In an agile team who is responsible for tracking the tasks

All team members

Explanation:

In respect of the question, the or those responsible for tracking the tasks in an agile team comprises of all the team members.

Agile in relation to task or project management, can be refer to an act of of division of project or breaking down of project or tasks into smaller unit. In my opinion, these is carried out so that all team members can be duly involved in the tasks or project.