Most of "our" information regarding species' distribution is derived from published data and Museum collection data. Although primary data are preferred, whether you can use secondary data to achieve useful distribution modeling depends upon the quality and quantity of data available. Turtle "fanciers", magazines

such as Elaphe often contain good data -- but can be difficult to access. Your PhD supervisors have the last vote on whether they will accept these data, however.

Good luck with your project, whatever it turns out to be.

While it is not needed for a PhD, primary data is often better appreciated by both your committee and supervisor. If possible, you should collect primary data.

You can use any data you like as long as you have approval. It's good to get in writing from your head of department that it will be sufficient, and definitely obtain copyright so that only you can publish from it, otherwise do not use it. But obtaining your own confidential primary data is best