Summary
This paper addresses risk and energetic considerations fundamentaly causative in the evolution of eusociality in the bathyergid molerats. Three simple mathematical models are presented which predict the probability of successful outbreeding in terms of dispersal risks and the energetic costs of foraging. The predictions of the models are compared with data from the literature, which mostly provide excellent empirical and theoretical support.
Inter-habitat dispersal risks are influenced most importantly by group size and resource characteristics, but also by body size, metabolic rate, thermoregulation, soil conditions, and caste structure. Intea-habitat foraging risks are temporaly dependent on rainfall — a factor critical for appropriate dispersal timing. High dispersal and foraging risks necessitate large group sizes and preclude a solitary existence. Outbreeding or inbreeding options are strongly influenced by dispersal risks, with high genetic relatedness in high risk habitats the likely consequence. Offspring should attain inclusive fitness values equal, if not more, than those possible by outbreeding by staying and helping with the colony reproductive effort.
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References
Abbott DH, Barrett J, Faulkes CG, George LM (1989) Social contraception in naked mole-rats and maramaset monkeys. J Zool (Lond) 219: 703–7710
Alexander RD (1974) The evolution of social behaviour. Annu Rev Ecol Syst 5: 325–383
Andersson M (1984) The evolution of eusociality. Annu Rev Ecol Syst 15: 165–189
Bartz SH (1982) On the evolution of male workers in the hymenoptera. Behav Ecol Sociobiol 11: 223–228
Bennett NC, Jarvis JUM (1988a) The social structure and reproductive biology of colonies of the mole-rat Cryptomys damarensis (Rodentia: Bathyergidae). J Mammal 62: 293–302
Bennett NC, Jarvis JUM (1988b) The reproductive biology of the Cape molerat, Georychus capensis (Rodentia, Bathyergidae). J Zool (Lond) 214: 95–106
Bennett NC, Jarvis JUM (1988c) Daily and seasonal temperatures in the burrows of African rodent moles. S Afr J Zool 23: 189–195
Brett RA 1986 The Ecology and Behaviour of the Naked Molerat (Heterocephalus glaber Rüppell) (Rodentia, Bathyergidae). Dissertation, University of London
Burda H (dy1988) Reproductive biology (behaviour, breeding, and postnatal development) in subterranean mole-rats, Cryptomys hottentotus (Bathyergidae). Z Säugetierk (in press)
Caraco T (1981) Risk-sensitivity and foraging groups. Ecology 62: 527–531
Cole BJ (1983) Multiple mating and the evolution of social behaviour in the Hymenoptera. Behav Ecol Sociobiol 12: 191–201
Crozier RH, Page RE (1985) On being the right size: mate contributions and multiple mating in social Hymenoptera. Behav Ecol Sociobiol 18: 105–115
Davies KC, Jarvis JUM (1986) The burrow systems and burrowing dynamics of the molerats Bathyergus suillus and Cryptomys hottentotus in the fynbos of the south-western Cape, South Africa. J Zool (Lond) 209: 125–147
Dawkins R (1989) The Selfish Gene — New edn. Oxford University Press, Oxford
De Graaff G (1981) The Rodents of Southern Africa. Butterworths, Pretoria
Faulkes CG, Abbott DH, (1990) Investigation of genetic diversity in wild colonies of naked mole-rats by DNA fingerprinting. J Zool (Lond) 221: (in press)
Faulkes CG, Abbott DH, Jarvis JUM (dy1990) Social suppression of ovarian cyclicity in captive and wild colonies of naked molerats, Heterocephalus glaber. J Reprod Fertil 88: (in press)
Haim A, Fairall N (1986) Physiological adaptations to the subterranean environment by the molerat Cryptomys hottentotus. Cimbebasia 8: 49–53
Hamilton WD (1964a) The genetical evolution of social behavior I. J Theor Biol 7: 1–16
Hamilton WD (1964b) The genetical evolution of social behavior II. J Theor Biol 7: 17–52
Hickman GC (1982) Copulation of Cryptomys hottentotus (Bathyergidae), a fossorial rodent. Mammalia 46: 293–298
Honeycutt RL, Edwards SV, Nelson K, Nevo E (1987) Mitochondrial DNA variation and the phylogeny of african molerats (Rodentia: Bathyergidae). Syst Zool 36: 280–292
Jarvis JUM (1978) Energetics of survival in Heterocephalus glaber (Rüppell), the Naked mole-rat (Rodentia: Bathyergidae). Bull Carn Mus Nat Hist 6: 81–87
Jarvis JUM (1981) Eusociality in a mammal: cooperative breeding in Naked mole-rat colonies. Science 212: 571–573
Jarvis JUM (1984) African mole-rats. In: MacDonald D (ed) The encyclopaedia of mammals 2. George Allen and Unwin, London Sydney
Jarvis JUM (1985) Ecological studies on Heterocephalus glaber, the Naked mole-rat, in Kenya. Nat Geogr Res Rep 1979 Projects 20: 429–431
Jarvis JUM, Sale JB (1971) Burrowing and burrowing patterns of east African mole-rats Tactyorctes, Heliophobius, and Heterocephalus. J Zool (Lond) 163: 451–479
Lovegrove BG (1986a) Thermoregulation of the subterranean rodent genus Bathyergus (Bathyergidae). S Afr J Zool 21: 283–288
Lovegrove BG (1986b) The metabolism of social subterranean rodents: adaptation to aridity. Oecologia 69: 551–555
Lovegrove BG (1987) Thermoregulation in the subterranean rodent Georychus capensis (Rodentia: Bathyergidae). Physiol Zool 60: 174–180
Lovegrove BG (1988a) Colony size and structure, activity patterns and foraging behaviour of a colony of the social molerat Cryptomys damarensis (Bathyergidae). J Zool (Lond) 216: 391–402
Lovegrove BG (1988b) The energetics of sociality in the molerats (Bathyergidae). Dissertation, University of Cape Town
Lovegrove BG (1989) The cost of burrowing by the social molerats (Bathyergidae) Cryptomys damarensis and Heterocephalus glaber: the role of soil moisture. Physiol Zool 62: 449–469
Lovegrove BG, Jarvis JUM (1986) Coevolution between molerats (Bathyergidae) and a geophyte, Micranthus (Iridaceae). Cimbebasia 8: 79–85
Lovegrove BG, Painting S (1987) Variations in the foraging behaviour and burrow structures of the Damara molerat Cryptomys damarensis (Bathyergidae) in the Kalahari Gemsbok National Park. Koedoe 30: 149–163
Lovegrove BG, Knight-Eloff A (1988) Soil and burrow temperatures, and the resource characteristics of the social molerat Cryptomys damarensis in the Kalahari Desert. J Zool (Lond) 216: 403–416
Lovegrove BG, Wissel C (1988) Sociality in molerats: metabolic scaling and the role of risk-sensitivity. Oecologia 74: 600–606
Nagy KA (1980) CO2 production in animals: analysis of potential errors in the doubly labelled water method. Am J Physiol 238: R466-R473
Nagy KA (1987) Field metabolic rate and food requirement scaling in mammals and birds. Ecol Monogr 57: 111–128
Nevo E (1979) Adaptive convergence and divergence of subterranean mammals. Annu Rev Ecol Syst 10: 269–308
Nevo E, Capanna E, Corti M, Jarvis JUM, Hickman GC (1986) Karyotype differentiation in the endemic subterranean molerats of South Africa (Rodentia: Bathyergidae). Z Säugetierk 51: 36–49
Nevo E, Ben-Shlomo R, Beiles A, Jarvis JUM, Hickman GC (1987) Allozyme differentiation and systematics of the endemic subterranean mole rats of South Africa. Biochem Syst Ecol 15: 489–502
Pamilo P (1984) Genetic relatedness and evolution of insect sociality. Behav Ecol Sociobiol 15: 241–248
Reilly LM (1987) Measurements of inbreeding and average relatedness in a termite population. Am Nat 130: 339–349
Taylor PJ, Jarvis JUM, Crowe TM, Davies KC (1985) Age determination in the Cape molerat Georychus capensis. S Afr J Zool 20: 261–267
Verdcourt B (1969) The arid corridor between the northeast and northwest areas of Africa. Pages 140–144 In: Van Zinderen Bakker (ed) Paleoecology of Africa, vol 4. Balkema, Amsterdam
Vleck D (1979) The energy cost of burrowing by the pocket gopher Thomomys bottae. Physiol Zool 52: 122–125
Vleck D (1981) Burrow structure and foraging costs in the fossorial rodent, Thomomys bottae. Oecologia 49: 391–396
Wade MJ (1980) Kin selection: its components. Science 210: 665–667
Wade MJ (1982) The effect of multiple inseminations on the evolution of social behaviors in diploid and haplo-diploid organisms. J Theor Biol 95: 351–368
Wade MJ (1985) The influence of multiple inseminations and multiple foundress on social evolution. J Theor Biol 112: 109–121
Weissburg M (1986) Risky business: on the ecological relevance of risk-sensitive foraging. Oikos 46: 261–262
Withers PC, Jarvis JUM (1980) The effect of huddling on the thermoregulation and oxygen consumption for the Naked molerat. Comp Biochem Physiol 66: 215–219
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Lovegrove, B.G. The evolution of eusociality in molerats (Bathyergidae): a question of risks, numbers, and costs. Behav Ecol Sociobiol 28, 37–45 (1991). https://doi.org/10.1007/BF00172137
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DOI: https://doi.org/10.1007/BF00172137