Irish Daltonia

Irish Daltonia

I have found several new populations of the rare Irish Daltonia moss

Irish Daltonia (Daltonia splachnoides) is a rare acrocarpous moss with a hyper-oceanic biogeography and is found primarily in the tropics and sub-tropics. Luckily, Ireland’s mild climate means we can find it here too. Due to its climatic demands, it is associated closely with temperate rainforest in Ireland and it is considered a good indicator of it. It has been historically quite rare, but seems to be increasing as an epiphyte on willow and conifers in upland plantations which would otherwise be pretty boring botanically.

It took me a while to find D. splachnoides, but randomly, I came across it for the first time in the Bragan mountains of co. Monaghan, growing as one might expect, on a willow along a stream set within a plantation. This marked the first Monaghan record of the moss. Thankfully, when it is sporophytic, there is nothing else like it. The leaves are rather indistinctive with the naked eye, but the calyptra on the capsule is characteristically fringed with small downward-projecting hairs, which I think look like tiny crested grebes. When the calyptrae fall off and the spores are released, the peristome teeth which border the mouth of the capsule are also long and distinctive. I also find that its growth habit appears as if the moss is melting off the tree, swept flat.

After the Monaghan find, I ventured to southwest Fermanagh which is a known D. splachnoides area, but even there I found a new site for it, and it was growing in relative abundance on willows within a humid willow/hazel woodland. Then of I went to Glenariff Forest Park, Antrim for a visit and once again on a willow growing on the bank of the steep-sided wooded ravine supported a few clumps of Irish Daltonia, the first for the county. This marks the most northwestern record of the moss to date, and it is a mighty 200 km northeast of the Monaghan record, the next closest population. It was at this point that I postulated that suitable upland habitat between the Bragan Mountains and the Glens of Antrim, such as the Sperrin and Mourne Mountains would be ideal places to do some searching.

It did not take long for me to find another new site and this time on the eastern flank of Camlough Mountain, west of Newry, co. Armagh. Reliably, on a willow within a sitka spruce plantation! How lucky I have been. I suspect other such plantations in the Ring of Gullion could support this rainforest moss. The prevailing westerly winds on this windy island, coupled with highly airborne spores, means that it was only a matter of time that the moss made its way from the southwest across the island.

Why do I care so much about this moss? The same reason why any of us care about anything: because I like it. But also, it is considered critically endangered and it also represents for me, a species of temperate rainforest which has an incredible hold on me. Plus, I am a bryologist! Common associates I have noted include common epiphytes like Radula complanata, Frullania dilatata and Metzgeria furcata, but also other oceanic to hyper-oceanic species such as Frullania tamarisci, Lejeunea patens, Colura calyptrifolia and Drepanolejeunea hamatifolia. Overall, three new vice-county firsts for D. splachnoides is pretty impressive. Counties Down and Louth are my next target regions.