Fig. 5

The origin of the insect sHSP-C and l(2)efl genes. The origin of the sHSP genes was before the divergence of the Arthropod lineage. The ancestral Arthropod sHSP genes were contained in a cluster. The ancestral insect sHSP-C likely contained two divergent sHSP genes. In the basal branching insect species Ladona and Ephemera this cluster is retained where there is at least one copy of each of the ancestral sHSP genes (l(2)efl and sHSP paralogs). In the higher branching hemiptera the two ancestral sHSPs are separated (l(2)efl and sHSP paralogs) and remain so in the holometabolous insects. This separation gives rise to the homologous non-linked insect sHSP l(2)efl, which is shared with all insects. After the split of the holometabola from the hemimetabola, the sHSP paralogs undergo extensive duplication and loss events to give rise to the lineage specific sHSP-C genes via birth-and-death evolution