Parallel developments in floral adaptations to obligate moth pollination mutualism in tribe Phyllantheae (Phyllanthaceae)
This article discusses the coevolution of several species of the tribe Phyllantheae and moths of the genus Epicephala.
- Peter van Welzen, Esmée Winkel, Roderick Bouman
- 02 May 2023
- Article in PhytoKeys
Phyllanthus and several related groups have a special relationship with their pollinators: small moths that do not only help the plant, but also themselves. These plants have either male or female flowers, which means that pollination takes more work and there is no immediate reward such as nectar to enjoy for the visitors. Instead, a special system has evolved in which the moths do not only visit the plants to help pollinate them. The moths also lay their eggs in the developing fruits and the larvae eat some of the seeds. In this way, both plant and pollinator benefit. This system looks a lot like that of the fig and fig wasp. Because the relationship between moth and plant can be very species-specific, it might be possible that this led to a large-scale coevolution of both groups. For example, on the island of New Caledonia more than 100 species of Dendrophyllanthus using this same system with the moths can be found.
This system between plant and pollinator has developed independently multiple times within Phyllanthus and other groups. That is why this study investigates whether these groups also show the same trends in the evolution of the flowers. With beautiful illustrations by Esmée Winkel, we show the flower diversity. We compared the characteristics of the flowers and their place in the phylogeny developed by Roderick Bouman during his PhD. We found a number of changes that repeatedly recurred. The pistil of the female flowers had become smaller of had sometimes fused into a small cone. This looks like an adaptation to the moths’ tongue and their ovipositor used for placing the eggs. Male flowers often showed fused stamens, which were oriented vertically for easy access. With studies like these, we discover more and more about the extraordinary relationship between plants and their pollinators.