Comparing plant life histories using elasticity analysis: the importance of life span and the number of life-cycle stages
- 1 January 1995
- journal article
- Published by Springer Science and Business Media LLC in Oecologia
- Vol. 104 (1), 79-84
- https://doi.org/10.1007/bf00365565
Abstract
Recent studies have used transition matrix elasticity analysis to investigate the relative role of survival (L), growth (G) and fecundity (F) in determining the estimated rate of population increase for perennial plants. The relative importance of these three variables has then been used as a framework for comparing patterns of plant life history in a triangular parameter space. Here we analyse the ways in which the number of life-cycle stages chosen to describe a species (transition matrix dimensionality) might influence the interpretation of such comparisons. Because transition matrix elements describing survival (“stasis”) and growth are not independent, the number of stages used to describe a species influences their relative contribution to the population growth rate. Reduction in the number of stages increases the apparent importance of stasis relative to growth, since each becomes broader and fewer individuals make the transition to the next stage per unit time period. Analysis of a test matrix for a hypothetical tree species divided into 4–32 life-cycle stages confirms this. If the number of stages were defined in relation to species longevity so that mean residence time in each stage were approximately constant, then the elasticity of G would reflect the importance of relative growth rate to λ. An alternative, and simpler, approach to ensure comparability of results between species may be to use the same number of stages regardless of species longevity. Published studies for both herbaceous and woody species have tended to use relatively few stages to describe life cycles (herbs: n=45, \(\bar x = 6.16 \pm 4.63\) ; woody plants: n=21, \(\bar x = 8.38 \pm 3.57\) ) and so approximate this approach. By using the same number of stages regardless of longevities, the position of species along the G-L side of the triangular parameter space largely reflects differences in longevity. The extent of variation in elasticity for L, G and F within and between species may also be related to factors such as successional status and habitat. For example, the shade-tolerant woody species, Araucaria cunninghamii, shows greater importance for stasis (L), while the gap-phase congener species, Araucaria hunsteinii, shows higher values for G (although values are likely to vary with the stage of stand development).
Keywords
This publication has 20 references indexed in Scilit:
- Simple Methods for Calculating Age‐Based Life History Parameters for Stage‐Structured PopulationsEcological Monographs, 1992
- Population dynamics of the nikau palm,Rhopalostylis sapida(Wendl. et Drude), in a temperate forest remnant near Auckland, New ZealandNew Zealand Journal of Botany, 1992
- A matrix population model analysis for the tropical tree, Araucaria cunninghamiiAustralian Journal of Ecology, 1991
- Demographic Models for Leptogorgia Virgulata, A Shallow‐Water GorgonianEcology, 1991
- Comparative Plant EcologyPublished by Springer Science and Business Media LLC ,1988
- Stable Population Structure and Reproductive Value for Populations with Complex Life CyclesEcology, 1982
- The ecology of Araucaria species in New Guinea. III. Population dynamics of sample standsAustralian Journal of Ecology, 1982
- Applications of transition matrix models in forest dynamics: Araucaria in Papua New Guinea and Nothofagus in New ZealandAustral Ecology, 1979
- A general formula for the sensitivity of population growth rate to changes in life history parametersTheoretical Population Biology, 1978
- Evidence for the Existence of Three Primary Strategies in Plants and Its Relevance to Ecological and Evolutionary TheoryThe American Naturalist, 1977