The offspring size/fecundity trade-off and female fitness in the Atlantic molly (Poecilia mexicana, Poeciliidae)
- 217 Downloads
Across a variety of taxa, large offspring have been demonstrated to have a fitness advantage over smaller offspring of the same species. However, producing large offspring often comes at the cost of having to produce fewer young, and the payoff (and thus, evolutionary outcome) of this trade-off is expected to vary between environments. Atlantic mollies (Poecilia mexicana: Poeciliidae, Teleostei), inhabiting a sulfidic cave and various non-sulfidic surface habitats in Tabasco (Mexico), are reproductively isolated and evolved divergent female life-history traits: females of the cave ecotype produce considerably fewer, but larger offspring. Stressful (sulfidic) environments may favor the production of larger offspring, as they are better able to cope with chemical stressors. It remains to be determined though if increased offspring survival outweighs the fitness cost of producing fewer but larger offspring even under benign laboratory conditions. We tested 30-day newborn survival of offspring from wild-caught P. mexicana females from diverging populations in a low-density, no predation, no cannibalism, and ad-libitum-food, benign laboratory environment. Survival rates were highly skewed towards larger cave molly offspring; however, surface molly females still had a higher fitness than cave molly females in terms of higher total numbers of surviving offspring. Our study provides evidence for an innate fitness advantage of larger cave molly offspring. Furthermore, the observed differences in life-history strategies could promote further divergence and reproductive isolation among these ecotypes of P. mexicana, because cave molly females immigrating into the adjacent surface habitats would most likely be selected against.
KeywordsCave fish Ecological speciation Extremophile teleost Immigrant fitness Local adaptation Offspring size/number trade-off
We thank J. Curtis for help with fish care, T. J. Colston for help in the field, and the Mexican Government (Permiso de Pesca de Fomento: DGOPA.06192.240608.-1562) for kindly providing permits. We appreciate the support rendered to this project by F.J. García de León, and R. Brian Langerhans helped improve a previous version of this manuscript. The experiments comply with the current laws on animal experimentation of the United States of America (AUS-IACUC approved protocol: R06-026). Funding came from the National Science Foundation of America (DEB-0743406).
- Bierbach D, Klein M, Sassmannshausen V, Schlupp I, Riesch R, Parzefall J, Plath M (2012) Divergent evolution of male aggressive behaviour: another reproductive isolation mechanism in extremophile poeciliid fishes? Internat J Evol Biol (special edition: Mechanisms of Speciation)Google Scholar
- Einum S, Fleming IA (2004) Environmental unpredictability and offspring size: conservative versus diversified bet-hedging. Evol Ecol Res 6:443–455Google Scholar
- Horstkotte J, Riesch R, Plath M, Jäger P (2010) Predation by three species of spiders on a cave fish in a Mexican sulphur cave. Bull Brit Arachnol Soc 15:55–58Google Scholar
- Kelley JL (2008) Assessment of predation risk by prey fishes. In: Magnhagen C, Braithwaite VA, Forsgren E, Kapoor BG (eds) Fish behaviour. Science, Enfield, pp 269–301Google Scholar
- Pianka ER (1976) Natural selection of optimal reproductive tactics. Am Zool 16:775–784Google Scholar
- Plath M, Riesch R, Oranth A, Dzienko J, Karau N, Schießl A, Stadtler S, Wigh A, Zimmer C, Arias-Rodriguez L, Schlupp I, Tobler M (2010b) Complementary effects of natural and sexual selection against immigrants maintains differentiation between locally adapted fish. Naturwissenschaften 97:769–774PubMedCrossRefGoogle Scholar
- Plath M, Riesch R, Culumber Z, Streit B, Tobler M (2011) Giant water bug (Belostoma sp.) predation on a cave fish (Poecilia mexicana): effects of female body size and gestational state. Evol Ecol Res 13:133–144Google Scholar
- Riesch R, Oranth A, Dzienko J, Karau N, Schießl A, Stadler S, Wigh A, Zimmer C, Arias-Rodriguez L, Schlupp I, Plath M (2010b) Extreme habitats are not refuges: poeciliids suffer from increased aerial predation risk in sulfidic, southern Mexican habitats. Biol J Linn Soc 101:417–426CrossRefGoogle Scholar
- Riesch R, Plath M, Schlupp I (2011b) Speciation in caves: experimental evidence that permanent darkness promotes reproductive isolation. Biol Lett, in pressGoogle Scholar
- Sinervo B, Daughty P, Huey RB, Zamudio K (1992) Allometric engineering: a causal analysis of natural selection on offspring size. Science 258:1927–1930Google Scholar
- Trivers RL (1974) Parent-offspring conflict. Am Zool 14:249–264Google Scholar