According to the biological species concept, distinct species are defined by reproductive isolation--that is, by a lack of interbreeding and a failure to produce viable or fertile offspring if they do mate. In some cases, reproductive isolation may not be complete, and there may be rare instances of interbreeding. As long as hybridization is rare, biologists generally classify species as distinct under the biological species concept. Given what you've learned about the biological species concept, should G. fortis and G. scandens continue to be considered separate species?