Review of secondary reproduction in termites (Insecta : Isoptera) with comments on its role in termite ecology and social evolution

This review assembles records of neotenic reproductives in 199 species in 6 1 genera in 6 families and adultoid reproductives in 35 species In 14 gener a in 2 families of in the order Isoptera. Neotenic reproductives are report ed for 61.7% of lower termite genera, but for only 13.4% of higher termite genera (Termitidae). Secondary reproduction is assessed in relation to the following nine termite ecotypes: 1) dry endoxylophagy, 2) damp endoxylophag y, 3) xylophagous foraging, 4) arborealxylophagy, 5) epigeous nesting, 6) m ound building, 7) humivory, 8) grass and litter feeding, and 9) nest inquil inism. Neotenics appear to be common in termites that occupy all xylophagou s ecotypes, but rare or obsolete in mound building and humivorous termites. Hypotheses concerning the role of neotenic reproduction in termite social evolution are discussed. Cross taxa comparisons show that facultative neote ny is a primitive element in termite caste systems, supporting the hypothes is that neotenics evolved as the first physical caste in termites due to in dividual-level selection forces associated with the primitive endoxylophago us ecotype. The origin of the neotenic caste would have introduced a reprod uctive alternative to alate development, and thus provided a direct-fitness component to the fitness outlook of nondispersing colony members. This pot ential for reproduction without dispersal would have reduced the fitness co st of not dispersing, and thereby may have promoted selection for further d iversification of termite caste potentialities as pseudergates and reproduc tive soldiers. Thus, it is concluded that neotenic reproduction was an impo rtant enabling mechanism in the early eusocial evolution of termites. Neote nic reproduction has evolved as a less prominent feature of the biology of most higher termites and has been lost and replaced by adultoid replacement reproduction in the Macrotermitinae, and in other groups among the Termiti dae. Adultoids appear to be selected over neotenics in taxa with a stable f ood base, centralized nesting, secure royal cells, and highly physogastric primary queens.