Woodpeckers’ drumming, new research

This 2016 video from the USA says about itself:

World’s Loudest Woodpecker Drumming and Pecking! Northern Flickers use real man-made steel drums – metal chimney caps – that makes them intelligent “tool-users” and likely among the loudest woodpecker drummers in the world. But loud doesn’t begin to describe what the 15-minute long drumming and calling sessions sound like inside the house whose chimney top is used as a drum. Enjoy this short documentary and imagine what this sounds like at the break of dawn as a male Northern Flicker defends his territory, mate and nest box!

From the University of Zurich in Switzerland:

Woodpeckers’ drumming: Conserved meaning despite different structure over the years

October 2, 2020

Summary: How do animals produce and perceive biological information in sounds? To what extent does the acoustic structure and its associated meaning change during evolution? An international team has reconstructed the evolutionary history of an animal communication system, focusing on drumming signals of woodpeckers.

Animal acoustic signals are amazingly diverse. Researchers from the University of Zurich and the University of Saint-Etienne, together with French, American and Dutch collaborators, explored the function and diversification of animal acoustic signals and the mechanisms underlying the evolution of animal communication systems.

To this end, they used Shannon & Weaver’s ‘Mathematical Theory of Communication’ originally applied to telecommunications in 1949, which has transformed the scientific understanding of animal communication. This theory allows the amount of information in a signal to be quantified. The researchers were the first to use this framework within an evolutionary perspective to explore the biological information encoded in an animal signal.

How drumming structure evolves over time

In deciding which biological model to choose, the researchers selected the woodpeckers’ drumming as their ideal candidate. This bird family is known for rapidly striking their beaks on tree trunks to communicate. The team combined acoustic analyses of drumming from 92 species of woodpeckers, together with theoretic calculations, evolutionary reconstructions, investigations at the level of ecological communities as well as playback experiments in the field.

“We wanted to test whether drumming has evolved to enhance species-specific biological information, thereby promoting species recognition,” says lead author Maxime Garcia of the UZH Department of Evolutionary Biology and Environmental Studies.

Constant amount of information for 22 million years

Results demonstrate the emergence of new drumming types during woodpeckers evolution. Yet, despite these changes in drumming structure, the amount of biological information about species identity has remained relatively constant for 22 million years. Selection towards increased biological information thus does not seem to represent a major evolutionary driver in this animal communication system. How then can biological information be concretely maintained in nature? Analyses of existing communities around the globe show that ecological arrangements facilitate the efficiency of drumming signals: Communities are composed of only a few species, which distribute their drumming strategies to avoid acoustic overlap. “The responses to different drumming structures seen in our experimental approach show the ability of individuals to recognize their own species based on acoustic cues about species identity found in drumming signals,” says Garcia. This way, biological information about species identity can be maintained without necessarily inducing a strong evolutionary pressure on drumming signals.

The present study shows that random and unpredictable changes in the structure of communication signals over time can occur while maintaining the signals overall informative potential within and across species. This work leads the way to further investigate the evolution of meaning associated with communicating through multiple communication channels.

Millipede evolution, new research

This 2016 video says about itself:

My friend Dani sent me two unidentified Millipedes. After a bit of research and investigation they turned out to be European White Legged Snake Millipedes (Tachypodoiulus niger ) so i thought i would show a size comparison to my adult female African Giant Millipede (Archispirostreptus gigas)

From PLOS:

Genomes of two millipede species shed light on their evolution, development and physiology

September 29, 2020

Millipedes, those many-legged denizens of the soil surface throughout the world, don’t always get the recognition they deserve. But a new study by Jerome Hui of Chinese University of Hong Kong and colleagues puts them in the spotlight, sequencing and analyzing complete genomes from two very different millipede species. The study, publishing on September 29th in the open-access journal PLOS Biology, provides important insights into arthropod evolution, and highlights the genetic underpinnings of unique features of millipede physiology.

Millipedes and centipedes together comprise the Myriapoda — arthropods with multi-segmented trunks and many legs. CentipedesHow centipedes walk and swim sport one pair of legs per segment, while millipedes bear two. Despite the apparent numeric implications of their names, different centipede species bear between 30 and 354 legs, and millipedes between 22 and 750. There are about 16,000 species of myriapods, including over 12,000 species of millipedes, but only two myriapod genomes have so far been characterized; a complete genome for the centipede Strigamia maritima, and a rough “draft” sequence of a millipede genome.

The authors of the new study fully sequenced the genomes of two millipede species, the orange rosary millipede Helicorthomorpha holstii, and the rusty millipede Trigoniulus corallinus, from two different orders, each distributed widely throughout the world. They also analyzed the gene transcripts (transcriptomes) at different stages of development, and the proteins (proteomes) of the toxin-producing “ozadene” glands.

The researchers found that two species have genomes of vastly different sizes — the orange rosary’s genome is 182 million base pairs (Mb), while the rusty’s is 449 Mb — which the authors showed was due mainly to the rusty millipede’s genome containing larger non-coding regions (introns) within genes and larger numbers of repetitive “junk” DNA sequences.

Homeobox genes play central roles in body plan formation and segmentation during animal development, and the authors found lineage-specific duplications of common homeobox genes in their two species, which differed as well from those found in the previously published millipede genome. None of the three, however, displayed the massive duplications seen in the homeobox genes in the centipede genome. They made further discoveries about the organization and regulation of the homeobox genes as well.

Many millipedes bear characteristic glands on each segment, called ozadene glands, which synthesize, store, and secrete a variety of toxic and noxious defensive chemicals. The authors identified multiple genes involved in production of these chemicals, including genes for synthesizing cyanide, as well as antibacterial, antifungal, and antiviral compounds, supporting the hypothesis that ozadene gland secretions protect against microbes as well as predators.

The results of this study provide new insights into evolution of the myriapods, and arthropods in general. “The genomic resources we have developed expand the known gene repertoire of myriapods and provide a genetic toolkit for further understanding of their unique adaptations and evolutionary pathways,” Hui said.

Mutual aid among animals

This 2009 video says about itself:

Kropotkin on ants & mutual aid

A few excerpts from Mutual Aid: A Factor in Evolution.

Ants seem to be evolutionarily much more successful than us due to their social organization. They’ve been around for hundreds of millions of years, and will probably be around way after we’re gone. I think this may provide some food for thought to the egoistic, laissez faire propertarians who dislike communal and altruistic tendencies.

From the Max Planck Institute for Chemical Ecology in Germany:

How does cooperation evolve?

Researchers unravel why organisms frequently help each other

July 23, 2020

Summary: In nature, organisms often support each other in order to gain an advantage. However, this kind of cooperation appears to contradict the theory of evolution proposed by Charles Darwin: Why would organisms invest valuable resources to help others? Instead, they should rather use them for themselves, in order to win the evolutionary competition with other species.

A new study led by Prof. Dr. Christian Kost from the Department of Ecology at the Osnabrueck University now solved this puzzle. The results of the study were published in the scientific journal Current Biology. The research project was performed in collaboration with the Max Planck Institute for Chemical Ecology in Jena.

Interactions between two or more organisms, in which all partners involved gain an advantage, are ubiquitous in nature and have played a key role in the evolution of life on Earth. For example, root bacteria fix nitrogen from the atmosphere, thus making it available to plants. In return, the plant supplies its root bacteria with nutritious sugars. However, it is nevertheless costly for both interaction partners to support each other. For example, the provision of sugar requires energy, which is then not available to the plant anymore. From this results the risk of cheating interaction partners that consume the sugar without providing nitrogen in return.

The research team led by Prof. Dr. Christian Kost used bacteria as a model system to study the evolution of mutual cooperation. At the beginning of the experiment, two bacterial strains could only grow when they provided each other with essential amino acids. Over the course of several generations, however, the initial exchange of metabolic byproducts developed into a real cooperation: both partners increased the production of the exchanged amino acids in order to benefit their respective partner. Even though the increased amino acid production enhanced growth when both partners were present, it was extremely costly when individual bacterial strains had to grow without their partner.

The observed changes were caused by the fact that individual bacterial cells had assembled into multicellular clusters. In these cell groups, cooperative mutants were rewarded. The more resources they invested in the growth of other cells, the more nutrients they received in return from their partners.

“This kind of feedback represents a previously unknown mechanism, which promotes the evolution of cooperative interactions between two different organisms,” says Prof. Dr. Christian Kost, leader of the study. Although the study was performed with bacteria in a test tube, the mechanism discovered can most likely explain the evolution of cooperation in many different ecological interactions.

Three-spined stickleback fish evolution, new research

This 2014 video says about itself:

Natural selection leads to the evolution of new traits. In this educational video, see how stickleback fish have adapted to live permanently in freshwater environments. Explore a case study of natural selection with this classroom-ready biology video.

Though stickleback fish once lived in the ocean, some populations now thrive in freshwater environments. This change resulted in drastic physical transformations. Explore topics in gene expression and adaptation in this fascinating short film.

From the University of Helsinki in Finland:

Parallel evolution in three-spined sticklebacks

What happens in the Eastern Pacific, stays in the Eastern Pacific

June 22, 2020

A group of researchers from the University of Helsinki used novel and powerful methods to disentangle the patterns of parallel evolution of freshwater three-spined sticklebacks at different geographic scales across their distribution range. The group concludes that the conditions under which striking genome-wide patterns of genetic parallelism can occur may in fact be far from common — perhaps even exceptional.

The three-spined stickleback (Gasterosteus aculeatus), a thumb-sized fish distributed across the Northern hemisphere, is a textbook model species in evolutionary biology. With the retreat of ice sheets since the last glacial maximum, ancestral marine populations have repeatedly colonised newly-formed freshwater habitats. Across their distribution range, sticklebacks in these novel freshwater environments exhibit remarkable similarities in their morphology, physiology and behaviour, a phenomenon known as “parallel evolution.”

“What is really remarkable in our results is that the repeatability of evolution in response to similar selection pressures in different oceans can be so different,” says group leader Juha Merilä, Professor at the Faculty of Biological and Environmental Sciences, University of Helsinki.

The genetic underpinnings of such parallel evolution have fascinated scientists for years, and they have discovered that the observed marine-freshwater differentiation is underlain by surprisingly parallel changes also at the genetic level. However, most studies on this topic have been based on either limited geographic sampling or focused only on populations in the Eastern Pacific region.

“As scientists, we are often tempted to provide simple narratives to extremely complex problems. What I liked the most about this project is that we did the exact opposite: we show that the story behind the three-spined stickleback’s spectacularly fast adaptation to novel habitats may be more complex than previously thought. I think that deciphering the role of demographic history in shaping evolutionary adaptation is a necessary step in solving the mystery,” says co-author Paolo Momigliano, postdoctoral researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki.

Genetic parallelism 10 times higher in the Eastern pacific

With novel and powerful methods, a group of researchers from the University of Helsinki disentangled patterns of parallel evolution of freshwater three-spined sticklebacks at different geographic scales across their distribution range. They found that the extraordinary level of genetic parallelism observed in the Eastern Pacific region is not observed in the rest of the species’ range. In fact, they found approximately 10-fold higher levels of genetic parallelism in the Eastern Pacific compared to the rest of the world.

“I have been studying the worldwide population histories of the species in my PhD. We found their ancestral populations are residing in the Eastern Pacific. We predicted that the region harbours the source of ancestral genetic variations for parallel evolution, and such genetic variation could be lost during colonisation to the rest of the world, for instance in the Atlantic. These predictions were tested by both empirical and simulated data,” explains first author Bohao Fang, PhD candidate from the Faculty of Biological and Environmental Sciences, University of Helsinki.

What happens in the Eastern Pacific, stays in the Eastern Pacific

Their simulations showed that this difference in the degree of parallelism likely depends on the loss of standing genetic variation — the raw material upon which selection acts — during the colonisation of the Western Pacific and Atlantic Oceans from the Eastern Pacific Ocean.

This discrepancy could have been further accentuated by periods of strong isolation and secondary contact between marine and freshwater habitats in the Eastern Pacific, consistent with the group’s results and the geological history of the area. This secondary contact likely happened after the colonisation of the Atlantic Basin, resulting in much more genetic variation available for local adaptation in the Eastern Pacific — variation that never had the chance to spread to the Atlantic. In other words, the discrepancy in genetic patterns of parallel evolution between the two oceans is a result of the complex demographic history of the species, which involved range expansions and demographic bottlenecks.

“Our less assumption-burdened methods have been a key to quantifying parallel evolution at different geographic scales for the type of data that was available for this study. I thoroughly enjoy developing novel methods to study adaptation and evolution, and the idea that parallel evolution might be exceptional in the Eastern Pacific compared to the rest of the world has intrigued me for a long time. It was a lucky coincidence that I became a part of the Ecological Genetics Research Unit led by Juha Merilä where the samples to finally test this hypothesis became available,” concludes Petri Kemppainen, co-first author, method developer, and postdoctoral researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki.

Terrestrial animals smarter than aquatic ones, why?

This 17 June 2020 video says about itself:

Using simulations, Prof. Malcolm MacIver has discovered that hunting in savanna-like landscapes may have helped give rise to planning circuits in the brain. Rife with obstacles and occlusions, terrestrial environments gave prey spaces to hide and predators cover for sneak attacks.

From Northwestern University in the USA:

Hunting in savanna-like landscapes may have poured jet fuel on brain evolution

Rife with obstacles and occlusions, terrestrial environments potentially helped give rise to planning circuits in the brain

June 16, 2020

Summary: Compared to the vast emptiness of open water, land is rife with obstacles and occlusions. By providing prey with spaces to hide and predators with cover for sneak attacks, the habitats possible on land may have helped give rise to planning strategies — rather than those based on habit — for many of those animals.

Ever wonder how land animals like humans evolved to become smarter than their aquatic ancestors? You can thank the ground you walk on.

Northwestern University researchers recently discovered that complex landscapes — dotted with trees, bushes, boulders and knolls — might have helped land-dwelling animals evolve higher intelligence than their aquatic ancestors.

Compared to the vast emptiness of open water, land is rife with obstacles and occlusions. By providing prey with spaces to hide and predators with cover for sneak attacks, the habitats possible on land may have helped give rise to planning strategies — rather than those based on habit — for many of those animals.

But the researchers found that planning did not give our ancestors the upper hand in all landscapes. The researchers’ simulations show there is a Goldilocks level of barriers — not too few and not too many — to a predator’s perception, in which the advantage of planning really shines. In simple landscapes like open ground or packed landscapes like dense jungle, there was no advantage.

“All animals — on land or in water — had the same amount of time to evolve, so why do land animals have most of the smarts?” asked Northwestern’s Malcolm MacIver, who led the study. “Our work shows that it’s not just about what’s in the head but also about what’s in the environment.”

And, no, dolphins and whales do not fall into the category of less intelligent sea creatures. Both are land mammals that recently (evolutionarily speaking) returned to water.

The paper will be published June 16 in the journal Nature Communications.

It is the latest in a series of studies conducted by MacIver that advance a theory of how land animals evolved the ability to plan. In a follow-up study now underway with Dan Dombeck, a professor of neurobiology at Northwestern, MacIver will put the predictions generated by this computational study to the test through experiments with small animals in a robotic reconfigurable environment.

MacIver is a professor of biomedical and mechanical engineering in Northwestern’s McCormick School of Engineering and a professor of neurobiology in the Weinberg College of Arts and Sciences. Ugurcan Mugan, a Ph.D. candidate in MacIver’s laboratory, is the paper’s first author.

Simulating survival

In previous work, MacIver showed that when animals started invading land 385 million years ago, they gained the ability to see around a hundred times farther than they could in water. MacIver hypothesized that being a predator or a prey in the context of being able to see so much farther might require more brain power than hunting through empty, open water. However, the supercomputer simulations for the new study (35 years of calculations on a single PC) revealed that although seeing farther is necessary to advantage planning, it’s not sufficient. Instead, only a combination of long-range vision and landscapes with a mix of open areas and more densely vegetated zones resulted in a clear win for planning.

“We speculated that moving onto land poured jet fuel on the evolution of the brain as it may have advantaged the hardest cognitive operation there is: Envisioning the future,” MacIver said. “It could explain why we can go out for seafood, but seafood can’t go out for us.”

To test this hypothesis, MacIver and his team developed computational simulations to test the survival rates of prey being actively hunted by a predator under two different decision-making strategies: Habit-based (automatic, such as entering a password that you have memorized) and plan-based (imagining several scenarios and selecting the best one). The team created a simple, open world without visual barriers to simulate an aquatic world. Then, they added objects of varying densities to simulate land.

Survival of the smartest

“When defining complex cognition, we made a distinction between habit-based action and planning,” MacIver said. “The important thing about habit is that it is inflexible and outcome independent. That’s why you keep entering your old password for a while after changing it. In planning, you have to imagine different futures and choose the best potential outcome.”

In the simple aquatic and terrestrial environments examined in the study, survival rate was low both for prey that used habit-based actions and those that had the capability to plan. The same was true of highly packed environments, such as coral reefs and dense rainforests.

“In those simple open or highly packed environments, there is no benefit to planning,” MacIver said. “In the open aquatic environments, you just need to run in the opposite direction and hope for the best. While in the highly packed environments, there are only a few paths to take, and you are not able to strategize because you can’t see far. In these environments, we found that planning does not improve your chances of survival.”

The Goldilocks landscape

When patches of vegetation and topography are interspersed with wide-open areas similar to a savanna, however, simulations showed that planning results in a huge survival payoff compared to habit-based movements. Because planning increases the chance of survival, evolution would have selected for the brain circuitry that allowed animals to imagine future scenarios, evaluate them and then enact one.

“With patchy landscapes, there is an interplay of transparent and opaque regions of space and long-range vision, which means that your movement can hide or reveal your presence to an adversary,” MacIver said. “Terra firma becomes a chess board. With every movement, you have a chance to unfurl a strategy.

“Interestingly,” he noted, “when we split off from life in the trees with chimpanzees nearly seven million years ago and quickly quadrupled in brain size, paleoecology studies point to our having invaded patchy landscapes, similar to those our study highlights, as giving the biggest payoff for strategic thinking.”

The study, “Spatial planning with long visual range benefits escape from visual predators in complex naturalistic environments,” was supported by the National Science Foundation Brain Initiative (award number ECCS-1835389).

Tree of Life, new research needed

This 19 February 2020 video says about itself:

The Tree of Life Is Messed Up

Taxonomy is a powerful tool, and one that modern biology wouldn’t be able to function without. But trying to shoehorn the messy, complicated web of interrelationships that is biology into neat boxes has resulted in a pretty messy tree of life.

Hosted by: Olivia Gordon

Darwin’s finches evolution, new research

This 2017 video says about itself:

Evolution by Natural Selection – Darwin’s Finches | Evolution | Biology

In December 1831 a naturalist called Charles Darwin boarded the HMS Beagle, bound on a surveying voyage of South America. Whilst the ship and crew carried out coastline surveys, Darwin was free to explore the islands en route. In 1835 the Beagle arrived at the Galapagos islands, near Ecuador. What Darwin found there surprised him greatly. As well as giant tortoises and marine iguanas, Darwin collected and preserved a variety of different songbirds called finches. Upon returning to the UK he examined them together with ornithologist John Gould, and made some fascinating discoveries.

From the University of Bristol in England:

How the development of skulls and beaks made Darwin’s finches one of the most diverse species

February 3, 2020

Darwin’s finches are among the most celebrated examples of adaptive radiation in the evolution of modern vertebrates and now a new study, led by scientists from the University of Bristol, has provided fresh insights into their rapid development and evolutionary success.

Study of the finches has been relevant since the journeys of the HMS Beagle in the 18th century which catalysed some of the first ideas about natural selection in the mind of a young Charles Darwin.

Despite many years of research which has led to a detailed understanding of the biology of these perching birds, including impressive decades-long studies in natural populations, there are still unanswered questions.

Specifically, the factors explaining why this particular group of birds evolved to be much more diverse in species and shapes than other birds evolving alongside them in Galapagos and Cocos islands have remained largely unknown.

A similar phenomenon is that of the honeycreepers endemic to the Hawaiian archipelago. These true finches (unlike Darwin’s finches which are finch-like birds belonging to a different family) radiated to achieve an order of magnitude more in species and shapes than the rest of the birds inhabiting those islands.

An international team of researchers from the UK and Spain tackled the question of why the rapid evolution in these birds from a different perspective.

They showed in their study published today in the journal Nature Ecology & Evolution that one of the key factors related to the evolutionary success of Darwin’s finches and Hawaiian honeycreepers might lie in how their beaks and skulls evolved.

Previous studies have demonstrated a tight link between the shapes and sizes of the beak and the feeding habits in both groups, which suggests that adaptation by natural selection to the different feeding resources available at the islands may have been one of the main processes driving their explosive evolution.

Furthermore, changes in beak size and shape have been observed in natural populations of Darwin’s finches as a response to variations in feeding resources, strengthening these views.

However, recent studies on other groups of birds, some of which stem from the previous recent research of the team, have suggested that this strong match between beak and cranial morphology and ecology might not be pervasive in all birds.

Professor Emily Rayfield, from the University of Bristol’s School of Earth Sciences, co-authored the new study. She said: “Other factors such as constraints on skull shape during development, the use of the beak for many other functions and the fact that the skull and beak develop and function as a coherent unit may have contributed to this mismatch.

“Therefore, the strong connection between beak, cranial morphology and feeding ecology over the evolution of Darwin’s finches, Hawaiian honeycreepers, and perhaps other lineages of birds, might have been only possible if this tight coevolution of cranial regions is somehow ‘relaxed’ and those regions are able to evolve more freely.”

Lead author Guillermo Navalón, recently graduated from a PhD at the University of Bristol and now a Postdoctoral Researcher at the University of Oxford, added: “By taking a broad scale, numerical approach at more than 400 species of landbirds (the group that encompasses all perching birds and many other lineages such as parrots, kingfishers, hornbills, eagles, vultures, owls and many others) we found that the beaks of Darwin’s finches and Hawaiian honeycreepers evolved in a stronger association with the rest of the skull than in most of the other lineages of landbirds.

“In other words, in these groups the beak is less independent in evolutionary terms than in most other landbirds.”

Jesús Marugán-Lobón co-author of the study and Lecturer at the Autonomous University of Madrid, said: “We found that as a result of this stronger cranial integration, these birds could evolve in a more versatile way but mostly constrained along a very specific direction of adaptive change in the shape of their skulls.

“Paradoxically, we hypothesised that this allowed them to evolve many different shapes very rapidly, filling many of the available niches in their archipelagos as a result.”

In contrast, the authors asserted that the other sympatric bird lineages that occupied the island archipelagos at similar time to the ancestors of finches and honeycreepers all belong to the group with the lowest cranial integration in their study and suggest that this was a limiting factor for rapid evolution in other lineages.

Guillermo Navalón added: “While these results are exciting, this is mainly the work of my PhD and at the minute we are working on solving different unanswered questions that stem from this research.

“For instance, are these evolutionary situations isolated phenomena in these two archipelagos or have those been more common in the evolution of island or continental bird communities? Do these patterns characterise other adaptive radiations in birds?

“Future research will likely solve at least some of these mysteries, bringing us one step closer to understanding better the evolution of the wonderful diversity of shapes in birds.”

Butterflies’ smell and evolution, new research

This 2010 video says about itself:

Bicyclus anynana: male and female butterflies performing courtship behavior

From the National University of Singapore:

Butterflies can acquire new scent preferences and pass these on to their offspring

February 3, 2020

Summary: New studies demonstrate that insects can learn from their previous experiences and adjust their future behavior for survival and reproduction.

It was long believed that physical characteristics acquired by organisms during their lifetime could not be passed on to their offspring. However, in recent years, the theory of inheritance of acquired traits has gained support, with studies showing how offspring of rats and tiny worms inherit behaviours that were acquired by their parents in response to particular environmental stimuli, even when the stimulus is no longer present in the offspring’s generation.

This theory is further supported by recent studies conducted by researchers from the National University of Singapore (NUS), in which they found that the inheritance of acquired traits also happens in butterflies, especially in the bush brown butterfly Bicyclus anynana.

Two research teams supervised by Associate Professor Antónia Monteiro, who is from the Department of Biological Sciences at the NUS Faculty of Science, as well as from Yale-NUS College, showed that both Bicyclus anynana caterpillars and adult butterflies can learn to prefer new odours if they are exposed to them during their development or early in life. The researchers also found that the offspring of the exposed caterpillars and butterflies show the same new preferences as their parents, even though they were not exposed themselves, indicating that their parents have passed their new acquired preferences to their children.

The findings of the two studies were published online in the scientific journals Evolution in October 2019 and Nature Communications in January 2020.

Learning to like new odours for feeding and mating

In the study that was published in Evolution, NUS doctoral student Ms V. Gowri, research fellow Dr Emilie Dion, and their collaborators exposed caterpillars and butterflies to new odours they typically do not experience in their natural environment. In the experiments, caterpillars were fed with corn leaves — their usual food — coated with banana or with mango essence throughout their development. Most of these caterpillars preferred to eat leaves with the fruit essence after only a few days of exposure.

In the second study, which was published in Nature Communications, Dr Dion and her collaborators exposed young female butterflies to new sex pheromone blends, a perfume produced by males to entice females to mate with them. The results showed that the exposed females later preferred to mate with males having the new pheromone blend.

“These results are significant because they show that insects are not only driven by their instincts, but can also learn from their previous experience and adjust their future behaviour accordingly. The consequences of their learning abilities on their survival and reproduction can be very important,” shared Dr Dion.

Offspring acquired the learned preferences of their parents

Both studies examined the behaviour of the offspring of the exposed Bicyclus anynana caterpillars and butterflies. The results revealed that the new generation also exhibited the same preference for the new food odours, or the new sex pheromone blends, although they were never exposed to these odours themselves. The teams concluded that the offspring inherited the preferences acquired by their parents.

While these learning and inheritance processes are hypothesised to facilitate the evolution of diet diversity across insects, and mate selection over the course of insect diversification, the impact of this inheritance mechanism on evolution is still unknown.

“We are now investigating whether this behavioural transmission is maintained for more than one generation, and also probing the underlying molecular mechanisms in our model species, as these remain some of the most exciting unanswered questions in the field of evolutionary biology,” said Assoc Prof Monteiro.

The study reveals that the African satyrid butterfly Bicyclus anynana (B. anynana), a member of the sub-family of the nymphalidae (or ‘brush-footed’) butterflies, changes its eyespot size using a complex physiological and molecular response that evolved gradually over millions of years. The findings also highlight that while temperature modulates hormone levels in various species of satyrid butterfly, B. anynana is just one of a few that take advantage of this response to regulate eyespot size: here.