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

Abstract

a b s t r a c tHarpacticoids are an important component of meiofaunal assemblages in springs. No information so far has been available on harpacticoid assemblages of the Western Carpathian spring fens, unique biotopes of high conservation value which cover a very long gradient of mineral content of groundwater, due to the variable geological background setting. Spring fens are isolated habitats of different age which can be assessed by radiocarbon dating of their basal sediment layers. This enables to test a possible effect of habitat age on species composition and species richness. In this study, we examined harpacticoid assemblages in 50 permanent tree-less spring fens (helocrenes) in the Western Carpathians (Slovakia and Czech Republic) in terms of species composition, total abundance, species density, and species richness. We tested mainly the effect of 12 explanatory variables describing water chemistry and temperature, climatic conditions, amount of nutrients, organic carbon, sediment structure, habitat age and size, using Canonical Correspondence Analyses (CCA) with stepwise forward selection. For the computation of species richness rarefaction was used. In total, 20 harpacticoid species were recorded with the total median density of 950 individuals in m −2 . Three significant explanatory variables, Ellenberg Indicator Values of plant community for nutrients, in situ measured pH, and average January temperature, explained together 19.0% (adj. 13.7%) of the total variance in the species composition data. The relationships of harpacticoids to these three explanatory variables were species specific and no uniform response of the total assemblage to the environmental variables was found (in terms of total abundance and number of species). The only exception was the influence of overall unfavourable conditions in the mineral-poor acidic Sphagnum-fens. Pilocamptus pilosus was significantly associated with a higher amount of nutrients and warmer climate. Nutrient enrichment was clearly indicated by a decrease or absence of crenophile Bryocamptus cuspidatus, and accompanied by an increase in ubiquitous Attheyella crassa. Moraria brevipes was confined to low pH, B. cuspidatus showed a high tolerance for low pH, whereas Bryocamptus echinatus preferred alkaline conditions. Despite a significant correlation between habitat age and species density we found no clear evidence that any colonisation driven process could influence the number of harpacticoid species within the tested time scale. We hypothesize that rather other habitat characteristics connected with age, i.e. habitat heterogeneity and stability, may be determinant for species richness. The occurrence of some species (e.g. P. pilosus, B. cuspidatus) was clearly geographically limited, but due to the spatial structuring of significant environmental variables no conclusion on dispersal limitations could be made.

Does predator abundance influence species diversity of equilibrium macroinvertebrate assemblages in spring fens?

“…We selected 16 environmental variables that describe important physico‐chemical characteristics of the water, substrate, and site (Table S1), to partition their effect from the contribution of predators. These variables had been previously identified as important predictors of spring invertebrate diversity and community composition when chosen from a larger set of 41 variables, either measured directly in the field, gained from laboratory analyses, or derived from database systems (Horsák et al, ; Zhai, Hřívová, & Peterka, ). Before collecting each biological sample, we measured water temperature, pH, conductivity, and dissolved oxygen (O 2 ) concentration in situ using a portable instrument (HACH HQ40d; HACH Co.).…”

“…To estimate nutrient availability and moisture, which are difficult to measure directly in the field, we used Ellenberg indicator values based on vegetation composition (Ellenberg et al, ). The nutrient availability reflects the natural degradation of sites caused by soil surface desiccation and a consequent release of nutrients (Zhai et al, ). The vegetation composition was recorded in the central 16‐m 2 area at each site during sampling.…”

Ellenberg-type indicator values for the Czech flora

“…Ellenberg indicator values for the central-European flora (Ellenberg et al 1991) are routinely used to rapidly estimate site conditions from species composition, when measured values of environmental variables are not available (Diekmann 2003). In spite of certain limitations (Schaffers & Sýkora 2000, Wamelink et al 2002, Diekmann 2003, Chytrý et al 2009, Zelený & Schaffers 2012, Bartelheimer & Poschlod 2016, Berg et al 2017, they remain a very popular tool in vegetation science and are also used for assessing ecological conditions in invertebrate research (Horsák et al 2007, Zhai et al 2015. The main reasons for their popularity include persistent difficulties with exactly measuring doi: 10.23855/preslia.2018.083 some environmental variables and absence of environmental measurements in most historical datasets of vegetation plots (Dengler et al 2011).…”

Meiofauna as a model to test paradigms of ecological metacommunity theory

“…The intercorrelation of environment and space is very common in nature and it complicates distinguishing the influence of species sorting from that of dispersal. The overlap between environment and space may be minimized by appropriate study design (e.g., Grönroos et al, 2013) but it can be rarely completely avoided (Zhai et al, 2015a). Thus, to reliably assess the role of dispersal limitations in a metacommunity, it is preferable to use a combination of several statistical methods.…”