Molly R. Morris
Molly R. Morris
Assistant Professor, Ohio University
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My research interests are in sexual selection, the evolution of alternative mating strategies, and the evolution of communication. 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 genus Xiphophorus (swordtail and platyfishes) . 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. I plan to determine if this pattern is more general by examining the responses of males and females to the bars in several species within the genus
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. I am considering several different published data sets, a large previously unpublished allozyme data set, and some new morphological characters.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).
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.
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). Female choice for large males in the swordtail X. 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, Volume 53 (Supplement A), 56-63.
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. (in press) Why are some
male pygmy swordtails large? Copeia.
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.
I will be teaching Introduction to Zoology (BIOS 172) spring quarter 2001 (MWF 2:10-3:00), Animal Behavior ( BIOS 473/573) spring quarter 2001(MWF 10:10 - 12:00) and Behavioral Ecology (BIOS 682) fall quarter 2001 (TTH 10:10-12:00). Visitors can check out the web pages for these courses by logging on as "guest" with the password "guest".
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Office Phone: (740) 593-0337
FAX: (740) 593-4527
Department of Biological Sciences
Ohio University
Athens, OH 45701