Lack of synchronized breeding success in a seabird community: extreme events, niche separation, and environmental variability

Synchrony in ecological systems, the degree to which elements respond
similarly over time or space, can inform our understanding of how
ecosystems function and how they are responding to global change. While
studies of ecological synchrony are often focused on within-species
dynamics, synchrony among species may provide important insights into how
dynamics of one species are indicative of conditions relevant to the
larger community, with both basic and applied implications. Ecological
theory suggests there may be conditions under which communities might
exhibit increased synchrony, however the degree to which these patterns
are borne out in natural systems is currently unknown. We used long-term
breeding success data from a community of Antarctic seabirds to assess the
degree of interspecific, community synchrony and the role that extreme
events play in driving these dynamics. We assessed theoretical links
between community synchrony, niche separation, and environmental
variability using data from this and three other seabird communities as
well as a simulation study. Results show that reproductive success for
individual species in the Antarctic seabird community fluctuated
relatively independently from one another, resulting in little synchrony
across this community, outside of extreme years. While an exceptionally
poor year for a given species was not necessarily associated with an
exceptionally poor year for any other species, one community-wide extreme
year existed. When compared to other seabird communities, this group of
Antarctic seabirds exhibited lower overall synchrony and higher estimated
niche separation, supporting theoretical predictions. Empirical and
simulation-derived results suggest that communities where temporal
variation is small for conditions in which species respond substantially
differently, and large for conditions in which species respond similarly,
may exhibit more synchronous dynamics. Identifying where and why
synchronous dynamics might be more apparent has the potential to inform
how ecological communities might respond to future global change.