( ( ( 6 ( -RRB- ( Two members ) ) ) ( of ( the ( same species ) ) ) ) ( ( ( can not ) ( produce ( fertile offspring ) ) ) . ) )
(ROOT (S (NP (NP (CD 6) (JJ -RRB-) (CD Two) (NNS members)) (PP (IN of) (NP (DT the) (JJ same) (NN species)))) (VP (MD can) (RB not) (VP (VB produce) (NP (ADJP (JJ fertile)) (NN offspring)))) (. .)))
6) Two members of the same species cannot produce fertile offspring.
(ROOT (S (SBAR (IN If) (S (NP (CD two) (NNS populations)) (VP (VBP do) (RB not) (VP (VB mate) (CC and) (VB produce) (NP (ADJP (JJ fertile)) (NN offspring)))))) (, ,) (NP (JJ separate) (NNS species)) (VP (VBP result)) (. .)))