Category: Environment

{Rapid population decline among vertebrate species began at the end of the 19th century when industrialization was at its peak, according to researchers at The University of Texas Health Science Center at Houston (UTHealth) and the Chinese Academy of Sciences. The research was recently published in Proceedings of the National Academy of Sciences.}

“Industrialization is the most natural explanation as to why we have rapid population decline in that period of time. It has to be somehow caused by human impact,” said Yun-Xin Fu, Ph.D., professor in the Department of Biostatistics and the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health.

To reach this conclusion, Fu and his co-authors, including first author Haipeng Li, Ph.D., who was a visiting School of Public Health student and postdoctoral fellow now with the Chinese Academy of Sciences, reviewed thousands of scientific articles about the genetic diversity of vertebrate species. Their efforts yielded genetic data from 2,764 vertebrate species, 600 of which are endangered.

The researchers used a population genetics approach to model when each threatened species began to rapidly decline in population size. On average, the population size of endangered species declined by about 25 percent every 10 years starting 123 years ago.

Rapid population decline is widespread among endangered species and when it occurs, genetic diversity suffers. While conservation efforts have typically focused on maintaining genetic diversity within a species, Fu believes that preserving ecosystems and natural habitats should hold more weight.

“Genetic diversity is important to preserving a species from a long-term standpoint. However, preventing the rapid population decline by protecting the native habitats of species appears to be and should be more important because the overall difference of genetic diversity between threatened and non-threatened species is not at an alarming level,” said Fu.

Fu hopes the study will better inform conservation efforts and encourage more of an emphasis on the effects of human impact on habitats and ecosystems.

{Scientists at the University of Southampton have discovered six new animal species in undersea hot springs 2.8 kilometres deep in the southwest Indian Ocean.}

The unique marine life was discovered around hydrothermal vents at a place called Longqi (‘Dragon’s Breath’), 2000 kilometres southeast of Madagascar and is described in the journal Scientific Reports.

A research team, led by Dr Jon Copley, explored an area the size of a football stadium on the ocean floor, pinpointing the locations of more than a dozen mineral spires known as ‘vent chimneys’. These spires, many of which rise more than two storeys above the seabed, are rich in copper and gold that is now attracting interest for future seafloor mining. However, the spires are also festooned with deep-sea animals, nourished by hot fluids gushing out of the vent chimneys.

The team, which includes colleagues at the Natural History Museum in London and Newcastle University, carried out genetic comparisons with other species and populations elsewhere to show that several species at Longqi are not yet recorded from anywhere else in the world’s oceans.

The expedition, which took place in November 2011, provides a record of what lives on the ocean floor in the area, which is licensed for mineral exploration by the International Seabed Authority of the United Nations, before any mining surveys are carried out.

The Longqi vents are the first known in the region and the expedition was the first to explore them using a deep-diving remotely operated vehicle (ROV).

The deep-sea animals that are so far only known from Longqi include: a species of hairy-chested ‘Hoff’ crab, closely related to ‘Hoff’ crabs at Antarctic vents; two species of snail and a species of limpet; a species of scaleworm; and another species of deep-sea worm. Apart from one species of snail, which has been given the scientific name Gigantopelta aegis, most have not yet been formally described.

“We can be certain that the new species we’ve found also live elsewhere in the southwest Indian Ocean, as they will have migrated here from other sites, but at the moment no-one really knows where, or how well-connected their populations are with those at Longqi,” said Dr Copley. “Our results highlight the need to explore other hydrothermal vents in the southwest Indian Ocean and investigate the connectivity of their populations, before any impacts from mineral exploration activities and future deep-sea mining can be assessed.”

The scientists also found other species at Longqi that are known at other vents far away in other oceans. Another new species of scaleworm lives at vents on the East Scotia Ridge in the Antarctic, 6,000 kilometres away, while a species of ragworm live at vents in the eastern Pacific, more than 10,000 km away.

“Finding these two species at Longqi shows that some vent animals may be more widely distributed across the oceans than we realised,” added Dr Copley.

{New research led by the American Museum of Natural History suggests that there are about 18,000 bird species in the world — nearly twice as many as previously thought. The work focuses on “hidden” avian diversity — birds that look similar to one another, or were thought to interbreed, but are actually different species. Recently published in the journal PLOS ONE, the study has serious implications for conservation practices.}

“We are proposing a major change to how we count diversity,” said Joel Cracraft, an author of the study and a curator in the American Museum of Natural History’s Department of Ornithology. “This new number says that we haven’t been counting and conserving species in the ways we want.”

Birds are traditionally thought of as a well-studied group, with more than 95 percent of their global species diversity estimated to have been described. Most checklists used by bird watchers as well as by scientists say that there are roughly between 9,000 and 10,000 species of birds. But those numbers are based on what’s known as the “biological species concept,” which defines species in terms of what animals can breed together.

“It’s really an outdated point of view, and it’s a concept that is hardly used in taxonomy outside of birds,” said lead author George Barrowclough, an associate curator in the Museum’s Department of Ornithology.

For the new work, Cracraft, Barrowclough, and their colleagues at the University of Nebraska, Lincoln, and the University of Washington examined a random sample of 200 bird species through the lens of morphology — the study of the physical characteristics like plumage pattern and color, which can be used to highlight birds with separate evolutionary histories. This method turned up, on average, nearly two different species for each of the 200 birds studied. This suggests that bird biodiversity is severely underestimated, and is likely closer to 18,000 species worldwide.

The researchers also surveyed existing genetic studies of birds, which revealed that there could be upwards of 20,000 species. But because the birds in this body of work were not selected randomly — and, in fact, many were likely chosen for study because they were already thought to have interesting genetic variation — this could be an overestimate. The authors argue that future taxonomy efforts in ornithology should be based on both methods.

“It was not our intent to propose new names for each of the more than 600 new species we identified in the research sample,” Cracraft said. “However, our study provides a glimpse of what a future taxonomy should encompass.”

Increasing the number of species has implications for preserving biodiversity and other conservation efforts.

“We have decided societally that the target for conservation is the species,” said Robert Zink, a co-author of the study and a biologist at the University of Nebraska, Lincoln. “So it follows then that we really need to be clear about what a species is, how many there are, and where they’re found.”

{Like humans learning to speak, juvenile birds learn to sing by mimicking vocalizations of adults of the same species during development. Juvenile birds preferentially learn the song of their own species, even in noisy environments with a variety of different birdsongs. But how they can recognize their species’ song has, until now, remained a mystery. In a collaborative study, neuroscientists and a physicist at the Okinawa Institute of Science and Technology Graduate University (OIST) have uncovered an innate mechanism for species identification based on the silent gaps between birdsong syllables.}

“We co-designed an experiment that works within the constraints of neuroscience while satisfying the requirements of physics,” says Professor Mahesh Bandi, head of the Collective Interactions Unit at OIST.

Dr. Makoto Araki and Professor Yoko Yazaki-Sugiyama of OIST’s Neuronal Mechanism for Critical Period Unit and Professor Bandi performed a cross-fostering experiment in which juvenile zebra finches were raised by Bengalese finch foster parents to examine how their birdsong develops under the tutoring of a different species. Birdsong is comprised of stereotypical repeats of a few syllables, called ‘song motifs’, in which syllables are separated by silent gaps. The findings, published in Science, reveal that the fostered zebra finches learned morphologies of Bengalese finch syllables, including syllable duration, but transposed onto zebra finch silent gap patterns. This suggests that temporal gaps between syllables are innate, while syllable morphology can be learned.

“The fostered zebra finches sang the Bengalese finch song with a zebra finch accent,” says Professor Yoko Yazaki-Sugiyama.

To determine the neural basis of this innate species detection mechanism, the researchers recorded the activity of neurons in the auditory cortex of adult zebra finch brains during exposure to birdsong. They discovered a first set of neurons which registered temporal gaps of zebra finch songs, as well as a separate second set of neurons that are responsive to syllable morphology.

Using trains of song syllables or white noise separated by silent intervals of varying lengths, they discovered that the first set of neurons are most sensitive to silent gaps with the same duration as the silent gaps found in natural zebra finch song. The neurons did not respond to syllable trains if the duration between syllables was too short or too long. This phenomenon persisted in juvenile zebra finches raised in isolation or cross-fostered by Bengalese finch parents.

This first set of neurons responded strongly to natural zebra finch song. They neither responded to artificial zebra finch song in which the duration of the silent gaps between syllables had been increased, nor to the songs of other species. Together these findings support the existence of neuronal mechanisms that use silent gaps between syllables of birdsong to detect songs of the same species during learning.

“This first set of neurons operate as a kind of neural barcode reader,” says Professor Yazaki-Sugiyama.

Each male zebra finch has to develop a unique song that is different from other zebra finches, while maintaining species specific identity. Parallel processing of syllable morphology and temporal silent gaps between syllables discovered by OIST researchers could help explain how these two competing criteria are satisfied.

Decades ago, researchers at Bell Laboratories seeking to boost telecommunication channel capacity developed tools in voice activity detection as well as Information Theory. This collaborative team work by researchers from different disciplines applied Information theoretic tools and discovered similar strategies are hardwired in bird brains to recognize and learn songs of their own species. These findings tell us there is information in silence.

{Monkeys and apes are unable to learn new vocalizations, and for decades it has been widely believed that this inability results from limitations of their vocal anatomy: larynx, tongue and lips.}

But an international team of scientists, led by Tecumseh Fitch at the University of Vienna and Asif Ghazanfar at Princeton University, has now looked inside monkeys’ vocal tracts with x-rays, and found them to be much more flexible than thought before. The study indicates that the limitations that keep nonhuman primates from speaking are in their brains, rather than their vocal anatomy.

The scientists used x-ray video to see within the mouth and throat of macaque monkeys induced to vocalize, eat food, or make facial expressions. They then used these x-rays to build a computer model of a monkey vocal tract, allowing them to answer the question “what would monkey speech sound like, if a human brain were in control?” This showed that monkeys could easily produce many different sounds, enough to produce thousands of distinct words. Examples of synthesized monkey speech can be heard here:

This implies that a basic form of spoken language could have evolved at any time in human evolution, without requiring any changes in vocal anatomy.

{Extinctions related to climate change have already happened in hundreds of plant and animal species around the world. New research, publishing on December 8th in the open-access journal PLOS Biology, shows that local extinctions have already occurred in 47% of the 976 plant and animal species studied.
}

Climate change is predicted to threaten many species with extinction, but determining how species will respond in the future is difficult. Dozens of studies have already demonstrated that species are shifting their geographic ranges over time as the climate warms, towards cooler habitats at higher elevations and latitudes. The new study, by Professor John J. Wiens from the University of Arizona, used these range-shift studies to show that local extinctions have already happened in the warmest parts of the ranges of more than 450 plant and animal species. This result is particularly striking because global warming has increased mean temperatures by less than 1 degree Celsius so far. These extinctions will almost certainly become much more widespread over time, because temperatures are predicted to increase by an additional 1 to 5 degrees in the next several decades. These local extinctions could also extend to species that humans depend on for food and resources.

The study also tested the frequency of local extinction across different regions, habitats, and groups of organisms. It found that local extinctions occurred in about half of the species surveyed across different habitats and taxonomic groups. However, the results showed that local extinctions varied by region and were almost twice as common among tropical species as among temperate species. This is important as the majority of plant and animal species live in the tropics. The results of this study contribute to our understanding of how plants and animals will respond to global climate change and highlight the need to slow and prevent further warming.

{Over 700 newly recognized bird species have been assessed for the latest update of The IUCN Red List of Threatened SpeciesTM, and 11% of them are threatened with extinction. The update also reveals a devastating decline for the giraffe, driven by habitat loss, civil unrest and illegal hunting. The global giraffe population has plummeted by up to 40% over the last 30 years, and the species has been listed as Vulnerable on the IUCN Red List.}

Today’s IUCN Red List update also includes the first assessments of wild oats, barley, mango and other crop wild relative plants. These species are increasingly critical to food security, as their genetic diversity can help improve crop resistance to disease, drought and salinity.

The update was released at the 13th Conference of the Parties to the Convention on Biological Diversity (CBD COP13) in Cancun, Mexico. The IUCN Red List now includes 85,604 species of which 24,307 are threatened with extinction.

“Many species are slipping away before we can even describe them,” says IUCN Director General Inger Andersen. “This IUCN Red List update shows that the scale of the global extinction crisis may be even greater than we thought. Governments gathered at the UN biodiversity summit in Cancun have the immense responsibility to step up their efforts to protect our planet’s biodiversity — not just for its own sake but for human imperatives such as food security and sustainable development.”

Birds: Newly recognized, already threatened

This IUCN Red List update includes the reassessment of all bird species. Thanks to a comprehensive taxonomic review compiled by BirdLife International, working in collaboration with the Handbook of the Birds of the World, the overall number of bird species assessed has reached 11,121.

A total of 742 newly recognized bird species have been assessed, 11% of which are threatened. For example, the recently described Antioquia wren (Thryophilus sernai) has been listed as Endangered as more than half of its habitat could be wiped out by a single planned dam construction. Habitat loss to agriculture and degradation by invasive plants have also pushed the striking Comoro blue vanga (Cyanolanius comorensis) into the Endangered category.

Thirteen of the newly recognized bird species enter the IUCN Red List as Extinct. Several of these have been lost within the past 50 years — such as the Pagan reed-warbler (Acrocephalus yamashinae), O’ahu akepa (Loxops wolstenholmei) and Laysan honeycreeper (Himatione fraithii). All of these species were endemic to islands, and were most likely wiped out by invasive species.

“Unfortunately, recognizing more than 700 ‘new’ species does not mean that the world’s birds are faring better,” says Dr Ian Burfield, BirdLife’s Global Science Coordinator. “As our knowledge deepens, so our concerns are confirmed: unsustainable agriculture, logging, invasive species and other threats — such as the illegal trade highlighted here — are still driving many species towards extinction.”

IUCN Red List assessments also reveal that some of the world’s most popular birds may soon disappear in the wild if appropriate action isn’t taken. Iconic species, such as the African grey parrot (Psittacus erithacus) — a prized pet with the ability to mimic human speech — are facing extinction in the wild due to unsustainable trapping and habitat loss. Native to central Africa, the grey parrot has seen its conservation status deteriorate from Vulnerable to Endangered. A study led by BirdLife International discovered that in some parts of the continent numbers of grey parrots have declined by as much as 99%.

The situation is most pressing in Asia, with the rufous-fronted laughingthrush (Garrulax rufifrons), scarlet-breasted lorikeet (Trichoglossus forsteni) and Straw-headed bulbul (Pycnonotus zeylanicus) among a suite of species being uplisted to higher threat categories as a result of the impacts of illegal wildlife trade. There is now evidence that unsustainable levels of capture for the cagebird trade, largely centred on Java, are driving the deteriorating status of many species.

However, there is good news for some of the rarest and most vulnerable birds on our planet — those that exist only on small, isolated islands. The Azores bullfinch (Pyrrhula murina), St Helena plover (Charadrius sanctaehelenae) and Seychelles white-eye (Zosterops modestus) are among the island endemic species to move to lower categories in this IUCN Red List update, as their populations recover from the brink of extinction thanks to tireless conservation efforts.

{{Giraffe}}

The iconic giraffe (Giraffa camelopardalis), one of the world’s most recognisable animals and the tallest land mammal, is now threatened with extinction. The species, which is widespread across southern and eastern Africa, with smaller isolated subpopulations in west and central Africa, has moved from Least Concern to Vulnerable due to a dramatic 36-40% decline from approximately 151,702-163,452 individuals in 1985 to 97,562 in 2015.

The growing human population is having a negative impact on many giraffe subpopulations. Illegal hunting, habitat loss and changes through expanding agriculture and mining, increasing human-wildlife conflict, and civil unrest are all pushing the species towards extinction. Of the nine subspecies of giraffe, three have increasing populations, whilst five have decreasing populations and one is stable.

A resolution adopted at the IUCN World Conservation Congress in September this year called for action to reverse the decline of the giraffe.

{{Crop wild relatives}}

With this update, the first assessments of 233 wild relatives of crop plants such as barley, oats and sunflowers have been added to the IUCN Red List. Habitat loss, primarily due to agricultural expansion, is the major threat to many of these species. The assessments were completed as part of a partnership between Toyota Motor Corporation and IUCN, whose aim is to broaden the IUCN Red List to include the extinction risk of many species that are key food sources for a significant portion of the global population.

Crop wild relatives are a source of genetic material for new and existing crop species, allowing for increased disease and drought resistance, fertility, nutritional value and other desirable traits. Almost every species of plant that humans have domesticated and now cultivate has one or more crop wild relatives. However, these species have received little systematic conservation attention until now.

Four mango species have been listed as Endangered, and the Kalimantan mango (Mangifera casturi) has been listed as Extinct in the Wild. These species are relatives of the common mango (Mangifera indica) and are threatened by habitat loss. Native to South Asia, mangoes are now cultivated in many tropical and sub-tropical countries and they are one of the most commercially important fruits in these regions.

A relative of cultivated asparagus, hamatamabouki (Asparagus kiusianus), which is native to Japan, has been listed as Endangered due to habitat loss caused by urban expansion and agriculture. Loss of habitat is also the main threat to the Anomalus sunflower (Helianthus anomalus) which has been listed as Vulnerable and is a relative of the sunflower (H. annuus). Cicer bijugum, native to Iran and Turkey, is a wild relative of the chickpea (C. arietinum); it has been listed as Endangered due to habitat conversion to agriculture.

“Crop wild relative species are under increasing threat from urbanisation, habitat fragmentation and intensive farming, and probably climate change,” says Mr. Kevin Butt, General Manager, Regional Environmental Sustainability Director, Toyota Motor North America. “To conserve this vital gene pool for crop improvement we need to urgently improve our knowledge about these species. Toyota is pleased to provide support for the assessment of these and other species on The IUCN Red List.”

{{Freshwater species — Lake Victoria}}

All freshwater molluscs, crabs, dragonflies and freshwater fishes native to Lake Victoria in central Africa are included in this update. Key threats to Lake Victoria — known as Darwin’s dream pond due to its high biodiversity — include invasive species such as the Nile perch (Lates niloticus), overharvesting, sedimentation due to logging and agriculture, as well as water pollution from pesticides and herbicides.

{Despite their obvious physical differences, elephants, lizards and trout all have something in common. They possess elongated, flexible structures at the rear of their bodies that we call tails. But a new study by a University of Pennsylvania paleobiologist reveals that the tails of fish and the tails of tetrapods, or four-limbed animals, are in fact entirely different structures, with different evolutionary histories.}

With an analysis of 350-million-year-old fossil fish hatchlings, Lauren Sallan, an assistant professor in the School of Arts & Science’s Department of Earth and Environmental Science, showed that these ancient juvenile fish had both a scaly, fleshy tail and a flexible fin, one sitting atop the other. A similar dual tail structure is seen in the embryos of modern teleosts, a group of ray-finned fish that make up more than 95 percent of living fish species.

Over evolutionary time, to adapt to their environments, adult teleosts and tetrapods each lost one of these tails.

“The tetrapod tail likely started as a limb-like outgrowth in the first vertebrates, while the fish caudal fin started as a co-opted median fin, like the dorsal fin,” Sallan said. “All vertebrate tail diversity might be explained by the relative growth and loss of these two tails, with the remaining fleshy tail stunted in humans as in fishes.”

Sallan reported her findings in the journal Current Biology.

For nearly 200 years, scientists from Darwin contemporary Thomas Henry Huxley to Stephen Jay Gould pointed to the larval stage of modern teleost fish, which have an asymmetrial tail that resembles those of ancient adult ray-finned fish, as a prime example of recapitulation theory, the idea that the growth and development of organisms takes them through stages that mirror the evolutionary steps from simple to more complex organisms.

This example, however, had a notable weakness: a lack of fossils of juvenile fish ancestors. The linchpin for Sallan’s study came in the form of a series of 350-million- year-old fossil specimens of Aetheretmon valentiacum, a fish species related to teleosts. The fossils were recovered from Scotland over decades and stored in museums, but most had never been examined in detail. Unstudied specimens included the smallest known examples of the species — only 3 centimeters long — representing the earliest known stage of development for such fishes. These fossils allowed the first direct comparison between the growth stages of ancient fish and their modern teleost descendants.

Adult Aetheretmon fish possessed an asymmetrical tail, longer on the top than the bottom, which contains vertebrae. A group of modern fish called chondrosteans, which includes species such as sturgeon and paddlefish, are sometime referred to as “living fossils” and have a similar tail structure. Adult teleost tails, on the other hand, are nearly symmetrical and comprised entirely of fin.

According to recapitulation theory, juvenile Aetheretmon would have appeared to be smaller versions of the adults, exhibiting what is called direct development. Sallan’s observations found that this was not the case. The juvenile Aetheretmon in fact closely resembled modern teleost juveniles; both have a small fleshy tail containing vertebrae, similar to a lizard’s tail, overlaying a fin. As they matured, the upper tail of Aetheretmon continued to extend. In contrast, the upper portion of the tail of modern teleosts’ is stunted early and so ends up embedded in the growing body, their caudal fin instead becoming their only “tail.”

Sallan examined the tail forms of a variety of different species of fish, living and extinct, at different developmental stages, and found the same two-part structure, differently arranged, in each.

“What this shows is that ancient fish and modern fish had the same developmental starting point that has been shared over 350 million years,” said Sallan. “It’s not the ancestral tail showing up in modern teleost larvae; it’s that all fish have two different structures to their tail that have been adjusted over time based on function and ecology for all of these species.”

The analysis allows for new insights to be drawn not only about fish evolution but the evolution of vertebrates in general, as the bony, fish-like ancestors of Aetheretmon, living fishes and land-dwelling tetrapods likely had both types of tail. The vertebrae-containing tail present in Aethretmon likely represents the first limb-like growth that became the true tails in animals like lizards.

Sallan said it’s likely that the two outgrowths are governed by two different groups of genes and thus could have been subject to natural selection independently, generating large numbers of innovative forms throughout evolution.

“It tells us why we have all this diversity in fins and limbs in past and present,” Sallan said. “There might have been some lineages that favored one form over another for functional or ecological reasons. If a fish couldn’t adapt this trait, which is so vital for swimming, they might have gone extinct.”

Sallan is excited by the possibility that these findings could be evaluated by a developmental biologist to confirm the molecular pathways that generate limb outgrowth or fin placement.

“This would be an easy way of testing evolution in the lab,” she said.

{In honey bee colonies, a single queen is laying eggs from which thousands of worker bees are born. At a young age, workers care for the brood, then build and defend the nest and eventually, towards the end of their lives, leave the safety of the nest to forage for food. This major step in their lives is speeding up aging because searching the environment for food exposes these foragers to a wide range of stressors, such as pathogens, predators and adverse weather conditions.}

Despite her title, the queen is not deciding who does what in the honey bee colony. How work is distributed between nestmates in these societies is not fully understood. Previous research has shown that tasks are allocated based on communication between the queen, brood and individual workers performing these tasks. For example, the presence of foragers in hives reduces the number of younger bees leaving the hives to start foraging. It is also known that the presence of larvae reduces the life expectancy of bees due to the need for adult workers to tend to them and forage to feed them. This was shown by an increase in longevity of workers after experimental removal of larvae. Since their removal also resulted in the removal of young adults that develop from them, the observed effect could not be attributed to the young workers or to the brood until now.

‘By experimentally separating the effect of brood and of young adults on their nestmates’ destiny, we could tease apart the role of these two actors’ says senior author Vincent Dietemann from Agroscope. ‘We saw that both the presence of brood and of young workers shortened the life expectancy of their nestmates’ adds lead author Michael Eyer from both Agroscope and Institute of Bee Health. The newly discovered role of young workers in honey bee social organisation adds to our knowledge of how demography shapes colony functioning. ‘These social regulation mechanisms of food collection allow the fast adaptation of the colony to a changing environment’ says co-author Peter Neumann from the Institute of Bee Health.

{{Understanding insect societies, aging and significance for beekeeping}}

These findings are significant for our understanding of social organization in insects, which often inspires technological innovations. They also provide information on general aging processes beyond social insects. Indeed, honey bees are used as model system to understand aging in other organisms, including humans. The acquired knowledge has practical implications for beekeepers because colony management can include removal of brood and thus of young workers. This for example can occur before a treatment to control the parasitic mite Varroa destructor. The extension of worker lifespan induced by the removal allows the colony to compensate this absence and continue functioning.

{{Honey bee duties and pollination — Background}}

In spring and summer, honey bee colonies are composed of so called ‘summer bees’. During the first one to three weeks, they perform tasks such as nursing and cleaning within the nest and later leave its protection to forage for nectar and pollen required for colony growth, before dying. In late summer, falling temperature reduces foraging activity and brood rearing declines. The so-called long-lived ‘winter bees’ emerge from the last brood reared. Their tasks consist in maintaining the nest at temperatures that ensure the survival of the colony over several winter months and in resuming brood rearing in the next spring, before they start foraging again in spring. Worker life expectancy is thus plastic and varies according to each phase of a colony’s life history.

In addition to producing honey, wax, propolis and royal jelly, honey bees contribute to the pollination of a large variety of commercial food crops — a service valued at over 150 billions Euros globally. Moreover, honey bees together with other insects pollinate many wild flowers and are therefore central to the functioning of terrestrial ecosystems, of which the economical value is order of magnitudes higher.