Metapopulation dynamics of Primula vulgaris

Valverde Valdés, María Teresa (1996). Metapopulation dynamics of Primula vulgaris. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f770

Abstract

Primula vulgaris Huds. shows a patchy distribution within its forest habitat. Each patch is viewed as a local population within a metapopulation. Patches are associated with gaps in the canopy and the foundation and extinction of local populations are coupled with forest canopy dynamics. This study analyses the system formed by local populations and their forest environment with the aim of understanding the factors that affect P. vulgaris metapopulation dynamics. Data was collected on the demography of local populations in patches in different light conditions, and on the changes in the canopy brought about by the forest regeneration cycle. These were combined to model the effect of forest disturbance regime and seed dispersal on metapopulation dynamics and overall abundance of P. vulgaris in the forest.

The demography of local populations varied spatially in forest patches under different light conditions. Population growth rate (ƛ) was higher in brighter patches than in closed canopy patches. Population under closed canopy conditions may show negative growth rates which may result in eventual extinction.

The system of forest patches is a dynamic one: canopy gaps are constantly opening and closing. Canopy closure occurs at an exponential rate and the structure of the forest (i.e., proportion of patches with different light conditions) depends largely on the disturbance regime (i.e., rate of gap creation).

Simulation results showed that higher disturbance regimes produced higher metapopulation growth rate and higher overall P. vulgaris abundance in the forest. Long-distance seed dispersal reduced overall P. vulgaris abundance because it implied an amount of seed loss; however, it increased metapopulation growth rate, as it allowed the colonisation of newly-opened gaps. Under low disturbance regimes, P. vulgaris may form non-equilibrium metapopulations. Whether there is a balance between colonisations and extinctions depends on the effectiveness of seed dispersal in allowing the occupation of gaps.