Population cycles caused by overcompensating density-dependence in an annual plant

Abstract

We analyse demographic data from a seven-year study of the annual crucifer Erophila verna which showed two-year cycles of abundance in the field. The unusual behaviour of this population is shown to be the consequence of overcompensating density-dependence. Very local differences in germination succes between plots can account for observed differences in their population dynamics over the long term.

Allee effects, extinctions, and chaotic transients in simple population models

“…One source of population fluctuations is a high intrinsic rate of growth coupled with overcompensating density dependence. Models of populations with discrete generations exhibiting these characteristics can exhibit complex dynamical patterns (May, 1975;Stone, 1993;Getz, 1996) that have been observed in insect populations (Turchin and Taylor, 1992;Costantino et al, 1997;Cushing et al, 1998), annual plant populations (Symonides et al, 1986), and vertebrate populations (Grenfell et al, 1992;Turchin and Taylor, 1992;Turchin, 1993).…”

The impact of competition and litter accumulation on germination success in a model of annual plants

“…[7,16]). (8) As is well known [17,18], accumulated litter is subject to decomposition. Without it the soil would be totally covered by dead biomass, preventing any germination.…”

“…Cycles in plant population dynamics have been debated since a long time [15,18,21] and the role of litter in producing such cycles has been conjectured [17,18]. It is believed [15] that deviations from a stationary state, like oscillations or chaos, come from lagged density dependence.…”

Seed Bank in Annuals: Competition Between Banker and Non-banker Morphs

“…While external factors cause major fluctuations in plant populations, plants also face unpredictable fluctuations in the abundance of competing species and morphs of the conspecifics. It has been suggested that plant populations may fluctuate due to their intrinsically unstable dynamics (Symonides et al, 1986;Silvertown, 1991;Silvertown & Lovett Doust, 1993;Gonzales-Andujar & Hughes, 2000; but see Rees & Crawley, 1989, 1991 and of all life history strategies annuals show the greatest fluctuations (Silvertown, 1991). A seed bank has a ''storage effect'' (Chesson, 1986), which enables the renewal of the banker morph even after years of complete reproductive failure.…”