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Description

Abstract

Composite traits involve multiple components that, only when combined, gain a new synergistic function. Thus, how they evolve remains a puzzle. We combined field experiments, microscopy, chemical analyses and laser Doppler vibrometry with comparative phylogenetic analyses to show that two carnivorous Nepenthes pitcher plant species convergently evolved identical adaptations in three distinct traits to acquire a new, composite trapping mechanism. Comparative analyses suggest that this new trait arose convergently via ‘spontaneous coincidence’ of the required trait combination, rather than directional selection in the component traits. Our results indicate a plausible mechanism for composite trait evolution and highlight the importance of stochastic phenotypic variation as a facilitator of evolutionary novelty.

Data were collected from 55 Nepenthes pitcher plant species from Botanical collections in the UK, Germany and Switzerland, as well as from two species (N. gracilis and N. pervillei) from natural populations in Borneo and the Seychelles. Fotos and high-speed videos were used to assess two macromorphological traits: (1) lid orientation (deviation from horizontal in °), and (2) lid loading/impact response (qualitatively from Fotos, and quantitatively from high-speed video recordings). Laser Doppler vibrometry was used for detailed analysis of lid oscillations after a drop impact on the lid. Scanning electron microscopy was used to assess surface microtopography (images are shown in the article supplementary material, Figures S1 and S2, and are not included in this dataset). Gas-chromatography mass-spectrometry was used to investigate the chemical composition of surface waxes. For detailed descriptions of the experimental methods and sampling techniques see online supplementary material, Materials and Methods.

No specialist software is required. Data files are in .csv format. Images are in .tif format. Video files are in .avi format.