86
the male provides locomotion (Knoll, 1995). This
may allow the hermaphrodite to conserve and garner
energy resources during the reproductive process. If
hermaphrodites can benefit from mate guarding and
still fertilize a significant portion of the offspring, the
costs of sex would be reduced. If even a small amount
of the male's sperm is then used for fertilization by
the hermaphrodites, the male would also obtain some
fitness by performing guarding behavior.
If there are advantages conferred to a hermaphrodite
from mate guarding, they are not enough to entirely
explain maintenance of outcrossing since some populations have no males and hermaphrodites will self
even if males are present. Further research needs to
examine the roles of genetic drift, inbreeding depression, or other factors responsible for maintenance of
outcrossing within some populations but not within
others.
Acknowledgments
This paper is part of a masters thesis submitted to New
Mexico State University by L.K. We thank committee
members, Drs M. Cain, R. Cole & D. Howard for their
continuing suggestions throughout. Special thanks also
goes to L. Graves for his extensive help in data collection. Support for this project has come from the
New Mexico State University Department of Biology,
a Summer Research Award for Excellence in Graduate
Studies stipend from the NMSU Department of Biology and the Commission on Higher Education Graduate Research Project Award from the NMSU Graduate
School to L.K.
References
Baur, B., 1989. Growth and reproduction of the minute land snail
Punctum pygmaeum (Draparnaud). J. Moll. Stud. 55: 383-387.
Belk, D., 1972. The biology and ecology of Eulimnadia antlei
Mackin (Conchostraca). Southwest. Nat. 16: 297-305.
Charlesworth, B., 1980. The cost of sex in relation to mating system.
J. Theor. BioI. 84: 655-671.
Jame, P., L. Finot, B. Delay & L. Thaler, 1991. Self-fertilization
versus cross-fertilization in the hermaphroditic freshwater snail
Bulinus globosus. Evolution 45: 1136-1146.
Knoll, L., 1995. Mating behavior and time budget of an androdioecious crustacean, Eulimnadia texana (Crustacea: Conchostraca).
Hydrobiologia 298 (Dev. Hydrobiol. 103): 73-81.
Knoll, L. & N. Zucker, 1995. Is sexual selection operating in
the androdioecious clam shrimp, Eulimnadia texana (Crustacea:
Conchostraca)? Hydrobiologia 298 (Dev. Hydrobiol. 103): 6772.
MacKay, W. P., S. J. Loring, T. M. Frost & w. G. Whitford, 1990.
Population dynamics of a playa community in the Chihuahuan
desert. Southwest. Nat. 35: 393--402.
Otto, S. P., C. Sassman & M. W. Feldman, 1993. Evolution of sex
determination in the Conchostracan shrimp Eulimnadia texana.
Am. Nat. 141: 329-337.
Sassaman, C., 1988. Clutch sex-ratio polymorphism in the clam
shrimp Eulimnadia antlei. Am. Zool. 28: 135A.
Sassman, C., 1989. Inbreeding and sex ratio variation in femalebiased populations of a clam shrimp, Eulimnadia texana. Bull.
mar. Sci. 45: 425--432.
Sassman, C. & S. C. Weeks, 1993. The genetic mechanism of sex
determination in the Conchostracan shrimp Eulimnadia texana.
Am. Nat. 141: 314--328.
Strenth, N. E., 1977. Successful variation of sex ratios in Eulimnadia
texana Packard (Crustacea, Conchostraca). Southwest. Nat. 22:
205-212.
the male provides locomotion (Knoll, 1995). This
may allow the hermaphrodite to conserve and garner
energy resources during the reproductive process. If
hermaphrodites can benefit from mate guarding and
still fertilize a significant portion of the offspring, the
costs of sex would be reduced. If even a small amount
of the male's sperm is then used for fertilization by
the hermaphrodites, the male would also obtain some
fitness by performing guarding behavior.
If there are advantages conferred to a hermaphrodite
from mate guarding, they are not enough to entirely
explain maintenance of outcrossing since some populations have no males and hermaphrodites will self
even if males are present. Further research needs to
examine the roles of genetic drift, inbreeding depression, or other factors responsible for maintenance of
outcrossing within some populations but not within
others.
Acknowledgments
This paper is part of a masters thesis submitted to New
Mexico State University by L.K. We thank committee
members, Drs M. Cain, R. Cole & D. Howard for their
continuing suggestions throughout. Special thanks also
goes to L. Graves for his extensive help in data collection. Support for this project has come from the
New Mexico State University Department of Biology,
a Summer Research Award for Excellence in Graduate
Studies stipend from the NMSU Department of Biology and the Commission on Higher Education Graduate Research Project Award from the NMSU Graduate
School to L.K.
References
Baur, B., 1989. Growth and reproduction of the minute land snail
Punctum pygmaeum (Draparnaud). J. Moll. Stud. 55: 383-387.
Belk, D., 1972. The biology and ecology of Eulimnadia antlei
Mackin (Conchostraca). Southwest. Nat. 16: 297-305.
Charlesworth, B., 1980. The cost of sex in relation to mating system.
J. Theor. BioI. 84: 655-671.
Jame, P., L. Finot, B. Delay & L. Thaler, 1991. Self-fertilization
versus cross-fertilization in the hermaphroditic freshwater snail
Bulinus globosus. Evolution 45: 1136-1146.
Knoll, L., 1995. Mating behavior and time budget of an androdioecious crustacean, Eulimnadia texana (Crustacea: Conchostraca).
Hydrobiologia 298 (Dev. Hydrobiol. 103): 73-81.
Knoll, L. & N. Zucker, 1995. Is sexual selection operating in
the androdioecious clam shrimp, Eulimnadia texana (Crustacea:
Conchostraca)? Hydrobiologia 298 (Dev. Hydrobiol. 103): 6772.
MacKay, W. P., S. J. Loring, T. M. Frost & w. G. Whitford, 1990.
Population dynamics of a playa community in the Chihuahuan
desert. Southwest. Nat. 35: 393--402.
Otto, S. P., C. Sassman & M. W. Feldman, 1993. Evolution of sex
determination in the Conchostracan shrimp Eulimnadia texana.
Am. Nat. 141: 329-337.
Sassaman, C., 1988. Clutch sex-ratio polymorphism in the clam
shrimp Eulimnadia antlei. Am. Zool. 28: 135A.
Sassman, C., 1989. Inbreeding and sex ratio variation in femalebiased populations of a clam shrimp, Eulimnadia texana. Bull.
mar. Sci. 45: 425--432.
Sassman, C. & S. C. Weeks, 1993. The genetic mechanism of sex
determination in the Conchostracan shrimp Eulimnadia texana.
Am. Nat. 141: 314--328.
Strenth, N. E., 1977. Successful variation of sex ratios in Eulimnadia
texana Packard (Crustacea, Conchostraca). Southwest. Nat. 22:
205-212.