The effect of geographic range position on demographic variability in annual plants
Article first published online: 19 JAN 2011
© 2011 The Authors. Journal of Ecology © 2011 British Ecological Society
Journal of Ecology
Volume 99, Issue 2, pages 591–599, March 2011
How to Cite
Gerst, K. L., Angert, A. L. and Venable, D. L. (2011), The effect of geographic range position on demographic variability in annual plants. Journal of Ecology, 99: 591–599. doi: 10.1111/j.1365-2745.2010.01782.x
- Issue published online: 15 FEB 2011
- Article first published online: 19 JAN 2011
- Received 19 May 2010; accepted 1 December 2010 Handling Editor: Pieter Zuidema
- abundant centre model;
- annual plants;
- demographic variability;
- geographic range;
- niche modelling;
- plant population and community dynamics;
- Sonoran Desert
1. The abundant centre model predicts that species abundance will decline from the centre towards the periphery of the geographic range. Thus, we expect to find decreases from the centre towards the edge in variables related to population dynamics such as population density and reproductive output. However, evidence for this pattern is contradictory, suggesting that geographically peripheral sites may not be ecologically peripheral. Populations may thrive in pockets of suitable habitat at the edge of the range or may be locally adapted to peripheral conditions.
2. This study examines how the position of a site within geographic and climatic ranges of 13 species is related to the population dynamics at one common location, The Desert Laboratory at Tumamoc Hill, Tucson, AZ, USA.
3. We used data on survival, fecundity, germination fraction and population density from a 25-year long-term data set on winter annual plants to determine whether there was a relationship between distance to the centre of the range and population dynamics. Geographic distance was calculated by determining the distance from the Desert Laboratory to the centre of the observed range determined from locality records. Climatic distance was calculated using the niche modelling software, maxent, and subtracting the mean climatic profile for the species range from that of the Desert Laboratory.
4. There was no relationship between mean population metrics and distance metrics. We found significant relationships between some geographic distance metrics and variance in fecundity, survival and per-germinant fecundity, but not germination fraction or population density. We did not find a relationship with any metric of population dynamic variation and climatic distance.
5.Synthesis. Our results indicate that geographic distance from the centre of the range of 13 annual plant species more strongly predicts their population dynamics than climatic distance. This study reinforces the importance of examining vital rates and their variation in order to properly capture the effect of position within a range on population dynamics.