Evolution Archives - The Sciku Project

October 8, 2021October 8, 2021

Darwin’s Finches

islands diverging
beaks for seeds and bugs and blood
letters rearranged

Darwin’s finches are a group of 18 species of passerine birds found across the Galápagos Islands (hence their other name of Galápagos finches). The group are a poster child for Darwin’s theory of evolution by means of natural selection. During his voyage on the HMS Beagle he collected specimens from what later turned out to be 12 of the 18 species, although Darwin himself didn’t realise the significance at the time, not realising they were all types of finch (ornithologist John Gould corrected him about the species) and not recording which islands they came from (he was later able to correctly assign them based on the notes of others on the voyage).

As the finches colonised the islands and began to adapt to the varied habitats and food resources available, the different groups diverged from each other, resulting in the separate species we see today. The finches themselves have a huge variety of forms (likely leading to Darwin’s confusion), most notably in their beak shapes and sizes. Their beaks are highly specialised to the food sources available on the different islands, with different species feeding on nuts, seeds, flowers, nectar, leaves, cacti, and invertebrates (including insects, parasites, larvae and spiders).

Perhaps the strangest of all is the Vampire Ground Finch (Geospiza septentrionalis) which feeds on the blood of other birds such as blue-footed boobies and Nazca boobies. It’s theorised that this behaviour evolved from mutualistic behaviours where the finch would clean parasites from the plumage of larger birds. These days their sharp beaks are used to peck their victim’s skin until it starts bleeding and the finches feed on the blood. Their unpleasant behaviours don’t stop there, however, as they steal eggs and roll them into rocks to break the shells, and they’ll also eat guano – excrement from seabirds. Since fresh water is scarce on their home islands (Wolf Island and Darwin Island), they also feed on nectar from Galápagos prickly pear flowers.

Molecular studies of Darwin’s finches suggests that the timing and spatial expression of at least four genes are responsible for the differences in beak structure, alphabetic changes that led to anatomical changes: BMP4 (which encodes Bone morphogenetic protein 4), CaM (which encodes Calmodulin), ALX1 (which encodes ALX homeobox protein 1), and HMGA2 (which regulates the expression of other genes).

A note about the sciku: this sciku has been written using a scale and focussing structure – narrowing in from the vast islands to the beaks to the individual letters of DNA. Have you ever tried writing sciku with a focussing structure? If so, how did you get on? Let us know in the comments below!

Interested instances of evolution in action? Check out this sciku by Prof Matthew J. James on the classic example of evolution, the Peppered Moth: Dark Moths.

December 13, 2019December 18, 2019

Aye-Aye!

The northern monkey.
Never in need of a lift
with its pseudothumb.

The aye-aye is a curious primate found in Madagascar that has possibly the most unusual hands in the animal kingdom. Their hands are so elongated that they account for around 41% of their total length of the forelimb. The aye-aye’s long, bony third finger is its calling card – unique in the animal kingdom, it’s a specialised tool for getting grubs out of deep holes and probing for food whilst foraging.

Yet such specialisation can have costs, including weakening the ability of aye-ayes to grip. Hartstone-Rose & Dickinson et al. (2019) suggest that the aye-aye’s pseudothumb may have evolved to combat this disadvantage. The researchers found the pseudothumb has bony, cartilaginous and muscular features, suggesting that it enhances the aye-aye’s grip of smaller items such as thin branches.

A note about the sciku – Aye-ayes are lemurs and are not monkeys (they’re strepsirrhine primates). The sciku calls them northern monkeys because ‘aye’ is a common term in the north of England and in Scotland meaning ‘yes’, and ‘why-aye’ or ‘wey-aye’ are northern (mainly Geordie) terms for ‘well yes’ or ‘well, yes of course’. The term northern monkey is also a derogatory term in the UK for someone from the north of England (the counter of which is southern fairy).

Original research: https://doi.org/10.1002/ajpa.23936

September 12, 2019September 12, 2019

Tiny predator

Cambrian fossil,
your pincers – a coat of arms.
Ancient arachnid.

The Burgess Shale in the Canadian Rockies has some of the most complete and well preserved fossils found anywhere in the world, allowing researchers to gain huge insights into life millions of years ago during the middle Cambrian period.

Now a new species has been described that illuminates the early development of chelicerate – a group of over 115,000 species that contains spiders, scorpions and horseshoe crabs.

In their paper Aria & Caron (2019) describe the morphology of Mollisonia plenovenatrix, including robust but short chelicerae (pincers) that were located between the animal’s eyes, in front of its mouth. These are the predecessors of the pincers that spiders and scorpions use to kill, hold and cut their prey.

It’s likely that the species hunted close to the sea floor, using long walking legs and other sensory limbs to detect prey. The finding suggests that the origin of the chelicerate must be earlier in the Cambrian period and that the group must have rapidly expanded to fill an underutilised ecological niche.

A note about the sciku: For the sake of the poem I have simplified chelicerate to arachnids. Lead author Cédric Aria has described the pincers (chelicerae) as the ‘coat of arms’ of the chelicerate which felt suitably poetic.

Original research: http://dx.doi.org/10.1038/s41586-019-1525-4

August 29, 2019August 29, 2019

Spreading

Tiger mosquito,
spreading northwards, adapting.
Deadly time capsules.

Many mosquito species struggle to survive at low temperatures, preventing their spread into cooler climates and thus limiting the spread of diseases carried by the mosquitoes. Yet new research by Medley et al (2019) suggests that some mosquito species may be able to adapt part of their reproductive cycle to survive cold winters.

The Asian tiger mosquito is a vector for a number of pathogens, including Zika and dengue viruses. The species first arrived in the USA in Texas in 1985 and today the current range extends as far north New Jersey.

How has this tropical and sub-tropical species managed to survive the temperate conditions?

The secret lies with a process called diapause – a type of animal dormancy where development is delayed in response to unsuitable environmental conditions such as cold winters.

In the Asian tiger mosquito, the length of day or night (photoperiodism) can induce egg diapause – as the days get shorter with the approach of winter eggs become dormant and only start developing again once the days start to lengthen and temperatures are likely to be more suitable for the species.

In the new study the researchers found that northern diapause eggs survive northern winters a lot better than southern diapause eggs, but both northern and southern diapause eggs survive southern winters the same as each other. The research demonstrates the species adapting to colder conditions as it expands northwards over a period of around 30 years. Not only have northern populations adapted to northern climes by producing more eggs but those eggs are adapted to survive the northern winters better too.

Original research: https://doi.org/10.1111/1365-2664.13480

May 10, 2019May 10, 2019

Adaptation by Prof Fred W. Allendorf

Survive, reproduce
Mendel rules, pass on your genes
That’s adaptation
by Prof Fred W. Allendorf

Natural selection is one of the primary mechanisms of evolution. Those individuals with higher survival and greater reproductive success are more successful at passing on their genes to future generations. This brings about adaptation which increases the fitness of individuals in future generations.

Further reading: A brief history of the genetic theory of adaptation by H. Allen Orr (2005): http://dx.doi.org/10.1038/nrg1523

Prof Fred W. Allendorf is Regents Professor of Biology Emeritus at the University of Montana. His primary scientific interest is the application of population genetics to conservation biology. He is senior author of the book Conservation and the Genetics of Populations. Check out Fred’s other sciku on Genetic Drift, Inbreeding Depression and Gene Flow.

March 8, 2019May 10, 2019

Gene flow by Prof Fred W. Allendorf

Move away from home
Find a mate and reproduce
That is called gene flow
by Prof Fred W. Allendorf

Gene flow is the movement of alleles or genes from one population to another (Slatkin, 1987). Gene flow is crucial in reducing the harmful effects of genetic drift and inbreeding depression in populations. As global change, habitat destruction, and fragmentation rapidly progress, many natural populations are becoming smaller, more isolated, and more affected by inbreeding depression. However, Sewall Wright (1951) demonstrated that even very small amounts of gene flow are sufficient to avoid the harmful effects of genetic drift and inbreeding within local populations.

Original research:

Slatkin, M. 1987. Gene flow and the geographic structure of natural populations. Science 236: 787-792.

Wright, S. 1951. The genetical structure of natural populations. Annals of Eugenics 15: 323-354.

Prof Fred W. Allendorf is Regents Professor of Biology Emeritus at the University of Montana. His primary scientific interest is the application of population genetics to conservation biology. He is senior author of the book Conservation and the Genetics of Populations. Check out Fred’s other sciku on Genetic Drift, Inbreeding Depression and Adaptation.

October 31, 2018October 31, 2018

Small and spherical

Small and spherical,

the eggs of forest blue tits.

Urban differences.

Populations of many species live in different environments that provide varied resources and have differing selection pressures. Research by Bańbura et al (2018) investigated the eggs of blue tits living in a forest environment compared to a nearby urban park.

The researchers found that urban-dwelling blue tits produced eggs that were on average 5% larger than their forest-dwelling counterparts, and the urban eggs were less spherical as well. These differences are potentially the result of blue tit diets in each environment – the forest is caterpillar-rich but calcium-poor whilst the urban park is the opposite, with 5-6 times the density of snails which have calcium-rich shells. The smaller, rounder forest egg shape requires less calcium compared to the less spherical urban egg shape.

Original research: http://dx.doi.org/10.1186/s12983-018-0279-4

October 11, 2018October 11, 2018

Absentee parents

Absentee parents.

Selection pressure leads to

self-sufficiency.

Parents invest in the survival of their offspring to differing amounts across the animal kingdom. Some parents provide for their young until they reach independence, whilst in other species the parents are absent from birth onwards.

The burying beetle shows a mix of these tendencies. The parents use small dead mammals and other vertebrates as edible nests for their young. The larvae hatch and enter the carcass, while the parents may help the larvae enter the nest by biting small incisions in the carcass and may even feed them. Yet the larvae can also survive without parental care, using their mandibles to enter the edible nest and feed themselves.

By experimentally manipulating the levels of parental care across 13 generations, Jarrett et al (2018) found that both parental behaviour and offspring anatomy changed. Parents removed before larval hatching began to make the incisions earlier to provide support for the offspring before they hatched. The larvae of such absent parents also evolved larger mandibles to help enter the carcass and feed themselves.

In contrast, when parents were present the larvae had smaller mandibles, as the production of large mandibles is costly and unnecessary when parental support is provided. The research is nice evidence of evolutionary changes to different partners in the parent-offspring dynamic.

Original research: http://dx.doi.org/10.1038/s41467-018-06513-6

April 3, 2018April 12, 2018

Letter from Ternate by Prof Donald M Waller

Thinking to respond

Darwin despaired, paused, then shared.

Pressed to Origin.

Charles Darwin first conceived of his theory of evolution by natural selection in the late 1830s and began work in earnest on his “big book” in the 1840s. Yet it was not until he received a letter from Ternate, Indonesia, from the younger naturalist Alfred Russell Wallace in 1858, threatening to rob him of his originality for the idea, that he was pressed into months of intense activity to publish in 1859 an “abstract” of his longer work that appeared as “On the Origin of Species by Means of Natural Selection . . ”

Darwin was thrown into great anguish by Wallace’s letter and request from Wallace to help get it published. He confided in scientist friends who urged him to prepare a parallel brief summary of his own ideas, extracted from his private essay of 1842. They arranged for both papers to be read before the Royal Society. These did not attract much interest, but “On the Origin” certainly did.

Inbreeding Depression by Prof Fred W. Allendorf

More homozygous

brings inbreeding depression.

Cousins should not mate.

Inbreeding (mating between relatives) results in offspring having reduced fitness. This is known as inbreeding depression and is primarily caused by increased homozygosity at loci with harmful recessive alleles. Small populations, where most or all mates are relatively closely related, are particularly vulnerable to inbreeding and inbreeding depression. The effects of inbreeding depression in small populations can accumulate to reduce the population growth rate and increase the probability of extinction (Keller and Waller 2002).

Despite being of interest since Darwin, inbreeding depression remains a crucial area of research in conservation biology, ecology, and evolutionary biology. As global change, habitat destruction, and fragmentation rapidly progress, many natural populations will become smaller and more isolated and consequently more affected by inbreeding depression.

Original Research: Keller, L. F., and D. M. Waller. 2002. Inbreeding effects in wild populations. Trends in Ecology & Evolution 17:230-241. http://dx.doi.org/10.1016/S0169-5347(02)02489-8

Fred W. Allendorf is Regents Professor of Biology Emeritus at the University of Montana. His primary scientific interest is the application of population genetics to conservation biology. He is senior author of the book Conservation and the Genetics of Populations.

Enjoyed this sciku? Check out Fred’s other sciku: Genetic drift, Gene Flow, and Adaptation.

January 16, 2018May 10, 2019

Genetic drift by Prof Fred W. Allendorf

Unavoidable

Time and chance happen to all

Wright, genetic drift.

Genetic drift is one of the primary mechanisms of evolution. It is the change in allele frequencies in a population between generations due to the sampling of individuals that become parents and the random binomial sampling of alleles during meiosis. The theory of genetic drift was primarily developed by Sewall Wright.

Genetic drift causes the loss of genetic variation, and it is more pronounced in small and isolated populations. The ongoing human-caused loss of habitat has brought about the loss of genetic variation in many species throughout the world via genetic drift.

Original research:

Wright, S. 1931. Evolution in Mendelian populations. Genetics 16:97-159. http://www.genetics.org/cgi/reprint/16/2/97

Enjoyed this sciku? Check out Fred’s other sciku: Inbreeding Depression, Gene Flow, and Adaptation.

January 12, 2018August 14, 2018

Underground sound

Listening for sound

whilst deep underground requires

middle ears to hear.

Animals living in different environments will face different auditory challenges. To investigate how environment shapes evolution Koyabu et al (2017) compared middle ear morphology across terrestrial, aquatic and subterranean species from the order eulipotyphla (including hedgehogs, moles and shrews).

They found that a subterranean lifestyle involved adaptations that allow for improved sound transmission at low frequencies and reduced transmission of bone-conducted vibrations. The adaptations observed included “a relatively shorter anterior process of the malleus, an enlarged incus, an enlarged staples footplate and a reduction of the orbicular apophysis”.

Original research: https://doi.org/10.1098/rsos.170608

November 24, 2017December 11, 2017

Dark moths by Prof Matthew J. James

Industrial soot

Biston betularia

Quo vadis dark moths?

The Peppered Moth (Biston betularia) is a classic example of evolution in action, yet in recent years Darwin’s Finches seem to have eclipsed the Peppered Moth as the textbook example of natural selection.

This sciku, written by Professor Matthew J. James, celebrates the Peppered Moth as an example of rapid natural selection and asks where the dark moths are going, Quo vadis in Latin meaning “Where are you going?”. The question refers to both the population change in moth colouration from dark to light and also implies a nostalgic deeper meaning asking where the Peppered Moth explanation of natural selection has gone in light of the present-day dominance of Darwin’s Finches.

The wild-type Peppered Moth has light wing patterns that act as effective camouflage against its common environmental background. Industrial smog from 19th century coal burning in the United Kingdom resulted in the trees upon which they rested becoming blackened by soot, making the moths stand out. As a result the population of light-winged moths plummeted due to increased predation, however numbers of the melanic mutant form (black in colour) of the species rose – this process has been termed Industrial Melanism. As the Industrial Revolution waned and levels of pollution decreased, numbers of the light-winged form of the moth rose once again. Cook & Saccheri (2013) present an interesting review of the Peppered Moth as a natural selection case study.

Original research: https://dx.doi.org/10.1038%2Fhdy.2012.92

Professor Matthew J. James is Chair in the Department of Geology at Sonoma State University, California. His recent book, Collecting Evolution, examines a scientific collecting expedition to the Galapagos Islands in 1905-06 that resulted in the concept of Darwin’s Finches being developed by David Lack in his 1947 book by that same name.

October 23, 2017October 23, 2017

Arachnid genome

duplicated long-ago.

Arachnid genome.

Sometimes having two of something is a good thing. Genes are occasionally duplicated and whilst duplications are often lost, they may be retained and may help aid the evolutionary diversification of organisms. Normally only a few genes are duplicated but occasionally duplication can occur on a greater scale.

Schwager et al (2017) sequenced the genome of the common house spider and found evidence that whole genome duplication occurred in the house spider’s distant past. In fact, comparison with the genome of bark scorpions suggests that the duplication event took place in the common ancestor of spiders and scorpions more than 450 million years ago.

Original research: https://doi.org/10.1186/s12915-017-0399-x

September 18, 2017September 18, 2017

Alchemist goldfish

change acid to alcohol

through doubled proteins.

Many species of carp (including goldfish) can survive for months over winter in frozen lakes despite a lack of oxygen. Without oxygen they use anaerobic respiration resulting in the production of lactic acid. To avoid a deadly build up of lactic acid the fish convert it into ethanol which diffuses across their gills into the surrounding water.

Researchers have now discovered how the fish do this. During energy production in the absence of oxygen a mutated set of proteins switches the metabolic pathway within mitochondria to produce ethanol instead. The fish have two sets of these proteins, one set which is very similar to that found in other species and one set that appears to be a duplicate of the first. These sets of proteins appear to have arisen during a whole genome duplication event approximately 8 million years ago and have enabled the fish to survive in conditions other species can’t. Fagernes et al, 2017.

September 15, 2017September 15, 2017

The kids help out

Staying at home, the

kids help out. Breeding becomes

cooperative.

In cooperatively breeding species individuals help to raise offspring that are not their own, but how did this costly behaviour evolve? By comparing 3,005 species using phylogenetic analyses Griesser et al (2017) suggest that cooperative breeding in birds occurred in two stages.

First, families formed by the prolonging of parent-offspring associations, with chicks not leaving the nest when nutritionally independent. This appears to have occurred in productive environments where the cost of the offspring remaining at home for longer is less.

Second, the offspring remaining at the home nest then start to help out. In contrast to the formation of family units, the researchers suggest that this happened in more variable environments where the retained helpers can buffer in harsh years.

This theory helps to explain the geographic distribution of cooperatively breeding bird species too – areas where these species are found have often experienced historical declines in productivity. The pre-decline environment may have fostered family formation whilst the decline may have then resulted in the step to cooperative breeding.

September 8, 2017September 8, 2017

Ancestral origami

To fold life’s proteins:

Ancestral origami

around hockey pucks.

The basic way DNA is stored within cells is remarkably conserved suggesting a deep ancestral origin. Mattiroli et al (2017) have revealed that the way DNA is folded in eukaryotes (a domain containing animals, plants, fungi and protists) is very similar to the way its folded in archaea, a domain of single-celled microorganisms containing some of the oldest forms of life.

In both eukaryotes and archaea DNA is wrapped around proteins called histones creating the same DNA geometry. This suggests that eukaryote DNA folding method is ancestral, although a key difference is that in eukaryotes DNA is wrapped around bundles of 8 histones (sometimes referred to as a ‘hockey puck’) whilst in archaea its just wrapped around individual histones.

September 1, 2017September 1, 2017

Just nicker!

Don’t make yourself hoarse

in anticipation of

good times, just nicker!

Vocal communication is an important element of behavioural interactions within many social species. Przewalski’s horses produced more whinnies and squeals in response to negative contexts (agonistic interaction, social separation), but more nickers in positive contexts (anticipation of food or affiliative interactions).

Przewalski’s horses are the closest living relative of domestic horses and a comparison between the species revealed both similarities and intriguing differences in their vocalisations, suggesting that the expression of emotional valence (positive or negative) might be species specific as opposed to conserved across species. Maigrot et al, 2017.

Being able to understand vocal expression of animals could lead to the increased welfare of captive species and a better understanding of animal interactions and group behaviour, which in turn might help to aid population management or conservation in endangered species.

August 21, 2017August 21, 2017

Frozen anoles

must evolve cold tolerance…

and flipping quickly!

Evolutionary changes can occur quicker than you might think. A severe cold snap in the winter of 2013-2014 led green anole lizards to develop an increased cold tolerance as measured by a loss of coordination when flipped over. Further investigation of the populations revealed changes at six genomic regions that are known to be important for regulation of function in the cold. Campbell-Staton et al, 2017.

Interested in rapid lizard evolution? Try this sciku by Roy McGhie: A Heady Mixture.

August 11, 2017January 29, 2021

A heady mixture by Roy McGhie

Sun-basking lizards

plus man-made evolution –

A heady mixture.

Evolution doesn’t always have to take place over long periods of time. Recent research has shown that some lizards on Brazilian man-made islands have developed larger heads than their mainland counterparts in only 15 years. Eloy de Amorim et al, 2017.

Roy McGhie works for the North Yorkshire Moors National Park as a Countryside Manager. He has a strong background in environmental conservation and education, and plays a mean game of tennis. You can connect with him on LinkedIn here. If you enjoyed his sciku, check out his other poems Ghost Ponds, Fluttering By At Dusk and Hedgerow Snuffling.

August 7, 2017August 30, 2017

Orienteering

Oh little spined fish,

your habitat matters for

orienteering.

Animals navigating their environment may use a number of different spatial cues to find their way around, including the geometric structure of the environment or global landmarks. But some species are found in multiple habitat types where different cues might be more effective for navigation.

Three-spined sticklebacks live in rivers and ponds, environments which differ in terms of structure and rate of environmental change. When tested in an aquatic maze, sticklebacks collected from rivers used geometric and global cues to learn the maze, whereas sticklebacks collected from ponds only used geometric cues to navigate the maze. Within this one species of fish there appear to be multiple methods of navigation depending on the habitat in which the fish are found. Brydges et al, 2008.

July 12, 2017August 30, 2017

Plenty of fish

Plenty of fish yet

male voles choose monogamy

… but do their partners?

Monogamy is relatively rare in the animal kingdom, with extra-pairs matings happening a lot more than you might think. Males in particular are thought to gain the most from polygamy by being able to sire multiple offspring, whilst females may gain from monogamy through defence or paternal care of their young.

Yet despite having access to multiple females, male prairie voles choose to form exclusive pair bonds with individual females (Blocker & Ophir, 2016). In contrast, female prairie voles readily engage in promiscuous mating (Wolff et al, 2002).

So why (under laboratory settings) are male prairie voles monogamous whilst females are promiscuous?

Blocker & Ophir, 2016 argue that one explanation could be that the costs to males of trying to hang on to multiple females at once are too great, and that male prairie voles gain the most by aggressively monopolising just one female. Females on the other hand have nothing to lose from polygamy so will mate with other males if the opportunity presents itself.

In prairie voles it seems that monogamous behaviour may be male-driven.