not every observation is properly licensed, but those that are will end up in GBIF. if those observations also have certain observation fields that indicate interactions, they will also get exported to GloBI. over at GloBI you can get all that data either through their web interface or by downloading their dataset. that’s probably the easiest way to search for interactions between taxa.
it’s harder to parse out all the unique values from the observation fields from a given set of observations. it’s doable, but to automate the process, you’d probably have to use the API in some way.