Introductions question (1 Viewer)

[delia todd]

This is something I've been pondering on for a while.... would species that have been introduced into another country ever change their habits / develop a different bill shape / change their song (or whatever) over time to more suit the surroundings that they find themselves living in?

And if they did, would they then become a 'named' subspecies in their own right? Or even species, I suppose.

 

[KC Foggin]

Very good thinking D and an equally good question.

 

[delia todd]

Thanks KC. I was hoping someone would be able to understand my ramblings LOL

 

[Mysticete]

This is something I've been pondering on for a while.... would species that have been introduced into another country ever change their habits / develop a different bill shape / change their song (or whatever) over time to more suit the surroundings that they find themselves living in?

And if they did, would they then become a 'named' subspecies in their own right? Or even species, I suppose.

Yes, introduced species will, provide time and evolutionary pressure, change and potentially adapt to new environments. IIRC, you can see this already with southwestern House Sparrows, which IIRC are paler and smaller (?) than birds out east, a common occurrence in desert dwelling animals. You can also see this in domesticated species often evolving back into a animal that resembles more closely the wild type.

However, this mostly happens on the geological time scale. These sort of slight changes are usually considered to trivial and clinal to be worth recognizing as new taxonomic units. You CAN get speciation happening a lot quicker, even in a generation or two. I know such things happen via interspecies hybridization in plants and also within insects which specialize on a certain food plant but switch to a different type. But I don't believe this has occurred with any introduced bird species. The closest I can think of are some examples of "host-switching" in nest parasite birds, which have been associated with changes in vocalizations and host preference. Something like that can happen almost instaneously, but I don't think any of these sort of events have resulted in scientists knowingly recognizing a new species.

 

[delia todd]

I knew if someone understood my question I'd get an interesting answer.

Thanks so much for that Mysticete - fascinating, isn't it.

 

[KC Foggin]

Very fascinating!

 

[Paul Clapham]

Indeed, for examples look at the land birds of Hawaii and the Galapagos. They all arrived from the mainland -- not introduced by people but under their own steam, but that doesn't matter -- and in geological time they did turn into different species from their mainland relatives. It was Darwin who noticed that and it was part of his reasoning, I believe, when describing his theory of evolution.

 

[delia todd]

Yes, thanks Paul. It was partly thinking about the Galapagos birds that made me wonder about this.

Although I didn't know that they'd originated from the mainland, I thought it was just how they were developing on the different islands. And I didn't know that about the Hawaiian birds either.

 

[Julie50]

Hi Delia,

In natural populations it is called speciation - the link here has an excellent explanation:

Speciation | National Geographic Society

Speciation is how a new kind of plant or animal species is created. Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics.

education.nationalgeographic.org

I don’t see why it would be any different for an introduced species

 

[delia todd]

Oh thanks Julie. That's interesting... I'd heard the terms before, but struggled to understand them really (still not sure if I'll be able to keep them sorted in my head though LOL).

But it is clearly explained on that site.

I wasn't too sure if the taxonomy "purists" would ever agree to this with introduced birds.

 

[davercox]

I wasn't too sure if the taxonomy "purists" would ever agree to this with introduced birds.

Stepping in gingerly here (I'm not a scientist) - I don't see why there should be any difference between wild bird population expansions and introductions. Of course, there will be discussions about the status (for listers) of any such new species, but that shouldn't affect the recognition of their existence, surely ?

 

[delia todd]

Stepping in gingerly here (I'm not a scientist) - I don't see why there should be any difference between wild bird population expansions and introductions. Of course, there will be discussions about the status (for listers) of any such new species, but that shouldn't affect the recognition of their existence, surely ?

Nor do I Dave. But I wasn't really sure how it works.

 

[Mono]

Arguably the evolutionary pressure on introduced species is greater than on native species. The natives have evolved together, each carving a niche.

A spanner in the works to that theory is us humans. We mess about with things, either by design or by accident, and can force evolutionary pressures that weren't previously there.

There is also question about behavioural differences, prey type differences and song differences. Is this genetic evolution that will stick or is this learnt behaviour that could be easily lost.

 

[jurek]

I read that House Sparrows introduced to North America ca 200 years ago already became slightly paler in desert areas and darker in humid areas. I would be curious is somebody who studies house sparrows in the US can comment more.

 

[delia todd]

Yes, very true Mono.

 

[Welsh Peregrine]

There was a recent comment somewhere that DNA analysis showed very little difference between any of the Redpoll forms including Arctic Redpoll; the introduced New Zealand population has the greatest chance of diverging from the rest.

 

[Kirk Roth]

A major group of birds with named subspecies due to human-caused dispersal would be domestic subspecies - Coluba livia, Serinus canaria, Gallus gallus, Meleagris gallopavo, Anser anser, Anser cygnoides, and Anas platyrhynchos all have domesticus or domestica subspecies. Many of these have feral/introduced populations somewhere or another which have retained their derived characteristics.

A subspecies of House Sparrow in the western United States has been named Passer domesticus plecticus although that is not widely accepted. As others have noted, significant variation from the source population has been noted in this species in North America, but also in South Africa and New Zealand.

Keep in mind that a "subspecies" is just a philosophy, and it is unevenly applied across taxonomy. You may find better examples among mammals, where historically there seems to have been less reservation about population origins among the taxonomists. House mice have numerous subspecies derived from stocks introduced via ship movement from their "native" south Asia. Notable is Mus musculus helgolandicus from an island off of Germany. Dingoes are a subspecies derived from an introduced population. There is evidence that the three southern subspecies of Island Fox (Urocyon littoralis) were introduced by people. There are probably many other examples - rodents and ungulates may be good candidates.

 

[bonxie birder]

Speaking of house sparrows. You don’t see tree sparrows in the Uk in our cities’ streets, but in Hong Kong they are the street sparrows. A little off topic I know but different habits for different populations.

 

[Mysticete]

Speaking of house sparrows. You don’t see tree sparrows in the Uk in our cities’ streets, but in Hong Kong they are the street sparrows. A little off topic I know but different habits for different populations.

Same with Tokyo...Eurasian Tree Sparrows are one of the most common urban birds.

 

[James Lowther]

This seems linked to the distribution of house sparrows. In areas where they are absent tree sparrows occupy the urban niche but where both species occur tree sparrows are found predominantly in the countryside.
James