British butterflies are getting bigger

[PhilM]

I thought UKB members might be interested in a couple of links I came across while doing some research today. Scientists in the UK have used computer vision techniques to analyse tens of thousands of butterfly specimens kept by the Natural History Museum in London. They have found that some British butterfly species are becoming larger in response to climate change.

Here is a link to an article on the subject published by The NHM:
https://www.nhm.ac.uk/discover/news/202 ... igger.html

And a link to the corresponding scientific research paper published by The British Ecological Society, for people who like a more science based approach:
https://besjournals.onlinelibrary.wiley ... 210X.13844

Cheers,
Phil.

[Pete Eeles]

Or perhaps museum specimens get smaller over time ... I didn't see this possibility mentioned!

Cheers,

- Pete

[PhilM]

An interesting observation Pete. What I have gleaned from the research article is that the authors correlated historic weather data with the dimensions of individuals within the exhibits. They found that specimens collected during warmer years over a wide timespan were larger than those collected during cooler years, with a more pronounced increase during recent decades. This may be expected as larvae were likely to be more nourished during warmer times and developed into stronger, bigger adults?

So if historic pinned collections in museums are getting smaller over time, which may happen I guess, there still seems to be a growth in the species tested over time when weather temperature during larval periods are aligned with the size of the resulting adults. The authors are arguing that the specimens tested are becoming larger directly because of climate change.

A very interesting subject. I wonder how we as laypersons can find out if pinned specimens in museums do in fact shrink over time or not?

Cheers,
Phil.

[Padfield]

I'm interested to know where the data for recent decades comes from. In days of old, every schoolboy and vicar amassed vast collections of common butterflies, so you would expect historic data to reflect historic populations. More recently, collecting except in pursuit of a well-defined scientific goal has been considered taboo (rightly, in my opinion). Obviously, reared specimens must be excluded from a survey like this, as they benefit from artificial conditions, so we must assume all the butterflies are wild-caught. Is it still the case that properly random, representative samples of wild, British butterflies exist in collections? Or, if people are collecting more selectively, might that very selection influence the results?

Guy

[PhilM]

Hi Guy,

There are some references as to which decades the exhibits were collected in the article that might answer some questions. To quote from the text -

"The British butterfly specimens housed at the Natural History Museum (London) were among the first very large scientific collections to be mass digitised. A total of 184,533 specimens, comprising 94 species of butterflies collected from 1803 to 2006 have been digitised during the iCollections project" ..... A total of 17,726 specimens and 24 species are in the final analysis, collected between 1830 and 2000, with most collections from ~1900 to 1950" ..... While the use of natural history collections can give us valuable clues to how temperature affects size, and computer vision can greatly accelerate data collection and analysis, there will always be a need to conduct field, laboratory and long-term monitoring studies to better understand the complexities of how insects will respond to climate change".

I read that as meaning this particular research project only included species that were previously collected from the wild up to the year 2000. There is no doubt though that scientific collecting from the wild is still a common occurrence - I'll let others decide if it is a good a bad thing and keep out of that particular debate, it's well documented but a bit too thorny for me

Cheers,
Phil.

[jonhd]

Purely anecdotally, I'd claim the exact opposite!

Jon