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- Dahlgren, Johan Petter, et al.
(författare)
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Actuarial senescence in a long-lived orchid challenges our current understanding of ageing
- 2016
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 283:1842
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Tidskriftsartikel (refereegranskat)abstract
- The dominant evolutionary theory of actuarial senescence-an increase in death rate with advancing age-is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain the paucity of evidence for actuarial senescence in plants. We used a 32 year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment, for individuals under two types of land use, in two climatic regions. The mortality trajectory was best approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region. At older ages, senescence was evident only when accounting for a positive effect of reproductive investment on mortality. Our results demonstrate actuarial senescence as well as a survival-reproduction trade-off in plants, and indicate that environmental context may influence senescence rates. This knowledge is crucial for understanding the evolution of demographic senescence and for models of plant population dynamics.
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| 2. |
- Shefferson, Richard P., et al.
(författare)
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Drivers of vegetative dormancy across herbaceous perennial plant species
- 2018
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Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 21:5, s. 724-733
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Tidskriftsartikel (refereegranskat)abstract
- Vegetative dormancy, that is the temporary absence of aboveground growth for 1year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
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| 3. |
- Sletvold, Nina, et al.
(författare)
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Climate warming alters effects of management on population viability of threatened species : results from a 30-year experimental study on a rare orchid
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 19:9, s. 2729-2738
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to influence the viability of populations both directly and indirectly, via species interactions. The effects of large-scale climate change are also likely to interact with local habitat conditions. Management actions designed to preserve threatened species therefore need to adapt both to the prevailing climate and local conditions. Yet, few studies have separated the direct and indirect effects of climatic variables on the viability of local populations and discussed the implications for optimal management. We used 30years of demographic data to estimate the simultaneous effects of management practice and among-year variation in four climatic variables on individual survival, growth and fecundity in one coastal and one inland population of the perennial orchid Dactylorhiza lapponica in Norway. Current management, mowing, is expected to reduce competitive interactions. Statistical models of how climate and management practice influenced vital rates were incorporated into matrix population models to quantify effects on population growth rate. Effects of climate differed between mown and control plots in both populations. In particular, population growth rate increased more strongly with summer temperature in mown plots than in control plots. Population growth rate declined with spring temperature in the inland population, and with precipitation in the coastal population, and the decline was stronger in control plots in both populations. These results illustrate that both direct and indirect effects of climate change are important for population viability and that net effects depend both on local abiotic conditions and on biotic conditions in terms of management practice and intensity of competition. The results also show that effects of management practices influencing competitive interactions can strongly depend on climatic factors. We conclude that interactions between climate and management should be considered to reliably predict future population viability and optimize conservation actions.
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