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3 April 2017

How Seasonal Warming Affects Body Size within Multivoltine Arthropod Species

Img: Peellden/Wikimedia Commons 
Among multivoltine species, defined as those which have two or more broods of offspring per year, variations within the environment can have a substantial effect on their development, due to the relatively fast rate at which they reach maturity. Their size in particular is susceptible to change in response to various external factors, chief among them being environmental temperatures, which are linked to body size variation by major biological and biogeographical rules.

Although it is known that external temperatures do have an impact on body size among such species, the exact mechanisms at work have only recently been collectively analysed in a study published on 29 March in the journal Proceedings of the Royal Society B: Biological Sciences.

The study focused on the effects of seasonal temperature variation among multivoltine arthropods, analysing the seasonal temperature-size gradients of 102 aquatic and terrestrial species from 71 locations around the globe. Being cold-blooded, arthropods rely heavily upon external temperatures in order to regulate their own internal temperature, and as such, seasonal temperature variations are intrinsically linked to their development.

Curtis Horne, from QMUL's School of Biological and Chemical Sciences, said of the study, “Understanding how body size varies with temperature is crucial to understanding and predicting how species will cope in a warming world. Changes in the body size of species can impact the ecosystem services we rely on.

“Arthropods are of huge economic and ecological value to humans. For example, they include important species of pollinators, as well as zooplankton species, the most abundant animals in our ocean that form the basis of the food chain for commercially important fish species. It is in our interest to understand how these species will respond to warming.

 “Variation between species in the sensitivity of body size to warming can also give us an indication of why this response has evolved.”

The study found that in 86% of examined species, adult size declines in warmer seasons, showing for the first time that “strong correlations exist between seasonal temperature–size gradients, laboratory responses and latitudinal–size clines, suggesting that these patterns share common drivers.” Aquatic species are particularly susceptible, likely owing to the greater oxygen limitation in water than in air, which the study suggests may force aquatic species to exhibit greater plasticity in body size. The end result is that aquatic species experience a reduction in size approximately 2.5 times greater per °C as compared to terrestrial species.

Alarmingly, while the reduction in size among terrestrial species averages at approximately 11%, this rises as high as 31% for aquatic species. This makes such species particularly vulnerable to climate change, potentially threatening global ecosystems as the primary food sources of many aquatic species begin to dwindle in number.

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.