Spatial division of labour of Schoenoplectus americanus

Forest Research Alice Holt Lodge Wrecclesham, Farnham Surrey GU10 4LH UK
Plant Ecology (Impact Factor: 1.46). 11/2008; 199(1):55-64. DOI: 10.1007/s11258-008-9411-4
Source: OAI


If connected ramets are growing in heterogeneous environments, Division of Labour (DoL) among ramets potentially will result
in more efficient sharing of resources and an overall benefit to the plants. As a result of DoL, connected ramets growing
in a heterogeneous environment might achieve more biomass than ramets growing in a homogeneous environment. DoL has been demonstrated
to occur in a few clonal plant species, although most studies simply focussed on biomass allocation, not on actual resource
capturing such as water and nutrient consumption. The model system for our study is one in which two connected ramet groups
of Schoenoplectus americanus were placed into contrasting environments. In one treatment, the connected ramets grew in heterogeneous environments and
in the other treatment, the connected ramets grew in the same (i.e. homogeneous) environment. We manipulated two variables
(light and salinity) in the experiment. We hypothesized that ramets growing in a shaded and fresh water condition in a heterogeneous
environment would use more water than ramets growing in a similar condition but in a homogeneous environment. We further hypothesized
that ramets growing in a light and saline condition in a heterogeneous environment would assimilate less water than ramets
growing in a similar condition but in a homogeneous environment. These hypotheses are based on the assumption that ramets
in a heterogeneous environment would translocate water from ramets growing in a shaded and fresh water condition to ramets
growing in a light and saline water condition. We also hypothesized that ramets growing in heterogeneous environments achieve
larger biomass than ramets in homogeneous environments. Ramets grown in light and saline conditions in heterogeneous environments
allocated more biomass to aboveground parts, had taller shoots, larger Specific Green (leaf) Area and consumed less water
than ramets grown in similar conditions but in a homogeneous environment. Results confirm the hypothesis that connected ramets
in heterogeneous environments are specialised to capture locally abundant resources and share these with connected ramets
growing in other habitats. The result of DoL is that the entire connected ramet system benefits and achieves higher biomass.

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Available from: Makihiko Ikegami, Nov 24, 2014
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    • "For example, a genotype might forage across the landscape and develop modules that differentially specialize in the uptake of resources (reviewed in Hutchings and de Kroon 1994). As Wang et al. (2011) point out, this has been experimentally shown for Trifolium repens (Stuefer et al. 1996), Fragaria chiloensis (Roiloa et al. 2007), Potentilla anserina (van Kleunen and Stuefer 1999), Potentilla reptans (Stuefer et al. 1994), Glechoma hederacea (Birch and Hutchings 1994), Glechoma longituba (Chu et al. 2006), and Schoenoplectus americanus (Ikegami et al. 2008). "
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    ABSTRACT: Clonality in plants is widespread and includes species that span temporally and spatially heterogeneous environments. Yet, theory predicts that clonally reproducing plants evolve at slower rates, risk accumulating more mutations than sexuals, and potentially lack the benefits of DNA repair mecha- nisms afforded by meiosis. Does the apparent success of clonal plants contradict the severe costs of clonal reproduction suggested by theory? We examine how epigenetics may confer ecological advantages to clonal plants that could outweigh these evolutionary costs. Relying to various degrees on vegetative reproduction, the capacity to conserve or reverse gene regulation changes over cell divisions has clear potential for optimization of plasticity and acclimation in response to environmental variation encountered. Clonal plants may be one of the best examples of organisms taking advantage of epigenetic acclimation as an alternative to the slower mechanisms of adaptation through natural selection. If epigenetic processes are important in matching organismal response to the environment, this may prove to be a mechanism that will buffer plants against the challenges of current and future rapid environmental changes.
    Full-text · Article · Dec 2014 · Plant Ecology
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    • "Since plants are more effective in acquiring the abundant resources, division of labour between connected clonal ramets, which are negatively associated in availability of light and any edaphic factors, is believed to confer advantages on whole clonal fragments or entire clonal plants (genets), and hence to allow the plants to grow better8910. This has been experimentally shown for Trifolium repens [7,8], Fragaria chiloensis [5,6,11,12], Potentilla anserina [13], and P. reptans [14], Glechoma hederacea [15,16], G. longituba [17,18] and Schoenoplectus americanus [19]. These studies clearly showed the high potential benefits of division of labour to enhance resource capture of clonal plants and thereby to increase their performance in heterogeneous habitats compared to nonclonal plants. "
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    ABSTRACT: When growing in reciprocal patches in terms of availability of different resources, connected ramets of clonal plants will specialize to acquire and exchange locally abundant resources more efficiently. This has been termed division of labour. We asked whether division of labour can occur physiologically as well as morphologically and will increase with patch contrasts. We subjected connected and disconnected ramet pairs of Potentilla anserina to Control, Low, Medium and High patch contrast by manipulating light and nutrient levels for ramets in each pair. Little net benefit of inter-ramet connection in terms of biomass was detected. Shoot-root ratio did not differ significantly between paired ramets regardless of connection under Control, Low and Medium. Under High, however, disconnected shaded ramets with ample nutrients showed significantly larger shoot-root ratios (2.8∼6.5 fold) than fully-lit but nutrient-deficient ramets, and than their counterparts under any other treatment; conversely, fully-lit but nutrient-deficient ramets, when connected to shaded ramets with ample nutrients, had significantly larger shoot-root ratios (2.0∼4.9 fold) than the latter and than their counterparts under any other treatment. Only under High patch contrast, fully-lit ramets, if connected to shaded ones, had 8.9% higher chlorophyll content than the latter, and 22.4% higher chlorophyll content than their isolated counterparts; the similar pattern held for photosynthetic capacity under all heterogeneous treatments. Division of labour in clonal plants can be realized by ramet specialization in morphology and in physiology. However, modest ramet specialization especially in morphology among patch contrasts may suggest that division of labour will occur when the connected ramets grow in reciprocal patches between which the contrast exceeds a threshold. Probably, this threshold patch contrast is the outcome of the clone-wide cost-benefit tradeoff and is significant for risk-avoidance, especially in the disturbance-prone environments.
    Full-text · Article · Sep 2011 · PLoS ONE
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    • "Physiological integration between vegetatively connected ramets often facilitates the colonization of environments where parts of the clone experience contrasting conditions. Coastal dunes, deserts, and wetlands are often dominated by clonal perennials, whose vegetative connections permit the ''homogenization'' of patchy resources and the amelioration of environmental stress (Alpert 1996; Pennings and Callaway 2000; Ikegami et al. 2008). Translocation between ramets supported the encroachment of smooth brome into adjacent prairies ; however, sharing of resources with the mother clone inhibited the proliferation of ramets invading a nutrient-poor prairie. "
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    ABSTRACT: Predicting exotic invaders and reducing their impacts on the biodiversity and function of native ecosystems require understanding of the mechanisms that facilitate their success during key stages of invasion. We determined whether clonal growth, characteristic of the majority of successful invaders of natural areas, facilitates the proliferation of Bromus inermis (smooth brome), an exotic grass invading prairie ecosystems across the Great Plains. By manipulating the below-ground connections of proliferating rhizomes as well as the levels of soil nitrogen along the margins of clones invading northern fescue prairies in Manitoba, Canada, we hypothesized that physiological integration would most benefit ramets invading low resource environments. Severing clonal connections reduced the mass of smooth brome shoots invading native prairies and was exacerbated by the immobilization of soil nutrients with glucose. Clonal connections were equally important in the maintenance of smooth brome density and the horizontal proliferation of ramets. Our results demonstrate the role of physiological integration in the proliferation of a clonal exotic invader and may help explain the success of clonal invaders in other regions. Although integration among invading ramets suggests several possibilities for successful management, future research must continue to elucidate differences in the invasiveness of native versus exotic species as well as the persistence of clonal connections among exotic invaders.
    Preview · Article · Dec 2008 · Plant Ecology
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