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Title: Not all disturbances are created equal: disturbance magnitude affects predator–prey populations more than disturbance frequency
Award ID(s):
1909303
PAR ID:
10168088
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Oikos
Volume:
129
Issue:
1
ISSN:
0030-1299
Page Range / eLocation ID:
1 to 12
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract

    One objective of eco‐evolutionary dynamics is to understand how the interplay between ecology and evolution on contemporary timescales contributes to the maintenance of biodiversity. Disturbance is an ecological process that can alter species diversity through both ecological and evolutionary effects on colonization and extinction dynamics. While analogous mechanisms likely operate among genotypes within a population, empirical evidence demonstrating the relationship between disturbance and genotypic diversity remains limited. We experimentally tested how disturbance altered the colonization (gain) and extinction (loss) of genets within a population of the marine angiospermZostera marina(eelgrass). In a 2‐year field experiment conducted in northern California, we mimicked grazing disturbance by migratory geese by clipping leaves at varying frequencies during the winter months. Surprisingly, we found the greatest rates of new colonization in the absence of disturbance and that clipping had negligible effects on extinction. We hypothesize that genet extinction was not driven by selective mortality from clipping or from any stochastic loss resulting from the reduced shoot densities in clipped plots. We also hypothesize that increased flowering effort and facilitation within and among clones drove the increased colonization of new genets in the undisturbed treatment. This balance between colonization and extinction resulted in a negative relationship between clipping frequency and net changes in genotypic richness. We interpret our results in light of prior work showing that genotypic diversity increased resistance to grazing disturbance. We suggest that both directions of a feedback between disturbance and diversity occur in this system with consequences for the maintenance of eelgrass genotypic diversity.

     
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  2. Many natural disturbances have a strong climate forcing, and concern is rising about how ecosystems will respond to disturbance regimes to which they are not adapted. Novelty can arise either as attributes of the disturbance regime (e.g., frequency, severity, duration) shift beyond their historical ranges of variation or as new disturbance agents not present historically emerge. How much novelty ecological systems can absorb and whether changing disturbance regimes will lead to novel outcomes is determined by the ecological responses of communities, which are also subject to change. Powerful conceptual frameworks exist for anticipating consequences of novel disturbance regimes, but these remain challenging to apply in real-world settings. Nonlinear relationships (e.g., tipping points, feedbacks) are of particular concern because of their disproportionate effects. Future research should quantify the rise of novelty in disturbance regimes and assess the capacity of ecosystems to respond to these changes. Novel disturbance regimes will be potent catalysts for ecological change. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 54 is November 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. 
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  3. null (Ed.)