Main Club, 1 March 2024

Our speaker was Emerson (Em) Lamond, an amateur bryologist. A bryologist studies bryophytes, which are mosses, liverworts, and hornworts. These are non-vascular plants, which means they have no roots or vascular tissue but instead absorb water and nutrients from the air through their surface. Because of that, they have to be tiny.

Em started with a phylogenetic tree showing the evolution of life. It showed that mosses, liverworts, hornworts, and true plants are four distinct groups, each evolving from freshwater algae separately. So, bryophytes are not plants in the strict sense, and their “leaves” are not true leaves.

Bryophytes have a pattern of alternate generations, with a gametophyte stage alternating with a sporophyte stage. A gametophyte produces sperm and eggs. The sexual union of these produces a sporophyte, which produces spores. These spores blow in the wind, thus distributing the species, and may then germinate into a gametophyte. The sporophytes are usually on taller stems and grow off the “leafy” mass of the gametophytes. The gametophytes are haploid (have one set of chromosomes), while the sporophytes are diploid (two sets). Gametophytes need water on their surface for the sperms to swim in. Ferns also have alternating generations, but their sporophyte stage is big (think of a fern leaf) compared to the tiny sporophyte of moss, for example.

Mosses differ from the other bryophytes in having their “leaves” arranged spirally. Most liverworts have a flat, prostrate “thallus” with tall sporophytes. Hornworts are similar, with horn-like sporophytes. Em showed us pictures of some of the diversity within that miniature world of bryophytes, including a moss with beautiful sporophytes like tiny oranges.

In WA, two species of moss live on the burnt trunks of cycads (zamias). One of these, endemic to WA, had not been seen for 100 years until its rediscovery. One WA species lives on the edge of salt lakes, favouring freshwater puddles. Another species, at one stage of its life cycle, looks like an aquatic alga.

Could this possibly reflect the evolutionary transition from alga to bryophyte? Invasive species tend to out-compete native bryophytes, and they are impossible to eradicate because one sporophyte might produce thousands of tiny spores.

Em talked about the ecological role of bryophytes. They help slow rocks’ breakdown and can also form a “cryptogamic crust” that holds sand together on dunes. They can be used to take up toxic heavy metals in phytoremediation programs. And sphagnum moss plays a role in peat bogs, helping them store very large amounts of carbon. Two tiny creatures can often be seen in bryophytes through a dissecting microscope. They are rotifers or “Wheel Animals” at about 1mm long, and Tardigrades or “Water Bears” at about 0.5mm long. Is there an ecological relationship here?

Unfortunately, the WA Herbarium does not have bryologists. Em suggested that Citizen Science could help fill the need for more research in this area. We can record our observations on the iNaturalist website and share them with scientists worldwide.

Mike Gregson