ago: How does natural selection produce insect "worker" and "soldier" offspring who never reproduce, find mates or start their own colonies?
Apparently, the answer is because for offspring, there is no place like home.
"This question about the evolution of social behavior among insects really intrigued me," said lead researcher and University of Maryland evolutionary biologist Barbara Thorne, who has spent nearly 30 years pursuing the answer.
"Social insects are extremely successful and dominant in many different habitats all over the world, yet we don't understand how this thriving but complex colony structure evolved. It's why I got involved in these studies when I was a young graduate student."
Thorne's recent research, funded in part by the National Science Foundation (NSF), puts forth a novel theory that it was more advantageous for early termite offspring to stay at home and help their parents than risk dangerous attempts at creating independent colonies away from the nest where they would be more susceptible to predators. The termite youngsters had the best opportunity to take over the reproductive throne when their parents were killed by neighbors.
"The incentive to remain home with their siblings and inherit their parents' estate could provide a missing link to the evolution of sterility among social insects," Thorne said.
Thorne and her colleagues Philip Johns and Ken Howard, both now at Bard College, and fellow Maryland colleagues Nancy Breisch and Anahi Rivera, staged meetings between colonies of neighboring Dampwood termites--the most primitive living termites with traits similar to hypothesized ancestors--and also analyzed the termites' genetic markers.
Her team's research shows that when two neighboring termite families within the same log meet, they battle, often leading to the deaths of one or both families' kings and queens.
This paves the way for replacement "junior" kings and queens to develop from either or both colonies' worker offspring. In other words, sterile termites can become reproducers when their parents are killed, becoming the main progenitors for the colony.
Pheromones produced by healthy kings and queens normally suppress gonad development in "helper" classes, and when the kings and queens die, the pheromones disappear or diminish. As a result, suppression lifts and nonrelated, "sterile," helper offspring from both colonies are able to become new "reproductives" and assume the throne.
"Assassination of founding kings and queens may have driven young termite offspring to remain as non-reproducing workers in their birth colonies," said Thorne.  Rather than risk dangerous attempts at initiating independent colonies outside the nest, remaining at home may have given them a better opportunity to become reproducers.
It also turns out that hundreds of king and queen founding pairs simultaneously colonize the same dead tree, giving the insects greater opportunity to meet and battle their neighbors. When kings and queens are killed, termites from the unrelated families join forces and cooperate in a larger, stronger group in which new reproductive termites can emerge from either or both colonies' worker ranks. Termites from the two families may even interbreed.
Because these young colonies are relatively small, the offspring--that remain as helpers in their parents' nests--have a reasonable chance of inheriting the family's resources and becoming reproductive termites.
"The merged colony also has a size advantage in its next battle with a neighbor," Thorne said. "Thus, both unrelated families benefit following colony encounters."
"Ants, bees and wasps also have highly social colonies with queens and sterile helpers, but they have an unusual genetic system that complicates study of their social origins," Thorne said. "Termites have both kings and queens, and their colony organization is amazingly convergent with the ants, bees and wasps, yet they (termites) evolved completely independently and have a more normal genetic system. Termites haven't received a lot of attention from evolutionary biologists, yet their case may reveal some fundamental principles."
The primitive living termite featured in the research, genus Zootermopsis, shares social, developmental and habitat characteristics with ancient ancestors, and thus serves as a model system to draw inferences regarding how highly social behavior evolved in these insects 140 million years ago. Once primitive termites had an incentive to stay at home in their parents' nest due to the possibility of early or "accelerated" inheritance, that behavior became fixed and over evolutionary time, termite social behavior passed through what Harvard biologist Edward O. Wilson describes as the "point of no return."
"These findings demonstrate how ecological factors could have promoted the evolution of social organization by accelerating and enhancing direct fitness opportunities of helper offspring, rendering relatedness favoring kin selection less critical," Thorne said.
-- Bobbie Mixon, National Science Foundation, bmixon@nsf.gov
This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.
Investigators Barbara Thorne
Nancy Breisch
Ken Howard
Philip Johns
Anahi Rivera
Related Institutions/Organizations University of Maryland College Park
Bard College
Locations Maryland
New York
Related Programs Evolutionary Processes
Total Grants
 
The National Science Foundation (NSF)
Guillermo Gonzalo Sánchez Achutegui
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