Probably, but it depends on the species. When mixing, you need to have much more precise questions and information. Animals should share climate, but occupy different microhabitats or have different diets. None should be generalists large enough to swallow cohabitants, although certain small aposematic species may be safe. If you have a diurnal terrestrial species, consider arboreal, fossorial, aquatic, or nocturnal terrestrial species. That way they use different parts of the environment, or use them at different times.
Keep in mind that in captivity we generally provide environments that are far too small. A terrestrial species in the wild may perch several feet up in bushes, which would put it higher than we even offer to a captive arboreal species. Larger cages are better in this respect.
Again, while diets may differ appreciably in the wild, the choices in captivity may not. Where diet is concerned, I would say that the old line of "they'll compete for food" is nonsense: Animals of the SAME species will compete far more than animals of different species, so just feed them enough, and offer at different times of day if need be.
Also keep in mind that animals which occur within a mile of each other in the wild may live in radically different climates. The frog from the mountain ridge may be cool and damp ALL the time, and may even experience snow, while the one a short distance downstream is living in hot and seasonal forest with a distinct dry season.
Last, there's the question of interbreeding, although this tends to go hand in hand with other concerns. Species are most likely to interbreed if they are closely related and are normally physically isolated from one another in the wild. Being isolated means they never have to decide whether a mate is suitable, so put them together and the physical barrier is gone.
On the other hand, in poison frogs, geographic isolation also tends to go with changes in reproductive methods, changes in size, and changes in climate and habitat. I wouldn't mix any Dendrobates, although D.leucomelas and D.tinctorius may occur together in the wild. You could probably mix some Dendrobates with some Oophaga, Ranitomeya, Andinobates, Ameerega, Allobates, or others. Personally, I would prefer to mix them only if they naturally occur together. For instance, Oophaga pumilio, Andinobates claudiae, and Dendrobates auratus probably occur together.
By comparison, Mantella expectata, Mantella betsileo, Mantella viridis, and Mantella ebenaui all occur in hot and fairly arid lowlands most of the time. Mantella aurantiaca, M.crocea, M.milotympanum, M.madagascariensis, M.baroni, and M.cowani normally occur in fairly cool and damp highlands - sometimes places where temperatures approach freezing at night. Despite being the same genus, they may not have similar habitats.
You'll have to evaluate your caging and the species you're considering. Personally, I never make recommendations out of the blue. It makes more sense to research what you're interested in, and then decide if it's appropriate; than it is to pick the "perfect" animal at random from 10000 species, and discover it's expensive, unkeepable, protected, or just not available.