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  • 1.
    Berg, H
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Plant Ecology.
    Redbo-Torstensson, P
    Offspring performance in Oxalis acetosella, a cleistogamous perennial herb2000In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 2, no 6, p. 638-645Article in journal (Refereed)
    Abstract [en]

    Seed weight, seed germination, seedling survival, and juvenile/adult fitness in chasmogamously (CH) and cleistogamously (CL) derived offspring of Oxalis acetosella were compared during three growing seasons, to test hypotheses of fitness differences between the offspring types accounting for the maintenance of cleistogamy. In plots at three field sites, CH and CL seeds originating from all sites were sown to compare the performance of offspring growing in their habitat of origin and offspring growing in new habitats. Seeds were also sown in pots in a common garden, to test for effects of sibling competition. CL seeds had significantly lower germination than CH seeds in the field, possibly because of lower mean seed weight due to later flowering. Since the outcrossing rate in the CH flowers of O. acetosella is not known, it is uncertain whether the lower CL germination is a consequence of inbreeding depression. CH seeds had higher germination if sown at their home sites than at new sites, while for CL seeds this made no difference; this contradicts the local adaptation hypothesis for cleistogamy. No other fitness differences were found between the offspring types, and the findings did not support the sibling competition or local adaptation hypotheses. We suggest that the maintenance of the dimorphic reproductive system in O. acetosella is not explained by offspring characteristics, but rather by the two flowering phases complementing each other in maximizing annual seed production in the face of environmental variability. It is, therefore, important to include temporal and spatial variation in studies of reproductive strategies.

  • 2.
    Méndez, Marcos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Karlsson, P. Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Equivalence of three allocation currencies as estimates of reproductive allocation and somatic cost of reproduction in Pinguicula vulgaris2007In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 9, no 4, p. 462-468Article in journal (Refereed)
    Abstract [en]

    Which is the most appropriate currency (biomass, energy, water, or some mineral nutrient) for expressing resource allocation in plants has been repeatedly discussed. Researchers need to assess to which extent interindividual, interpopulational, or interspecific comparisons of resource allocation could be affected by the allocation currency chosen. The "currency issue" is relevant to at least three related aspects of resource allocation to reproduction: (a) reproductive allocation (RA), (b) size-dependence of reproductive allocation, and (c) somatic cost of reproduction (SCR). Empirical tests have mostly dealt with the first aspect only. We examined the equivalence of estimates for the three aspects above across three different allocation currencies (dry mass, N, P) in 11 populations of Pinguicula vulgaris. For RA we studied the equivalence of allocation currencies at three scales: among individuals of the same population, between populations of the same species, and among species. Equivalence of currencies in the ranking of RA for individuals within populations was high (R-s >= 0.43) and did not strongly decrease when comparing populations or species. Excepting for size-dependence of RA, ranking of RA, or SCR between populations was equivalent for biomass and N, but not for P. Our study gives two positive guidelines for empirical plant reproductive ecologists facing the "currency issue": (1) become increasingly concerned about the "currency issue" as you increase the scale of your comparison from individuals to populations to species, and (2) avoid estimating allocation in redundant currencies (biomass and N in our case) and choose preferentially "complementary" currencies that provide a broader view of allocation patterns (biomass and P in our case).

  • 3.
    Weih, M
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Plant Ecology.
    Growth of mountain birch seedlings in early-successional patches: a year-round perspective2000In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 2, no 4, p. 428-436Article in journal (Refereed)
    Abstract [en]

    Seedlings of mountain birch (Betula pubescens ssp. czerepanovii), a subarctic tree, mainly survive and establish in early-successional patches with low vegetation cover. In particular, during the first years after seed germination, a rapid seedling growth rate is important for winter survival. Seedling growth rate is controlled by plant nitrogen (N) concentration. On a year-round perspective, the N concentration is influenced by N uptake rate during both summer and winter and by N loss during autumn. The aim of the present study was to evaluate the effects of autumn N loss and winter N uptake for seedling growth during summer. The study used young seedlings growing in situ in northern Sweden. Since the growth rate of whole plants cannot be measured in situ, it was estimated using a simple, empirical seedling growth model. The model was based on data from controlled experiments and validated using growth data from a field study. The field study included sequential seedling harvests which were carried out at two sites differing in altitude, from autumn 1994 until autumn 1996. The seedling growth model was used to simulate the effects on growth rate of autumn N losses and winter N uptake. It was found that a decrease in the amount of N lost in autumn and an increase in the amount of N taken up during winter could enhance the growth rate of mountain birch seedlings by the same order of magnitude as an increase in growing season soil temperature by 1 to 2 K.

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