Northward Expansion: Butterflies Benefit from Climate Change?

[Karl]

ScienceDaily (Jun. 6, 2008) —

Global warming is generally thought to have a negative effect on the habitats of many animals and plants. Not for the Brown Argus butterfly, however, which is expanding its numbers quicker and more effectively, according to new research. The Brown Argus butterfly Aricia agestis has expanded northwards in Britain during the last 30 years. It is thought that the recent expansion of the species is due to the increasing summer temperatures caused by global warming.

Research carried out by scientists in the UK and Spain reveals that by moving into new areas, the Brown Argus may be escaping from some of its “natural enemies” (parasitoids). This is not because natural enemies are absent from the new areas, but that the parasitoids are not able to locate the Brown Argus. Instead, the parasitoids rely on the common blue butterfly Polyommatus icarus in these northern habitats. This species has a long-established range throughout Britain and suffers a larger amount of parasitism than the Brown Argus in these northern habitats. Although the researchers cannot yet say for certain why the Brown Argus has fewer parasites in its new range, they suggest it could be due to the differences between the plants that the caterpillars eat. The common blue and brown argus feed on different plants and therefore the parasitoids are used to looking for caterpillars on the common blue's favourite plants.

Dr Rosa Menendez said: "Climate change can have unpredicted consequences by altering the interaction between species and their enemies, whilst in this case the butterfly may be a welcome addition in other cases the release from enemies might favour pests or other unwanted species".

Source: Brown Argus Butterfly Sees Positive Effects Of Climate Change

[Karl]

Predicting ecosystem response to climate change

By Liz Kalaugher, environmentalresearchweb.org

While many plant and animal species have responded to climate change by altering their behaviour and distribution, it's not clear what the mechanism behind these changes is. The main candidates are reactions by individuals, a micro-evolutionary change in the population brought about by natural selection, or a combination of the two. With this in mind, researchers have found that individual great tits (Parus major) in the UK are adjusting their behaviour to changes in temperature.

"[Our results] demonstrate clearly how important phenotypic plasticity – call it flexibility if you like – can be for responding to a rapidly changing environment," Ben Sheldon of the University of Oxford told environmentalresearchweb. "In some cases, species or populations can track quite rapid changes in their environment without any difficulty." Sheldon stressed, however, that that doesn't mean that all populations will track rapid changes, or even that this population would if there were even more dramatic warming. "But it does at least suggest that studying the ability of individuals to adjust their behaviour in different environments might be a useful way to categorise populations as to the likelihood that they will be able to adjust easily," he said.

Sheldon and colleagues at the University of Oxford and University of Edinburgh, UK, and CNRS, France, looked at data from a population of great tits (Parus major) in Wytham Wood near Oxford over the past 47 years. The mean egg-laying date of the birds has advanced by about 14 days, with the change appearing to begin in the mid-1970s. The peak availability of winter moth larvae – a key food source for the birds – has also advanced by around 14 days.

"We have been aware for some time that the population has been breeding earlier and earlier, and that the change was related to the ongoing changes in the climate," said Sheldon. "We realised that because we had observations of individuals in multiple years we could work out the mechanism that was causing the population to change, and because we'd also been collecting data on the timing of the birds' main food source – caterpillars – over that time that we could ask whether the birds' change had been appropriate given how other parts of the system were responding." In this work, individual females showed similar responses to changes in spring temperatures. That's in contrast to a Dutch study in which individual great tits changed their laying date by different amounts for a given spring temperature change. This Dutch population did not track its environment closely and its fitness has declined, whereas the UK population is thriving. Now the team will investigate the differences between UK and Dutch birds, try to understand whether their UK great tit populations are invariant with respect to other forms of plasticity, and look at the importance of large-scale (regional) and small-scale (individual tree) differences in timing for the birds' behaviour.

Source: Predicting ecosystem response to climate change - environmentalresearchweb

[Karl]

UK: Ancient Tree Helps Birds Survive

BBC News – August 17, 2008

An ancient species of tree is helping Britain's birds survive the effects of climate change, scientists have found. Frequent early spring weather means blue tits and great tits have been laying eggs ahead of schedule, making it difficult for them to find food. However ecologists say birds have been feeding on gall wasps, which make their homes in Turkey oak trees, rather than the usual young caterpillars. The discovery was made during a study by the University of Edinburgh.

It had been feared that the Turkey oak, reintroduced to Britain three centuries ago after an absence of thousands of years, may pose a threat to native plants and animals. The species was native to northern Europe before the previous ice age, about 120,000 years ago. But now it appears to be providing the country's birds with a food source.

Dr Graham Stone of the university said: "The reintroduction of Turkey oak and the re-invasion of gall wasps into northern Europe may simply represent restoration of a previous natural situation. "As the Turkey oak re-asserts itself in its ancient home, it is helping to alleviate some of the effects of the very modern problem of climate change."

Source: BBC NEWS | UK | Scotland | Ancient tree helps birds survive