Fig. 4

Alewife morphological evolution affected by a the effect of body size on foraging for small prey and b the effect of clogged gill rakers on foraging for large prey. A low eb value indicated that alewives’ small body size substantially improved the efficiency of their foraging for small prey. A high lp value indicated that alewives’ small gill-raker spacing greatly undermine the efficiency of their foraging for large prey. The intensity of within-trophic competitions was low (eA=0.75). μ _P(A) was the mean frequency of the allele improving alewives’ growth. \(\bar {P(B)}\) was the mean frequency of the allele increasing alewives’ gill-raker number. Trophic interaction were strong (eI=0.25). Alewives’ small gill-raker spacing moderately undermined the efficiency of their foraging for large prey (lp=0.5). Allele frequencies were recorded every 150 years in this figure