TY  - JOUR
A1  - Coutinho, Renato Mendes
A1  - Klauschies, Toni
A1  - Gaedke, Ursula
T1  - Bimodal trait distributions with large variances question the reliability of trait-based aggregate models
JF  - Theoretical ecology
N2  - Functionally diverse communities can adjust their species composition to altered environmental conditions, which may influence food web dynamics. Trait-based aggregate models cope with this complexity by ignoring details about species identities and focusing on their functional characteristics (traits). They describe the temporal changes of the aggregate properties of entire communities, including their total biomasses, mean trait values, and trait variances. The applicability of aggregate models depends on the validity of their underlying assumptions that trait distributions are normal and exhibit small variances. We investigated to what extent this can be expected to work by comparing an innovative model that accounts for the full trait distributions of predator and prey communities to a corresponding aggregate model. We used a food web structure with well-established trade-offs among traits promoting mutual adjustments between prey edibility and predator selectivity in response to selection. We altered the shape of the trade-offs to compare the outcome of the two models under different selection regimes, leading to trait distributions increasingly deviating from normality. Their biomass and trait dynamics agreed very well for stabilizing selection and reasonably well for directional selection, under which different trait values are favored at different times. However, for disruptive selection, the results of the aggregate model strongly deviated from the full trait distribution model that showed bimodal trait distributions with large variances. Hence, the outcome of aggregate models is reliable under ideal conditions but has to be questioned when confronted with more complex selection regimes and trait distributions, which are commonly observed in nature.
KW  - Fitness gradient
KW  - Communities as complex adaptive systems
KW  - Moment closure for trait-based aggregate model approaches
KW  - Multimodal trait distributions
KW  - Lumpiness in pattern formation and self-organization
KW  - Shape of trade-offs and stabilizing and disruptive selection
Y1  - 2016
U6  - https://doi.org/10.1007/s12080-016-0297-9
SN  - 1874-1738
SN  - 1874-1746
VL  - 9
SP  - 389
EP  - 408
PB  - Springer
CY  - Heidelberg
ER  -