Apopulation of animals is split in half by a river. before speciation is completed the two halves are rejoined when a drought causes the river to run dry. how would this impact the two populations? o a the two halves would be reproductively isolated. o b speciation would still occur, because the two halves would be too different genetically to interbreed. o g individuals could now freely mate, and gene flow would increase. o r. traits that had developed through mutation would still exist only in one of the halves