Last updated: June 2, 2012 12:04 am

Butterflies spread their wings

A study of the brown argus butterfly shows that species do not respond to climate change in isolation
Brown argus butterfly©Jim Asher

Over the past 20 years, the brown argus butterfly has travelled northwards due to changes in its diet

Many species are altering their ranges in response to climate change, but the patterns of expansion and contraction vary enormously as a result of complex interactions with other species, particularly the ones they eat.

Ecologists are just beginning to investigate these interactions. One of the first studies looks at the brown argus butterfly, which has sped northwards across England at an exceptional rate.

Over the past 20 years its range has doubled in area, with the leading edge 80km further north than it was in 1990. The research team, based at York University, found that a change in diet made this rapid expansion possible. The study is published in the journal Science.

Historically the brown argus was a rare butterfly with a declining population living mainly on south-facing slopes of chalk downland in southern England, where the caterpillars ate rockrose plants. Its reversal of fortune came when the species switched to an alternative food – wild geranium plants, particularly cranesbill, which are much more widespread.

Geranium is the most common food for brown argus caterpillars in continental Europe but the species was not in a position to switch from rockrose to geranium in England until temperatures began to rise in the 1990s.

The reason, says lead author Rachel Pateman, is that the brown argus, which is on the northern edge of its range in England, needs summer heat to complete its lifecycle. It could always find that warmth on south-facing downs, where the rockrose grows, but the geranium-rich habitats were not warm enough for the brown argus to thrive there in colder summers – until recently.

One concern about species living in localised pockets is whether they can move to the next niche over what may be a long stretch of inhospitable territory. The problem disappeared for the brown argus when it switched food; geranium is far more widespread than rockrose so the butterfly can spread without the need for long-distance dispersal.

“This study has highlighted that species do not respond to climate change in isolation, and that climate change affects how species interact with one another,” says Pateman. “In the case of the brown argus butterfly, changes in interactions with its food plants have helped it to respond to climate change very rapidly. However, changes to interactions may hinder other species, potentially putting them at risk of extinction.”

“There will be winners and losers from climate change,” adds co-author Jane Hill. “It is important that we begin to understand how the complex interactions between species affect their ability to adapt to climate change so we can identify those that might be at risk and where to focus conservation efforts.”

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‘Fish forensics’ may expose illegal catches

When we buy a fish pie, how can we be sure it really is made from, say, Swedish Eastern Baltic cod as it says on the packet and not from North Sea cod, asks Paul Miles.

Since last year, any fish and fish product sold in the EU must be labelled with its origin. With many stocks over-fished, the temptation to declare cod is from Eastern Baltic fisheries (certified “sustainable” by the Marine Stewardship Council) rather than the depleted North Sea, is obvious.

Scared, me?

tarantula

Psychologists at Northwestern University, Chicago, have cured 12 adults of a debilitating spider phobia in a therapy session of two to three hours. Six months later, participants could hold a tarantula.

According to the UN Food and Agriculture Organization, illegal, unregulated and unreported fishing constitutes a fifth of the global catch. But soon DNA analysis will enable authorities to pinpoint where fish have been caught, even if they have already been filleted, cooked and frozen. The new technique of “fish forensics” – developed by the Technical University of Denmark (DTU) as part of a European project led by Bangor University – can detect differences between populations separated by only a few hundred miles.

It is more sensitive than DNA “bar-coding”, which identifies fish species and their broad geographical origin. The researchers have identified genetic variations between fish populations in individual chemical letters of the DNA sequence. Looking for these “single nucleotide polymorphism” (SNP) markers is a simple laboratory process and details are reported in the journal Nature Communications.

“By comparing the sequence of DNA of a fish with the database of SNP markers, laboratories can determine whether, say, a cod was spawned in the North Sea or Eastern Baltic,” says Einar Nielsen, professor of fisheries genetics at DTU.

The method has been developed for herring, cod, sole and hake, and Nielsen and his team are identifying markers for sea bass, turbot and sea bream.

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Fossil ink sac

Black attack: a squid’s getaway success tip

Squid swimming in Jurassic-era seas more than 160 million years ago escaped from predators in the same way as their modern descendants – by squirting out a cloud of black ink.

An international team analysed two fossilised ink sacs about 6cm long, found by Philip Wilby of the British Geological Survey: one at Christian Malford in Wiltshire (162 million years old) and the other from Lyme Regis, Dorset (195 million years old).

They had been separated from their parent organisms but were unmistakable ink sacs, says Wilby. Both were extremely well preserved and came from rocks that had undergone little geological change since their formation. They contained black pigment, melanin, that is chemically indistinguishable from squid ink today. The results are published in Proceedings of the National Academy of Sciences.

“I would argue that the pigmentation in this class of animals has not evolved in 160 million years,” says John Simon, chemistry professor at the University of Virginia. “The whole machinery apparently has been locked in time and passed down through succeeding generations of cuttlefish. It’s a very optimised system for this animal.”

The multidisciplinary analysis was successful only because melanin is resistant to degradation over aeons of geological time. “Out of all of the organic pigments in living systems, melanin has the highest odds of being found in the fossil record,” says Simon.

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More cholesterol can be good news ...

For many years the dominant theme of pharmaceutical research into heart disease has been to find better ways to cut levels of low-density lipoprotein (LDL) in the blood while raising high-density lipoprotein (HDL).

LDL, sometimes dubbed “bad cholesterol”, lays down the fatty deposits that clog up arteries and cause heart attacks. Statins, drugs that have made a fortune for the pharmaceutical industry, reduce LDL quite well in most people.

The complementary action of building up beneficial HDL – “good cholesterol” that removes fat from the lining of blood vessels – turns out to be much more difficult. HDL-boosting drugs, seen as potential bestsellers, have been failing in clinical trials.

So cardiologists are looking with interest at a new approach to raising HDL. A small Canadian biotech company, Resverlogix, is developing a drug called RVX-208 that boosts the body’s production of the protein ApoA-1. Its mechanism of action involves the complex “epigenetic” system that controls gene activity.

The idea is that increasing the amount of ApoA-1, the active protein within HDL, will remove fat effectively from arteries. It is a different approach to the one taken by the big drug companies, which attempts to raise total HDL levels.

Steven Nissen, head of cardiovascular medicine at the Cleveland Clinic, is leading a clinical trial of RVX-208. He is cautiously optimistic but warns: “We are still at an early stage and it is too soon to predict success.”

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