MALADAPTED GENE COMPLEXES WITHIN POPULATIONS OF THE INTERTIDAL COPEPOD<i>TIGRIOPUS CALIFORNICUS</i>?

Edmands, Suzanne; Northrup, Sara L.; Hwang, A. S.

doi:10.1111/j.1558-5646.2009.00689.x

Cited by 34 publications

(47 citation statements)

References 52 publications

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“…In the case of the maternal backcross that produces a better match, both fitness and ATP energy production are restored, while in the paternal backcross both were still lowered in comparison to the parental populations. This restoration of fitness in maternal backcrosses does not appear to be universal, in a similar study by Edmands et al (2009) using a different pair of populations, they found a contrary pattern for a different measure of fitness. This could suggest that genomic coadaptation plays a larger role in some crosses than others within this species.…”

Section: Breakdown In Genomic Coadaptation In Crosses Of T Californicusmentioning

confidence: 66%

“…The scale bar shows the number of changes on this phylogram out of the coding sequence of 1,131 bp for CYTB. Outgroups for the analysis are two CYTB sequences from the congener T. japonicus; further details of phylogenetic analysis can be found in Willett and Ladner (2009) and Edmands 2006;Edmands et al 2009). In these two studies there were also patterns that were suggestive of epistatic interactions between select pairs of markers that could be consistent with the involvement of these genome regions in DM incompatibilities.…”

Section: Postzygotic Reproductive Isolation In Population Crossesmentioning

confidence: 99%

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The nature of interactions that contribute to postzygotic reproductive isolation in hybrid copepods

Willett

2010

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Deleterious interactions within the genome of hybrids can lower fitness and result in postzygotic reproductive isolation. Understanding the genetic basis of these deleterious interactions, known as Dobzhansky-Muller incompatibilities, is the subject of intense current study that seeks to elucidate the nature of these deleterious interactions. Hybrids from crosses of individuals from genetically divergent populations of the intertidal copepod Tigriopus californicus provide a useful model in which to study Dobzhansky-Muller incompatibilities. Studies of the basis of postzygotic reproductive isolation in this species have revealed a number of patterns. First, there is evidence for a breakdown in genomic coadaptation between mtDNA-encoded and nuclear-encoded proteins that can result in a reduction in hybrid fitness in some crosses. It appears from studies of the individual genes involved in these interactions that although this coadaptation could lead to asymmetries between crosses, patterns of genotypic viabilities are not often consistent with simple models of genomic coadaptation. Second, there is a large impact of environmental factors on these deleterious interactions suggesting that they are not strictly intrinsic in nature. Temperature in particular appears to play an important role in determining the nature of these interactions. Finally, deleterious interactions in these hybrid copepods appear to be complex in terms of the number of genetic factors that interact to lead to reductions in hybrid fitness. This complexity may stem from three or more factors that all interact to cause a single incompatibility or the same factor interacting with multiple other factors independently leading to multiple incompatibilities.

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Section: Breakdown In Genomic Coadaptation In Crosses Of T Californicusmentioning

confidence: 66%

Section: Postzygotic Reproductive Isolation In Population Crossesmentioning

confidence: 99%

The nature of interactions that contribute to postzygotic reproductive isolation in hybrid copepods

Willett

2010

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“…However the persistence of these PA alleles, which likely have both beneficial and detrimental effects in different hybrid gene combinations (e.g. Edmands 2008;Edmands et al 2009) may explain the significant fitness decline for one hybrid replicate in the final time point. Results of short-term controlled crosses help explain why long-term consequences of hybridization in the current study are very different from those in a previous study (Hwang et al 2011).…”

Section: Discussionmentioning

confidence: 98%

Long-term experimental hybrid swarms between nearly incompatible Tigriopus californicus populations: persistent fitness problems and assimilation by the superior population

et al. 2012

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For the intertidal copepod Tigriopus californicus, outbreeding depression for a variety of fitness measures is typically observed in early-generation interpopulation hybrids. We examined both controlled crosses and longterm, freely mating experimental hybrid swarms composed of individuals from Baja California (Mexico) populations Playa Altamira and Punta Morro. In controlled crosses, F1 and F2 hybrids showed large and significant declines in hatching numbers compared to parentals, while reciprocal backcrosses produced no offspring at all. For long-term studies, four treatment groups were initiated: 100%PA, 100%PM, 50%PA: 50%PM, and 80%PA: 20%PM. Replicates were surveyed at 3-month intervals for morphometric, census and fitness measures. The PA and 80PA:20PM treatments had initial fitness below the PM treatment, and went extinct within the first 12 months of the experiment. The 50:50 treatment had fitness below the PM parent at the 3-and 6-month time points, recovered to equivalent or superior fitness from months 9 to 18, and dropped again below PM at month 21. Limited genotyping of diagnostic microsatellites was consistent with PM alleles going nearly to fixation in hybrid replicates and male morphological data were concordant with a shift toward PM values. Results were strikingly different from a recent study of a different pair of populations showing extensive introgression and superior fitness in hybrid populations. This demonstrates how longterm consequences of population mixing depend on the relative fitness and level of compatibility between hybridizing populations.

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“…1), the backcrosses produced by this particular pair of populations showed high fitness and this may have largely contributed to the recovery from outbreeding depression. Recent evidence shows that Tigriopus populations may harbor an epistatic load of maladapted gene combinations so that hybridization may create gene combinations that are both better and worse than those of the parental populations (Edmands et al 2009). This is consistent with scenario number four in which selection promotes recombinant genotypes with Bold numbers indicate alleles in excess of expected frequencies.…”

Section: Duration Of Outbreeding Depressionmentioning

confidence: 98%

Long-term experimental hybrid swarms between moderately incompatible Tigriopus californicus populations: hybrid inferiority in early generations yields to hybrid superiority in later generations

et al. 2011

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The deleterious effects of hybridization are a serious concern for the conservation and management of species, particularly when populations mix as a result of human activity. Outbreeding depression is the typical result observed in early-generation interpopulation hybrids of Tigriopus californicus. We examined both controlled crosses and long-term, freely-mating, experimental hybrid populations composed of southern California populations Royal Palms (RP) and San Diego (SD). Controlled crosses included parentals plus all reciprocal F1, F2, F3 and backcross cohorts, and only F2 cohorts showed significant declines in fitness compared to midparent values, indicating recovery in the F3. For long-term studies, four treatment groups were initiated: 100% RP, 100% SD, 50% RP: 50% SD, and 80% RP: 20% SD. Replicates were surveyed at 3-month intervals for morphometric, census and fitness measures. Fitness of hybrid treatments showed declines relative to midparent values followed by rapid recovery, with two hybrid replicates ultimately showing higher fitness than parentals at the final 15-month time-point (up to 20 generations). In contrast, both males and females in hybrid treatments were larger than the midparent for several morphometric characters at the first time-point, and smaller than the midparent at the final time-point, indicating a possible tradeoff between fitness and body size. Microsatellites for a subset of samples revealed extensive introgression in hybrid treatments. This adds to previous evidence that hybrid breakdown in early generations may be a temporary phenomenon followed by the persistence of highly fit recombinant genotypes.

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MALADAPTED GENE COMPLEXES WITHIN POPULATIONS OF THE INTERTIDAL COPEPODTIGRIOPUS CALIFORNICUS?

Cited by 34 publications

References 52 publications

The nature of interactions that contribute to postzygotic reproductive isolation in hybrid copepods

The nature of interactions that contribute to postzygotic reproductive isolation in hybrid copepods

Long-term experimental hybrid swarms between nearly incompatible Tigriopus californicus populations: persistent fitness problems and assimilation by the superior population

Long-term experimental hybrid swarms between moderately incompatible Tigriopus californicus populations: hybrid inferiority in early generations yields to hybrid superiority in later generations

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