Bergmann and Converse Bergmann Latitudinal Clines in Arthropods: Two Ends of a Continuum?

Abstract

Two seemingly opposite evolutionary patterns of clinal variation in body size and associated life history traits exist in nature. According to Bergmann's rule, body size increases with latitude, a temperature effect. According to the converse Bergmann rule, body size decreases with latitude, a season length effect. A third pattern causally related to the latter is countergradient variation, whereby populations of a given species compensate seasonal limitations at higher latitudes by evolving faster growth and larger body sizes compared to their low latitude conspecifics. We discuss these patterns and argue that they are not mutually exclusive because they are driven by different environmental causes and proximate mechanisms; they therefore can act in conjunction, resulting in any intermediate pattern. Alternatively, Bergmann and converse Bergmann clines can be interpreted as over- and undercompensating countergradient variation, respectively. We illustrate this with data for the wide-spread yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae), which in Europe shows a Bergmann cline for size and a converse Bergmann cline (i.e., countergradient variation) for development time. A literature review of the available evidence on arthropod latitudinal clines further shows a patterned continuum of responses. Converse Bergmann clines due to end-of-season time limitations are more common in larger species with longer development times. Our study thus provides a synthesis to the controversy about the importance of Bergmann's rule and the converse Bergmann rule in nature.

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

“…Even though there is some empirical evidence for Bergmann's rule also in ectotherms, the mechanisms are not fully understood and debated (e.g. van Voorhies 1996, Mousseau 1997, Blanckenhorn & Demont 2004, Kivelä et al 2011). The trend is partly accredited to the so-called temperature-size rule, which states that ectotherms grow larger at lower temperatures (von Bertalanffy 1960, Atkinson & Sibly 1997, Chown and Gaston 1999, Angiletta et al 2004.…”

“…The opposite trend, where adult body size decreases with increasing latitude is called the converse Bergmann's rule, and has received significant both theoretical and empirical support (e.g. Mousseau 1997, Chown & Gaston 1999, Blanckenhorn & Demont 2004. The converse Bergmann's rule has in ectotherms often a strong genetic component (contrary to the temperature mediated temperature-size rule), and suggests that selection by short growth season has favored reaching reproductive maturity with small adult body size, thereby speeding up the life-cycle by decreasing the time needed for development (Blanckenhorn & Demont 2004).…”

“…Mousseau 1997, Chown & Gaston 1999, Blanckenhorn & Demont 2004. The converse Bergmann's rule has in ectotherms often a strong genetic component (contrary to the temperature mediated temperature-size rule), and suggests that selection by short growth season has favored reaching reproductive maturity with small adult body size, thereby speeding up the life-cycle by decreasing the time needed for development (Blanckenhorn & Demont 2004). 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.…”

“…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).…”

Life history evolution and cellular mechanisms associated with increased size in high‐altitude Drosophila

“…2008), but not in all studied cases (Louis et al. 1982; James and Partridge 1995; Blanckenhorn and Demont 2004; Hodkinson 2005; Collinge et al. 2006).…”