When do new arrivals become natives?

[James M]

One thing I've been wondering about, is when we get new species arriving in the UK, seemingly under their own steam with no human intervention, when do we class them as natives to Britain? Take the Collared Dove for example, it had a massive expansion to it's range last century, we class it as part of our native fauna now don't we?

The question occured to me when reading about butterflies such as the Queen of Spain Fritillary. There have been a fair number of sightings in the past few years and even evidence that a breeding population may be gaining a foothold in the south east. However there is some doubt as to whether they are natural vagrants, even though there are nearby populations across the channel. We don't really know and probably never will, so (and this I suppose is a slightly different question) at what point do we decide when it is likely a natural expansiona and part of our native fauna?

Sorry if some of that doesn't make sense, it's been a long day

[Ferret]

I think it is generally accepted that a species that has arrived under its own steam is native as soon as it has a self supporting population that no longer relies on vagrants to support its population. So Collard Dove was added, I suspect, to the BTO’s official list as soon as this could be proved.

To be ‘official’ it needs to be on someone’s list i.e. DEFRA or a local council, this probably wont happen until someone decides it either needs protecting or exterminating, probably both. Although it will probably be added to semi-official lists before that i.e. RSPB, BTO, British Dragonfly Society, Butterfly Conservation, etc.

At the end of the day if its here its here, and if its not going to be a pest or a threat to other species nobody if likely to put to much effort into where it came from, especially if it looks like it could be a natural expansion of its range. Some species that we consider as British species i.e. Painted Lady, Red Admiral and Hummingbird Hawkmoth probably still rely on migrants and do not have self sustaining populations.

Awkward little buggers aren’t they; just refuse to fit into our neat little lists

Ferret

[david156]

There is also a differance between a wild species expanding its range into britain and an escaped species naturalising in britain. Collard Dove was a species that expanded so was already on the british list before it became very common, whilst other species escaped and then formed breeding colonies ie Ruddy Duck, and once these were self sustaining they were then added to the list. Also do native species have to be breeding species. I would class pink footed goose as native as they are very common up here in norfolk in the winter, and are swifts native as they only spend about four months here a year when they breed.
I think part of it is down to personal intepretation, its all very confusing!!!!

[James M]

Thanks guys, yes it certainly is confusing! But I think I understand things a bit better now, thanks to your posts.

It'll be interesting to see what species turn up in the future.

[thebeard]

Originally Posted by Ferret

I think it is generally accepted that a species that has arrived under its own steam is native as soon as it has a self supporting population that no longer relies on vagrants to support its population.

i'd completely agree with that, if its own range extends here then i'd say it can be seen as naturally being here, if its introduced then its certianly not native. i think 'native' is however a difficult one, IMO i'd say that they'd have been here from the start, ie evolved here maybe? but then you could argue that those that migrated here after the channel seperated us from the continent were immigrants, and thus could be classified under my first comment.
ARGH
yes, confusing once you actually think about it

[david156]

Would you class these species as native, Fallow Deer, Grey Squirrel and Common Pheasent. They are very common but they are all introduced species. Yet because they are so common and they have become so successfull breeders they are now part of the british countryside. In a vote i would think a large number of people would class them as native.

[James M]

Originally Posted by david156

Would you class these species as native, Fallow Deer, Grey Squirrel and Common Pheasent. They are very common but they are all introduced species. Yet because they are so common and they have become so successfull breeders they are now part of the british countryside. In a vote i would think a large number of people would class them as native.

Personally I wouldn't, as they haven't made it to Britain under their own steam, then again someone might disagree.

[david156]

Originally Posted by James M

Personally I wouldn't, as they haven't made it to Britain under their own steam, then again someone might disagree.

How about the Brown Rat. Was ship assisted here around the 18th century period so technically didn't get here under their own steam!
Its all down to personal interpretations I suppose.
Just to confuse matters a little further. Take a species like the white tailed sea eagle. It became extinct in this country through persicusion and has now been reintroduced. So was this a native species that is no longer a native species!

[tom00_uk]

Originally Posted by david156

Would you class these species as native, Fallow Deer, Grey Squirrel and Common Pheasent. They are very common but they are all introduced species. Yet because they are so common and they have become so successfull breeders they are now part of the british countryside. In a vote i would think a large number of people would class them as native.

i would say they have gone under naturalization

[Fritillary]

I agree with Tom. A exotic species does not become native but naturalised and in the worst of cases, invasive. Generally it is in function of transport by human activities.

Native implies that plants and plants have been evolving by generations (millions of years) and interacting with the environment. It is said that before of neolithic period when species were able to transport by themselves without human intervention (1).
After that species that arrived by human intervention, and began to form part of natural ecosystem without negative impacts are considered naturalised and if they produce damage to ecosystems, they are considered invasives.

1)Assessment and management of plant invasions By James O. Luken, John W. Thieret pag 9 Assessment and management of plant ... - Google Books