Co-extinction refers to extinction due to the obligatory association of plants or animals.
This phenomenon of co-extinction can be defined as the loss or decline of related species.
When a species becomes extinct, then plants and animals that were dependent on it also become extinct in due time.
Examples:
When a fish species extinct then all the parasites associated with it in an obligatory manner also become extinct.
The mutualistic relationship of the plant-pollinator is also an example, where the extinction of one will ultimately cause the extinction of the other.
Co-extinction is also a cause of biodiversity loss.