Can an exotic species be also endemic?

Question

While talking about the evolution and conservation of dingoes in Australia, someone asked an interesting question:

Can I define the dingo as an endemic species?

That question, despite apparently simple, deals with some terminological conflicts and I must confess that I was not able to say yes or no at the moment.

The context:

As everybody knows, the dingoes (Canis lupus, but for some people Canis dingo¹) were introduced in Australia by human beings, between 4,000 and 12,000 YBP. That being said, it's acceptable to define the dingo as an invasive, exotic species. Using Campbell's² definition:

Invasive species: a species, often introduced by humans, that takes hold outside its native range.

However, some researchers argue that the dingoes, being isolated in Australia for a relatively long time, have a unique genetic profile. As this is controversial, let's suppose, just for the sake of the argument, that they do have a unique, distinctive genetic profile (and that they became a distinct species).

That being the case, the dingoes may be defined as endemic. Quoting Campbell again:

Endemic: referring to a species that is confined to a specific, relatively small geographic area.

I have taught biology for many years and I must confess that, for me, endemic and exotic were always opposite, mutually exclusive terms. However, in this case (and many others), it makes sense to say that the dingoes are exotic and endemic.

Maybe one can say that, from the moment the population became a distinct species on, it stopped to be exotic and started to be endemic, which would keep the two terms mutually exclusive.

My question

So, my question is: can a given species (or population) be defined as exotic and endemic simultaneously?

PS: I'm not asking for opinions, which would make this question off topic for SE Biology. I'm asking for rules and guidelines in the use of the terms, preferably with references.

Answer 1

I think this partially depends on the timeframe. Endemism is usually divided into paleoendemism and neoendemism (see e.g. Kier er al in PNAS for use of both terms). Here, neoendemism is referring to the result of recent adaptive radiations that have led to new endemic species. This is then in contrast to paleoendemism, which refers to previously widespread species that are now confined to isolated areas.

Neoendemism is clearly related to your question, but whether dingos should be labelled as neoendemic depends on if it can be seen as a unique subspecies. If it is, it might be more suitable to view it as neoendemic and not exotic (nothing prohibits neoendemic species to be ecologically "problematic" to the previous fauna though).

In the literature (from what I've seen), neoendemism is usually used to describe historical events though (the result from adaptive radiations etc), so timeframe is obviously important (see e.g. Mishler er al, 2014). Even so, all taxa that has led to neoendemic species (through adaptations to local conditions) was by definition exotic at one point in time (e.g. when the most recent common ancestor of the Galapagos finches colonized the Galapagos islands). The same goes for the relatively recent adaptive radiation of Drosophila on Hawaii.

To me, neoendemic and invasive are not mutually exclusive terms, while the division between neoendemic and exotic may depend on time since colonization and whether the population now forms an independent taxon (e.g. subspecies) instead of a subpopulation still connected to its host population. I cannot find a reference or definition to support this interpretation right now though.