( ( Invasive species ) ( ( ( represent ( a ( serious threat ) ) ) ( to ( natural areas ) ) ) . ) )
(ROOT (S (NP (JJ Invasive) (NNS species)) (VP (VBP represent) (NP (DT a) (JJ serious) (NN threat)) (PP (TO to) (NP (JJ natural) (NNS areas)))) (. .)))
Invasive species represent a serious threat to natural areas.
(ROOT (S (NP (NNP Overharvesting)) (VP (VBZ is) (NP (DT a) (JJ serious) (NN threat)) (ADVP (RB particularly)) (PP (TO to) (NP (JJ aquatic) (NNS species)))) (. .)))