Ecophysiological determinants of sexual size dimorphism: integrating growth trajectories, environmental conditions, and metabolic rates
Sexual size dimorphism (SSD) often results in dramatic differences in body size between females and males. Despite its ecological importance, little is known about the relationship between developmental, physiological, and energetic mechanisms underlying SSD. We take an integrative approach to understand the relationship between developmental trajectories, metabolism, and environmental conditions resulting in extreme female-biased SSD in the crab spider Mecaphesa celer (Thomisidae). We tested for sexual differences in growth trajectories, as well as in the energetics of growth, hypothesizing that female M. celer have lower metabolic rates than males or higher energy assimilation. We also hypothesized that the environment in which spiderlings develop influences the degree of SSD of a population. We tracked growth and resting metabolic rates of female and male spiderlings throughout their ontogeny and quantified the adult size of individuals raised in a combination of two diet and two temperature treatments. We show that M. celer’s SSD results from differences in the shape of female and male growth trajectories. While female and male resting metabolic rates did not differ, diet, temperature, and their interaction influenced body size through an interactive effect with sex, with females being more sensitive to the environment than males. We demonstrate that the shape of the growth curve is an important but often overlooked determinant of SSD and that females may achieve larger sizes through a combination of high food ingestion and low activity levels. Our results highlight the need for new models of SSD based on ontogeny, ecology, and behavior.
KeywordsGrowth trajectories Ontogeny SSD Temperature-size rule Thomisidae
D. Izaguirre, D. Myers, M. Potts, A. Schmidt, R. Pettit, R. N’Guyen, A. Lehman, and K. Clay helped with spider maintenance. W. Wagner, D. Ledger, J. Stevens, and J.P. Gibert provided us feedback on this manuscript.
Author contribution statement
MCC, JPD, and EH conceived the ideas and designed methodology, MCC collected and analyzed the data, MCC wrote the first version of the manuscript, and all authors contributed to subsequent versions.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest to declare.
All applicable institutional and/or national guidelines for the care and use of animals were followed.
- Atkinson D (1994) Temperature and organism size—a biological law for ectotherms? Advances in ecological research. Elsevier, New York, pp 1–58Google Scholar
- Bates D, Maechler M, Bolker B, Walker S (2015) Fitting linear mixed-effects models using Ime4. J Stat Soft 67(1):1–48Google Scholar
- Beck CA, Iverson SJ, Bowen WD, Blanchard W (2007) Sex differences in grey seal diet reflect seasonal variation in foraging behaviour and reproductive expenditure: evidence from quantitative fatty acid signature analysis. J Anim Ecol 76:490–502. https://doi.org/10.1111/j.1365-2656.2007.01215.x CrossRefGoogle Scholar
- DeLong JP (2012) Experimental demonstration of a ‘rate–size’ trade-off governing body size optimization. Evol Ecol Res 14:343–352Google Scholar
- Foelix RF (2011) Biology of spiders, 3rd edn. Oxford University Press, Oxford, New YorkGoogle Scholar
- Foellmer MW, Moya-Larano J (2007) Sexual size dimorphism in spiders: patterns and processes. In: Sex, size and render roles: evolutionary studies of sexual size dimorphism. Oxford Biol , p 266Google Scholar
- Legrand RS, Morse DH (2000) Factors driving extreme sexual size dimorphism of a sit-and-wait predator under low density. Biol J Linn Soc 71:643–664. https://doi.org/10.1111/j.1095-8312.2000.tb01283.x CrossRefGoogle Scholar
- Leigh SR, Shea BT (1996) Ontogeny of body size variation in African apes. Am J Phys Anthropol 99:43–65. https://doi.org/10.1002/(SICI)1096-8644(199601)99:1%3c43:AID-AJPA3%3e3.0.CO;2-0 CrossRefGoogle Scholar
- Prenter J, Montgomery WI, Elwood RW (1995) Multivariate morphometrics and sexual dimorphism in the orb-web spider Metellina segmentata (Clerck, 1757) (Araneae, Metidae). Biol J Linn Soc 55:345–354. https://doi.org/10.1111/j.1095-8312.1995.tb01070.x CrossRefGoogle Scholar
- Preziosi RF, Fairbairn DJ (2000) Lifetime selection on adult body size and components of body size in a waterstrider: opposing selection and maintenance of sexual size dimorphism. Evolution 54:558–566. https://doi.org/10.1111/j.0014-3820.2000.tb00058.x CrossRefGoogle Scholar
- R Core Team (2014) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/
- Scharff N, Coddington JA (1997) A phylogenetic analysis of the orb-weaving spider family Araneidae (Arachnida, Araneae). Zool J Linn Soc 120:355–434. https://doi.org/10.1111/j.1096-3642.1997.tb01281.x CrossRefGoogle Scholar
- Shillington C, Peterson CC (2002) Energetics of male and female tarantulas. J Exp Biol 205:2909–2914Google Scholar
- Stillwell RC, Blanckenhorn WU, Teder T et al (2010) Sex differences in phenotypic plasticity affect variation in sexual size dimorphism in insects: from physiology to evolution. Annu Rev Entomol 55:227–245. https://doi.org/10.1146/annurev-ento-112408-085500 CrossRefGoogle Scholar
- Walker SE, Rypstra AL (2001) Sexual dimorphism in functional response and trophic morphology in Rabidosa rabida (Araneae: Lycosidae). Am Midl Nat 146:161–170. https://doi.org/10.1674/0003-0031(2001)146%5b0161:sdifra%5d2.0.co;2 CrossRefGoogle Scholar
- Weatherhead PJ, Teather KL (1994) Sexual size dimorphism and egg-size allometry in birds. Evolution 48:671–678. https://doi.org/10.1111/j.1558-5646.1994.tb01352.x CrossRefGoogle Scholar