Rapid evolution of larval life history, adult immune function and flight muscles in a poleward‐moving damselfly

Abstract

Although a growing number of studies have documented the evolution of adult dispersal-related traits at the range edge of poleward-expanding species, we know little about evolutionary changes in immune function or traits expressed by nondispersing larvae. We investigated differentiation in larval (growth and development) and adult traits (immune function and flight-related traits) between replicated core and edge populations of the poleward-moving damselfly Coenagrion scitulum. These traits were measured on individuals reared in a common garden experiment at two different food levels, as allocation trade-offs may be easier to detect under energy shortage. Edge individuals had a faster larval life history (growth and development rates), a higher adult immune function and a nearly significant higher relative flight muscle mass. Most of the differentiation between core and edge populations remained and edge populations had a higher relative flight muscle mass when corrected for latitude-specific thermal regimes, and hence could likely be attributed to the range expansion process per se. We here for the first time document a higher immune function in individuals at the expansion front of a poleward-expanding species and documented the rarely investigated evolution of faster life histories during range expansion. The rapid multivariate evolution in these ecological relevant traits between edge and core populations is expected to translate into changed ecological interactions and therefore has the potential to generate novel eco-evolutionary dynamics at the expansion front.

Higher investment in flight morphology does not trade off with fecundity estimates in a poleward range‐expanding damselfly

“…We consider it unlikely that processes other than range expansion per se underlie the differentiation in core and edge populations documented here. However, we consider it unlikely that this would explain the higher investment in relative thorax size observed here, as results are in accordance with previous studies incorporating one other core and two other edge populations (Therry et al, 2014b(Therry et al, ,2014c and a priori theoretical predictions of a higher dispersal ability at the expansion front (Shine et al, 2011). Theory predicts an increased selection for higher dispersal ability in population dynamics with frequent extinctions and colonisations (Comins et al, 1980), which is reflected by the high frequency of fast-dispersing individuals in newly established populations in metapopulations (Hanski et al, 2006).…”

Sex-dependent effects of larval food stress on adult performance under semi-natural conditions: only a matter of size?

“…Additionally, costs of larval food stress may include alterations of metabolic rates and changes in the investment in immune defenses (De Block and Stoks 2008; Saastamoinen and Rantala 2013). Such changes may greatly affect adult performance and fitness, for example, via impacts on lifespan or flight performance (Moret 2000; Therry et al 2014; Woestmann et al 2017). Finally, body size is sexually dimorphic in the majority of insects, with females being prevalently larger than males (Stillwell et al 2010).…”

Rapid evolution of increased vulnerability to an insecticide at the expansion front in a poleward‐moving damselfly

“…) and a higher investment in immune function to avoid a reduction in dispersal rates (Therry et al. ). Note that these evolutionary changes are not driven by adaptation to the range edge or any new biotic conditions met, but are driven by the dynamic process of range expansion itself.…”

“…) and a higher investment in flight muscles and immune response (Therry et al. ) at the range front. As pesticide we used esfenvalerate, a widely applied pyrethroid insecticide (Spurlock and Lee ; Stehle and Schulz ) that is highly toxic to aquatic invertebrates (Rasmussen et al.…”