How dangerous is a Drosera? Limb autotomy increases passive predation risk in crickets

Abstract

Autotomy, the voluntary shedding of body parts, is a strategy employed by many organisms to evade predation and escape entanglement. Although this strategy may allow an individual to survive one threat encounter it can come at significant cost, with studies indicating that autotomized individuals exhibit reduced fitness and increased susceptibility to active predators. However, little is known about the interplay between autotomy state and passive predation risk. We explored this interaction experimentally using prey of different size and autotomy state (laboratory‐raised crickets) exposed to a sessile predator (the carnivorous plant Drosera collina). Data indicated a strong relationship between capture likelihood and autotomy state, with capture likelihood increasing from 6% in intact crickets (those retaining both hind legs) to 31% in single autotomized and 44% in double autotomized individuals. A weaker, though still strong, relationship was observed between capture likelihood and prey size, with smaller crickets (7–32 mg) paying a markedly greater cost for limb loss than larger crickets (100–280 mg). Capture likelihood for small crickets after single‐ or double‐autotomy was increased by 56 and 72% respectively compared to intact individuals, while this risk only increased by 2 and 13% respectively for large crickets. Our results further highlight the costs of autotomy to fitness and the long‐term survival of individuals, suggesting not only that this strategy may markedly increase the susceptibility of organisms to future passive predation but also that the cost is higher for earlier ontogenetic stages.

Size matters: trap size primarily determines prey spectra differences among sympatric species of carnivorous sundews

“…These largest prey groups were conspicuously absent from the two smallest species, D. hartmeyerorum and D. nana (and from the Madagascan population of D. indica ), potentially due to large prey being able to escape from the smaller traps of these species (a process described as “differential escape”; Gibson 1991). A similarly increased likelihood of larger prey escaping Drosera traps, often facilitated by limb autotomy, was observed by Cross and Bateman (2018).…”

“…Research in this area has generally focused on the detection of competition‐driven prey selectivity in the animal kingdom and even uncovered several cases of likely sympatric speciation events (Knudsen et al 2010). However, few studies have examined the potential for prey selectivity to act as an evolutionary driver in carnivorous plants (CPs), species notorious for trapping, killing, and deriving nutritional benefit from animal prey (Juniper et al 1989, Ellison and Adamec 2018), despite evidence that CPs represent true passive predators (Cross and Bateman 2018). Despite the ecological novelty of CPs, there have been surprisingly few published studies documenting their prey spectra, particularly in terms of prey quantity and quality (i.e., the number and composition of captured prey; Darnowski et al 2018).…”

The ecology and evolution of autotomy

“…Another non‐predatory entrapment scenario can include getting stuck in tree sap/resin (hypothesized in Maginnis, ), although in certain contexts this may be considered predatory entrapment as well [e.g. arthropods caught by carnivorous sundews (Cross & Bateman, )].…”

A novel approach for reliable qualitative and quantitative prey spectra identification of carnivorous plants combining DNA metabarcoding and macro photography

“…This flaw of metabarcoding is most commonly a consequence of procedural errors resulting in cross-contamination within the DNA extraction procedure 27 , usually resulting in low read numbers. However, in-situ macro photographs may also fail to detect species if prey captured by the sundew escaped from the trap 33 , 42 , or was stolen by larger animals. In both cases, a DNA imprint left on the Drosera leaves as excretions, detached scales, hairs or, frequently, as autotomised (shedded) body parts 42 could have been detected by metabarcoding.…”