Climate, Colonisation and Celibacy: Population Structure in Central European Trichomanes speciosum (Pteridophyta)

Abstract

The Killarney fern Trichomanes speciosum Willd. (Hymenophyllaceae) is unique in possessing both extensive sexual (sporophyte and gametophyte generations present) and asexual (gametophyte only) ranges. It was first discovered in central Europe in 1993 and is represented in this area only by its perennial, vegetatively propagating gametophyte generation. Genetic variation has been investigated at 35 sites. Allozyme diversity is partitioned primarily between, not within, sites. Although genetic variation exists at a fine scale « 5 m) within some populations, the results suggest that clones were not intimately associated in these cases. The majority of sites support unique multilocus phenotypes. Where phenotypes were present at more than one site they tended to recur at the next closest site. However, similar phenotypes link eastern and western Pfiilzerwald sites up to c. 70 km apart. This pattern of diversity suggests that colonisation was not solely of a "stepping stone" or "leading edge" type. We suggest that during a climatically favourable period, probably the Atlantic hypsithermal, there may have been an explosive colonisation by long-distance dispersal from refugial areas. This was followed by a short period during which sporophyte production, sexual reproduction and local spread were possible. With climatic change, reduction in the available habitat and the loss of the sporophyte generation, different individual genets became fixed within small, favourable, but scattered, sites. The possibility that some central European sites north of the Alps acted as periglacial refugia cannot be discounted, but would appear less likely than (re-)colonisation from the Atlantic fringe.

Development of polymorphic microsatellite markers for the Killarney Fern (Vandenboschia speciosa, Hymenophyllaceae)

“…Moreover, future studies using these 10 microsatellite markers will allow questions about the biogeographic history of V. speciosa to be tested, such as the refugial status of its populations. Our results in this study show two sporophyte populations in the Iberian Peninsula—considered a glacial refuge (Bennett et al, 1991)—to be moderately diverse (AZK in the north being more diverse than COQ in the south), which contrasts with the lack of genetic diversity detected within Northern and Central European populations using allozyme markers (Rumsey et al, 1998b, 1999, 2005). …”

“…Earlier studies on the population genetics of V. speciosa have used allozymes as molecular markers and, although with low resolution, they have contributed to an understanding of the current distribution of V. speciosa (Rumsey et al, 1996(Rumsey et al, , 1998b(Rumsey et al, , 1999(Rumsey et al, , 2005. Because V. speciosa is a tetraploid species (Manton, 1950;Manton et al, 1986), the allozyme banding patterns were coded as phenotypes in all the cited studies, thus decreasing further the resolution capacity of the allozymes.…”

Genetic structure, reproductive biology and ecology of isolated populations of Asplenium csikii (Aspleniaceae, Pteridophyta)

“…At some localities the two taxa grow very closely together on the same outcrop. Rumsey et al . (1998a ) investigated the genetic diversity in isolated gametophyte colonies of T. speciosum from the same area in western Germany.…”

“…However, these gemmae are unlikely to survive long‐range transport because of irreversible desiccation ( Rumsey & Sheffield, 1996). A local clustering of genetic variation was observed in T. speciosum gametophyte populations from the same area and genetic variability was partitioned mainly between populations ( Rumsey et al ., 1998a ).…”

Distributions of vascular plants in the Czech Republic. Part 7

“…Trichomanes speciosum represents an obvious Tertiary relict. However, it is suggested that the colonies of gametophytes in central Europe arose through colonization by long-distance dispersal from refugia in Macaronesia during the Atlantic period (Rumsey et al 1998b). Gametophytes in central Europe inhabit crevices and small caves in acidic sandstone rocks.…”