Evolution of avian clutch size along latitudinal gradients: do seasonality, nest predation or breeding season length matter?

Authored by E M Griebeler, T Caprano, K Boehning-Gaese

Date Published: 2010

DOI: 10.1111/j.1420-9101.2010.01958.x

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative Flow charts Mathematical description

Model Code URLs: Model code not found

Abstract

Birds display a latitudinal gradient in clutch size with smaller clutches in the tropics and larger in the temperate region. Three factors have been proposed to affect this pattern: seasonality of resources (SR), nest predation and length of the breeding season (LBS). Here, we test the importance of these factors by modelling clutch size evolution within bird populations under different environmental settings. We use an individual-based ecogenetic simulation model that combines principles from population ecology and life history theory. Results suggest that increasing SR from the tropics to the poles by itself or in combination with a decreasing predation rate and LBS can generate the latitudinal gradient in clutch size. Annual fecundity increases and annual adult survival rate decreases from the tropics to the poles. We further show that the annual number of breeding attempts that (together with clutch size) determines total annual egg production is an important trait to understand latitudinal patterns in these life history characteristics. Field experiments that manipulate environmental factors have to record effects not only on clutch size, but also on annual number of breeding attempts. We use our model to predict the outcome of such experiments under different environmental settings.

Tags

Population-growth Geographic-variation Density-dependence Life-history evolution Reproductive effort Brood-manipulation experiments African sylvia warblers Tits parus-caeruleus Annual fecundity Ashmoles hypothesis