PARENT SESSION
Contributed Oral Session 117: Biodiversity: Climate and Environmental Effects
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal

At what spatial scale do environmental factors control species richness? A dissection of spectial dependence patterns in species richness.

Heegaard, Einar^{*,1, 3}, Grytnes, John-Arvid², Legendre, Pierre³, Gibson, Chris E.^{4, 5}, ¹ Bjerknes Centre for Climate Research, Bergen, Norway³ Université de Montréal, Montreal, Canada² University of Bergen, Bergen, Norway⁴ Department of Agricultural and Rural Development, Belfast, Northern Ireland⁵ Queen's University of Belfast, Belfast, Northern Ireland

ABSTRACT- We studied the relationship between scale-dependent distributions of species richness (aquatic macrophytes) and environmental conditions for 574 lakes throughout Northern Ireland. The aims of the research are summarized with two questions: 1) Is there a need for different combinations of environmental variables to explain species richness at different scales? 2) Is the effect of particular environmental variables on species richness similar across spatial scales? We dissected the spatial patterns of species richness by a Principal Coordinate of Neighbour Matrices (PCNM). This approach provides orthogonal spatial base functions representing different spatial scales. Through a regression (Generalised Linear Models) of the species richness, significant PCNM vectors were selected representing the spatial distribution of species richness. The PCNM vectors were subsequently divided into 5 groups according to the scale. The scale-dependent species richness (fitted values of richness on groups of PCNMs) was then regressed against the environmental variables in a series of multiple regressions. The results show that different sets of environmental variables explain different sets of spatial structures in species richness. The effect of individual environmental variables is, in general, similar for different groups of PCNMs, i.e. across spatial scale. Altitude is influential at broad and intermediate scales, whereas chemistry and lake size are influential at both fine and broad scales. The broad-scale trends in species richness are due to the spatially autocorrelated distribution of chemical variables and lake sizes. This means that variables influencing the physiology of species at fine scale can be important in determining the pattern across broader scales. There is a complex alteration of the environmental combinations across the scales. Species richness tends to show similar responses to the individual environmental variables across scales.

Key words: Biodiversity, Spatial scale, PCNM, Generalised Linear Models