A space-for-time approach for evaluating community keystoneness in
metacommunities under disturbance
Abstract
Understanding how metacommunities respond to natural and anthropogenic
disturbances is a key objective in ecology. In this study, we introduce
a robust analytical framework to identify communities whose extirpation
triggers stronger (hereafter keystone communities) or weaker (hereafter
idle communities) cascading effects on extinction and colonization
events that ultimately drive temporal changes in compositional patterns
of the remaining communities. These cascading dynamics reflect the
impact of extirpated communities on connectivity and subsequent
dispersal dynamics. Since the framework uses spatial information on
compositional similarities to infer changes that would unfold over time
due to the extirpation of one or more communities, we describe it as a
space-for-time approach. Through mechanistic simulation models that
replicate removal experiments, we demonstrate that our framework
accurately estimates ”keystoneness”, ranking local communities by their
role in maintaining the metacommunity’s compositional patterns. As such,
our models demonstrate that the relationship between patch
characteristics and our keystoneness metric is closely linked to the
structure and dynamics of their metacommunities. A key feature of our
framework is its ability to generate community keystoneness estimates
that are statistically independent of local diversity, providing a
valuable tool for assessing the relevance and conservation value of
local communities. This is particularly important in cases where high
local diversity reflects an influx of individuals into demographic
sinks, a common consequence of human activities near natural areas. To
showcase the unique insights of this framework, we examined and
contrasted the effects of artificial light at night on the diversity and
keystoneness of a moth metacommunity sampled over two decades. We
conclude with a discussion of the framework’s potential applications and
underlying assumptions, emphasizing its relevance for addressing both
conceptual and applied ecological questions, particularly its potential
to assess the conservation value of local communities under ecological
stress.