title: Copulation with immature females increases male fitness in cannibalistic widow spiders.
abstract: Copulatory cannibalism of male 'widow' spiders (genus Latrodectus) is a model example of the extreme effects of sexual selection, particularly in L. hasselti and L. geometricus where males typically facilitate cannibalism by females and mate only once. We show that these males can increase their reproductive success by copulating with final-instar, immature females after piercing the female's exoskeleton to access her newly developed sperm storage organs. Females retain sperm through their final moult and have similar fecundity to adult-mated females. This is an adaptive male tactic because immature mating increases insemination success relative to adult mating (which predicts higher paternity) and moreover, rarely ends in cannibalism, so males can mate again. Although successful only during a brief period before the female's final moult, males may employ this tactic when they associate with final-instar females in nature. Consistent with this, one-third of L. hasselti females collected as immatures in nature were already mated. Immature mating alters sexual selection on these otherwise monogynous males, and may explain male traits allowing facultative polygyny in Latrodectus Since male cohabitation with immature females is common among invertebrates, immature mating may be a widespread, previously unrecognized mating tactic, particularly when unmated females are of high reproductive value.
authors.affiliation: Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada M1C1A4 Department of Ecology and Evolutionary Biology, University of Toronto Scarborough, Toronto, Canada M1C1A4.
authors.forename: M Daniela
authors.initials: MD
authors.lastname: Biaggio
authors.affiliation: Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Beersheba 8499000, Israel.
authors.forename: Iara
authors.initials: I
authors.lastname: Sandomirsky
authors.affiliation: Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Beersheba 8499000, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Lubin
authors.affiliation: Department of Entomology, Volcani Center, Bet Dagan 50250, Israel.
authors.forename: Ally R
authors.initials: AR
authors.lastname: Harari
authors.affiliation: Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada M1C1A4 Department of Ecology and Evolutionary Biology, University of Toronto Scarborough, Toronto, Canada M1C1A4 maydianne.andrade@utoronto.ca.
authors.forename: Maydianne C B
authors.identifier: 0000-0002-2931-5378
authors.initials: MC
authors.lastname: Andrade
mesh_terms: D000818:Animals; D002190:Cannibalism; D003307:Copulation / Q000502:physiology*; D005260:Female; D005298:Fertility; D008297:Male; D052586:Mating Preference, Animal / Q000502:physiology; D018978:Molting / Q000502:physiology; D013112:Spiders / Q000254:growth & development / Q000502:physiology*
keywords: alternative male mating tactic; mating immature females; sexual selection