Panamanian Heliconius butterflies’ colours, new research


This 31 October 2019 video from the USA says about itself:

New research published in Science reveals that Heliconius butterflies have an unexpected evolutionary history. Rather than resembling a traditional evolutionary “tree”, the species’ history was more like a bush with many instances of introgression or genetic sharing after speciation.

“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”

In generating 20 whole genome assemblies for Heliconius butterflies, Frandsen and coauthors from Harvard and MIT had the biggest data set they could bring to bear on the situation.

From the Smithsonian Tropical Research Institute in Panama:

Butterflies take different paths to arrive at same color pattern

November 14, 2019

An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: How do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again? The answer, published in Current Biology, forever changes the way evolution is understood.

“Our team is the first to report that although evolution of similar color patterns in Heliconius may be driven by similar forces — like predators avoiding a particular kind of butterfly — the pathway to that outcome is not predictable,” said Carolina Concha, lead author of the paper and a post-doctoral fellow at STRI. “This really surprised us because it reveals the importance of history and chance in shaping the genetic pathways leading to butterfly wing-pattern mimicry.”

Heliconius’ bright wing colors signal to bird predators that the butterflies are toxic. Flashy male wing patterns signal to females that they are choosing the right species to mate with. Somehow these two forces, predation and mating, lead to similar wing patterns in groups of butterflies isolated in the mountain valleys and foothills of the Andes. By knocking out a single gene called WntA in 12 different species and their variants, the molecular biologists on the team could tell whether the butterflies in a pair with the same wing patterns were using the same genetic pathways to color and pattern their wings. They were not.

“Imagine two teams given the same Lego blocks are asked to build the same device,” said Arnaud Martin, co-author and head of the Butterfly Evo-Devo Lab at George Washington University. “Each team goes about the task in a different way, but in the end, the result is the same. Butterflies face much more serious challenges: they build structures made of wing scales that are essential to their survival and ability to reproduce.”

Questions regarding butterfly mimicry have intrigued biologists for decades, but the technology to selectively remove a single gene in a live organism did not exist until about five years ago. Now, with CRISPR/Cas 9 gene editing, it is getting much easier to tinker with the genetic code. When researchers knock out a major patterning gene like WntA, it changes the microscopic structure and color of the scales that compose the butterfly’s wing and, as a result, the pattern changes. The study raises a number of questions, such as how WntA interacts with other genes to end up with an area that is red or black. Now the team wants to know how the WntA gene is controlled.

“We learned that while a developmental gene (WntA) can have a broad role in the evolution of most butterfly wing color patterns, its precise use to color a butterfly’s wing is not completely predictable,” said Riccardo Papa, co-author and professor at the University of Puerto Rico. “Distinct species with identical wing-color patterns, such as co-mimetic butterflies, can evolve using different molecular strategies. Imagine the same notes played on different instruments!”

“Some people say that Panama was an indigenous word meaning abundance of butterflies,” said Owen McMillan, staff scientist and head of the ecological genomics lab at STRI. “The Smithsonian labs in Gamboa are certainly one of the best places in the world to understand how butterflies evolve, and we hope that inspired researchers will join us here as we continue to ask questions about these incredibly beautiful creatures.”

Heliconius butterflies, new research


This 31 October 2019 video from the USA says about itself:

New research published in Science reveals that Heliconius butterflies have an unexpected evolutionary history. Rather than resembling a traditional evolutionary “tree”, the species’ history was more like a bush with many instances of introgression or genetic sharing after speciation.

“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”

In generating 20 whole genome assemblies for Heliconius butterflies, Frandsen and coauthors from Harvard and MIT had the biggest data set they could bring to bear on the situation.

From Harvard University in the USA:

Gene flow among distantly-related butterfly species

November 1, 2019

An international team of researchers analyzed the genomes of 20 butterfly species and discovered a surprisingly high amount of gene flow among them — even between species that are distantly related. The findings, published in the journal Science, challenge conventional views about species and point to hybridization as a key process in the emergence of biological diversity.

Different species of passion vine butterflies (Heliconius) have similar color patterns that serve as warnings to predators. Scientists have previously found that one reason for their similarity is that they actually share parts of their DNA, thanks to hybridization that occurred at some point in their ancestry. The new findings suggest that this process of DNA sharing is far more common than previously thought.

To understand how butterflies pass genes to other species by hybridizing, a process known as introgression, the researchers analyzed new genome assemblies of 20 Heliconius butterfly species.

“DNA sharing had been shown in closely related species, but we wanted to probe deeper into the phylogenetic tree,” said senior author James Mallet, Professor of Organismic and Evolutionary Biology in Residence and Associate of Population Genetics in the Museum of Comparative Zoology. “What we found is really astonishing: introgression even among species that are distantly related. “Species” are simply not what we thought they were, and now we have the data to show it. The evolutionary tree of butterflies is a complete morass of inter-connectedness — every bit of the butterfly genome seems to have a different tree.”

Lead author Nate Edelman, a graduate student in the Mallet group, explained that the new genome assemblies function as detailed genomic maps. They are constructed by sequencing short fragments of DNA, then assembling them in the proper order. Genome assemblies are an important resource for researchers, as they make it possible to map genes back to the genome.

“The cool thing about making genome assemblies instead of simple genome “resequencing” is that it’s not just the DNA bases that change — the entire structures of genomes can change through evolutionary time,” Edelman said. “And using the assemblies, we can detect those changes.”

When they began analyzing the assemblies, the team found evidence that some genes were capable of moving between species, and others were far more resistant to the process. One of the key factors that determine whether a gene could or could not move is a basic biological process called “recombination”.

“In humans and most animals, every individual inherits two copies of their genome, one from her mother, and one from her father,” explained Mallet. “The reason you differ genetically from your sibling is due to recombination. Your father contributed to you a newly scrambled, recombined copy of his own parents’ genomes, as did your mother with her parents’ genomes. So the combination of components from each parent is different in every individual.”

Recombination is thought to be advantageous if the goal is to generate diverse genotypes for future generations. The system of recombination described in this study suggests that it also occurs during gene flow between species. According to the authors, this could provide a possible route for adaptive genes to be passed occasionally between species, as well within species.

“It might seem that useful genes are more likely to be transferred between species,” said co-author Michael Miyagi of Harvard University. “That’s true, but there are also more mundane structural issues with the genome that mean some regions are more likely to have genes go back and forth.”

According to Edelman, whether those genes flow back and forth often depends on how much those different regions recombine.

“In low recombination regions, we tend to see more resistance to gene flow than in high recombination regions,” he said. “What we think happens is that in very high recombination regions, the genes that are resistant or incompatible become dissociated from the genes that can flow across the species boundary.”

The team was able to identify a key gene that acts to switch color patterns as one that moved between species.

“Heliconius butterflies are famous for their color patterns. We found that in one particular region of the genome, there are about 500,000 base pairs that have been inverted relative to the ancestral sequence,” said Miyagi. “And smack in the middle of that inversion is that gene that we know controls color pattern. When you have an inversion like that, it means you’re keeping all the things within it together, so they can’t recombine.”

The new genome assemblies also led to the discovery of a new, larger inversion on a different chromosome.

Using the new analysis method developed by Miyagi, the researchers showed that one of those inverted sequences was transferred among species.

“If we look at any specific chunk of DNA, each one has a specific history,” Miyagi explained. “So the method we developed looks at these bits of DNA and can tell us which ones are more or less likely to be introgressed.”

The study concludes that hybridization is one way for species to derive their genomes, and may be a key process in the creation of the diversity of life we see today.

“In nature, it’s very unlikely that any individual will mate with a member of another species,” Mallet said. “But over evolutionary time, it does happen. It probably only happens in the ‘youngest’ groups of species — species that are rapidly evolving. Most of the diversity of life is probably created in these rapid radiations. They are involved in events such as the origin of mammals. During these radiations, the hybridization and introgression we document here could be an important means of shuffling variation and recombining adaptations from different lineages.”

The study has its roots in the Heliconius Genome Consortium, which set out in 2009 to address questions about evolution and adaptation by sequencing the genome of one Heliconius butterfly species. The new study has made 20 new genome assemblies available. Data from the study have been made freely available in public archives.

“Open data and sharing between laboratories is so important for understanding evolution, and how bursts of diversity happen,” said Mallet. “In this international consortium we’ve each brought very different strengths and helped each other do much better science overall, and the result has been a resource that our collaborators, as well as anyone else, can use well into the future.”

Butterflies, lobsters threatened by climate change


This 18 July 2014 video from England says about itself:

One of Britain’s rarest butterflies, the Silver-studded Blue, is being reintroduced on National Trust land at Black Down, West Sussex, in a bid to help safeguard its future.

The Silver-studded Blue has declined rapidly over the past few decades and can now only be seen in small colonies on heathland in the south of England and on some coastal limestone grasslands and dune systems.

Black Down was identified as a suitable habitat for the Silver-studded Blue following a heathland restoration project which took 12 years to complete. Carried out by National Trust rangers and volunteers, the work restored the land to open heath complete with a canvas of purple heather attracting walkers who can experience uninterrupted views across the South Downs.

From the University of York in England:

Scientists identify British butterflies most threatened by climate change

October 24, 2019

Scientists have discovered why climate change may be contributing to the decline of some British butterflies and moths, such as Silver-studded Blue and High Brown Fritillary butterflies.

Many British butterflies and moths have been responding to warmer temperatures by emerging earlier in the year and for the first time scientists have identified why this is creating winners and losers among species.

The findings will help conservationists identify butterfly and moth species most at risk from climate change, the researchers say.

The study, led by the University of York, found that emerging earlier in the year may be benefitting species which have multiple, rapid breeding cycles per year and are flexible about their habitat (such as the Speckled Wood butterfly), by allowing them more time to bulk up in numbers before winter and expand their range towards the north.

In contrast, early emergence may be causing species that are habitat specialists and have only a single life-cycle per year, to shrink in numbers and disappear from northern parts of the country within their historical range.

Single generation species that are habitat specialists (like the rare High Brown Fritillary butterfly) are most vulnerable to climate change because they cannot benefit from extra breeding time and emerging earlier may throw them out of seasonal synchrony with their restricted diet of food resources, the researchers suggest.

The researchers studied data on butterflies and moths, contributed by citizen scientists to a range of schemes including Butterflies for the New Millennium and the National Moth Recording Scheme (both run by Butterfly Conservation), over a 20 year period (1995-2014) when the average spring temperatures in Britain increased by 0.5 degrees.

Temperature increases are causing butterflies and moths to emerge on average between one and six days earlier per decade over this time period.

Lead author of the study, Dr Callum Macgregor, from the Department of Biology at the University of York, said: “Because butterflies in general are warmth loving, scientists predicted that the range margin of most species would move north as a result of global heating. However this hasn’t happened as widely or as quickly as expected for many species.

“Our study is the first to establish that there is a direct connection between changes in emergence date and impacts on the habitat range of butterflies and moths. This is because emerging earlier has caused some species to decline in abundance, and we know that species tend only to expand their range when they are doing well.”

Professor Jane Hill, from the Department of Biology at the University of York, who leads the NERC Highlight project, said: “Our results indicate that while some more flexible species are able to thrive by emerging earlier in the year, this is not the case for many single generation species that are habitat specialists — these species are vulnerable to climate change.”

Co-author Professor Chris Thomas, from the Leverhulme Centre for Anthropocene Biodiversity at the University of York, added: “These changes remind us how pervasive the impacts of climate change have already been for the world’s biological systems, favouring some species over others. The fingerprint of human-caused climate change is already everywhere we look.”

Professor Tom Brereton of Butterfly Conservation said: “The study shows that we urgently need to conduct ecological research on threatened butterflies such as the High Brown Fritillary, to see if we can manage land in a new way that can help them adapt to the current negative effects of climate change.”

Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year is published in Nature Communications.

This study was carried out in collaboration with researchers at the universities of Bristol, Liverpool, Melbourne (Australia) and Stockholm (Sweden), in addition to researchers at Butterfly Conservation; the Centre for Ecology & Hydrology; Rothamsted Research; and the Natural History Museum. The research was supported by a grant from the Natural Environment Research Council.

This 2015 video from the USA says about itself:

Northern Lobsters of Maine | JONATHAN BIRD’S BLUE WORLD

In the north Atlantic, the American Lobster is the undisputed king of crustaceans. It’s also a tremendously important commercial catch.

Two new studies published by University of Maine scientists are putting a long-standing survey of the American lobster‘s earliest life stages to its most rigorous test yet as an early warning system for trends in New England’s iconic fishery. The studies point to the role of a warming ocean and local differences in oceanography in the rise and fall of lobster populations along the coast from southern New England to Atlantic Canada: here.

Butterfly, plant, moth, bat evolution, new research


This October 2016 video from the USA says about itself:

Find out how butterfly pollination behavior influences plant evolution! Drs. Robin Hopkins & Heather Briggs take us through their research into the effects of pipevine swallowtail behavior on the evolution of flower color in the wildflower Phlox.

From the Florida Museum of Natural History in the USA:

Butterflies and plants evolved in sync, but moth ‘ears’ predated bats

October 21, 2019

Summary: A new study cross-examines classic hypotheses about the coevolution of butterflies with flowering plants and moths with bats, their key predators. The findings show flowering plants did drive much of these insects’ diversity, but in a surprise twist, multiple moth lineages evolved ‘ears’ millions of years before the existence of bats, previously credited with triggering moths’ development of hearing organs.

Butterflies and moths rank among the most diverse groups in the animal kingdom, with nearly 160,000 known species, ranging from the iconic blue morpho to the crop-devouring armyworm.

Scientists have long attributed these insects’ rich variety to their close connections with other organisms. Butterflies, they hypothesized, evolved in tandem with the plants they fed on, and moths developed sophisticated defense mechanisms in response to bats, their main predators.

Now, a new study examines these classic hypotheses by shining a light on the early history of Lepidoptera, the order that includes moths and butterflies. Using the largest-ever data set assembled for the group, an international team of researchers created an evolutionary family tree for Lepidoptera and used fossils to estimate when moths and butterflies evolved key traits.

Their findings show that flowering plants did drive much of these insects’ diversity. In a surprise twist, however, multiple moth lineages evolved “ears” millions of years before the existence of bats, previously credited with triggering moths’ development of hearing organs.

“Having a fossil-dated family tree gives us our most detailed look yet at the evolutionary history of moths and butterflies,” said the study’s lead author Akito Kawahara, University of Florida associate professor and curator at the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity. “We’ve thought for a long time that flowering plants must have contributed to the extraordinary number of moth and butterfly species we see today, but we haven’t been able to test that. This study helps us see if prior hypotheses line up, and what we find is that the plant hypothesis does, but the bat hypothesis does not.”

The research also suggests lepidopterans are much older than previously thought, with the shared ancestor of today’s butterflies and moths likely appearing about 300 million years ago — roughly 100 years earlier than previous estimates.

A seminal 1964 paper by Paul Ehrlich and Peter Raven used the tightly interwoven relationships between butterflies and flowering plants as the foundation for the theory of coevolution — the idea that different organism groups evolve in response to one another.

As plants developed toxins to ward off hungry caterpillars, they reasoned, butterflies evolved ways of tolerating them. Plants, in turn, would ramp up their weaponry, and the cycle of one-upmanship continued.

Similarly, scientists, including Kawahara, have cited bats as the driving force behind moths’ evolution of special defenses, including ultrasonic-sensitive hearing organs, sonar jamming and long, twisted tails that can deflect an attacker in flight.

Cross-examining these hypotheses requires a trip back in deep time — no easy task with a group of insects that is notoriously rare in the fossil record. Further complicating matters, fossils are often tricky to identify accurately as a moth or butterfly, Kawahara said. One originally labeled as Lepidoptera was later revealed to be a leaf.

Kawahara’s team used two analytical approaches to avoid making the same mistake. They examined previous studies of Lepidoptera fossils, tossing out any examples that seemed questionable. They vetted the 16 remaining fossils with other lepidopterists, looking for consensus that they really represented moths and butterflies. They then used these fossils to date their evolutionary tree, built from more than 2,000 genes from 186 existing moth and butterfly species. To double-check those dates, they carried out the same analysis using just three fossils, each displaying all the hallmark characteristics of a particular Lepidoptera group.

Journeying into moth ‘ears’

A major shocker was the fossil-dated tree’s revelation that nocturnal moths evolved hearing organs nine separate times, four of which occurred around 91 million years ago — about 30 million years before bats dominated the night sky.

What could moths have been listening to in a pre-bat world?

Small pterosaurs, Cretaceous birds, maybe?

“We don’t know,” Kawahara said. He and study co-author Jesse Barber, a bat expert and associate professor at Boise State University, hypothesize that “they probably used these hearing organs to detect the sounds made by other predators, like footfall, flight or rustling, and later co-opted them to pick up on bat sonar.”

Many moths and a few butterflies have “ears” on various parts of the body, depending on the family. The majority of hearing organs, however, are near the wings, the optimal location for swiftly cueing an insect to move toward or away from a sound, said study co-author Jayne Yack, a professor of neuroethology at Carleton University in Ottawa, Ontario.

“It makes sense to have your ears close to flight machinery, if your response to sound is to escape by flight,” she said.

While the finding that some of these organs predated bats came as a surprise, Yack cautioned against jumping to the conclusion that there is no connection between bats and moths’ ability to hear. She pointed out that many species with ears appear just prior to the proposed time when bats developed echolocation, “so something around that time period appears to have been an important selection pressure.”

“The vast majority of ears in today’s Lepidoptera are sensitive to ultrasound, and at least some of them have been shown to function in evading bats,” she said. “Some also evolved after bats first used echolocation. But the evidence does require that we reconsider the currently held assumption that all ears in nocturnal Lepidoptera evolved in response to bat echolocation.”

Nectar straw was a game-changer

The earliest moths likely tunneled and fed inside non-vascular plants such as bryophytes as larvae and had chewing mouthparts as adults. The development of the proboscis, a coiled straw-like mouthpart that can suck up nectar, plant sap and other fluids, helped moth diversity rocket off, Kawahara said. More than 99% of today’s moths and butterflies have a proboscis.

The fossil-dated tree puts the origin of the proboscis around 241 million years ago, coinciding with the time when flowering plants were quickly diversifying. The proboscis helped early moths access nectar and may have enabled them to fly farther and colonize new host plants.

Butterflies, a much younger and less diverse group than moths, did not originate until about 100 million years ago and are just day-flying moths, Kawahara said.

“This study underscores previous studies that show butterflies really belong in the much bigger group of moths,” he said. “We tend to appreciate butterflies because they’re often flashy and charismatic, but we shouldn’t forget about moths, which can be just as striking. Moths and plants were interacting some 50 million years before the first dinosaur roamed the Earth, and those interactions helped lead to the diversity we see on our planet today.”