|
r `? Ll t h Y\
<br />612
<br />COPEIA, 1985, NO. 3
<br />, AND B. LAvtE. 1977. The genetic basis of
<br />dispersal behavior in the flour beetle Tribolium cas-
<br />taneum. Can. J. Genet. Cytol. 19:717-722.
<br />RorF, D. A. 1974. The analysis ofa population model
<br />demonstrating the importance of dispersal in a het-
<br />erogeneous environment. Oecologia 15:259-275.
<br />. 1975. Population stability and the evolution
<br />of dispersal in a heterogeneous environment. Ibid.
<br />19:217-237.
<br />SELANDER, R. K., M. H. SMITH, S. Y. YANG, W. E.
<br />JOHNSON AND J. B. GENTRY. 1971. Biochemical
<br />polymorphism and systematics in the genus Pero-
<br />myscus. I. Variation in the old-field mouse (Pero.
<br />myscus polionotus). Studies in Genetics VI., Univ. of
<br />Texas Publ. 703:49-90.
<br />SMITH, M. H., M. N. MANLOVE, AND J. JOULE. 1978.
<br />Spatial and temporal dynamics of the genetic or-
<br />ganization of small mammal populations, p. 99-
<br />113. In: Populations of small mammals under nat-
<br />ural conditions. D. P. Snyder, (ed.). Spec. Pub. Ser.,
<br />Pymatuning Lab Ecol. 5.
<br />SNELSON, F. F., JR. 1982. Indeterminate growth in
<br />males of the sailfin molly, Poecilio latipinna. Copeia
<br />1982:296-304.
<br />SOKAL, R. R. 1979. Testing statistical significance of
<br />geographical variation patterns. Syst. Zoo]. 28:227-
<br />232.
<br />, AND F. J. ROHLF. 1981. Biometry. W. H.
<br />Freeman, San Francisco.
<br />SPIETH, P. T. 1974. Gene flow and genetic differ-
<br />entiation. Genetics 78:961-965.
<br />. 1979. Environmental heterogeneity: A prob-
<br />lem of contradictory selection pressures, gene flow
<br />and local polymorphism. Am. Nat. 113:247-260.
<br />STEARNS, S. C. 1983. A natural experiment in life-
<br />history evolution: Field data on the introduction of
<br />mosquitofish (Gambusia affinis) to Hawaii. Evolution
<br />37:601-617.
<br />THIBAULT, R. E., AND R. J. SCHULTZ. 1978. Repro-
<br />ductive adaptations among viviparous fishes (Cy-
<br />prinodontiformes: Poeciliidae). Evolution 32:320-
<br />333.
<br />TRENDALL, J. T. 1982. Covariation of life-history
<br />traits in the mosquitofish, Gambusia affinis. Am. Nat.
<br />119:774-783.
<br />. 1983. Life-history variation among experi-
<br />mental populations of the mosquitofish, Gambusia
<br />affinis. Copeia 1983:953-963.
<br />TURNER, C. L. 1941. Morphogenesis of the gono-
<br />podium in Gambusia affinis affinis. J, Morphol. 69:
<br />161-185.
<br />WEISE, C. M., AND J. R. MEYER. 1979. Juvenile dis-
<br />persal and development of site-fidelity in the Black-
<br />capped Chickadee. Auk 96:40-55.
<br />WILLIAMS, G. C. 1966. Adaptation and natural se-
<br />lection: A critique of some current evolutionary
<br />thought. Princeton Univ. Press, Princeton, New
<br />Jersey.
<br />WORKMAN, P. L., AND J. D. NISWANDER. 1970. Pop-
<br />ulation studies on southwestern Indian tribes. 11.
<br />Local genetic differentiation in the Papago. Amer.
<br />J. Hum. Genet. 22:24-49.
<br />WRIGHT, S. 1940. Breeding structure ofpopulations
<br />in relation to speciation. Am. Nat. 74:232-248.
<br />1965. The interpretation of population
<br />structure by F-statistics with special regard to sys-
<br />tems of mating. Evolution 9:395-420.
<br />YEATON, R. I. 1972. Social behavior and social or-
<br />ganization in Richardson ground squirrel (Spey.
<br />mophilus richardsonni) in Saskatchewan. J. Mammal.
<br />53:139-147.
<br />SAVANNAH RIVER ECOLOGY LABORATORY, P.O.
<br />DRAWER E, AIKEN, SOUTH CAROLINA 29801.
<br />PRESENT ADDRESS: DEPARTMENT OF BIOLOG-
<br />ICAL SCIENCES, WICHITA STATE UNIVERSITY,
<br />WICHITA, KANSAS 67208. Accepted 4 Nov.
<br />1984.
<br />Copra, 1985(3), pp. 613-618
<br />
<br />Non-annual Spawning in the White Sucker,
<br />Ca.tostomus commersoni
<br />STEPHEN P. QUINN AND MICHAEL R. ROSS
<br />Sexually mature white suckers in the Mill River (Amherst-Hadley, MA) spawned
<br />less frequently than on an annual basis. Biased sex ratios favored males in the
<br />spawning runs of this population; mature males were approximately three times
<br />as likely to spawn in a given year as were females. The spawning frequency of
<br />females increased with age, supporting the hypothesis that organisms exhibiting
<br />reduced reproductive effort as part of their life history should increase repro-
<br />ductive effort with increasing age. Excellent growth of white suckers in this
<br />watershed indicates that their reproductive schedule probably is adaptive and is
<br />not the outcome of poor nutritional or physiological status.
<br />ITEROPAROUS fishes generally have been
<br />thought to spawn annually. Exceptions to
<br />this pattern have been documented for only a
<br />few taxa: acipenserids (Roussou, 1957; Dads-
<br />well, 1979); the paddlefish Polydon spalhula
<br />('Meyer 1960); the striped bass Aforone saxalilis
<br />(Jackson and Tiller, 1952); and several Eurasian
<br />species of salmonids, cyprinids and silurids
<br />(Maksunov, 1971). Here, we document a non-
<br />annual spawning cycle for the white sucker Ca-
<br />loslomus commersoni, and analyze the sex and age
<br />specific characteristics of spawning frequency
<br />in this species.
<br />The white sucker is a widely distributed, long-
<br />lived, ?North American freshwater species that
<br />exhibits great variation in growth rate, age and
<br />size at maturity, and fecundity (Carlander, 1969;
<br />Beamish, 1973; Scott and Crossman, 1973).
<br />White suckers are usually potadromous with
<br />adults migrating up tributary streams to spawn
<br />in early spring. Early studies suggested that the
<br />sex ratio of fishes participating in a spawning
<br />migration was 1:1 (Spoor, 1938; Raney and
<br />Webster, 1942). However, biased sex ratios have
<br />been measured in spawning migrations by other
<br />investigators (Dente, 1948; Bouchard, 1955;
<br />Geen et al., 1966).
<br />Numerical dominance of one sex among
<br />spawners could be caused by: 1) differential
<br />mortality of the sexes, 2) deferred maturity of
<br />one sex, or 3) a greater tendency for members
<br />ofone sex to spawn on a non-annual basis. Olson
<br />and Scidmore (1963), monitoring the later por-
<br />tion of a spawning migration, found that suck-
<br />ers fin-clipped two years previously outnum-
<br />bered those marked during the previous
<br />spawning run by nearly 2:1. Geen et al. (1966)
<br />found that at least 22% of repeat spawners had
<br />apparently skipped at least one spawning op-
<br />portunity over a five-year period. The repeat
<br />spawners were not analyzed by sex or age. These
<br />studies indicate that suckers in some popula-
<br />tions may reproduce on a non-annual basis. A
<br />biased sex ratio among spawners could result in
<br />such populations if one sex tended to spawn less
<br />frequently than the other. However, none of
<br />the above studies characterized the population
<br />from which the spawners originated.
<br />Reproductive effort that produces less than
<br />the immediate, apparent-maximum number of
<br />offspring could evolve if the number of surviv-
<br />ing offspring produced in the lifetime of an in-
<br />dividual is potentially enhanced (Williams, 1966;
<br />Gadgil and Bossert, 1970; Goodman, 1974). Bull
<br />and Shine (1979) have suggested that a corre-
<br />lation exists between "low frequency reproduc-
<br />tion" and "accessory reproductive activities"
<br />(including breeding migrations, egg brooding
<br />and live bearing) among iteroparous poikilo-
<br />thermic vertebrate species. They postulated that
<br />lifetime fecundity can be increased by non-an-
<br />nual spawning if the associated reproductive ac-
<br />tivities significantly increase the mortality rate
<br />or require storage of energy which could be
<br />otherwise channelled into gametes.
<br />Reduced reproductive effort should be of
<br />greatest benefit to younger age classes that could
<br />increase fitness most by increasing the proba-
<br />bility of producing offspring in future repro-
<br />ductive seasons; thus, reproductive effort should
<br />increase with age (Williams, 1966; Gadgil and
<br />Bossert, 1970; Schaffer, 1974). Such an increase
<br />in reproductive effort has been demonstrated
<br />for a few fishes (Stearns, 1976). If white suckers
<br />spawn on a non-annual basis and the reproduc-
<br />tive schedule is adaptive, one might expect to
<br />1985 by she American Society of Ichthyologists and 1lerpemlogists
<br />Itl
<br />I `u
<br />r?,i?
|