Total Species Turnover, Total Rewiring, and Traits
Using linear regression models, we explored how different species traits
and abundances influenced the total number of rewirings (bottom panel of
Figure 3). While we did not find any meaningful models regarding key
life history traits or species’ abundances, we found that species traits
related to maximum length and feeding helped explain around 35% of the
total number of rewirings. Specifically, total number of rewirings had a
significant and negative relationship with a species piscivore status
and a significant positive relationship with the interaction between
maximum length of a species and its piscivore status, Figure 4
(βMax length =0.39, p >0.05;
βPiscivore=-9.49, p <0.01;
βMax length*Piscivore=0.05, p <0.01;
adjusted R2 =0.344; Table S2). The negative
relationship between piscivore status and the total number of rewirings
suggested that non-piscivores have a greater number of rewirings than
piscivores when controlling for the maximum length of a species.
Interestingly, despite there being no overall effect of max length on
the total number of rewirings, the significant interaction indicates
that for piscivores, there is a strong positive relationship between the
total size and the number of rewirings that does not exist for the
non-piscivores.
We also note that while no specific traits or species abundances
explained the total number of species turnover connections, all fish
that contributed to species turnover (n =7) had preferences for
large rivers (compared to only 60% of the non-turnover fish).
Furthermore, Micropterus salmoides , one of the seven turnover
species, explained about 24% of the total number of species turnover
connections at a threshold of 0.5 (βMicropterus
salmoides=7.136, p <0.001;R2 =0.24).