title: Sibling cannibalism in a web-building spider: effects of density and shared environment.
abstract: Sibling cannibalism occurs across diverse taxa and can affect population size and structure, as well as the fitness of parents and the cannibal, via density effects and variation in individual propensity to cannibalize. We examined these effects on sibling cannibalism in juveniles of a web-building spider (Latrodectus hasselti, Australian redbacks). Adult redbacks are solitary, but juveniles live in clusters of variable density for a week after hatching. We confined newly hatched siblings from a singly-mated female to a low or high density treatment in a split-clutch design, then left spiderlings unfed for a week. Our results showed no effect of density on overall cannibalism levels, but a strong correlation between cannibalism counts from the same maternal lines across densities. Unlike web-bound sit-and-wait predators, wandering spiders that are active hunters have been shown to experience density-dependent cannibalism. In contrast, we suggest sibling cannibalism in web-building spiders may be density independent because early cohabitation on the web selects for elevated tolerance of conspecifics. We conclude that, rather than being linked to density, cannibalism of siblings in these species may be controlled more strongly by variation in individual propensity to cannibalize.
authors.affiliation: Integrative Behaviour and Neuroscience Group, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4(2); Department of Neurobiology and Behavior, Cornell University, 215 Tower Road, Ithaca, NY 14853, USA(3). Electronic address: mm2474@cornell.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Modanu
authors.affiliation: Integrative Behaviour and Neuroscience Group, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4(2).
authors.forename: Lucy Dong Xuan
authors.initials: LD
authors.lastname: Li
authors.affiliation: Integrative Behaviour and Neuroscience Group, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4(2).
authors.forename: Hosay
authors.initials: H
authors.lastname: Said
authors.affiliation: Integrative Behaviour and Neuroscience Group, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4(2).
authors.forename: Nizanthan
authors.initials: N
authors.lastname: Rathitharan
authors.affiliation: Integrative Behaviour and Neuroscience Group, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4(2).
authors.forename: Maydianne C B
authors.initials: MC
authors.lastname: Andrade
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002190:Cannibalism / Q000523:psychology*; D004777:Environment; D011156:Population Density; D035781:Siblings / Q000523:psychology*; D013112:Spiders / Q000502:physiology*
keywords: Density; Latrodectus; Redback; Sibling cannibalism; Spider