Reappearance of
            <i>Eulimnadia agassizii</i>
            with Notes on Its Biology and Life History

Zinn, Donald Joseph; Dexter, Ralph W.

doi:10.1126/science.137.3531.676

Cited by 18 publications

(7 citation statements)

References 1 publication

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“…Natural populations of Eulimnadia are typically hermaphrodite biased (Mattox 1954), with some populations completely lacking males (Zinn and Dexter 1962;Stern and Stern 1971). Eulimnadia texana populations range from zero to 40% males, and inbreeding is positively correlated with hermaphrodite-biased sex ratios (Sassaman 1989(Sassaman 1995.…”

Section: Natural History Of Eulimnadia Texanamentioning

confidence: 98%

Inbreeding Depression in a Self-Compatible, Androdioecious Crustacean, Eulimnadia texana

Weeks¹,

Marcus²,

Crosser³

1999

Evolution

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The observation that offspring produced by the mating of close relatives are often less fit than those produced by matings between unrelated individuals (i.e., inbreeding depression) has commonly been explained in terms of the increased probability of expressing deleterious recessive alleles among inbred offspring (the partial dominance model). This model predicts that inbreeding depression should be limited in regularly inbreeding populations because the deleterious alleles that cause inbreeding depression (i.e., the genetic load) should be purged by regularly exposing these alleles to natural selection. We indirectly test the partial dominance model using four highly inbred populations of an androdioecious crustacean, the clam shrimp Eulimnadia texana. These shrimp are comprised of males and hermaphrodites, the latter capable of either self-fertilizing or mating with a male (i.e., outcrossing between hermaphrodites is impossible). Hermaphrodites are further subdivided into monogenics (produced via self-fertilization) and amphigenics (produced via self-fertilization or outcrossing). Electrophoretic evidence suggests significant differences in heterozygosity among populations, but that selfing rates were not statistically different (average s = 0.67). Additional electrophoretic analyses reveal that three previously described sex-linked loci (Fum, Idh-1, and Idh-2) are all tightly linked to each other, with crossing over on the order of 1% per generation. Although selfing rates are clearly high, we present evidence that early inbreeding depression (hatching rates, juvenile survival, and age at sexual maturity) exists in all four populations. For all of these factors, inbreeding depression was inferred by the positive correlation of multilocus heterozygosity and fitness. Cumulative inbreeding depression (8) is between 0.41 and 0.47 across all populations, which appears to be too low to limit the effects of purging via identity disequilibrium. Instead, we suggest that the maintenance of inbreeding depression in these populations is due to the observed linkage group, which we suggest contains a large number of genes including many related to fitness. Segregation of such a large linkage group would explain our observations of the predominance of amphigenic hermaphrodites in our field samples and of survival differences between monogenics and amphigenics within selfed clutches. We propose that a modified form of the overdominance model for inbreeding depression operating at the level of linkage groups maintains the observed levels of inbreeding depression in these populations even in the face of high rates of selfing.

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Section: Natural History Of Eulimnadia Texanamentioning

confidence: 98%

Inbreeding Depression in a Self-Compatible, Androdioecious Crustacean, Eulimnadia texana

Weeks¹,

Marcus²,

Crosser³

1999

Evolution

View full text Add to dashboard Cite

show abstract

“…Natural populations of Eulimnadia are typically hermaphrodite biased (Mattox 1954), with some populations completely lacking males (Zinn and Dexter 1962;Stern and Stern 1971). Eulimnadia texana populations range from 0% to 40% males (average ϭ 25% males; Weeks and Zucker 1999), and inbreeding is positively correlated with female-biased sex ratios (Sassaman 1989(Sassaman , 1995Weeks and Zucker 1999).…”

Section: Natural History Of Eulimnadia Texanamentioning

confidence: 99%

Maintenance of Androdioecy in the Freshwater Shrimp, Eulimnadia Texana: Estimates of Inbreeding Depression in Two Populations

et al. 2000

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Androdioecy is an uncommon form of reproduction in which males coexist with hermaphrodites. Androdioecy is thought to be difficult to evolve in species that regularly inbreed. The freshwater shrimp Eulimnadia texana has recently been described as both androdioecious and highly selfing and is thus anomalous. Inbreeding depression is one factor that may maintain males in these populations. Here we examine the extent of "late" inbreeding depression (after sexual maturity) in these clam shrimp using two tests: (1) comparing the fitness of shrimp varying in their levels of individual heterozygosity from two natural populations that differ in overall genetic diversity; and (2) specifically outcrossing and selfing shrimp from these same populations and comparing fitness of the resulting offspring. The effects of inbreeding differed within each population. In the more genetically diverse population, fecundity, size, and mortality were significantly reduced in inbred shrimp. In the less genetically diverse population, none of the fitness measures was significantly lowered in selfed shrimp. Combining estimates of early inbreeding depression from a previous study with current estimates of late inbreeding depression suggests that inbreeding depression is substantial (delta = 0.68) in the more diverse population and somewhat lower (delta = 0.50) in the less diverse population. However, given that males have higher mortality rates than hermaphrodites, neither estimate of inbreeding depression is large enough to account for the maintenance of males in either population by inbreeding depression alone. Thus, the stability of androdioecy in this system is likely only if hermaphrodites are unable to self-fertilize many of their own eggs when not mated to a male or if male mating success is generally high (or at least high when males are rare). Patterns of fitness responses in the two populations were consistent with the hypothesis that inbreeding depression is caused by partially recessive deleterious alleles, although a formal test of this hypothesis still needs to be conducted.

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“…Natural populations of Eulimnadia are typically hermaphrodite biased (Mattox 1954), with some populations completely lacking males (Zinn and Dexter 1962;Stern and Stern 1971). Eulimnadia texana populations range from 0% to 40% males (average ϭ 25% males; Weeks and Zucker 1999), and inbreeding is positively correlated with female-biased sex ratios (Sassaman 1989(Sassaman , 1995Weeks and Zucker 1999).…”

Section: Natural History Of Eulimnadia Texanamentioning

confidence: 99%

Maintenance of Androdioecy in the Freshwater Shrimp, Eulimnadia Texana: Estimates of Inbreeding Depression in Two Populations

Weeks¹,

Crosser

Bennett

et al. 2000

Evol

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Androdioecy is an uncommon form of reproduction in which males coexist with hermaphrodites. Androdioecy is thought to be difficult to evolve in species that regularly inbreed. The freshwater shrimp Eulimnadia texana has recently been described as both androdioecious and highly selfing and is thus anomalous. Inbreeding depression is one factor that may maintain males in these populations. Here we examine the extent of ''late'' inbreeding depression (after sexual maturity) in these clam shrimp using two tests: (1) comparing the fitness of shrimp varying in their levels of individual heterozygosity from two natural populations that differ in overall genetic diversity; and (2) specifically outcrossing and selfing shrimp from these same populations and comparing fitness of the resulting offspring. The effects of inbreeding differed within each population. In the more genetically diverse population, fecundity, size, and mortality were significantly reduced in inbred shrimp. In the less genetically diverse population, none of the fitness measures was significantly lowered in selfed shrimp. Combining estimates of early inbreeding depression from a previous study with current estimates of late inbreeding depression suggests that inbreeding depression is substantial (␦ ϭ 0.68) in the more diverse population and somewhat lower (␦ ϭ 0.50) in the less diverse population. However, given that males have higher mortality rates than hermaphrodites, neither estimate of inbreeding depression is large enough to account for the maintenance of males in either population by inbreeding depression alone. Thus, the stability of androdioecy in this system is likely only if hermaphrodites are unable to self-fertilize many of their own eggs when not mated to a male or if male mating success is generally high (or at least high when males are rare). Patterns of fitness responses in the two populations were consistent with the hypothesis that inbreeding depression is caused by partially recessive deleterious alleles, although a formal test of this hypothesis still needs to be conducted.

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Reappearance of Eulimnadia agassizii with Notes on Its Biology and Life History

Abstract: After being unreported for 83 years, Eulimnadia agassizii Packard was collected from a temporary pool in Woods Hole, Massachusetts, in 1956 and again in 1961. This conchostracan attains maturity in 5 days and may reappear several times during the summer months in the same location.

Cited by 18 publications

References 1 publication

Inbreeding Depression in a Self-Compatible, Androdioecious Crustacean, Eulimnadia texana

Inbreeding Depression in a Self-Compatible, Androdioecious Crustacean, Eulimnadia texana

Maintenance of Androdioecy in the Freshwater Shrimp, Eulimnadia Texana: Estimates of Inbreeding Depression in Two Populations

Maintenance of Androdioecy in the Freshwater Shrimp, Eulimnadia Texana: Estimates of Inbreeding Depression in Two Populations

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