( Reproduction ( usually ( ( occurs sexually ) . ) ) )
(ROOT (S (NP (NNP Reproduction)) (ADVP (RB usually)) (VP (VBZ occurs) (ADVP (RB sexually))) (. .)))
Reproduction usually occurs sexually.
(ROOT (S (NP (JJ Sexual) (NN reproduction)) (ADVP (RB usually)) (VP (VBP occur) (PP (IN during) (NP (NP (NNS times)) (PP (IN of) (NP (JJ environmental) (NN stress)))))) (. .)))