PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 2 - Population dynamics I: plants
Chickasaw, Mezzanine Level, Cook Convention Center
Presiders: K Klemow
Spatial vs temporal variation in survival and growth in Carduus nutans.
Metcalf, Jessica*,3, Rees, Mark1, Sheppard, Andy2, 3 Max Planck Institute for Demographic Research, Rostock, Germany1 University of Sheffield, Sheffield, UK2 CSIRO European Laboratory, Montpellier, France
ABSTRACT- Carduus nutans is a thistle native to Europe and invasive in many parts of the world, including Australia. It is monocarpic and reproduction is fatal. Rosettes are relatively short-lived, mostly flowering and dying after one year, but this species has a long lived seed bank. Such life cycle delays are an evolutionary puzzle, whose existence is generally attributed to increased fitness via bet-hedging. If conditions for germination fluctuate from year to year, and individuals only flower once, then it makes sense for individual's seeds to germinate after variable delays, thereby in a range of different years. Recent work based on seven years of data from Australia has suggested that this is indeed the case for Carduus nutans: the long-lived seed bank appears to play a vital role in buffering the population against considerable year to year variation in survival and growth. However, this analysis neglected the role of spatial variation. If the spatial variation that individual seeds may be exposed to outweighs temporal variation, then this conclusion may be flawed. Using spatial information available from this dataset, information on the average dispersal distance of Carduus nutans seeds available in the literature, survival analysis and mixture models, I explore the relative magnitudes of spatial and temporal heterogeneity that individuals are likely to be exposed to in terms of both survival and growth. I use Integral Projection Models to model the resulting demography to consider to what degree the role of each is likely to be important.
Key words: monocarp, bet-hedging, stochasticity