( ( ( ( The rationale ) ( for ( character displacement ) ) ) ( stems ( from ( ( ( ( ( the ( competitive ( exclusion principle ) ) ) , ) ( also ( called ( ( Gause 's ) Law ) ) ) ) , ) ( which ( contends ( that ( to ( coexist ( in ( a ( stable environment ) ) ) ) ) ) ) ) ) ) ) ) ( ( two ( competing species ) ) ( ( must ( differ ( in ( their ( respective ( ecological niche ) ) ) ) ) ) ; ) ) )
(ROOT (S (SBAR (S (NP (NP (DT The) (NN rationale)) (PP (IN for) (NP (NN character) (NN displacement)))) (VP (VBZ stems) (PP (IN from) (NP (NP (DT the) (JJ competitive) (NN exclusion) (NN principle)) (, ,) (VP (ADVP (RB also)) (VBN called) (NP (NP (NNP Gause) (POS 's)) (NN Law))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ contends) (SBAR (IN that) (S (VP (TO to) (VP (VB coexist) (PP (IN in) (NP (DT a) (JJ stable) (NN environment))))))))))))))) (NP (CD two) (JJ competing) (NNS species)) (VP (MD must) (VP (VB differ) (PP (IN in) (NP (PRP$ their) (JJ respective) (JJ ecological) (NN niche))))) (: ;)))
The rationale for character displacement stems from the competitive exclusion principle, also called Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche;
(ROOT (S (NP (NNP Character) (NNP displacement)) (VP (VBZ is) (NP (NP (DT the) (NN concept)) (PP (IN by) (SBAR (WHNP (WHNP (WDT which) (CD two) (NNS species)) (PP (IN within) (NP (DT the) (JJ same) (NN area)))) (S (VP (TO to) (VP (VB coexist) (PP (IN by) (S (VP (VBG adapting) (PP (IN by) (S (VP (VBG developing) (NP (JJ different) (NNS specializations))))))))))))))) (. .)))