Long‐term trends in gastropod abundance and biodiversity: Disentangling effects of press versus pulse disturbances

Aim: Climate-induced pulse (e.g., hurricanes) and press (e.g., global
warming) disturbances represent threats to populations, communities, and
the ecosystem services that they provide. We leveraged three decades of
annual data on tropical gastropods to quantify the effects of major
hurricanes, associated secondary succession, and global warming on
abundance, biodiversity, and species composition. Location: Luquillo
Mountains, Puerto Rico. Methods: Gastropod abundance, biodiversity, and
composition were estimated annually for each of 27 years in a tropical
montane forest that experienced three major hurricanes (Hugo, Georges, and
Maria). Generalized linear mixed-effects, linear mixed-effects, and linear
models evaluated population- and community-level responses to year,
ambient temperature, understory temperature, hurricane, and time since
hurricane. Variation partitioning determined the unique and shared
variation in biotic responses associated with temperature, disturbance,
and succession. Results: Rather than declining, gastropod abundances
generally increased through time, whereas the responses of biodiversity
were weak and scale dependent. Hurricanes and associated secondary
succession, rather than ambient atmospheric temperature, molded long-term
trends in abundances and biodiversity. Main conclusions: Global warming
over the past 30 years has not progressed sufficiently to elicit
significant responses by gastropods in the Luquillo Mountains. Rather,
effects from pulse disturbances (i.e., hurricanes) and secondary
succession currently drive long-term variation in abundance and
biodiversity. Gastropods evince high resilience in this tropical
ecosystem. Historical exposure to recurrent hurricanes likely imbued the
fauna with broad niches that make them resistant to current levels of
global warming. We predict that biotic resiliency will be challenged once
changes in temperature exceed interannual and inter-habitat differences
that typify this hurricane-mediated system, or combine with an increased
frequency of hurricanes and droughts to alter associations among
environmental characteristics that define the fundamental niches of
species. Only then might significant declines in abundance or the
appearance of novel communities characterize the gastropod fauna in the
Luquillo Mountains.