Weather variation affects the dispersal of grasshoppers beyond their
elevational ranges
Abstract
1.) Understanding how abiotic conditions influence dispersal patterns of
organisms is important for understanding the degree to which species can
track and persist in the face of changing climate. 2.) The goal of this
study was to understand how weather conditions influence the dispersal
pattern of multiple non-migratory grasshopper species from lower
elevation grassland habitats in which they ¬¬complete their life-cycles
to higher elevations that extend beyond their range limits. 3.) Using
over a decade of weekly spring to late-summer field survey data along an
elevational gradient, we explored how abundance and richness of
dispersing grasshoppers were influenced by temperature, precipitation,
and wind speed and direction. We also examined how changes in population
sizes at lower elevations might influence these patterns. 4.) We
observed that the abundance of displaced grasshoppers along the gradient
declined 4-fold from the foothills to the subalpine and increased with
warmer conditions and when wind flow patterns were mild or in the
downslope direction. Thirty-eight unique grasshopper species from
lowland sites were detected as dispersers across the survey years, and
warmer years and weak upslope wind conditions also increased the
richness of these displaced grasshoppers. The pattern of grasshoppers
along the gradient was not sex biased. The positive effect of
temperature on dispersal rates was likely explained by an increase in
dispersal propensity rather than by an increase in the density of
grasshoppers at low elevation sites. 5.) The results of this study
support the hypothesis that the dispersal patterns of organisms are
influenced by changing climatic conditions themselves and as such, that
this context-dependent dispersal response should be considered when
modeling and forecasting the ability of species to respond to climate
change.