Diffuse Coevolution between Two Epicephala Species (Gracillariidae) and Two Breynia Species (Phyllanthaceae)

Jing Zhang,Xiaofei Yang,Zhibo Wang,Bingbing Hu,Houhun Li,Shuxia Wang,Dmitry A Filatov

doi:10.1371/journal.pone.0041657

Abstract

The diffuse coevolution between two moth species (Epicephala lativalvaris and E. mirivalvata) and two plant species (Breynia fruticosa and B. rostrata) is reported based on field observations and indoor experiments conducted in Hainan and Fujian, China. Study results showed that the two Epicephala species jointly pollinated the two Breynia species, which led to a unique obligate pollination mutualism of two−to−two species specificity. A single Epicephala larva exclusively fed on seeds of host plants and developed to maturity by consuming all six seeds of each fruit, whereas a fraction of intact fruits were left to ensure the reproduction of plants within the whole population. Larvae of the two Epicephala species are competitive for resources; the population of E. mirivalvata is much smaller than that of E. lativalvaris, which has resulted from the differences in the female ovipositor structures and oviposition mode. The life history of Epicephala species highly coincides with the phenology of Breynia plants, and different phenology of B. fruticosa resulted in the different life history of the two Epicephala species in Hainan and Fujian. The natural hybridization of two host plants, possibly induced by the alternate pollination of two Epicephala species, is briefly discussed.

Highlights

The obligate pollination relationship between plants and their seed-parasitic pollinators is perhaps one of the most specialized cases in mutualism between insects and plants [1,2,3,4]
Our study revealed that B. fruticosa and B. rostrata distributed in Hainan and Fujian were dependent on the obligate pollination of E. lativalvaris and E. mirivalvata, forming a mutualism of two2to2two species specificity
The life history of two Epicephala species correlated with the phenology of two Breynia species; Breynia plants bloomed after dark, which coincided with the activity of Epicephala moths

Summary

Introduction

The obligate pollination relationship between plants and their seed-parasitic pollinators is perhaps one of the most specialized cases in mutualism between insects and plants [1,2,3,4]. In the known classical obligate pollination mutualism between figs–fig wasps and yuccas– yucca moths, figs and yuccas depend exclusively on pollination of fig wasps and yucca moths respectively, while sacrificing some seeds for larvae of fig wasps and yucca moths to feed [6,7]. The obligate pollination mutualism between Epicephala moths of Gracillariidae and Glochidion plants of Euphorbiaceae was discovered in 2003 [3]. Three pollination relationships were proposed [8]: (1) one Epicephala species obligately pollinates one Glochidion species, (2) two Epicephala species jointly pollinate one Glochidion species, and (3) two Epicephala species jointly pollinate two closely related parapatric Glochidion species. The most distinctive floral features associated with the pollination mode are the structures of the pistils and stamens: styles are usually reduced to entire tips and medially fused, or filaments and anthers are variously fused [9,10]

Methods

Results

Discussion

Conclusion