PHP MVC Multiple databases, multiple data mappers?

I am working on my HMVC project.

Right now I am using data mappers in order to move data between the models (domain objects) and a MySQL database. Each mapper receives a MySQL adapter as dependency. The injected adapter receives a PDO instance (a database connection) as dependency and runs sql queries on the database.

I also use a dependency injection container (Auryn).

I'd like to be able to simultaneously retrieve data from storages of different types (MySQL database, PostgreSQL database, XML feeds, etc).

Let's say, I want to retrieve User data from a PostgreSQL database (by using PDO data-access abstraction), to change it, and to save it into a MySQL database (by using mysqli data-access abstraction) on another server.

My question is:

Should I create a different mapper for each storage type (like

UserMapperPgsql(PgsqlAdapter $adapter) 
UserMapperMySql(MySqlAdapter $adapter)

), or should I create only one mapper with more adapters (one for each data type) as dependencies (like

UserMapper(PgsqlAdapter $adapter1, MySqlAdapter $adapter2, ...)

)?

Thank you all for your suggestions!