Fenestration: a window of opportunity for carnivorous plants

Abstract

A long-standing but controversial hypothesis assumes that carnivorous plants employ aggressive mimicry to increase their prey capture success. A possible mechanism is that pitcher plants use aggressive mimicry to deceive prey about the location of the pitcher's exit. Specifically, species from unrelated families sport fenestration, i.e. transparent windows on the upper surfaces of pitchers which might function to mimic the exit of the pitcher. This hypothesis has not been evaluated against alternative hypotheses predicting that fenestration functions to attract insects from afar. By manipulating fenestration, we show that it does not increase the number of Drosophila flies or of two ant species entering pitchers in Sarracenia minor nor their retention time or a pitcher's capture success. However, fenestration increased the number of Drosophila flies alighting on the pitcher compared with pitchers of the same plant without fenestration. We thus suggest that fenestration in S. minor is not an example of aggressive mimicry but rather functions in long-range attraction of prey. We highlight the need to evaluate aggressive mimicry relative to alternative concepts of plant-animal communication.

The cobra's tongue: Rethinking the function of the “fishtail appendage” on the pitcher plant Darlingtonia californica

“…The low capture probability of Darlingtonia was later estimated to be approximately 1.7% of vespulid wasps that had already landed on a pitcher leaf (Dixon et al, 2005). The probability of successful prey capture (compared with the overall number of visits) in other pitcher plant species is similarly low, and experimental and observational studies have failed to support the hypothesized roles of numerous other foliar traits in prey capture (Cresswell, 1993; Green and Horner, 2007; Bennett and Ellison, 2009; Schaefer and Ruxton, 2014). These findings, along with the common observation of insects feeding on pitcher leaves and avoiding capture, beg an alternative explanation for the fishtail appendage's role.…”

“…For instance, certain morphological characters of Nepenthes (Nepenthaceae) pitcher organs have been shown to serve mutualistic, rather than predatory, roles with arthropods and mammals (Clarke et al, 2010; Grafe et al, 2011; Bazile et al, 2012). Likewise, many leaf traits hypothesized to facilitate prey capture in Sarracenia (Sarraceniaceae) serve either an alternative or no detectable function upon empirical evaluation (Cresswell, 1993; Green and Horner, 2007; Bennett and Ellison, 2009; Schaefer and Ruxton, 2014).…”

Partly transparent young legume pods: Do they mimic caterpillars for defense and simultaneously enable better photosynthesis?

“…Moran et al 37 found that in the pitcher plant species Nepenthes aristolochioides, the light coming through the translucent pitcher windows causes a visual illusion of false exits, helping to keep the prey inside the trap. However, Schaefer and Ruxton 38 found that the windows in the species Sarracenia minor do not serve as false exits but rather function in long-range visual attraction of prey. (2) "Windows in traps aimed for pollination that cause pollinating trapped insects to stay longer within the trap.…”

“…Plant-animal communication via transparent tissues was considered in 2 plant types: (1) For pitcher carnivorous plants, 37,38 although via 2 different mechanisms, demonstrating that illumination through transparent plant tissues can be used in more than one way. Moran et al 37 found that in the pitcher plant species Nepenthes aristolochioides, the light coming through the translucent pitcher windows causes a visual illusion of false exits, helping to keep the prey inside the trap.…”

A classification of functional pitcher types in Nepenthes (Nepenthaceae)

“…(as pointed out by Jebb 1991), and Sarracenia psittacina Michx. (Schaefer & Ruxton 2014). In laboratory conditions Moran et al (2012) showed with N. aristolochioides that flies of Drosophila melanogaster arriving under the opaque lid, which shades the mouth, land on the vertically held peristome, feed on the nectar, and depart towards the light window at the rear and top of the pitcher, becoming stuck to the non-waxy wall and due to the viscid fluid slowly slide down towards the base where digestion occurs.…”