Shift in predation regime mediates diversification of foraging behaviour in a dragonfly genus

Abstract

1. Behavioural adaptations to avoid and evade predators are common. Many studies have investigated population divergence in response to changes in predation regime within species, but studies exploring interspecific patterns are scant. Studies on interspecific divergence can infer common outcomes from evolutionary processes and highlight the role of environmental constraints in shaping species traits. 2. Species of the dragonfly genus Leucorrhinia underwent well‐studied shifts from habitats being dominated by predatory fish (fish lakes) to habitat being dominated by predatory invertebrates (dragonfly lakes). This change in top predators resulted in a set of adaptive trait modifications in response to the different hunting styles of both predator types: whereas predatory fish actively search and pursue prey, invertebrate predator follow a sit‐and‐wait strategy, not pursuing prey. 3. Here it is shown that the habitat shift‐related change in selection regime on larval Leucorrhinia caused species in dragonfly lakes to evolve increased larval foraging and activity, and results suggest that they lost the ability to recognise predatory fish. 4. The results of the present study highlight the impact of predators on behavioural trait diversification with habitat‐specific predation regimes selecting for distinct behavioural expression.

Inter- and Intraspecific Trait Compensation of Behavioural and Morphological Defences in a Damselfly Genus

“…Increasing lamella size represents an ineffective defence as larval burst escape swimming is not fast enough to outswim predatory fish (Convey, 1988;Stoks and De Block, 2000;Gyssels and Stoks, 2005;Strobbe et al, 2010). Reducing foraging activity on the other hand is an effective defence as it reduces the encounter rate with predatory fish and predation by fish therefore imposes strong selection on foraging activity (Werner and Anholt, 1993;Stoks and McPeek, 2006;Strobbe et al, 2011;Jiang and Mikolajewski, 2018). Conversely, fishless habitat species trade-off foraging activity for lamella size.…”

“…Investment into behavioural defences (i.e., reducing foraging activity), however, is lower in fishless habitat species. Reducing activity decreases encounter rates with predators (Werner and Anholt, 1993;Stoks and McPeek, 2006;Strobbe et al, 2011;Jiang and Mikolajewski, 2018), but carries the cost of reduced encounter rates with food and reduced growth rate (Stoks et al, 2005a,b;Biro et al, 2006). Increased activity is common in freshwater prey facing invertebrate predators compared to prey facing predatory fish [e.g., Richardson (2001), Stoks and McPeek (2006), and Jiang and Mikolajewski (2018)].…”

“…We gently introduced one larva to the bottom of the bowl and recorded behaviour after a brief adaptation time (30 s). The following six variables were recorded during observations (Jiang and Mikolajewski, 2018): (i) orientation (= total number of orientations toward prey without advancing toward the prey); (ii) advance (=total number of directed advances toward prey); (iii) strike (= total number of strikes at prey with the extendable labium); (iv) capture (=total number of successfully caught prey items); (v) walk (=total number of walks defined by movements with contact to the bottom but not in the direction of prey); and (vi) swim (=total number of swims defined by movements with no contact with the bottom but not in the direction of prey). Walk was easily distinguishable from orient and advance because larvae would adapt a lurking position whenever targetting a daphnid as prey.…”

“…The expression of behavioural and morphological defences strongly depends on the current predation regime (Laurila et al, 2004;Relyea, 2004a;Bourdeau, 2009;Mikolajewski et al, 2010;Marshall and Wund, 2017). Such different phenotypes could for instance arise through developmental plasticity [i.e., intraspecific differences; e.g., Relyea (2001), Hoverman and Relyea (2009), and Herzog et al (2016)] or can be the result of evolutionary changes [i.e., interspecific differences; e.g., Mikolajewski et al (2006), Stoks and McPeek (2006), Langerhans (2009), and Jiang and Mikolajewski (2018)]. In cases where closely related species occupy different levels of the predator gradient, we are able to study inter-and intraspecific phenotypic changes using different predator treatments in a common garden experiment and by this to compare developmental with evolutionary timescales (Mikolajewski et al, 2015a).…”

“…Thus, we also predicted intraspecific trait compensation of behavioural and morphological defences within fish habitat species but not within fishless habitat species. Prediction (c) and (d) are based on previous findings that showed that freshwater prey might show reduced or even lack responses to allopatric predator species (Richardson, 2001;Stoks et al, 2003;Åbjörnsson et al, 2004;Jiang and Mikolajewski, 2018).…”