( ( ( Species interactions ) ( in communities ) ) ( ( are ( ( important factors ) ( in ( natural selection ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Species) (NNP interactions)) (PP (IN in) (NP (NNS communities)))) (VP (VBP are) (NP (NP (JJ important) (NNS factors)) (PP (IN in) (NP (JJ natural) (NN selection))))) (. .)))
Species interactions in communities are important factors in  natural selection.
(ROOT (S (NP (NNP Community) (NNS interactions)) (VP (VBP are) (NP (NP (JJ important) (NNS factors)) (PP (IN in) (NP (JJ natural) (NN selection))))) (. .)))