Testing a relict distributional pattern of fen plant and terrestrial snail species at the Holocene scale: a null model approach

Abstract

Aim The term relict refers to a formerly widespread species currently occurring in refugia that provide a persistent combination of specific ecological conditions. In peatlands, direct palaeoecological evidence of relict status exists for some plant species and, in the case of calcareous sediments, for some snail species. We tested whether some species are significantly linked to old calcareous fens at the millennial scale independent of the effect of recent fen area. We focused on three organism groups -vascular plants, bryophytes and land snails -that differ in the degree of preservation of their remains in calcareous fen sediments and in their dispersal ability. Location Western Carpathians (Slovakia and the Czech Republic).Methods The sample sites comprised 47 well-preserved calcareous fens, from which we compiled complete recent species lists, measured the area and analysed radiocarbon-dated samples from the deepest sediment and from the beginning of complete deforestation, as indicated by plant and snail fossils. Using the species co-occurrences in large data sets, we identified calcareous fen specialists and compared their recent distribution patterns against a null model that controlled for the effect of fen area.Results Two land snail species, eleven vascular plant species and no bryophyte species have statistically significant affinities with old fens, independent of the effect of recent fen area. For one bryophyte and one snail, the effects of age and area are not distinguishable. Main conclusionsThe results for land snails, being abundantly preserved and easily determinable in calcareous fen deposits, are in full accordance with the direct macrofossil evidence. This suggests that our approach indirectly revealed a relict distribution of the species. Identification of species that are significantly linked to ancient localities at the millennial scale has great potential in palaeoecology for the detection of stands with old sediments, and in nature conservation as a tool for the identification of long-term-persisting rare species that infrequently colonize young sites and thus deserve priority in the protection of their habitats. From a theoretical perspective, limited dispersal from old to new localities of the same habitat can contribute to spatial effects in biotic assemblages, even at relatively fine scales.

The age of island‐like habitats impacts habitat specialist species richness

“…Further, the positive response of specialized species richness to habitat age should be inversely related to dispersal ability, being most pronounced in poorly dispersing groups that take considerable time to colonize all suitable sites. While for bryophytes and vascular plants, colder high-altitude sites may actually have increased richness due to the presence of several late-Pleistocene relicts (Rybnı´ček 1966, Ha´jek et al 2011a), a negative correlation is expected for mollusks, as only two such relicts are known from the study area (Horsa´k and Cernohorsky 2008), and many land snail species apparently do not have cryoprotective chemicals (Riddle 1983). 1).…”

The harpacticoid assemblages (Copepoda: Harpacticoida) in the Western Carpathian spring fens in relation to environmental variables and habitat age

“…In the Western Carpathian spring fens, habitat age is often positively linked to habitat size and discharge (Horsák et al, , 2015 Table 3), which is the consequence of larger spring fens with bigger water volume having a higher probability to endure Holocene climatic changes (Hájek et al, 2011b). In this study, species density and total abundance were weakly correlated with size and discharge too (R S : 0.36-0.38; Table 4).…”

Mollusc assemblages in palaeoecological reconstructions: an investigation of their predictive power using transfer function models

“…2). In contrast, the sites located in the Outer Western Carpathians are much younger (up to 800 years before present) (Hors´ak & H´ajkov´a 2005;H´ajek et al 2010). These sites are also usually small (around 150 m 2 ), which enables the frequent spreading of forest snails and plant species from the adjacent forest and shrubby habitats to central parts of the fens.…”

“…The top section of the axis includes sites located in the Inner part of the Western Carpathians. Fen sites in this region have existed throughout the Holocene (Jankovsk´a 1988;Hors´ak et al 2007;H´ajek et al 2010). They harbour several relict species (e.g.…”