Altitudinal body size clines: latitudinal effects associated with changing seasonality

Abstract

Chown, S. L. and Klok, C. J. 2003. Altitudinal body size clines: latitudinal effects associated with changing seasonality. -Ecography 26: 445-455.Within ectotherms, increases in body size with latitude are thought to be the consequence of the effect of a decline in development temperature, which results in a larger final body size. In contrast, latitudinal declines in body size are usually ascribed to limited resources. It has been suggested that if generation time is similar to or constitutes a significant proportion of the growing season length, then season length is likely to have a considerable influence on body size because of constraints on resource availability, so resulting in a decline in body size with temperature (latitude). However, if generation time declines relative to season length, resources effectively become available for longer. Temperature influences on growth and differentiation are likely to be most significant, resulting in an increase in body size with latitude. Here, we test the hypothesis by comparing intraspecific altitudinal body size clines in a monophyletic group of weevils from two regions that differ substantially in seasonality. On the relatively aseasonal Marion Island, body size increases with altitude, whereas on the more seasonal Heard Island the opposite is found. In addition, overlapping generations on Marion Island indicate year-round resource availability, whereas more discrete generations on Heard Island indicate winter cessation of growth and development. Our data provide support for the hypothesis that the seasonality of resource availability has a major influence on body size clines. Furthermore, we argue that analysis of interspecific body size clines should be preceded by nested analyses of variance to determine the influence of clinal replacement of higher taxa on these patterns.

Seasonality, Climate Cycles and Body Size Evolution

“…Positive relations between body size and seasonality were found for muskrats [2], western bobcats [44], western rattlesnake [1], weevils [4] and sifakas [23]. In contrast, data on moose [10] and thirteen species of western Palaearctic carnivores [29] did not show clear correlations and thus did not support the hypothesis.…”

Seasonal variation in metabolic rate, flight activity and body size of Anopheles gambiae in the Sahel

“…Considering the abundance of flowers and fruits during the dry season (Müller et al, 2010), continued availability of human hosts and the hospitable temperature range, mosquitoes may amass nutritional reserves until they can later allocate them to reproduction. It is possible that these seasonal shifts in body size are mostly due to the drying of larval sites at the end of the wet season, which in turn affects larval density and thus food availability and larval growth patterns, as it is well known that growing conditions affect adult size (Lanciani, 1992;Fischer and Fiedler, 2002;Chown and Klok, 2003;Aboagye-Antwi and Tripét, 2010;Russell et al, 2011). In the riparian population, body mass was also increased in the transition period and early dry season, but fell starting in the late dry season, indicating that aestivation predictions were not closely met.…”

Population dependent effects of photoperiod on diapause related physiological traits in an invasive beetle (Leptinotarsa decemlineata)

“…The third major hypothesis explaining latitudinal variation in adult body size is through countergradient variation (also known as the latitudinal compensation mechanism) and relates to variation in development rate. By accelerating development rate in populations at high latitude or altitudes (Chown & Klok 2003), adult size remains constant when compared to populations at lower latitude or altitude (Blanckenhorn & Demont 2004).…”