BIOL 312 Lecture Notes - Lecture 18: Nuptial Gift, Dung Beetle, Spermatophore

• School: University of Victoria
• Department: Biology
• Course: BIOL 312
• Professor: Steve Perlman

Document Summary

Lecture 18 sexual selection and mating systems. Incredible diversity of mating systems (polygyny, polyandry, monogamy) and traits related to reproduction (e. g. ornaments and weapons, sexual dimorphism, mating displays). Sexual selection depends on a struggle between males for possession of females. The result is not death to the unsuccessful competitor but few or no offspring. Sexual selection of a trait = differences in reproductive success, caused by competition over mates and related to the expression of the trait. Differences in investment; (cid:862)sper(cid:373) is (cid:272)heap, eggs are e(cid:454)pe(cid:374)si(cid:448)e(cid:863). Fe(cid:373)ales: fe(cid:449), large gametes (eggs) vs males: many small gametes (sperm). A) fe(cid:373)ales, (cid:271)(cid:455) resour(cid:272)es a(cid:448)aila(cid:271)le for egg production. B) males, only limited by access to females and/or eggs. With repeated matings, male fitness increases more than female fitness. Exceptions: females often mate multiply, sex-role reversal (cid:858)e(cid:454)pe(cid:374)si(cid:448)e(cid:859) sper(cid:373). Very unusual case of sex-role reversal in insects. Female penis, male vagina and their correlated evolution in a cave insect: bark lice, neotrogla (psocodea).