Coexistence in Unisexual‐Bisexual Species Complexes of Poeciliopsis (Pisces: Poeciliidae)

All—female forms of Poeciliopsis rely on males of closely related bisexual species for sperm. The natural habitat of Poeciliopsis in Sonora Mexico, consists of a variety of small ponds connected by intermittent watercourses. Optimal areas, containing mixed female aggregates, are defended by territor...

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Bibliographic Details
Published in:Ecology (Durham) 1971-09, Vol.52 (5), p.791-799
Main Authors: Moore, William S., McKay, Francis E.
Format: Article
Language:English
Subjects:
Bisexuality
Ecological balance
Female animals
Fish
Insemination
Male animals
Mating behavior
Reproduction
Social interaction
Spermatozoa
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Summary:All—female forms of Poeciliopsis rely on males of closely related bisexual species for sperm. The natural habitat of Poeciliopsis in Sonora Mexico, consists of a variety of small ponds connected by intermittent watercourses. Optimal areas, containing mixed female aggregates, are defended by territorial males. Social structure in natural populations very closely resembles that of laboratory experiments, wherein subordinant males show reduced mate discrimination and inseminate unisexuals. An equation relating male density to unisexual inseminations is used in a computer simulation model of a population. A stable equilibrium is inherent in unisexual—bisexual species complexes but the level of equilibrium is affected by the environment. Coexistence does not require niche separation. The simulations predict the percentage of unisexuals pregnant in natural populations and explain their distribution pattern. The strength of the mechanism is demonstrated by a natural population in which the percentage of unisexuals pregnant responded strongly to a modest change in unisexual—bisexual composition.
ISSN:0012-9658
1939-9170
DOI:10.2307/1936026