Examining the role of volatile compounds in influencing moss-microarthropod transport mutualisms

Background/Question/Methods

Sexual reproduction in non-vascular plants, including mosses, requires that unicellular free-motile sperm travel from male to female reproductive structures across the terrestrial landscape.  It is generally assumed that moss reproductive success is significantly limited by sperm transport, however recent data suggest that microarthropods may facilitate sperm transport and delivery in some mosses, functionally acting as ‘pollinating’ agents in the moss reproductive life cycle. Despite the wide-spread ecological occurrence and evolutionary significance of mosses, remarkably little is known about the factors influencing sexual systems and reproductive success in these basal land plants; even less is known about the possible chemical cues that may facilitate the recently proposed moss-microarthropod sperm transport mutualism.

Results/Conclusions

In this study, we show that mosses produce a wide diversity of volatile compounds and, similar to tracheophytes, the diversity of compounds emitted is highly species specific.   In addition, we discuss the diversity of chemical compounds released by male and female plants of two dioecious moss species, Ceratadon purpureus and Bryum argentum. Analysis of reproductively active tissues of these species, by comprehensive GC-GC TOF-MS, reveals a surprisingly complex, and sex-specific, pattern of volatile emission, similar in complexity to the volatile composition of reproductive structures observed in flowering-plants with well-established patterns of insect pollination. The nature and chemical diversity of this sex-specific pattern will be discussed.  In addition, we will present results from experimental microcosms, showing how the presence of microarthropods within the moss canopy significantly increases fertilization rates in these two cosmopolitan moss species, and we will discuss how sex-specific volatile cues may be important for mediating the moss-microarthropod transport mutualism.   Results from this work suggest that complicated plant ‘pollinator’ relationships may also be important in moss breeding systems and, like flowering plants, volatile cues may be involved in mediating this fundamental, and likely ancient, ecological association.