Total Rewiring, Total Turnover, and Traits
As fish species’ traits may have high plasticity (Frimpong & Angermeier
2010), detecting relationships between traits and fish interaction
dynamics can be an especially arduous task. Furthermore, given that
rewiring can be both an active and/or passive process, it
is perhaps especially difficult to identify key traits describing their
ability to rewire. For example, a predator will actively rewire
when it switches a prey item, whereas its prey passively rewires in
response. In this case, we do not expect the predator and prey to
exhibit the same traits. As traits related to the passive andactive process of rewiring likely differ, we do not expect to
find a very strong relationship between any single trait and the total
number of rewirings.
The significant relationship we found between the total number of
rewirings and the interaction between the maximum length of a species
and its piscivore status likely captures traits associated withactive rewiring. Indeed, larger species of piscivores generally
do consume a larger range of prey size than their smaller counterparts
(Gaeta et al. 2018). In addition, when holding maximum length
constant, we also captured a significant negative relationship between
piscivore status and the total number of rewirings indicating that
overall non-piscivores have a higher total number of rewirings. This
negative relationship may be in part due to many smaller non-piscivorespassively rewiring with a few larger key predators. Additionally,
as our network captures more than food web dynamics, this negative
relationship may also be capturing rewiring due to competition and other
biological interactions. If this is the case, lower trophic levels may
be more heavily competing with different species for space and food
across seasons whereas piscivores may maintain competitive interactions
with the same species year-round.
Interestingly, all species that contributed to species turnover and thus
the total number of species turnover interactions, were those that also
preferred large rivers. Given this, we strongly suspect that these fish
may be seasonally migratory species. Regarding the total number of
species turnover interactions, we were unable to find a specific trait
that explains its variability. However, we found that Micropterus
salmoides explained almost 25% of the total number of species turnover
interactions. This result is not surprising as this species has been
shown to exhibit trophic plasticity allowing them to be a successful
invasive species even in stable food webs (Almeida et al. 2012).