Molly Morris Webpage

Molly R. Morris

Associate Professor, Ohio University

morrism@ohio.edu

Research Interests

Publications

Courses

Contact Information

Students and Postdoctoral Fellows

Research Interests:

The long term objectives of my research are to gain a better understanding of the role sexual selection plays in producing and maintaining biodiversity. I am particularly interested in the evolution of female mating preferences, alternative mating strategies and communication during male-male competition. I have used field studies, laboratory studies, phylogenetic studies, and game theory to address questions concerning the function and evolution of behavior and other sexually selected traits. Currently I am examining the evolution of a pattern of vertical bars found throughout the swordtail and platyfishes (Xiphophorus). I have found that bars on males function as a sexual signal that attracts females and deters rival males. By comparing the responses of males and females of three species, I have hypothesized that the responses of males to the bars have evolved in a more correlated fashion with the signal (bars) than female preference for the bars over the same temporal time scale. In a comparative study across all of the Northern Swordtails we have demonstrated that preference for this pigment pattern evolved before male response, suggesting that males may co-opt signals used in mate choice for use in male-male competition.

Vertical Bars on a male Xiphophorus cortezi (photo by K. de Queiroz)

The accuracy of my conclusions about the evolution of the bars and responses to the bars depends on the accuracy of the phylogeny I use. Therefore, I am currently working on a revision of the Xiphophorus phylogeny in collaboration with Laurie Dries, Carla Gutiérrez-Rodriquez, Kevin de Queiroz and Natalie Dubois, we are collecting new DNA sequence data, considering several different published data sets and some new morphological characters.

The conclusions of comparative studies that use phylogenies are also critically dependent on how the traits are defined. I am examining the role of several different components of the bars (bar intensity, bar number, bar width, and bilaterally symmetry of bar number) in sexual selection so that I can better define the bars as a sexual signal. I use videotaped images and video animations to tease apart female preference for very specific components of this visual cue.

(Photo by K. de Queiroz)

"Vertical bars on a male Xiphophorus cortezi". This male was naturally asymmetrcial in bar number (A) right = 7 bars, (B) left = 8 bars. A freeze-branding technique was used to increase his asymmetry to two bars (one bar was removed from the right side). Manipulation by freeze-branding has allowed us to examine female preferences and male responses to the presence of bars, bar number and bar symmetry (Morris 1998).

Oscar Rios-Cardenas and I are currently examining mechanisms that maintain the genetically controlled alternative mating strategies in Xiphophorus multilineatus. We have detected variation in the strength of female mating preference for different male mating strategies across the lifetime of females in X. multilineatus. In addition to variation in female mating preferences, we will examine frequency dependent selection and spatial and temporal variation in environmental factors such as predation as potential mechanisms maintaining these alternative strategies.

Finally, I am interested in the application of game theory to studies of the evolution of behavior. My work in this area has included studies of the evolution of alternative mating strategies, bluffing and communication during aggressive interactions. Currently, I am working with Winfried Just from the department of Mathematics on a model to explain why individuals that have a high probability of losing a contest might be the aggressors and initiate an escalated contest. In collaboration with Jason Moretz, I have also examined the evolution of vertical bars as an aggressive signal in male-male competition.

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Publications:

Gardner, R., Morris, M.R. and Nelson, C.E. (1987) Conditional evolutionarily stable strategies. Animal Behaviour, 35, 507-519.

Morris, M.R. & Yoon, S.L. (1989) A mechanism for female choice of large males in the treefrog Hyla chrysoscelis. Behavioral Ecology and Sociobiology, 25, 65-71.

Gardner, R. & Morris, M.R. (1989) The evolution of bluffing in animal contests: an ESS approach. Journal of Theoretical Biology, 137, 235-243.

Morris, M.R. (1989) Female choice and selection for male size in the treefrog Hyla chrysoscelis. Behavioral Ecology and Sociobiology, 25, 275-281.

Morris, M.R. & Ryan M.J. (1990) Age at sexual maturity of male Xiphophorus nigrensis in nature. Copeia 1990, 747-751.

Morris, M.R. (1991) Mating behaviour in the treefrog Hyla ebraccata. Journal of Zoology 223, 371-378.

Gardner, R. & Morris, M.R. (1991) The evolution of bluffing in animal contests: an extended model. In: Game Equilibrium Models I: Evolution and Game Theory. Ed. Selten, R. pp 182-194. Springer-Verlag, Berlin.

Ryan, M.J., Pease, C.E. and Morris, M.R. (1992) Maintenance of a genetic polymorphism in the swordtail Xiphophorus nigrensis: A general life history model. American Naturalist 139, 21-31.

Morris, M.R. and Ryan, M.J. (1992) Breeding cycles in natural populations of Xiphophorus nigrensis, X. multilineatus, and X. pygmaeus. Copeia, 1074-1077.

Morris, M.R., Batra, P., and Ryan, M.J. (1992) Male-male competition and access to females in the swordtail Xiphophorus nigrensis. Copeia 1992, 980-986.

Morris, M.R. and Ryan, M.J. (1995) Large body size in the pygmy swordtail Xiphophorus pygmaeus. Biological Journal of the Linnean Society 54, 383-395.

Morris, M.R., Mussel, M. and Ryan, M. J. (1995) Vertical body bars on male X. multilineatus: a signal that deters rival males and attracts females. Behavioral Ecology 6, 274-279.

Morris, M.R., Gass, L. & Ryan, M.J. (1995). Assessment and individual recognition of opponents in the swordtails Xiphophorus nigrensis and Xiphophorus multilineatus. Behavioral Ecology and Sociobiology 37, 303-310.

Wiens, J.J. and Morris, M.R. (1996) Sexual selection and the evolution of swords. American Naturalist, 147, 866-869.

Morris, M.R. and Ryan, M.J. (1996) Sexual difference in sender-receiver coevolution. Animal Behaviour, 52, 1017-1024.

Morris, M.R., Wagner Jr, W.E. and Ryan, M.J. (1996). A negative correlation between trait and mate preference in Xiphophorus pygmaeus. Animal Behaviour, 52, 1193-1203.

Morris, M.R. and Casey, K. (1998) Female swordtail fish prefer symmetrical sexual signal. Animal Behaviour, 55, 33-39.

Morris, M. R. (1998) Female Preference for Trait Symmetry in Addition to Trait Size in Swordtail Fishes. Proceedings of the Royal Society, B. 1399, 907-911.

Morris, M. R. (1998) Further examination of female preference for vertical bars in swordtails: preference for "no bars" in a species without bars. Journal of Fish Biology Supplement A to Volume 53, 57-64.

Hoefler , C. H. and Morris, M. R. (1999) A technique for the temporary application and augmentation of pigment patterns in fish. Ethology 105, 431-438.

Merry, J. W. and Morris, M. R. (2001) Preference for symmetry in swordtail fish. Animal Behavior 61, 477-479.

Morris, M.R., de Queiroz, K. and Morizot, D. (2001) Phylogenetic relationships among the Northern Swordtails (Xiphophorus) as inferred from allozyme data. Copiea 2001, 65-81.

Dries, L., Morris, M.R. and Ryan, M. J. (2001) Why are some male pygmy swordtails large? Copeia 2001, 355-364.

Morris, M.R., Elias, J. A. and Moretz, J. A. (2001) Defining the sexually selected male trait vertical bars in relation to female preference in the swordtail fish Xiphophorus cortezi. Ethology 107, 827-837.

Hankison, S.J. and Morris, M.R. (2002) Sexual selection and species identification in Xiphophorus pygmaeus: conflicting preferences. Behavioral Ecology and Sociobiology 51, 140-145.

Morris, M. R. Hesselman, L. and Nicoletto, P. (2003) A Polymorphism in female preference for a polymorphic male trait in the swordtail Xiphophorus cortezi. Animal Behaviour 65(1), 45-52.

Hankison, S. J. and Morris, M. R. (2003) Avoiding a compromise between sexual selection and species recognition: female swordtail fish assess multiple species-specific cues. Behavioral Ecology 14, 282-287.

Moretz, J. A., Morris, M. R (2003) Evolutionarily Labile Responses to a Conventional Threat Signal. Proceedings of the Royal Society, London B 270, 2271-2277.

Just, W. and Morris, M. R. (2003) The Napoleon Complex: Why Smaller Males Pick Fights. Evolutionary Ecology 17, 509-522.

Morris, M. R., Moretz, J. A., Farley, K. and Nicoletto, P. (2005) The Role of Sexual Selection in the Loss of Sexually Selected Traits in the Swordtail Fish Xiphophorus continens. Animal Behaviour 69, 1415-1424.

Morris, M. R., Cardenas-Rio, O. and Tudor, M. S. (2006) Larger swordtail females prefer asymmetrical males. Biology Letters Royal Society of London 2, 8-11

Wiegmann, D. D. and Morris, M. R. (2006) Search Behavior and Mate Choice. Recent Research Developments in Experimental and Theoretical Biology

Moretz, J. A. and Morris, M. R. (2006) Moretz, J. A. and Morris, M. R. (2006) Phylogenetic Analysis of the Evolution of a Signal of Aggressive Intent in Northern Swordtail Fishes. American Naturalist 168, 336–349.

Gutiérrez-Rodríguez, C. Morris, M. R., Dubois, N. S. and de Queiroz, K. (2007) Genetic variation and phylogeography of the swordtail fish Xiphophorus cortezi (Cyprinodontiformes, Poeciliidae). Molecular Phylogenetics and Evolution 43:111-123.

Just, W., Morris, M. R., and Sun, X. (2007) The evolution of aggressive losers. Behavioural Processes 74, 342-350

Rios-Cardenas, Tudor, M. S. and Morris, M. R. (2007) Variation in female preference has implications for the maintenance of an alternative mating strategy in a swordtail fish. Animal Behaviour 74, 633-640.

Fernandez, A. A. and Morris, M. R. (2007). Sexual Selection and Trichromatic Color Vision in Primates: Statistical Support for the Pre-existing Bias Hypothesis. American Naturalist 170, 10-20.

Morris, M. R., Tudor, S. M. and Dubois, N. S. (2007). Sexually selected signal attracted females prior to deterring aggression in rival males. Animal Behaviour 74, 1189-1197 .

Gutiérrez-Rodríguez, C., Shearer, A., Morris, M. R., and de Queiroz, K. (in press). Phylogeography and monophyly of the swordtail fish species Xiphophorus birchmanni (Cyprinodontiformes, Poeciliidae). Zoologica Scripta

Rios-Cardenas O. and Morris M. R. (in press). The implications of variation in female preferences for swordtail fishes. In: Viviparous Fishes II, the proceedings of the III International Symposium on Viviparous Fishes

Other publications:

Greig, N. and Morris, M. (1992) eds. Tropical Biology: An Ecological Approach 92-1. Organization for Tropical Studies, Inc., Duke University, Durham, NC

Morris, M.R. (1996) Book Review. Amphibian Biology, Volume 2, Social Behavior (Editors Heatwole, H. and Sullivan, B.) Herpetological Review, 27, 220-221.

Wiens, J.J and Morris M.R. (2003) Book Review. Sexual Selections by M. Zuk, Quarterly Review of Biology 78, 127.

Morris, M.R. (2005) Book Review. Animal Signals by Maynard Smith, J. & Harper, D. Oxford Series in Ecology and Evolution, Oxford University Press, New York. Ethology

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Courses:

I will be teaching Principles of Evolution (BIOS 330) Spring 2009 (TWTHF 1-2); Animal Behavior (BIOS 473/573) Winter 2009. Please contact me if you have questions concerning these classes.

Students:

Donelle Robinson