The Role of Beetle Marks and Flower Colour on Visitation by Monkey Beetles (Hopliini) in the Greater Cape Floral Region, South Africa

M Van Kleunen,J S Donaldson,J C Manning,I Nanni

doi:10.1093/aob/mcm256

Abstract

A deviation from the classical beetle pollination syndrome of dull-coloured flowers with an unpleasant scent is found in the Greater Cape Floral Region of South Africa. Here, monkey beetles (Scarabaeidae) visit brightly coloured, odourless flowers with conspicuous dark spots and centres (beetle marks). The role of flower colour and markings in attracting monkey beetles is still poorly understood. Artificial model flowers with different marking patterns were used to test the effect of beetle marks on visitation by monkey beetles. To test whether monkey beetles are conditioned to the colour of the local matrix species, model flowers of different colours were placed in populations of three differently coloured species of Iridaceae. Among all three matrix species the presence of dark markings of some kind (either centres or spots) increased visitation rates but the different matrix species differed in whether the effect was due to a dark centre or to dark spots. Monkey beetles were not conditioned for the colour of the matrix species: model colour was not significant in the Hesperantha vaginata and in the Romulea monadelpha matrices, whereas yellow model flowers were preferred over orange ones in the orange-flowered Sparaxis elegans matrix. This study is the first to demonstrate that beetle marks attract pollinating monkey beetles in the Greater Cape Floral Region. In contrast to plants with the classical beetle pollination syndrome that use floral scent as the most important attractant of pollinating beetles, plants with the monkey beetle pollination syndrome rely on visual signals, and, in some areas at least, monkey beetles favour flowers with dark beetle markings over unmarked flowers.

Highlights

Convergent evolution has resulted in the recurrent development of the same suites of floral characteristics among different plant taxa that are pollinated by the same guild of pollinators (Faegri and van der Pijl, 1979)
In the H. vaginata matrix, the model flowers were visited by three monkey beetle species, of which Clania glenlyonensis was by far the most frequent (94.6 %)
In the R. monadelpha matrix, the model flowers were visited by four monkey beetle species, of which C. glenlyonensis again predominated (91.1 %)

Summary

Introduction

Convergent evolution has resulted in the recurrent development of the same suites of floral characteristics among different plant taxa that are pollinated by the same guild of pollinators (Faegri and van der Pijl, 1979). Beetles were among the earliest pollinators of angiosperms, and plants that rely on these insects for pollination have classically been characterized by dull-coloured, chamber- or urn-shaped flowers with a strong, often unpleasant scent (Faegri and van der Pijl, 1979). A deviation from the classical beetle pollination syndrome of dull-coloured flowers with an unpleasant scent is found in the Greater Cape Floral Region of South Africa. In contrast to plants with the classical beetle pollination syndrome that use floral scent as the most important attractant of pollinating beetles, plants with the monkey beetle pollination syndrome rely on visual signals, and, in some areas at least, monkey beetles favour flowers with dark beetle markings over unmarked flowers

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