Poison dart frog evolution, new research


This 2008 video is called A strawberry poison dart frog mother checks up on her tadpole brood.

From the Smithsonian Tropical Research Institute in Panama:

Imprinting on mothers may drive new species formation in poison dart frogs

What do marrying one’s parents, Oedipus complex have to do with evolution?

October 3, 2019

Summary: By rearing frogs with parents — or foster parents — of different colors, biologists discovered that behavior in response to color may be more important than genetics in the evolution of new species.

The old saying that people marry their parents may be true for poison dart frogs, and it may even lead to the formation of new species, according to a new study in Nature based on work at the Smithsonian Tropical Research Institute (STRI).

Strawberry poison dart frogs live on the mainland in Panama’s Bocas del Toro province and have been isolated on islands in the archipelago that formed during the past 10 million years as sea level rose. Only a single color morph exists on some islands — orange or green, for example, but on other islands several color morphs exist together, like blue and red frogs.

“In the past, people assumed that this group of brightly colored poison dart frogs were warning predators that their skin is toxic,” said Corinne Richards-Zawacki, research associate at STRI and professor of biological sciences at the University of Pittsburgh. “But predators don’t seem to care what color the frogs are, at least based on our earlier experiments. That’s why we started asking whether the way they choose mates might lead to populations of different colors on different islands.”

The team set up three different situations: baby frogs raised with two parents of the same color (red baby, red parents), baby frogs raised with each parent a different color (red baby, one red and one blue parent) and baby frogs raised by foster parents of a different color (red baby, blue parents). In each case they asked which color the female offspring would choose as mates and which color the male offspring would perceive as a rival.

“We discovered that female frogs with parents of the same color tended to choose mates of that same color, whereas frogs with foster parents of a different color would choose mates the color of the foster parents,” said Yusan Yang, who is completing her doctoral thesis at the University of Pitts-burgh. “The same was true for male-male aggression. This tells us that imprinting was more important than genetics when it comes to shaping these behaviors that are based on color.”

When baby frogs were raised with one parent of the same color and one parent of a different color, females chose mates the color of their mother, and males chose rivals the color of their mother, indicating that maternal imprinting was probably more important than paternal imprinting.

They also created a mathematical model showing that male aggression based on imprinting, in concert with female mate choice based on imprinting was enough to cause a scenario to evolve, where like mates with like, which could lead to two color morphs becoming separate species.

“We’re fascinated by the idea that behavior can play such an important role in evolution,” Richards-Zawacki said.

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Poison frog colours, new research


This 2013 video from French Guiana is called Dendrobates tinctorius in its natural habitat.

From the University of Jyväskylä – Jyväskylän yliopisto in Finland:

Toxic frogs with weak defenses persist in the gene pool alongside stronger competitors

A multi-national team of evolutionary biologists shows that diversity exists even when expecting otherwise

September 2, 2019

Diversity is a hallmark of life and it shows up in unexpected places. A multi-national team of evolutionary biologists investigated how two types of poison frog co-exist when we expect only one. Their innovative study uncovers conditions where diversity flourishes against the odds, and offers new perspectives on chemical defense. The project was a collaboration between the University of Jyvaskylä, the University of Mississippi, Centre national de la recherche scientifique (CNRS) and John Carroll University. The findings were published in the Proceedings of the National Academy of Sciences (PNAS) on September 2nd 2019.

Many creatures carry warning colors that signal toxicity, such as wasps with yellow bands. The Dyeing Poison Frog (Dendrobates tinctorius) of French Guiana also has yellow stripes to keep predators away, but some have white stripes instead. This is an anomaly of evolution because predators learn to avoid warning colors through bad experience, and rare warning colors are harder to learn.

The team headed by Doctors Bibiana Rojas from University of Jyvaskyla and J.P Lawrence from the University of California Irvine propose evolutionary explanations for how nature allows rare warnings to persist.

Firstly, rare or weak signals can persist under the protection of stronger signals. The researchers show that predators learn to avoid more distasteful yellow frogs and generalize this avoidance to white frogs. Although the stronger defenses of yellow frogs should allow them to out-compete the whites over time, genomic analysis revealed that the population of white frogs is genetically separate from the yellows. Thus, diversity can exist within a single population (due to generalized learning) and between different populations (due to genetic isolation).

New methods to measure chemical defence were developed

The initial experiments were modest in scope, but strange results inspired the researchers to develop new methods.

“We faced the difficulty of not having an established method to quantify predator reaction to the chemical defenses. However, that difficulty turned into one of the biggest assets of our study, as we eventually succeeded at developing a method,” says Doctor Bibiana Rojas from University of Jyvaskyla.

The new method improves the ecological relevance and precision of measuring predator-prey interactions. Past studies have assumed that toxicity is everything, and measure it by injecting mice with defensive chemicals. But prey survival and evolution depends on whether they are eaten or spat out, not the blood chemistry of their predators. Thus, the researchers used skin extracts mixed with oats to get a separate measure of distastefulness. They show that toxicity and distastefulness are better considered independently.

“The biggest surprise came from the fact that the frogs [with] higher amount of toxins in their skin are not necessarily the ones that birds find most distasteful. This finding challenges previous assumptions that most toxic equals most unpalatable,” says Rojas.

Goliath frogs build their own ponds


This 2015 video says about itself:

Over the millennia, amphibians both large and small have dominated the Earth. Today, there are over 5000 different species of frogs inhabiting all corners of the globe—from tropical jungles and dark swamps to desert wastelands and frozen tundra. A select few evolved some extreme and bizarre adaptations to survive. An extraordinary family that comes in many weird forms, shapes and sizes.

From bone claws and glass skin to antifreeze and deadly poisons, we’ll show you the jumpers, the climbers, the killers and high flyers. And hidden deep in the jungles of Central Africa, the Goliath frog still lives today. It is one of the largest and rarest frogs to ever walk the Earth. This is Monster Frog.

From ScienceDaily:

World’s largest frogs build their own ponds for their young

Laborious pond-building could explain gigantism in Goliath frogs

The first example of “nest”-building in an African amphibian, the Goliath frog, has been described in a new article in the Journal of Natural History, and could explain why they have grown to be giant.

Researchers observed adult Goliath frogs in the wild and found that they move rocks weighing up to 2kg while building ponds for their young, which they then guard. Goliath frogs themselves weigh up to 3.3kg and their bodies reach over 34cm, without including their legs.

“Goliath frogs are not only huge, but our discovery shows they seem to be attentive parents as well,” says author Marvin Schäfer from the Berlin Natural History Museum. “The little ponds they make at the edges of fast-flowing rivers provide their eggs and tadpoles with a safe haven from sometimes torrential waters, as well as from the many predators living there. We think that the heavy work they put into excavation and moving rocks may explain why gigantism evolved in these frogs in the first place.”

Despite their renown, they’re found only in Cameroon and Equatorial Guinea and little is known about their biology, particularly their reproductive behaviour. Numbers of the endangered species have declined by more than 50 per cent in just 10 years, due to overhunting and deforestation; and researchers first learned about the unusual level of parental care they provide from local frog hunters, who trap adults for bush meat.

To investigate the behaviour, two researchers waded along opposite edges of the Mpoula River looking for breeding sites. At first, they could only distinguish them by finding eggs or tadpoles. However, they learned to spot material excavated and piled up in a way that defied the effects of the water current. They identified 22 potential breeding sites, 14 of which contained nearly 3,000 eggs each, spread across the entire area. At the nest which showed the most recent signs of activity, they recorded a time-lapse video using a camera trap.

The scientists found that Goliath frogs create three different types of pond. For some, they simply clear naturally-occurring rock-pools of leaf-litter and debris. The effect is still strikingly different to surrounding puddles, which have thick layers of leaves, debris and gravel. For the second type, frogs dig out leaf litter and gravel from shallow pools and push it to the edges, forming a dam. Dams are most obvious in the third type, for which frogs clear depressions of shallow water of any large stones, moving them to edge and creating circular pond. This was the most reliable type, as eggs were least likely to spill out or become over-flooded after heavy rain.

Infrared time-lapse revealed an adult spending all night guarding a nest from predators, only ending the vigil just before dawn. The scientists were unable to determine which sex was responsible for building ponds or which for guarding them, although one hunter who described the behaviours in detail suggested that males do the construction while females are the guards. They didn’t directly observe the cleaning or digging, but over five days followed progress of a nest, from the first digging attempts to the depositing of eggs.

Dr Mark-Oliver Rödel, project leader and president of Frogs & Friends, says: “The fact that we’ve only just discovered these behaviours shows how little we know about even some of the most spectacular creatures on our planet. We hope that our findings, combined with further ongoing research, will improve our understanding of the needs of the Goliath frog so we can help support its continued survival.”

The study was funded by Amphibian Funds in cooperation with the Association of Zoological Gardens, with additional supplies from Frogs & Friends and the Vienna Zoo.

Central American leaf frogs, new discovery


This 5 August 2019 video from England says about itself:

He Spent His Career Studying a Frog. Then He Discovered Its True Identity. | Short Film Showcase

Andrew Gray, Curator of Herpetology at Manchester Museum spent his career studying the Splendid leaf frog. However, when a supposed new species arrived from Central America, he made a shocking discovery. Using the original specimen of the Splendid leaf frog—first collected in 1902—as a comparison, Gray noticed several unique distinctions between the latest arrivals and those he had been studying. These were, in fact, the Splendid leaf frog and the frogs Gray had been studying were the new species.

Eleven new frog species discovered in Ecuador


This 23 March 2017 video says about itself:

Researchers described a new endangered frog species: Pristimantis ecuadorensis (Ecuadorian rainfrog or Cutín de Ecuador). The species lives on the western slopes of the Ecuadorian Andes, provinces of Cotopaxi and Pichincha, at elevations between 1450–1480 m, and it is related to the Neotropical rainfrog, Pristimantis ornatissimus.

And now, more relatives of that species have been discovered.

From ScienceDaily:

Eleven new species of rain frogs discovered in the tropical Andes

August 2, 2019

Summary: Eleven new frog species were recently discovered in the tropical Andes. This is the largest number of frog species described in a single article from the western hemisphere in over a decade.

Eleven new to science species of rain frogs are described by two scientists from the Museum of Zoology of the Pontifical Catholic University of Ecuador in the open-access journal ZooKeys. Discovered in the Ecuadorian Andes, the species are characterized in detail on the basis of genetic, morphological, bioacoustic, and ecological features.

On the one hand, the publication is remarkable because of the large number of new species of frogs. Regarding vertebrate animals, most studies only list between one and five new to science species, because of the difficulty of their collection and the copious amount of work involved in the description of each. To put it into perspective, the last time a single article dealt with a similar number of newly discovered frogs from the western hemisphere was in 2007, when Spanish scientist Ignacio de la Riva described twelve species from Bolivia.

On the other hand, the new paper by Nadia Paez and Dr Santiago Ron is astounding due to the fact that it comes as part of the undergraduate thesis of Nadia Paez, a former Biology student at the Pontifical Catholic University, where she was supervised by Professor Santiago Ron. Normally, such a publication would be the result of the efforts of a large team of senior scientists. Currently, Nadia Paez is a PhD student in the Department of Zoology at the University of British Columbia in Canada.

Unfortunately, amongst the findings of concern is that most of the newly described frog species are listed as either Data Deficient or Threatened with extinction, according to the criteria of the International Union for Conservation of Nature (IUCN). All of the studied amphibians appear to have very restricted geographic ranges, spanning less than 2,500 km2. To make matters worse, their habitats are being destroyed by human activities, especially cattle raising, agriculture, and mining.

Amongst the newly described species, there is the peculiar Multicolored Rain Frog, where the name refers to its outstanding color variation. Individuals vary from bright yellow to dark brown. Initially, the studied specimens were assumed to belong to at least two separate species. However, genetic data demonstrated that they represented a single, even if highly variable, species.

The rest of the previously unknown frogs were either named after scientists, who have made significant contributions in their fields, or given the names of the places they were discovered, in order to highlight places of conservation priority.

New frog species discoveries in Ecuador


This 7 March 2017 video says about itself:

In the Pui Pui Protected Forest, Peruvian Andes, researchers discovered a new species of terrestrial-breeding frog. The species was named Pristimantis attenboroughi, Attenborough’s Rubber Frog, in honour of Sir David Attenborough.

Now, two yeas later, more relatives of that frog species.

From the University of Central Florida in the USA:

New frog species discovered

July 18, 2019

Summary: An international team of researchers have identified and described two new frog species.

UCF student Veronica Urgiles has helped describe two new frog species discovered in Ecuador, and she named one of them after one of her professors.

Urgiles and an international team of researchers just published their findings in the journal ZooKeys.

“Frogs are by far my favorite”, said Urgiles, who is pursuing a master’s degree in biology. “So, getting to describe and name two of them is terrific. I have been looking at these frogs for years now, so going over the whole process of observing them in their habitats and then analyzing them and comparing them under the microscope, to finally naming them is a long, but very satisfying journey.”

Urgiles, a 2017 Fulbright scholar and the lead author, said she chose to attend UCF for its integration of genetics and genomics in biodiversity research and the emphasis on real-world application. She works with Assistant Professor Anna Savage who specializes in species diversity based on molecular analyses.

“One of the things that I found most interesting about these guys is that they don’t have metamorphosis like a regular frog, but instead they develop entirely inside eggs that adult females deposit in the ground,” Urgiles said. “They really don’t need water bodies for their development. Both of the new frog species inhabit high elevation ecosystems in the mountain range over 8,000 feet, so even though we are right there in the equator, it’s very cold and windy most of the year.”

The team of researchers has been studying frogs in Ecuador the past few years. In 2017, Urgiles found the first new species and named it Pristimantis quintanai, after one of her biology professors — Pedro Quintana-Ascencio. She and Savage found the second species — Pristimantis cajanuma — in 2018. Both were found in the Paramo and montane forest of the southern Ecuadorean Andes.

The frogs are tiny, measuring .8 inch. Pristimantis quintanai females are brown and black and Pristimantis cajanuma are green and black, both easily blending into the foliage. They have a distinct call that is sharp and continuous, sounding like tik-tik-tik-tik.

Urgiles examined DNA samples collected by the international team back in Savage’s lab at UCF, generated genetic sequences, and constructed the phylogenetic analysis. Other team members also worked the morphological diagnosis and comparisons with other frogs and an acoustic analysis of the frogs’ calls.

“In these analyses, we use all of the genetic similarities and differences we find to build phylogenetic trees, and when we find that a ‘branch’ on the ‘tree’ has strong support and contains all of the individuals that share the same morphological characteristics, then we have good evidence to describe it as a new species,” says Savage, whose expertise includes describing species diversity based on molecular analyses. “We used this method, along with vocalization and location data, to conclude that the two species we describe are distinct from any other species that have ever been characterized.”

The work is critical because of the vast diversity that has yet to be discovered in the tropical Andes of South America, Urgiles says. In 2018, 13 new species of frogs were documented in the tropical Andes of Ecuador and so far in 2019 five new frogs have been documented.

There are potentially thousands of new plants and animals in the area that may hold the key to other discoveries. It’s important to know what is there, to better understand the threats to habitat loss and disease so conservation methods can be established to protect the resources.

Saving frogs from deadly virus


This 2010 video from England says about itself:

Looking at a couple of common frogs I found in my garden.

From the University of Exeter in England:

Skin bacteria could save frogs from virus

June 21, 2019

Bacteria living on the skin of frogs could save them from a deadly virus, new research suggests.

Ranavirus kills large numbers of European common frogs — the species most often seen in UK ponds — and is one of many threats facing amphibians worldwide.

Scientists from the University of Exeter and ZSL’s Institute of Zoology compared the bacteria living on frogs — known as their “microbiome” — from groups with varying histories of ranavirus.

They found that populations with a history of outbreaks had a “distinct” skin microbiome when compared to those where no outbreaks had occurred.

“Whether a population of frogs becomes diseased might depend on the species of bacteria living on their skin”, said Dr Lewis Campbell.

“Ranavirus is widespread, but its presence in the environment doesn’t necessarily mean frogs become diseased — there appears to be some other factor that determines this.

“The skin is often the first infection point in ranavirus, and the first stage of the disease can be skin sores.

“It’s possible that the structure of a frog’s microbiome — the mix of bacteria on its skin — can inhibit the growth and spread of the virus so it can’t reach a level that causes disease.

“While the results of our study demonstrate a clear link between the frog skin microbiome and disease, further research will be needed to understand the exact mechanisms which cause this relationship to form.”

Laboratory trials will help establish whether a history of ranavirus infection causes the microbiome differences, or whether these are pre-existing differences that predispose some populations to infection.

The scientists tested the skin bacteria of more than 200 wild adult European common frogs (Rana temporaria) from ten populations.

They found that the microbiome of individual frogs is usually most similar to that of others in the same population (those living in the same geographical area), but that populations with the same disease history were more similar to each other than to populations of the opposite disease history.

Even though amphibians can partially “curate” their microbiome by producing proteins that benefit specific bacteria, they are limited to those bacteria which are available in their environment.

Ranavirus can wipe out entire common frog populations and, though the new findings need further investigation, the researchers hope their work could help the species.

Dr Xavier Harrison said: “There’s growing evidence that skin bacteria may protect amphibians from lethal pathogens such as chytrid fungus, and that we can develop cocktails of probiotic bacteria to prevent vulnerable individuals from contracting a disease.

“Our work suggests that given enough effort and research, similar probiotic therapies may be effective against ranavirus.”