Abstract
Sexual size dimorphism is common in many taxa and results from various pressures, including competition, reproductive requirements, functional differences, and sexual recognition. For mammals, males are typically the larger sex; however, for vespertilionid bats, females are more often the larger sex. Forearm length, a feature that influences overall wing and body size and is often sexually dimorphic, is a standard morphological measurement taken from bats. Forearm length was measured in two vesper bat species (Corynorhinus rafinesquii and Myotis austroriparius) that co-occur across much of the southeastern United States. Forearm length was greater in females of both species, and females of both species also exhibited regional variation in forearm length. By having a longer forearm and therefore being larger in size, females may be more maneuverable and better equipped to carry young. While this study did not directly investigate the mechanisms behind regional variation in forearm length, it is possible this is the result of variability in habitat types, resources, or thermodynamic constraints. Knowledge of sexually dimorphic characteristics is important for obtaining a general understanding of a species and its morphology.
Acknowledgments
We thank the countless people who took forearm measurements across the range of both species. Thank you for taking the time out of your busy schedule to collect data for this project. We also thank two anonymous reviewers for comments that greatly improved this manuscript.
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Author contributions: All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Jessica Vannatta and Brian Carver. The first draft of the manuscript was written by Jessica Vannatta and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Research funding: No funding was received for conducting this study.
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Conflict of interest statement: The authors declare that they have no conflicts of interest regarding this article.
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Research ethics: This study was conducted under Tennessee Technological University Institutional Animal Care and Use Committee (IACUC) approval (#TTU-IACUC-15-16-003) and with all appropriate state permits, and followed the Guidelines of the American Society of Mammologists for the use of wild mammals in research and education (Sikes et al. 2016).
References
Anthony, E.L.P. (1988). Age determination. In: Kunz, T.H. (Ed.), Ecological and behavioral methods for the study of bats. Washington D.C.: Smithsonian Institution Press, pp. 47–58.Search in Google Scholar
Barbour, R.W. and Davis, W.H. (1969). Bats of America. Lexington: The University Press of Kentucky.Search in Google Scholar
Fairbairn, D.K., Blanckenhorn, W.U., and Székely, T. (2007). Sex, size, and gender roles. New York: Oxford University Press Inc.10.1093/acprof:oso/9780199208784.001.0001Search in Google Scholar
Handley, C.O. (1959). A revision of American bats of the genera Euderma and Plecotus. Smithsonian Institution 110: 95–246, https://doi.org/10.5479/si.00963801.110-3417.95.Search in Google Scholar
Iliopoulou-Georgudaki, J. (1986). The relationship between climatic factors and forearm length of bats: evidence from the chiropterofauna of Lesvos Island (Greece – East Aegean). Mammalia 50: 475–482, https://doi.org/10.1515/mamm.1986.50.4.475.Search in Google Scholar
Jiang, T., Wang, J., Wu, H., Csorba, G., Puechmaille, S.J., Benda, P., Boireau, J., Toffoli, R., Courtois, J., Nyssen, P., et al.. (2019). The patterns and possible causes of global geographical variation in the body size of the greater horseshoe bat (Rhinolophus ferrumequinum). J. Biogeogr. 46: 2362–2377, https://doi.org/10.1111/jbi.13658.Search in Google Scholar
Krüger, O. (2005). The evolution of reversed sexual size dimorphism in hawks, falcons and owls, a comparative study. Evol. Ecol. 19: 467–486.10.1007/s10682-005-0293-9Search in Google Scholar
LaVal, R.K. (1970). Infraspecific relationships of bats of the species Myotis austroriparius. J. Mammal. 51: 542–552, https://doi.org/10.2307/1378393.Search in Google Scholar
Lisόn, F., Haz, A., González-Revelles, C., and Calvo, J.F. (2012). Sexual size dimorphism in greater mouse-eared bat Myotis myotis (Chiroptera: Vespertilionidae) from a Mediterranean region. Acta Zool. 95: 137–143.10.1111/azo.12012Search in Google Scholar
McDonald, P.G., Olsend, P.D., and Cockburn, A. (2004). Selection on body size in a raptor with pronounced reversed sexual size dimorphism: are bigger females better? Behav. Ecol. 16: 48–56, https://doi.org/10.1093/beheco/arh118.Search in Google Scholar
Myers, P. (1978). Sexual dimorphism in size of vespertilionid bats. Am. Nat. 112: 701–711, https://doi.org/10.1086/283312.Search in Google Scholar
Piaggio, A.J., Saugey, D.A., and Sasse, D.B. (2011). Phylogenetic and population genetic assessment of Rafinesque’s Big-eared Bat (Corynorhinus rafinesquii). General Technical Report SRS-145. Paper 1339. U.S. Department of Agriculture National Wildlife Research Center, Lincoln, Nebraska. http://digitalcommons.unl.edu/icwdm_usdanwrc/1339.Search in Google Scholar
Ralls, K. (1976). Mammals in which females are larger than males. Q. Rev. Biol. 51: 245–276, https://doi.org/10.1086/409310.Search in Google Scholar
Ralls, K. (1977). Sexual dimorphism in mammals: avian models and unanswered questions. Am. Nat. 111: 917–938, https://doi.org/10.1086/283223.Search in Google Scholar
Schulte-Hostedde, A.I., Millar, J.S., and Gibbs, H.L. (2002). Female-biased sexual size dimorphism in the Yellow-Pine Chipmunk (Tamias amoenus): sex-specific patterns of annual reproductive success and survival. Evolution 56: 2519–2529, doi:https://doi.org/10.1111/j.0014-3820.2002.tb00176.x.Search in Google Scholar
Sikes, R. and the Animal Care and Use Committee of the American Society of Mammalogists (2016). 2016 Guidelines of the American Society of Mammalogists for the use of wild mammals in research and education. J. Mammal. 97: 663–688, https://doi.org/10.1093/jmammal/gyw078.Search in Google Scholar
Stevens, R.D., Johnson, M.E., and MuCulloch, E.S. (2013). Absolute and relative secondary-sexual dimorphism in wing morphology: a multivariate test of the ‘Big Mother’ hypothesis. Acta Chiropterol. 15: 163–170, https://doi.org/10.3161/150811013x667966.Search in Google Scholar
Stevens, R.D. and Platt, R.N. (2015). Patterns of secondary sexual size dimorphism in New World Myotis and a test of Rensch’s rule. J. Mammal. 96: 1128–1134, https://doi.org/10.1093/jmammal/gyv120.Search in Google Scholar
United States Environmental Protection Agency [U.S. EPA] (2013). Level III ecoregions of the continental United States: Corvallis, Oregon, U.S. EPA – National Health and Environmental Effects Research Laboratory, map scale 1:7,500,000, Available at: <https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states> (Accessed 21 May 2019).Search in Google Scholar
Vannatta, J. (2019). Range-wide population genetic structure of Rafinesque’s Big-eared Bat (Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius), Ph.D. dissertation, Cookeville, Tennessee Technological University.Search in Google Scholar
Weckerly, F.W. (1998). Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. J. Mammal. 79: 33–52, https://doi.org/10.2307/1382840.Search in Google Scholar
Williams, D.F. and Findley, J.S. (1979). Sexual size dimorphism in vespertilionid bats. Am. Midl. Nat. 102: 113–126, https://doi.org/10.2307/2425072.Search in Google Scholar
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