Sib cannibalism can be adaptive for kin

Abstract

1Sib cannibalism seems to be paradoxical behaviour, since it decreases the survival rate of the 2 closest relative juveniles, so the rate of sib cannibalism changes the demography of the 3 cannibal phenotype. In the general kin demographic selection model presented here, the long-4 term growth rate of a phenotype is determined by a Leslie matrix that depends on the life 5 history strategy, and a uniform density-dependent selection process takes place, keeping the 6 total population size at the level of the carrying capacity. Using this model, where different 7 phenotypes are described by different Leslie matrices, we point out that the phenotype 8 optimizing the phenotypic long-term growth rate will select out any other optimizing 9 phenotype. We find that sib cannibalism is adaptive if the sib cannibal can decrease its 10 developmental time, and the shorter development time can increase the rate of survival from 11 sib cannibal juvenile to adult, and also when sib cannibalism increases fecundity in the adult 12 stage. Cannibalism between the closest relatives can be considered as a mutualistic kin 13 strategy when the benefit of cannibalism is greater than the cost of it. 14 Keywords: collector hypothesis, kin demography, Leslie model 15 16 3

Caring for parents: an evolutionary rationale

“…Since in our problem, pre-fertile, fertile, and post-fertile individuals live together in a family, we have to consider a kin demographic selection model [3, 33, 34], in which the survival and the fecundity parameters depend on the costs and benefits of intra-familiar supports. After setting up the model, we investigate whether the Fifth Rule (as a biological distillation of the Fifth Commandment; see Additional file 1) wins in a Darwinian struggle for existence.…”

Social density, but not sex ratio, drives ecdysteroid hormone provisioning to eggs by female house crickets (Acheta domesticus)

“…Addressing our first hypothesis, we predicted that in high social density, female crickets would deposit more ESH to their eggs (resulting in larger, faster‐growing hatchlings). We made this prediction because there is evidence that in many taxa, parents produce more competitive offspring at higher densities (Benton et al., ; Meylan, Miles, & Clobert, ), and because development rate in a cannibalistic species may been linked to the level of competition faced during development (Garay, Varga, Gamez, & Cabello, ). Regarding our second hypothesis, we predicted that female house crickets reared in a female‐skewed environment would deposit more ESH to their eggs (thus, producing larger, faster‐growing hatchlings) than would females reared in male‐skewed social environments.…”

“…Addressing our first hypothesis, we predicted that in high social density, female crickets would deposit more ESH to their eggs (resulting in larger, faster-growing hatchlings). We made this prediction because there is evidence that in many taxa, parents produce more competitive offspring at higher densities (Benton et al, 2005;Meylan, Miles, & Clobert, 2012), and because development rate in a cannibalistic species may been linked to the level of competition faced during development (Garay, Varga, Gamez, & Cabello, 2016).…”

Survival phenotype, selfish individual versus Darwinian phenotype

“…We seek phenotypes which maximize interesting objective functions (cf. Garay et al 2016, Garay & Varga 2005).…”

“…The selfish individual maximizes her life reproductive success (e.g., Yearsley et al 2002), which is the average number of offspring during the individual life span. Finally, the fourth objective function is the growth rate of a phenotype (e.g., Caswell 2001, Garay et al 2016.…”