Earthworms, ants, termites: The real engineers of the ecosystem

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations. Credit: Image courtesy of Investigación y Desarrollo

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations.

Although the research was conducted from different perspectives, head of research Esperanza Huerta Lwanga focused on the study of soil invertebrates because they are indicators of its quality.

"These organisms fulfill various functions,like allowing the soil to absorb processed organic matter such as leaves, wood, trunks and branches and with this nourishing crops; they also maintain an ecological balance capable of preventing the invasion of pests and provide greater fertility without using chemicals. This happens when growing different types of plants, allowing the existence of a wide variety of soil invertebrates" the researcher explains.

The project, which began in 2009 and was funded by the Ministry of Energy, Natural Resources and Environmental Protection (SERNAPAM), arises because home gardens are places where there is a wealth of soil. In total, the research team worked in 50 home gardens located in different physiographic regions of the state: mountains, coast, floodplain and hillocks.

"During the fieldwork I realized that the orchards whose owners had family harmony, were characterized by a rich vegetation and greater diversity of soil invertebrates was found. However, in other orchards we observed garbage instead vegetation and organisms, revealing a gap between people and nature, " relates Huerta Lwanga.

An important finding of this project was when the researcher found a anecic earthworm, initially thought to be a new species, however, it was only a new entry in the state of Tabasco. "Such organism is characterized by its vertical movements, thereby creating tunnels, helping to integrate the organic matter in the soil, aerating it and forming its structure," the researcher says.

Other species were also identified, like earthworms, ants, termites, centipedes, beetles, grasshoppers, cockroaches and woodlice, which may also be called "ecosystem engineers" (specifically earthworms, termites and some ants) because their activities modify the soil, enriching its productivity.

According to the researcher, it is important to note that the presence of such organisms does not mean that the garden is infested with pests. "If you let me live there, they fulfill their tasks and at the same time control their population because the variety of invertebrates generates food chains."

The pest problem, she says, appears when the land is handled as a monoculture. In these cases only one type of organisms thrives and rapidly increases in number and , because nobody eats them, they become a threat to the plantations.

The research results revealed that the coastal region was the one with more garbage, followed by the hillocks. "In the mountains we found healthy vegetation and a great variety of crops, high diversity of invertebrates and greater earthworm biomass, which was estimated at more than 33 grams per square meter," highlights Huerta Lwanga.

That amount is important because according to previous studies it was established that if biomass is equal or greater than 30 grams per square meter germination induction and plant growth are achieved.

Additionally, this project included environmental education, which was given by mini-workshops and training in the production of vermi-compost.

"At Ecosur, we designed a box for composting, which is equiped with a small mill and worms, where we place the fresh waste to be processed. A device like this was given to all farmers, but was only accepted by 47 percent of them," she sadly concludes.

Source: Investigación y Desarrollo

Genetically identical ants help unlock the secrets of larval fate

Cerapachys biroi ants, native to Asia and introduced globally on tropical and subtropical islands, have no queens and have minimal genetic variation, making them ideal for research on social behavior. Credit: Image courtesy of Rockefeller University

A young animal's genes are not the only genes that determine its fate. The genetic identity of its caretakers matters too. Researchers suspect the interaction between the two can sway the fate of the young animal, but this complex dynamic is difficult to pin down in lab experiments.

However, social insect researchers have found a solution. Rockefeller University's Daniel Kronauer, head of the Laboratory of Insect Social Evolution, and his colleagues are developing a species of small raider ants as a model organism in order to ask questions about the relationships between genes, social behavior and evolution.

In a pair of recent papers, the researchers first explain the unique, and potentially useful, biology of this 2.5-millimeter-long ant. Then, in work with collaborators at the University of Paris 13, they put it to work exploring the interaction between the larvae and their nursemaids, and the influence on the young ants' reproductive success as adults.

Clonal raider ants, the species Cerapachys biroi, reproduce by cloning, and they live in colonies of as many as a few hundred nearly genetically identical workers. This makes these ants ideal for studies testing how a particular genetic makeup responds to different conditions, the researchers write in Current Biology. With the help of collaborators at BGI China, researchers in Kronauer's lab have sequenced the clonal raider ant's genome. This is an important step toward using the ant in the sorts of experiments conducted for years in traditional model organisms, such as mice and fruit flies.

"We have shown that colony mates are extremely closely related to one another, with all of the individuals in a colony being essentially genetically identical. This gives us precise control in experiments because we don't need to account for individual genetic variation," says Peter Oxley, a postdoc in the laboratory who led work establishing the clonal raider ant as a promising new model organism.

In the second study, one of the first to make use of the clonal raider ant, a team led by Serafino Teseo of the University of Paris 13 used the unique aspects of the ants' biology to test the indirect role genes play in shaping the future identity of larvae and whole colonies by looking at the interaction between larvae and adults. They did so by observing the success of two ant clones, A and B, in pure colonies or mixed together into chimeric colonies. They also swapped broods, so A adults raised B larvae and vice versa.

It turned out that A and B larvae developed differently depending on whether A or B nurses raised them. Left alone, pure A colonies produced the most young after six generations, making them more successful than B. However, in mixed colonies, B did better because its larvae more frequently turned into large adults that specialize in egg-laying rather than smaller, foraging-focused individuals.

The researchers suspect an indirect genetic effect -- specifically, a social influence. To begin to tease apart the dynamic, they had adults from one clone raise larvae from the other. Again, B did better when raised by A nurses than any of the other combinations. The results were published in Nature Communications.

The B colony's strategy of favoring reproduction over foraging when raised by A colony nurses smacks of social parasitism, in which one organism exploits another's social behavior for its own benefit. "This doesn't mean B is a parasite in the making, just that uncoupling the normal interaction between larvae and their nearly identical adult nursemaids reveals the presence of this mechanism," Kronauer says.

The study shows that, in social species, genetic makeup alone does not provide enough information to predict social behavior. Instead, interactions between social partners, such as larvae and their caregivers, are crucial determinants and can lead to surprising outcomes.

Source: Rockefeller University

A kingdom of cave beetles found in Southern China

Credit: Mingyi Tian; CC-BY 4.0

A team of scientists specializing in cave biodiversity from the South China Agricultural University (Guangzhou) unearthed a treasure trove of rare blind cave beetles. The description of seven new species of underground Trechinae beetles, published in the open access journal ZooKeys, attests for the Du'an karst as the most diverse area for these cave dwellers in China.

"China is becoming more and more fascinating for those who study cave biodiversity, because it holds some of the most morphologically adapted cavernicolous animals in the world. This is specifically true for fishes and the threchine beetles, the second of which is also the group featured in this study," explains the senior author of the study Prof. Mingyi Tian.

Like most cavernicolous species, Trechinae cave beetles shows a number of specific adaptations, such as lack of eyes and colour, which are traits common among cave dwellers.

The new Trechinae beetles belong to the genus Dongodytes whose members are easily recognizable by their extraordinary slender and very elongated body. Members of this genus are usually very rare in caves, with only five species reported from China before now.

During the recent study of the cave systems in Du'an karst however this numbers drastically changed, Out of the 48 visited caves 12 held populations of trechine beetles. A total of 103 samples were collected, out of which the team of scientists determined ten different species, seven of which are new to science.

"This new discovery casts a new light on the importance of the Du'an Karst as a biological hotspot for cavernicolous Trechinae in China," adds Prof. Mingyi Tian.

Source: Pensoft Publishers