3.4 Gene family expansion and contraction
This approach revealed 1,191 contracted gene families in the S.
peregrina , and only 568 gene families had a greater degree of expansion(Fig. 3, Additional file 1: Table S22) . The
corresponding genes were identified from these gene families, including
367 contracted genes and 2,805 expanded genes, which were utilized for
enrichment analyses of KEGG and GO, respectively. They mainly encoded
synthesis of hydrolases, amino acid metabolism, fatty acid synthase
activity, olfactory receptor activity, fibroblast growth factor receptor
activity as well as chorionic membrane formation, etc. (Additional file
2: Tables S24 and S25). Besides, a total of 692 positively selected
genes were identified and then analyzed by KEGG and GO enrichment
analyses (Additional file 2: Table S26 and S27). These genes encoded
fatty acid alpha-hydroxylase activity, epidermis morphogenesis,
transferase activity, etc.