Major Patterns of Body Size Variation within Arthropod Species: Exploring the Impact of Habitat, Temperature, Latitude, Seasonality and Altitude
Abstract
Body size affects rates of most biological and ecological processes, from individual
performance to ecosystem function. Within species, emergent body size patterns have
been formalised into prominent biogeographical and biological rules, including James’
Rule (larger individuals are found at higher, colder latitudes), and the Temperature-Size
Rule (individuals reared in warmer conditions grow to a smaller adult size). Body size
also varies seasonally and with altitude. Yet, the patterns and drivers of these size
gradients, and the degree to which they co-vary and share explanatory mechanisms,
have never been systematically evaluated. We undertake the most comprehensive metaanalyses
to date of temperature- and biogeographical-size clines within arthropod
species. Aquatic species show greater reductions in body size with warming and
decreasing latitude compared to terrestrial species, likely an adaptive response to deal
with increased metabolic demand in the warm and the greater difficulty to uptake
oxygen in water than in air. Voltinism explains variation in laboratory temperature- and
latitudinal-size clines in terrestrial species. While size decreases with warming and with
decreasing latitude in multivoltine terrestrial arthropods, size increases on average in
univoltine species, consistent with predictions from size vs. season-length trade-offs. In
the globally distributed sub-class Copepoda, seasonal temperature-size (T-S) gradients
differ between current-feeding calanoids and ambush-feeding cyclopoids, suggesting
that differences in the size- and temperature-dependence of alternative feeding
strategies may influence the T-S response. Finally, through experimentation, we explore
the progression of the T-S response of Copepoda during ontogeny. The T-S response is
more strongly generated in particular life stages, and even reduced in some periods,
providing evidence that the temperature-dependence of growth and developmental rates
is modified during ontogeny. Ultimately, close similarities between T-S responses
measured in controlled laboratory conditions, and seasonal and biogeographical size
clines in the field across different arthropod taxa, suggests that these patterns share
similar selective pressures.
Authors
Horne, Curtis RobertCollections
- Theses [4121]