Mechanism matters: the cause of fluctuations in boom-bust populations governs optimal habitat restoration strategy
Authored by Cheryl B Schultz, Elizabeth E Crone, Gina K Himes Boor, William F Morris
Date Published: 2018
DOI: 10.1002/eap.1652
Sponsors:
No sponsors listed
Platforms:
NetLogo
Model Documentation:
Other Narrative
Flow charts
Model Code URLs:
https://datadryad.org/resource/doi:10.5061/dryad.k46r2
Abstract
Many populations exhibit boom-bust dynamics in which abundance
fluctuates dramatically over time. Past research has focused on
identifying whether the cause of fluctuations is primarily exogenous,
e.g., environmental stochasticity coupled with weak density dependence,
or endogenous, e.g., over-compensatory density dependence. Far fewer
studies have addressed whether the mechanism responsible for boom-bust
dynamics matters with respect to at-risk species management. Here, we
ask whether the best strategy for restoring habitat across a landscape
differs under exogenously vs. endogenously driven boom-bust dynamics. We
used spatially explicit individual-based models to assess how butterfly
populations governed by the two mechanisms would respond to habitat
restoration strategies that varied in the level of resource patchiness,
from a single large patch to multiple patches spaced at different
distances. Our models showed that the restoration strategy that
minimized extinction risk and boom-bust dynamics would be markedly
different depending on the governing mechanism. Exogenously governed
populations fared best in a single large habitat patch, whereas for
endogenously driven populations, boom-bust dynamics were dampened and
extinction risk declined when the total restored area was split into
multiple patches with low to moderate inter-patch spacing. Adding
environmental stochasticity to the endogenous model did not alter this
result. Habitat fragmentation lowered extinction risk in the
endogenously driven populations by reducing their growth rate,
precluding both boom phases and, more importantly, bust phases. Our
findings suggest that (1) successful restoration will depend on
understanding the causes of fluctuations in at-risk populations, (2) the
level and pattern of spatiotemporal environmental heterogeneity will
also affect the ideal management approach, and (3) counterintuitively,
for at-risk species with endogenously governed boom-bust dynamics,
lowering the intrinsic population growth rate may decrease extinction
risk.
Tags
Animal
populations
Environmental stochasticity
Local extinction
Metapopulations
Insect populations
Endogenously and exogenously driven fluctuations
Irruptive dynamics
Over-compensatory density dependence
Population
cycles
Resource concentration hypothesis
Caterpillars euphydryas-phaeton
Delayed density-dependence
Checkerspot
butterflies
Baltimore checkerspot
Area requirements
Intrinsic-factors