Selection for Phenotypic Divergence Between Diploid and Autotetraploid Heuchera Grossulariifolia

Nuismer, Scott L.; Cunningham, Bradley M.

doi:10.1111/j.0014-3820.2005.tb01062.x

Cited by 68 publications

(75 citation statements)

References 48 publications

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“…We also calculated average Xower day to evaluate diVerences in seasonal patterns of Xower production. Average Xower day estimates the day the mean Xower was produced and was calculated by weighting each of the repeated Xower counts by the census date on which the count was made (Nuismer and Cunningham 2005). Fruit number (ln + 1 transformed) includes plants that died as zero so it reXects both the survival and fecundity components of Wtness.…”

Section: Discussionmentioning

confidence: 99%

Environmental context determines within- and potential between-generation consequences of herbivory

Lin

Galloway

2010

Oecologia

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Plant tolerance to herbivory may depend on local environmental conditions. Models predict both increased and decreased tolerance with increasing resources. Transgenerational effects of herbivory may result in cross-generation tolerance. We evaluated within- and potential between-generation consequences of deer browsing in light-gap and understory habitats in the forest-edge herb, Campanulastrum americanum. Plants were assigned to deer-browsed, simulated-herbivory, and control (undamaged) treatments in the two light environments. In light gaps, plants were eaten earlier, more frequently, and had less vegetative recovery relative to uneaten plants than in the understory. As a result, browsed light-gap plants had a greater reduction in flowers and fruit than understory plants. This reduced tolerance was in part because deer browsing damaged plants in light gaps more than those in the understory. However, in the simulated herbivory treatment, where damage levels were similar between light habitats, plants growing in high-resource light gaps also had reduced tolerance of herbivory relative to those in the forest understory. C. americanum's reproductive phenology was delayed by reduced light and the loss of the apical meristem. As a result, deer-browsed plants in the light gap flowered slightly later than uneaten plants in the understory. C. americanum has a polymorphic life history and maternal flowering time influences the frequency of annual and biennial offspring. The later flowering of deer-browsed plants in light gaps will likely result in a reduced frequency of high-fitness annual offspring and an increase in lower fitness biennial offspring. Therefore, additional between-generation costs of herbivory are expected relative to those predicted by fruit number alone.

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Section: Discussionmentioning

confidence: 99%

Environmental context determines within- and potential between-generation consequences of herbivory

Lin

Galloway

2010

Oecologia

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“…This difference may reflect greater morphological divergence between cytotypes in H. grossulariifolia than C. angustifolium, which may be influenced by the time since the duplication event, the impact of genome duplication on traits affecting pollinators, and the effects of divergent selection after the duplication event (Nuismer and Cunningham 2005).…”

Section: Discussionmentioning

confidence: 99%

Pollinator-mediated assortative mating in mixed ploidy populations of Chamerion angustifolium (Onagraceae)

et al. 2006

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Establishment of polyploid individuals within diploid populations is theoretically unlikely unless polyploids are reproductively isolated, pre-zygotically, through assortative pollination. Here, we quantify the contribution of pollinator diversity and foraging behaviour to assortative pollen deposition in three mixed-ploidy populations of Chamerion angustifolium (Onagraceae). Diploids and tetraploids were not differentiated with respect to composition of insect visitors. However, foraging patterns of the three most common insect visitors (all bees) reinforced assortative pollination. Bees visited tetraploids disproportionately often and exhibited higher constancy on tetraploids in all three populations. In total, 73% of all bee flights were between flowers of the same ploidy (2x-2x, 4x-4x); 58% of all flights to diploids and 83% to tetraploids originated from diploid and tetraploid plants, respectively. Patterns of pollen deposition on stigmas mirrored pollinator foraging behaviour; 73% of all pollen on stigmas (70 and 75% of pollen on diploid and tetraploid stigmas, respectively) came from within-ploidy pollinations. These results indicate that pollinators contribute to high rates of pre-zygotic reproductive isolation. If patterns of fertilization track pollen deposition, pollinator-plant interactions may help explain the persistence and spread of tetraploids in mixed-ploidy populations.

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“…This hypothesis, however, has not been tested rigorously. Ecological studies have traditionally focused on simple comparisons of diploids and naturally occurring polyploids that diverged in the distant past (15)(16)(17)(18)(19)(20). This approach confounds phenotypic differences caused by polyploidy with those caused by genic changes arising since the time of polyploid formation (21-23).…”

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Polyploidy and ecological adaptation in wild yarrow

Ramsey

2011

Proc. Natl. Acad. Sci. U.S.A.

357

380

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Chromosome evolution in flowering plants is often punctuated by polyploidy, genome duplication events that fundamentally alter DNA content, chromosome number, and gene dosage. Polyploidy confers postzygotic reproductive isolation and is thought to drive ecological divergence and range expansion. The adaptive value of polyploidy, however, remains uncertain; ecologists have traditionally relied on observational methods that cannot distinguish effects of polyploidy per se from genic differences that accumulate after genome duplication. Here I use an experimental approach to test how polyploidy mediates ecological divergence in Achillea borealis (Asteraceae), a widespread tetraploid plant with localized hexaploid populations. In coastal California, tetraploids and hexaploids occupy mesic grassland and xeric dune habitats, respectively. Using field transplant experiments with wild-collected plants, I show that hexaploids have a fivefold fitness advantage over tetraploids in dune habitats. Parallel experiments with neohexaploids-first-generation mutants screened from a tetraploid genetic background-reveal that a 70% fitness advantage is achieved via genome duplication per se. These results suggest that genome duplication transforms features of A. borealis in a manner that confers adaptation to a novel environment.biogeography | ecological speciation | range boundary P olyploidy is a conspicuous and recurrent form of genetic variation in flowering plants (1-3). Since its discovery in the early 20th century, polyploidy has been postulated to mediate ecological differentiation, for three reasons. First, experimental polyploids in crop species exhibit altered morphological and growth characteristics (4-7). Second, in nature, closely related diploid and polyploid species have distinct geographic ranges (8, 9). Third, the occurrence of polyploidy varies across geographic regions, with highest incidences reported in alpine and arctic floras (10). Many evolutionists believe that polyploidy imbues plants with novel features that allow them to invade new environments or expand their geographic range (11)(12)(13)(14). This hypothesis, however, has not been tested rigorously. Ecological studies have traditionally focused on simple comparisons of diploids and naturally occurring polyploids that diverged in the distant past (15)(16)(17)(18)(19)(20). This approach confounds phenotypic differences caused by polyploidy with those caused by genic changes arising since the time of polyploid formation (21-23).Here I use an experimental approach to untangle the contributions of polyploidy per se to ecological divergence. Although sometimes regarded as a macroevolutionary event, genome duplication is an ongoing process in many plant populations (6, 24). First-generation polyploid mutants ("neopolyploids") form at rates equal to or exceeding the per locus mutation rate, and can thus be identified by en masse screening using flow cytometry (25,26). Because neopolyploids share a common genetic background with their diploid progenitors, the co...

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Selection for Phenotypic Divergence Between Diploid and Autotetraploid Heuchera Grossulariifolia

Cited by 68 publications

References 48 publications

Environmental context determines within- and potential between-generation consequences of herbivory

Environmental context determines within- and potential between-generation consequences of herbivory

Pollinator-mediated assortative mating in mixed ploidy populations of Chamerion angustifolium (Onagraceae)

Polyploidy and ecological adaptation in wild yarrow

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