Population structure and conservation biology of the endangered fern Trichomanes speciosum Willd. (Hymenophyllaceae) at its northern distributional limit

Abstract

Genetic diversity in the Killarney fern, Trichomanes speciosum Willd. has been investigated in south‐western Scotland, the northern‐most limit of the distribution of the sporophyte. T. speciosum is unique amongst European pteridophytes in that both phases of the life cycle are perennial and capable of vegetative propagation. Within sites no variation was revealed by allozyme electrophoresis, even where both generations were growing together. In contrast, diversity was observed among sites, with seven different multilocus phenotypes (MLPs) present in the area. Two of these MLPs covered large areas while the others were restricted to one, or few localities. Asexual reproduction of the gametophyte via gemmae is assumed to be the main means of dispersal in recent times, allowing single clones to become widespread, while the overall genetic variability may be attributed to sexual reproduction and spore dispersal in historic times under more favourable climatic conditions. We suggest that it is not inbreeding, nor lack of genetic variation that limits sporophyte production, but rather the prevailing climatic conditions. The sporophyte is extremely rare and vulnerable. However, when the gametophyte is considered, the species is neither threatened with extinction, nor does it appear to face the danger of marked genetic erosion, because the long‐lived gametophyte stage contains all of the genetic variability present in the area and can be regarded as a valuable ‘seed‐bank’.

Genetic diversity in populations ofSphagnum capillifoliumfrom the mountains of Bulgaria, and their possible refugial role

“…Just as filmy ferns, and particularly Trichomanes, have now been found in numerous sites far removed from localities where the sporophytes are known (Rumsey, Farrar & Sheffield, 1990;Rumsey et al, 1998;Rumsey et al, 1999), in the future the same could well prove to be the case for B. viridis.…”

Fine-spatial Paleoecological Investigations Towards Reconstructing Late Holocene Environmental Change, Landscape Evolution, and Farming Activity in Barrees, Beara Peninsula, Southwestern Ireland

“…T. speciosum has by far the most restricted distribution, the sporophyte stage being confi ned mainly to Ireland, where it is known from at least 30 sites (Ratcliffe et al 1993;EHSNI 2007). In Europe as a whole, it has a pronounced hyper-oceanic southern distribution pattern, with the northernmost stations located in Arran and Kintyre, SW Scotland (Rumsey et al 1999). The gametophyte generation on the other hand, which uniquely in the context of the vascular fl ora of Europe seems to occur independently of the presence of the sporophyte, is more frequent than the sporophyte and has a much a wider ecological amplitude and distribution (it has been recorded as far east as the Czech Republic; Kingston andHayes 2005, Rumsey et al 1998).…”

Habitat Assessment, Phytosociology and Conservation of the Tunbridge Filmy-fern Hymenophyllum tunbrigense (L) Sm. in its Isolated Locations in the Vosges Mountains

“…It is obviously the same for the sandstone area in the Vosges mountains, where Trichomanes speciosum gametophytes, very rarely accompanied by young sporophytes, are common nowadays (Rasbach et al 1993(Rasbach et al , 1995(Rasbach et al , 1999Je´roˆme et al 1994;Je´roˆme and Bizot 2002;Loriot et al 2003). Nevertheless, comparative genetic studies, as carried out by Rumsey et al (1999) for Trichomanes speciosum in Scotland, would provide more arguments to discuss the history of Hymenophyllum colonisation in the Vosges Mountains.…”

“…Only three species, Trichomanes speciosum, Hymenophyllum wilsonii and H. tunbrigense, are to be found in Europe (Dostal 1984;Page 1997), where they are often considered as relics of the Tertiary Age (Richards and Evans 1972;Von der Dunk 1975). Trichomanes speciosum sporophytes only occur in Europe in hyper Atlantic areas (Ratcliffe et al 1993;Page 1997;Rumsey et al 1999). However, since the first discovery of independent fern gametophytes in North 2002; Loriot et al 2002Loriot et al , 2003Je´roˆme 2003;etc.).…”