It depends on your setup. Typically one thermostat controls one heating element. If they are using the same element then you can only hook it up to one thermostat anyway. There are some that will controll 2 I doesn't however, but they get pricey.
Re: Do you need 2 thermostats for 2 different species?
their conditions are actually identical, both have 80-82 cool side, 90-94 hot, and 50-60% humidity with 70 for shedding, so for those two particular species, i'd say yes, it should be fine. if you use heat tape you can wire them together, but for uth's that might get a bit tricky