( ( When ( ( ( ( ( two or ) more ) populations ) ( of ( different species ) ) ) ( live ( in ( the ( same area ) ) ) ) ) ) ( , ( they ( ( form ( a community ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (QP (CD two) (CC or) (JJR more)) (NNS populations)) (PP (IN of) (NP (JJ different) (NNS species)))) (VP (VBP live) (PP (IN in) (NP (DT the) (JJ same) (NN area)))))) (, ,) (NP (PRP they)) (VP (VBP form) (NP (DT a) (NN community))) (. .)))
When two or more populations of different species live in the same area, they form a community.
(ROOT (S (NP (NP (DT All) (NNS members)) (PP (IN of) (NP (DT a) (NN species) (NN living)))) (ADVP (RB together)) (VP (VB form) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN population))) (. .)))