Examinando por Autor "Karlsson, P. S."

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Between-population variation in size-dependent reproduction and reproductive allocation in Pinguicula vulgaris (Lentibulariaceae) and its environmental correlates
(Oikos, 2004) Méndez, M.; Karlsson, P. S.
Several important fitness components in herbaceous perennial plants are commonly related to plant size: flowering probability, reproductive allocation and fecundity. However, evidence for such size-dependence of fitness components is mostly anecdotal and unconnected to other life history traits. Here we report size-dependence for flowering probability and reproductive allocation in 11 populations of Pinguicula vulgaris and relate it to environmental factors. Flowering probability was size-dependent in all populations of P. vulgaris, and indicated the existence of a threshold size for reproduction. Populations at low altitudes and in wet soils showed a significantly higher threshold size for reproduction. Reproductive mass was also size-dependent in all populations. We found considerable between-population differences in the slope and the intercept of the regression between plant size and reproductive mass. This variation was weakly related to the environmental factors measured. In general, relationships between different size-dependent fitness components were low. Instead of showing a covariation of traits, in line with interpretations in terms of life history ¿tactics¿, P. vulgaris seemed to independently vary each size-dependent fitness component in each locality. In particular, no significant relationship was found between threshold size for reproduction and the slope of size-dependent reproductive allocation, as predicted by previous authors. Neither we found a significant influence of somatic cost of reproduction on size-dependent fitness components.
Costs and benefits of carnivory in plants: insights from the photosynthetic performance of four carnivorous plants in a subarctic environment
(Oikos, 1999) Méndez, M.; Karlsson, P. S.
We measured photosynthetic performance in four subarctic carnivorous plants, Pinguicula alpina, P. villosa, P. vulgaris and Drosera rotundifolia, in order to test if there is a cost of combining photosynthetic and trapping devices into the same organ (leaves). We compared these data with published results on photosynthetic rates in subarctic non-carnivorous plants. In P. vulgaris, an experiment of prey addition and removal further tested the existence of a short-term benefit of increased nutrient gain from prey in terms of photosynthetic efficiency. Leaf area-based photosynthetic rates (Pa) ranged 2.0 - 3.0 µmol CO2 m-2 s-1, dry mass-based photosynthetic rates (Pw) 42 - 69 nmol CO2 g-1 s-1, and photosynthetic nitrogen use efficiency (PNUE) 29 - 45 µmol CO2 mol N-1 s-1. In general, Pa and Pw of carnivorous plants increased with leaf nitrogen content. When each species was analysed separately, those relationships were weak (P. alpina and P. villosa) or non-significant (P. vulgaris and D. rotundifolia). The photosynthetic rate of carnivorous plants was lower than that of other subarctic growth forms. In addition, Pw for a given leaf nitrogen content was significantly lower in carnivorous plants than in non-carnivorous ones. No change in Pa, Pw or PNUE occurred as a result of prey capture manipulation, but treatments differed only slightly in nutrient content. Pw and PNUE showed a trend to be higher in reproductive P. alpina plants as compared to vegetative ones. In P. vulgaris, however, an increased leaf respiration was found in reproductive plants.