no code implementations • 19 Dec 2023 • Evan Johnson, Mark Lewis
However, two life history traits -- MPB's size-dependent fecundity and preference for large trees -- are responsible for 25% of the peak number of beetles.
no code implementations • 20 Jan 2022 • Evan Johnson, Alan Hastings
Ecologists have put forward many explanations for coexistence, but these are only partial explanations; nature is complex, so it is reasonable to assume that in any given ecological community, multiple mechanisms of coexistence are operating at the same time.
1 code implementation • 20 Jan 2022 • Evan Johnson, Alan Hastings
This can be accomplished in three steps: 1) relating the construct of coexistence to invasion growth rates, 2) mathematically partitioning the invasion growth rates into coexistence mechanisms (i. e., classes of explanations for coexistence), and 3) relating coexistence mechanisms to simple explanations for coexistence.
1 code implementation • 18 Jan 2022 • Evan Johnson, Alan Hastings
Our approach focuses on dividing one of the key conditions for the storage effect, covariance between environment and competition, into two pieces, namely that there must be a causal relationship between environment and competition, and that the effects of the environment do not change too quickly.
1 code implementation • 17 Jan 2022 • Evan Johnson, Alan Hastings
Here, using theoretical arguments and case studies, we compare four such methods for calculating coexistence mechanisms: 1) Scaling factors, the traditional approach where resident growth rates are scaled by a measure of relative sensitivity to competition, obtained by solving a system of linear equations; 2) The simple comparison, which gives equal weight to all resident species; 3) Speed conversion factors, a novel method in which resident growth rates are scaled by a ratio of generation times, and; 4) The invader-invader comparison, another novel method in which a focal species is compared to itself at high vs. low density.