Conclusions
Life-history stages constitute part of biological diversity and increase
complexity of food webs. As a large majority of organisms grow in size,
often over orders of magnitude, during their lifetime and experience
various degrees of ontogenetic diet shifts (Werner & Gilliam 1984),
life-history structures are important to be considered in studies on the
stability of complex food webs. In this study, we demonstrated a
positive relationship between the complexity and stability of complex
food webs; food webs with stage-structured taxa exhibited lower biomass
variability and supported more taxa than did those with unlinked stages.
These results are qualitatively in agreement with the findings by Mougi
(2017). For aquatic systems and fishes in particular, ontogenetic stages
are well recognized and studied so that including life-history stages
explicitly in models can facilitate linking theory and data.
Practically, including separate stages makes it more mechanistic and
straightforward to implement allometrically scaled functions or
parameters and differences in behaviors among stages. For example,
simulating size-selective fishing and the evolutionary impacts of such
fishing on the population dynamics of exploited species in food webs
becomes more straightforward once a life-history structure is explicitly
incorporated (e.g., Kuparinen et al. 2016). Moreover, our work
contributes a way of incorporating another aspect of interaction
diversity via life histories to the growing research on multi-layered
networks . Biomass flow via growth and reproduction forms networks of
energy transfer analogously to consumer-resource interactions. Research
on multi-layered networks has so far revealed that non-trophic
interactions (thus interaction diversity) can ameliorate or degrade the
stability of trophic interactions and the persistence of species
(reviewed by Kéfi et al. 2018). Interestingly, showed that
network structures known to stabilize mutualistic interactions became
less effective when combined with trophic interactions in a
multi-layered network. Tritrophic food chain and omnivory modules have
been shown to stabilize complex food webs (Stouffer & Bascompte 2010),
and it will be instructive to examine if they still do so when embedded
in complex food webs including ontogenetic biomass flow.