A new framework for the measurement of biodiversity (MoB) decomposes changes in species richness into scale-specific components

Talk presented at the Ecological Society of America 2016 annual meeting (Aug. 2016).
Background/Question/Methods

Little consensus has emerged regarding how
various drivers (e.g., productivity, disturbance, temperature) influence
species richness. This is due in part to the fact that the majority of studies
examine richness at a single scale and ignore how the underlying components of
richness vary. We propose a new framework for the measurement of biodiversity
(MoB) which decomposes scale-specific changes in richness into components
attributed to: 1) the number of sampled individuals, 2) the degree of evenness,
and 3) the degree of intraspecific spatial aggregation. MoB accomplishes the
richness decomposition using a nested comparison of individual-based,
sample-based, and spatially explicit sample-based rarefaction curves. Each
curve provides some unique scale-specific information on the underlying
components of richness. We demonstrate our new framework by examining plant
richness in invaded and uninvaded grasslands. 

Results/Conclusions

The traditional single-scale analysis of average
species richness indicated that invaded sites had fewer species, but rarefying
richness to an equivalent number of individuals between the treatments suggests
that the invaded sites actually have more species.  In contrast to these contradictory, single
scale results our MoB analysis uncovered scale-consistent signatures that
invasion resulted in higher evenness (i.e., a positive effect on biodiversity)
but lower individual density (i.e., a negative effect on biodiversity).
Invasion does not appear to influence richness via changes to intraspecific
spatial aggregation in our study sites. The application of the MoB approach
demonstrates how species accumulation curves can be used to decompose changes
in richness into its underlying components which provides greater ecological
insight. Additionally, MoB can be used to decipher seemly contradicting
conclusions from single scale analyses. This general approach can also be
applied to other metrics of biodiversity (e.g., phylogenetic and functional
diversity) that can be examined using accumulation curves. We believe that it
is critical for biodiversity analyses to explicitly incorporate scale, and to
recognize that changes in richness can be driven by different components of biodiversity.