Intraspecific Competition and Population Structure in Rotifers

Snell, Terry W.

doi:10.2307/1936069

Cited by 63 publications

(33 citation statements)

References 27 publications

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“…A similar pattern of seasonal succession of demographically distinct clones is known from the cladocerans Daphnia pulex (Lynch, 1983), D. parvula (Pace et aI., 1984), and D. magna (Carvalho, 1987;Carvalho and Crisp, 1987); in these examples, genotype-specific fitnesses appear to depend upon abundance of particular predators or temperature changes. Snell (1979) suggested that interclonal competition for food mediates seasonal cycles of clonal succession in the rotifer Asplanchna brightwelli. In the Eel Pond population of B. schlosseri, the increase in mortality of semelparous colonies occurs considerably before recruitment of iteroparous colonies increases; thus, direct com- ment plates.…”

Section: Discussionmentioning

confidence: 99%

LIFE‐HISTORY VARIATION WITHIN A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI. I. THE GENETIC AND ENVIRONMENTAL CONTROL OF SEASONAL VARIATION

Grosberg

1988

Evolution

100

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Abstract.-Many empirical analyses of life-history tactics are based on the assumption that demographic variation ought to be greatest among populations or species living in different environments. However, in a single population of the sessile colonial sea squirt Botryllus schlosseri, there are two discrete life-history morphs. Semelparous colonies are characterized by a) death immediately following the production ofa single clutch, b) early age at first reproduction, c) rapid growth to first reproduction, and d) high reproductive effort. In contrast, iteroparous colonies a) produce at least three clutches before dying, b) postpone sexual reproduction until they are nearly twice the age of semelparous colonies, c) grow at about half the rate of semelparous colonies, and d) invest roughly 75% less in reproductive effort than semelparous colonies. Semelparous colonies numerically dominate the population through midsummer; later in the summer, iteroparous colonies are most numerous. Field and laboratory common-garden experiments, along with breeding studies, indicate that the demographic differences between the morphs are genetically determined. Consequently, the seasonal switch from dominance by semelparous colonies to dominance by iteroparous colonies may be an evolved response to a seasonally changing environment. On theoretical grounds, temporal variation in selection is thought to playa relatively unimportant role in maintaining genetic polymorphism; nonetheless, the seasonally recurrent life-history polymorphism shown in this study indicates that temporal variation in selection can lead to the maintenance of genetic polymorphism for traits strongly affecting fitness.

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Section: Discussionmentioning

confidence: 99%

LIFE‐HISTORY VARIATION WITHIN A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI. I. THE GENETIC AND ENVIRONMENTAL CONTROL OF SEASONAL VARIATION

Grosberg

1988

Evolution

100

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“…As a result, competition among Agaricia may have an important effect on the density and distribution of colonies, as well as possibly the genetic structure of adult populations. For example, competition among Agaricia at early life history stages could result in selection for competitively superior genotypes (Snell 1979, Yund 1991.…”

Section: Abstract: Competition · Size Asymmetry · Scleractinians · Smentioning

confidence: 99%

Competition among small colonies of Agaricia: the importance of size asymmetry in determining competitive outcome

Zilberberg¹,

Edmunds²

2001

Mar. Ecol. Prog. Ser.

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“…The genotypes AA, Aa, aa may differ ecologically so that their niches are not necessarily identical (examples in nature are provided in Si1ander [1979], Hebert [1978], Hebert and Crease [1980], Snell [1979], Jaenike etal. [1980], Browne [1980], Mitter et al [1979], and Solbrig and Simpson [1974]).…”

Section: One-locus Modelmentioning

confidence: 99%

“…Many asexual organisms have different clones, sometimes only distinguishable by electrophoretic techniques, each with quite different ecological properties and competitive abilities. The following studies are exemplary: fish (Vrijenhoek, 1978(Vrijenhoek, , 1984; Daphnia (Hebert and Crease, 1980); Spartina (Silander, 1979); Artemia (Browne, 1980); dandelions (Solbrig and Simpson, 1974); rotifers (Snell, 1979); aphids (Service and Lenski, 1982); winter moths (Mitter et al, 1979); weevils (Suomalainen et al, 1976). The studies of Suomalainen et al (1976) and Vrijenhoek (1978Vrijenhoek ( , 1984, in particular, indicate that adaptive evolution in asexual species is possible through the differential proliferation of clones with different ecologically relevant characteristics.…”

Section: Single-speciesmentioning

confidence: 99%

On the Coexistence and Coevolution of Asexual and Sexual Competitors

1986

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Abstract.-The coexistence and coevolution of sexual and asexual species under resource competition are explored with three models: a nongenetic ecological model, a model including single locus genetics, and a quantitative-genetic model. The basic assumption underlying all three models is that genetic differences are translated into ecological differences. Hence if sexual species are genetically more variable, they will be ecologically more variable. Under classical competition theory, this increased ecological variability can, in many cases, be an advantage to individual sexual genotypes and to the sexual species as a whole. The purpose of this paper is to determine the conditions when this advantage will outway three disadvantages of sexuality: the costs of males, of segregation, and of the additive component of recombination.All three models reach similar conclusions. Although asexuality confers an advantage, it is much less than a two-fold advantage because minor increases in the overall species niche width of the sexual species will offset the reproductive advantage of the asexual species. This occurs for two reasons. First, an increase in species niche width increases the resource base of the sexual species. Second, to the extent that the increase in niche width is due to increased differences between individuals, a reduction in intraspecific competition will result. This is not to imply that the sexual species will always win.The prime conditions that enable sexual species to stably coexist with or even supplant an asexual sister species are: I) relatively high between-genotype (but within-species) niche differentiation; 2) significant niche differences between the species; 3) low environmental variance; 4) severe resource exploitation; 5) larger within-phenotype niche width in the sexual species than in the asexual species.Spatial or temporal heterogeneities are not required in this model. This is an important difference between this model and other models for sexual advantage. Instead, depletion of resources used by common genotypes creates a rare-genotype advantage. The sexual species, with its great diversity of genotypes, is better equipped to capture this advantage. Although the mechanisms of our model are framed in terms of competition for shared resources, the important factor is that it generates frequency-dependent fitnesses. Other frequency-dependent ecological mechanisms, such as shared predators with functional responses, or shared genotypically-specific parasites, would work as well.

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Intraspecific Competition and Population Structure in Rotifers

Cited by 63 publications

References 27 publications

LIFE‐HISTORY VARIATION WITHIN A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI. I. THE GENETIC AND ENVIRONMENTAL CONTROL OF SEASONAL VARIATION

LIFE‐HISTORY VARIATION WITHIN A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI. I. THE GENETIC AND ENVIRONMENTAL CONTROL OF SEASONAL VARIATION

Competition among small colonies of Agaricia: the importance of size asymmetry in determining competitive outcome

On the Coexistence and Coevolution of Asexual and Sexual Competitors

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