Karstic Microrefugia Host Functionally Specific Ant Assemblages

Abstract

Karst landscapes are among the topographically most complex systems with various microhabitats, where species can persist despite unfavourable macro-environmental changes. These microhabitats can also function as stepping stones during range shifts. Although the enclosed depressions (dolines, sinkholes or tiankengs) of karst landscapes may act as such safe havens, data on the functional diversity of their animal assemblages are scarce. Here, we investigate the functional diversity (i.e., certain functional groups and functional traits) of ant assemblages in dolines and study whether dolines surrounded by resource-poor environments (i.e., Fagus sylvatica forests) may function as safe havens for different kinds of ants. We found that dolines have the potential to maintain distinctive ant assemblages characterised by specific functional groups and traits that are rare in the surrounding habitats. Although continuous Fagus sylvatica cover in dolines had a detrimental impact on ant assemblages, grassland dolines surrounded by grasslands or Fagus sylvatica forests supported the presence of some specific functional groups and traits. These results suggest that conservation management needs to consider the influence of vegetation characteristics not only in dolines but also on the surrounding plateau. Moderate grazing and/or mowing would be desirable in order to prevent shrub encroachment into grasslands to ensure optimal vegetation structure for ants in the long run. Therefore, proper management and conservation of these safe havens may mitigate the rate of biodiversity loss under global warming. There is a need to explore a wide variety of taxonomic groups and taxon-specific traits in parallel with the quality of the surrounding habitats when evaluating current and potential microrefugia.

Ancient Burial Mounds Provide Safe Havens for Grassland Specialist Plants in Transformed Landscapes—A Trait-Based Analysis

“…The slopes with different aspects and the top of kurgans are characterized by different microclimatic and soil conditions, resulting in contrasting microhabitats (north-facing slope: cool and humid microclimates, low amount of heat load, and high soil moisture; top and south-facing slope: hot and dry microclimates, high amount of heat load and low soil moisture; east-and westfacing slopes are characterized by dynamic and large-scale daily temporal changes regarding microclimates) within the small area of a mound (Deák et al, 2020c). Like on inselbergs (Ottaviani et al, 2016;De Smedt et al, 2018;de Paula et al, 2019;Yates et al, 2019) and in topographic depressions such as dolines (Bátori et al, 2017(Bátori et al, , 2019(Bátori et al, , 2020a, high environmental heterogeneity on kurgans also supports the co-existence of several species with different environmental preferences, resulting in high species richness within a small area (Deák et al, 2020c). The special environmental conditions provided by the kurgan microhabitats also support the development of unique vegetation (Deák et al, 2017).…”

Functional composition of ant assemblages in habitat islands is driven by habitat factors and landscape composition

“…A possible explanation is that mounds with high PC2 values were flat, while mounds with high PC1 values were high and had steep slopes, that can mitigate several negative effects received from the cropland matrix, such as fertilization, that can reduce ant diversity 50 . Steep slopes form a physical barrier against agricultural activities 24 , and also create a high level of environmental heterogeneity that can support the coexistence of several species 17 , 51 . This suggests that habitat islands embedded in croplands, but having steep slopes can support diverse ant assemblages by buffering negative effects received from the surrounding matrix and by creating environmental heterogeneity.…”

Turnover of Plant Species on an Ecological Gradient in Karst Dolines Is Reflected in Plant Traits: Chorotypes, Life Forms, Plant Architecture and Strategies

“…They offer favorable climatic conditions for cool-adapted plant species and are often treated as safe havens in the event of foreseen climatic changes [49], although it should be taken into consideration that probably some species (e.g., Sesleria autumnalis or Paeonia officinalis) might not be capable of retreating from increasing heat and drought to the bottom of dolines due to other factors, such as the lack of light and soil conditions at such sites. Dolines already offer space for various biota [8,63] that would otherwise be excluded from, or be much rarer, in the local species pool (e.g., Dentaria enneaphylos, which needs moist and cool conditions and Campanula pyramidalis, which needs rocky crevices). It is important to note that the species richness at the bottoms of the deep dolines is consistently higher compared to shallow dolines and tops on the plateau.…”

“…Horvat [2] presented vegetation zonation within various dolines over the whole Dinarides. Bátori and his team [3][4][5][6][7][8][9][10] elaborated on many aspects of dolines. They could be refugia for endangered cool-adapted plant species that have found safe havens here.…”