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

Date:February 3, 2020

Source:University of Bristol

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.

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A decade after the predators have gone, Galapagos Island finches are still being spooked

Date: November 20, 2019

Source: University of Cambridge

On some of the Galapagos Islands where human-introduced predators of Darwin's finches were eradicated over a decade ago, the finches are still acting as though they are in danger, according to research published today in the Journal of Animal Ecology.

The study found that the finches' fearful responses -- known as antipredator behaviour -- were sustained through multiple generations after the threat was gone, which could have detrimental consequences for their survival.

The work by Dr Kiyoko Gotanda, a zoologist at the University of Cambridge, is one of the first studies to look at behavioural adaptations in a species following the eradication of invasive predators. The research focused on one species of Darwin's iconic finches -- the small ground finch, Geospiza fuliginosa. Given their estimated life span, today's finches are not likely to be the same birds that had originally developed the response to defend themselves from predators.

"These surprising results suggest that whatever influences this fearful behaviour is more complicated than just the presence or absence of invasive predators," said Gotanda, sole author of the paper.

The Galapagos Islands provide a natural stage to compare different predator situations. Some islands have never had invasive predators, others currently have predators like domestic cats and rats that arrived with humans, while others have had these predators in the past and they have now been eradicated.

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Genetic diversity couldn't save Darwin's finches

AUGUST 21, 2019

by Michael Miller, University of Cincinnati

A study by the University of Cincinnati found that Charles Darwin's famous finches defy what has long been considered a key to evolutionary success: genetic diversity.

The research on finches of the Galapagos Islands could change the way conservation biologists think about a species' potential for extinction in naturally fragmented populations.

UC graduate Heather Farrington and UC biologists Kenneth Petren and Lucinda Lawson found that genetic diversity was not a good predictor of whether populations of finches would survive. The study was published in Conservation Genetics.

A UC lab analysis of century-old museum specimens found that six of eight extinct populations had more genetic diversity than similar museum specimens from which descendants survive today. In most other species, low genetic diversity is a signal of a population in decline.

Researchers examined 212 tissue samples from museum specimens and living birds. Some of the museum specimens in the study were collected by Darwin himself in 1835. Only one of the extinct populations, a species called the vegetarian finch, had lower genetic diversity compared to modern survivors.

Lawson said the findings are explained by the fact that these birds can migrate in between populations.

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Human activity can influence the gut microbiota of Darwin's finches in the Galapagos

Date:  April 25, 2019

Source:  University of Connecticut

In the Galapagos Islands, Darwin's finches drawn to junk food are experiencing changes in their gut microbiota and their body mass as compared to finches that don't encounter human food, according to a new University of Connecticut study.

The study of Darwin's Finches, published today in Molecular Ecology, builds upon a study on the effects of human activity on finch diet in the same location, says Sarah Knutie, assistant professor of ecology and evolutionary biology at UConn.

Researchers studied fecal samples and body mass data from female finches, who are the main caretakers for nestlings, or baby birds. They collected the fecal samples from birds in urban areas, where they would encounter human food, and in rural areas, where they were less likely to encounter human food, and used those to characterize the birds' gut microbiota.

Previous studies have shown that finch populations living near humans recognized human food as food, whereas the finches living in areas with less human activity don't recognize human food as something they can eat.

In total, researchers studied close to 100 finches, focusing on breeding female small ground finches (Geospiza fuliginosa) and medium ground finches (Geospiza fortis) in March 2016 on the eastern coast of Santa Cruz Island, Galapagos Islands, Ecuador.

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Darwin's finches have developed a taste for junk food, and it may be impacting their evolution

December 5, 2018 by Umass Boston Office Of Communications, University of Massachusetts Boston

A UMass Boston professor and his colleagues have published new research showing that feeding on human junk food may be altering the course of evolution in Darwin's finches.

Assistant Professor of Evolutionary Biology Luis De León says feeding on human foods is weakening natural selection on ground finch beaks, which is what drives the formation of new species in the wild. These findings, published in the journal Evolutionary Applications, suggest that the seemingly harmless activity of feeding birds might be altering the course of evolution in the iconic Darwin's finches in the Galápagos islands.

"If we continue to feed finches, we're not only affecting the individual species, but the processes that lead to the formation of new species," De León said. "We're getting in the way of evolution."

Galápagos finches are famed for being the inspiration behind Charles Darwin's pioneering work on evolution. They are an example of adaptive radiation, an evolutionary process that produces new species from a single, rapidly diversifying lineage. Their common ancestor arrived on the Galápagos about two million years ago, and since then Darwin's finches have evolved into more than a dozen recognized species differing in body size, beak shape, and feeding behavior.

De León and fellow researchers from UMass Amherst, Universidad San Francisco de Quito, McGill University, and Norwegian University of Science and Technology were on Santa Cruz Island when they found two forms of medium ground finches—a small and large version—while studying beak size at an isolated, pristine site.

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Epigenetics may explain how Darwin's finches respond to rapid environmental change

Date: August 24, 2017

Source: University of Utah

Summary:

Epigenetics may explain how Darwin’s finches respond to rapid environmental changes, outlines a new report.

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Lab-reared maggots may save Darwin's famous finches

Date: August 4, 2016

Source: Entomological Society of America

Raising maggots may not sound glamorous, but that doesn't mean it's not important. In the latest issue of the Journal of Insect Science, Paola Lahuatte, a junior researcher at the Charles Darwin Foundation, and her colleagues reveal how they used chicken blood to rear the larvae of the parasitic fly Philornis downsi in the lab. This protocol may be the first to effectively rear an avian blood-feeding fly from egg to adult in the absence of its host. More importantly, it may prove to be a crucial tool in the fight to save endemic birds in the Galapagos islands, including the critically endangered mangrove finch.

Adult Philornis downsi feed on fruit, but as larvae they parasitize baby birds, usually small songbirds. The female fly lays its eggs in bird nests. Once hatched, first-instar larvae crawl into the nostrils of the nestling birds, where they feed on both blood and tissue. Larger, second-instar larvae leave the confined space of the nostrils and hide out in nest material during the day. They emerge at night to continue feeding on the chicks.

Philornis downsi infestation takes a serious toll on nestlings. In some cases, all of the young in an infested nest are killed by the parasites.

Philornis downsi is not native to the Galapagos Islands. The species was likely introduced accidentally in the 1960s via imported fruit and has since wreaked havoc on the islands' endemic bird populations. Parasitism is the leading cause of nestling mortality for at least one species of Darwin's finch, and some believe it is the main cause of decline of landbirds in the Galapagos Islands.

One method that has been proposed to control Philornis downsi is the "sterile insect technique" or SIT. This method produces large numbers of artificially sterilized insects (usually males) that are released into the wild population. Females that mate with sterile males produce no offspring, thus reducing the size of the next generation. SIT has been used to successfully eradicate populations of screwworm flies and has been useful in the control of certain species of fruit fly.

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Beaks of Darwin’s finches evolve thanks to newly discovered gene

APRIL 23, 2016 BY MELISSA TAYLOR

Named after the father of evolution himself, Darwin’s finches played a pivotal role in helping Charles Darwin formulate and solidify his theory of evolution. An already fascinating species of enormous importance, the discovery of a rare gene just made these beautiful birds a good deal more interesting than they already are.

Scientists were able to discover a gene that plays a role in the shaping of the birds’ beaks. This gene, which is known as HMGA2, continues to work in evolving the beaks of Darwin’s finches. And while Darwin didn’t observe much change to his eponymous finches, biologists Peter and Rosemary Grant were able to, having worked over four decades in the birds’ habitat of the Galapagos Islands.

The story behind the discovery began about a decade ago, when the husband-and-wife biologists observed a drought on Daphne Major Island, which hosted two species of Darwin’s finch – the medium ground finch and the large ground finch. The smaller of the two bird species (the medium finches) didn’t attempt to compete with their larger equivalents due to the food shortage that came with this event. Still, the medium ground finch was able to outlive the large ground finch, with the average beak size for the former bird decreasing quitter markedly. And that’s where the HMGA2 gene came in.

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Darwin's finches have reached their limits on the Galapagos Islands

Date: June 23, 2015

Source: University of Groningen

Summary: The evolution of birds on the Galapagos Islands, the cradle of Darwin's theory of evolution, is a two-speed process. Most bird species are still diversifying, while the famous Darwin's finches have already reached an equilibrium, in which new species can only appear when an existing one becomes extinct. This finding expands the classical theory on island evolution put forward in the 1960s. The study is published online on June 23 in Ecology Letters.

Islands are seen as natural laboratories for the study of evolution. They form isolated ecosystems with barriers to migration. Classical Island Theory predicts that a dynamic equilibrium will occur between immigration and extinction of species. Recent theory adds that as species diversity increases, ever more ecological niches become occupied, which has a negative effect on immigration (new immigrants from outside of the Galápagos cannot settle) and diversification (radiation into new species is blocked).

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