According to a new discovery by scientists, two closely-related species of Asiatic dayflower can coexist in the wild despite their competitive relationship. The new study combined field survey and artificial pollination experiments to reveal that while reproductive interference exists between the two species, Commelina communis, and Commelina communis forma ciliata, both can counter the adverse effects of this interference through self-fertilization.
These discoveries provide a different perspective on theories surrounding co-existence and suggest a new significance for the ability of plants to self-fertilize. Japan Society for the Promotion of Science Research Fellow Koki-Katsuhara made the finding and Professor Atushi Ushimaru, both part of the Kobe University Graduate School of Human Development and Environment, and they published the study in Functional Ecology.
It has long fascinated scientists how plant species have been able to coexist. When species with shared pollinators flower at the same time in the same place, it is thought that the reproductive interference caused by pollinators makes it hard for these plant species to coexist. Reproductive interference happens when pollen from another species is deposited on the pistil, female reproductive part of the flower, and competition between pollen tubes causes a decrease in seed production.
The two species of Asiatic dayflower Commelina communis (Cc) and Commelina communis forma ciliate (Ccfc), commonly found in the fields and roadsides of Japan, produce very similar-looking flowers and attract the same pollinators. In the initial stage, the scientists looked at the two species in the wild. They discovered that pollinators such as bees and hoverflies visited both species indiscriminately, and both species showed a decrease in seed production as the other species' number of flower increased. In other words, mutual reproductive interference was occurring. Also, the investigation suggested that Cc is less affected by this interference than Ccfc. This is consistent with the dominance of Cc in the areas surveyed.
Through the combination of fieldwork surveys with artificial pollination experiments, the researchers discovered that self-pollination helps to reduce the negative impact of reproductive interference. Even when one species was heavily impacted by a large number of flowers produced by the other species, through self-pollination both species managed to produce enough seeds to survive. Cc was able to produce more seeds than Ccfc through self-pollination which is probably the cause of the asymmetrical production between the species.
Scientists believe that self-pollination developed so that plants can still produce seeds even when pollinators are scarce. This study suggests that the self-pollination can also mitigate the adverse effects when pollen from other species hinders seed production. Self-pollination could also be used to explain the coexistence of plants who share pollinators. This discovery marks a step forward in shedding more light on species coexistence and gives a new perspective to the evolutionary background of self-pollination.
