2.5| Data analyses
Changes in taxa composition between each subsequent sampling period was
measured as temporal beta-diversity index (TBI). We calculated two
different TBI indices, using the percentage difference form abundance
data and the Sorensen index based on presence-absence data. The
percentage difference (D%diff ) between two sampling
periods (ti and ti+1 ) was
defined as D%diff= (B+C)/(2A+B+C), where A is the sum
of the abundance of all taxa found in both sampling periodti and ti+1 . This
represents the unscaled similarity between the two sampling periods. B
is the part of abundance of the common taxa that is higher in samples atti than at ti+1 and is the
unscaled sum of taxa losses between sampling periods. C is the
part of the abundance that is higher ti+1 than atti and is the unscaled sum of taxa gainsbetween the two sampling periods. The equation for the Sorensen index,
using presence-absence data, is the same as for the
D%diff outlined above (see Legendre (2019) for more
details). Differences in abundances and presence-absence data among
subsequent sampling occasions were tested for significance with a paired
t-test. The p‐values (based upon 9999 random permutations) were
controlled for the family-wise error rate using Holm correction. The
calculations of the TBI indices and significance tests were done in the
R package “adespatial” (Dray et al., 2019).
We analyzed data from riverine and lake habitat separately. Responses to
rotenone treatment is expected to vary among habitats. The abundance of
each invertebrate taxon is expressed as average number of specimens per
kick-sample for each sampling period at each site.