Regional and local impact on species diversity - from pattern to processes

Area of Science:

• Ecology
• Biodiversity Science
• Spatial Ecology

Background:

• Understanding regional factors influencing local species richness is crucial in ecology.
• Comparing local species richness (S_L) with regional species richness (S_R) is a common method to infer regional impacts.
• Linear relationships between S_R and S_L have been interpreted as strong regional influence and weak local interactions.

Purpose of the Study:

• To investigate potential biases in the comparison of local and regional species richness.
• To assess the influence of spatial sampling scale and organism body size on the S_R-S_L relationship.
• To determine if linearity in S_R-S_L plots accurately reflects the strength of local ecological interactions.

Main Methods:

• Conducted a meta-analysis of 63 published studies examining the relationship between local and regional species richness.
• Analyzed the impact of the proportion of local to regional sampling area on the linearity of S_R-S_L plots.
• Evaluated the influence of organism body size and local area size on the observed relationships.

Main Results:

• The linearity of the relationship between S_L and S_R significantly increased with a higher proportion of local to regional sampling area.
• Organism body size and local area size did not show a significant relationship with the linearity of S_R-S_L plots.
• Observed linearity in S_R-S_L plots appears to be primarily influenced by sampling design rather than ecological interactions.

Conclusions:

• The prevalence of linear relationships in local-regional species richness plots may be an artifact of sampling bias.
• Existing studies are biased towards larger organisms and high similarity between local and regional sampling areas.
• Plots of S_L versus S_R are not a reliable tool for inferring the strength of local ecological interactions.