Costs of reproduction and terminal investment by females in a semelparous marsupial.
Evolutionary explanations for life history diversity are based on the idea of costs of reproduction, particularly on the concept of a trade-off between age-specific reproduction and parental survival, and between expenditure on current and future offspring. Such trade-offs are often difficult to detect in population studies of wild mammals. Terminal investment theory predicts that reproductive effort by older parents should increase, because individual offspring become more valuable to parents as the conflict between current versus potential future offspring declines with age. In order to demonstrate this phenomenon in females, there must be an increase in maternal expenditure on offspring with age, imposing a fitness cost on the mother. Clear evidence of both the expenditure and fitness cost components has rarely been found. In this study, we quantify costs of reproduction throughout the lifespan of female antechinuses. Antechinuses are nocturnal, insectivorous, forest-dwelling small (20-40 g) marsupials, which nest in tree hollows. They have a single synchronized mating season of around three weeks, which occurs on predictable dates each year in a population. Females produce only one litter per year. Unlike almost all other mammals, all males, and in the smaller species, most females are semelparous. We show that increased allocation to current reproduction reduces maternal survival, and that offspring growth and survival in the first breeding season is traded-off with performance of the second litter in iteroparous females. In iteroparous females, increased allocation to second litters is associated with severe weight loss in late lactation and post-lactation death of mothers, but increased offspring growth in late lactation and survival to weaning. These findings are consistent with terminal investment. Iteroparity did not increase lifetime reproductive success, indicating that terminal investment in the first breeding season at the expense of maternal survival (i.e. semelparity) is likely to be advantageous for females.
School of Biological Sciences, The University of Queensland, St. Lucia, Australia. d.fisher@uq.edu.au
Diana O
DO
Fisher
Simon P
SP
Blomberg
D000367:Age Factors; D000375:Aging; D000818:Animals; D005260:Female; D007774:Lactation; D008136:Longevity; D008394:Marsupialia / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D013534:Survival
J Evol Biol. 2003 Nov;16(6):1249-56
14640416
Biol Lett. 2005 Sep 22;1(3):271-5
17148185
Proc Biol Sci. 2006 May 22;273(1591):1239-44
16720397
Nature. 2004 Nov 25;432(7016):502-5
15565154
Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7841-6
20378836
Oecologia. 2010 Mar;162(3):627-39
20033822
Mol Ecol. 2006 Oct;15(11):3439-48
16968281
Trends Ecol Evol. 2007 Feb;22(2):80-6
17056152
Ecol Lett. 2010 Jul;13(7):915-35
20482573
Oecologia. 2010 Jan;162(1):261-71
19730892
Philos Trans R Soc Lond B Biol Sci. 2008 Jan 27;363(1490):375-98
17686735
Trends Ecol Evol. 2000 Oct 1;15(10):421-425
10998520
Nature. 2006 Nov 2;444(7115):89-92
17080089
Am Nat. 2006 Jan;167(1):E23-38
16475094