2024年5月8日 Thorsten Wiegand 教授：Spatial aggregation, animal seed dispersal and forest dynamics

主讲人：Thorsten Wiegand 教授

主持人：沈国春 教授

时间：5月8日 14:00 

讲座地址：资环楼269室

报告摘要：

        Animal seed dispersal is a key mechanism that can generate spatial patterns in plant communities. While it has been suspected for long that spatial patterns can stabilize plant community dynamics, mathematical models as well as individual-based simulations have indicated that spatial effects alone cannot lead to coexistence. Here we argue that this apparent contradiction arises as a consequence of the common, but too narrow assumption used in most models of placing recruits close to their parents.  While this assumption mimics dispersal limitation to explain the observed spatial aggregation, it overlooks that aggregation can also be caused by clumped seed dispersal by animals. We use a symmetric individual-based simulation model of forest community dynamics (where all species share the same parameters) to study the emergence of conspecific aggregation in dependence on different assumptions on the placement of recruits, and analyze the spatial patterns of trees species in several large ForestGEO forest plots along a latitudinal gradient. Placing recruits with a dispersal kernel close to conspecific adults leads indeed to instable dynamics, but also to a negative relationship between conspecific aggregation and abundance. As a consequence, rare species still compete with themselves, thereby preventing emergence of a rare species advantage required for coexistence. In contrast, assuming clumped animal seed dispersal can lead to coexistence of otherwise identical species. Linking the theoretical results to field data reveals a latitudinal gradient in the aggregation-abundance relationship, where tropical forests show no relationship, but temperate forests a strong negative relationship. We also find a latitudinal gradient in the proportion of species that show both, mostly animal seed dispersal and an arbuscular mycorrhizal association. We hypothesize that spatial patterns generated by the activity of animal seed dispersal can have profound impacts on the stability of plant communities and should therefore be studied in greater detail in theoretical models. 

报告人简介：

        Thorsten’s research centers on spatial ecology and the role of species interactions, spatial processes and structures for population and community dynamics and biodiversity. He was PI of the ERC advanced grant SpatioDiversity (Towards a Unified Spatial Theory of Biodiversity) and is PI of the ERC advanced grant SpatioCoexistence (Towards a Spatial Theory for Species-Rich Communities). He authored the handbook of spatial point pattern analysis in ecology, programmed the software Programita (www.Programita.org) to be used for spatial analyses, and has also extensive expertise in spatially-explicit multispecies individual-based models (IBMs).