Tracking the ice: Subterranean harvestmen distribution matches ancient glacier margins

Mammola, Stefano; Schönhofer, Axel L.; Isaia, Marco

doi:10.1111/jzs.12264

Cited by 9 publications

(7 citation statements)

References 37 publications

(55 reference statements)

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“…In this regard, Stoch (2000) noticed a high degree of endemism among stygobitic species in the caves of Northern Italy and speculated that deep karstic fissures may have served as refuges for the aquatic fauna during the Quaternary glaciations, in line with what has been argued by Galassi (2001), Galassi et al (2009a), and by Rouch (1986) for caves located in southern France. Interestingly, similar distribution patterns influenced by glaciation cycles have been observed in other alpine terrestrial subterranean groups, including harvestmen (Mammola et al, 2019c), microwhip scorpions (Mammola et al, 2021), and beetles (Assmann et al, 2010). The marginal location of the Lessinian caves with respect to the Würmian glacier borders and the extensive networks of fractures in the vadose zone of the Lessinian karst may indeed have allowed stygobites to move deep in the Lessinian karst to seek refuge during cold periods, later recolonizing ancestral habitats after the glaciers retreated (Galassi et al, 2009a).…”

Section: Discussionsupporting

confidence: 57%

Environmental factors shaping copepod distributions in cave waters of the Lessinian unsaturated karst (NE-Italy)

et al. 2023

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The unsaturated karst represents a transitional zone connecting the land surface to the water table of the underlying saturated zone through percolating water and small perched aquifers. It constitutes a significant groundwater reservoir and hosts a high biodiversity of specialized and endemic species. Whereas investigating this ecotone can shed light on the invertebrate diversity of the whole karst system, ecological studies in the unsaturated karst have been hampered by access, mapping, and sampling challenges. We studied the unsaturated zone of 52 caves in the Lessinian Massif (NE-Italy), which is dominated by carbonate rocks interspersed with spot areas composed mainly of igneous rocks. Our aim was to understand which ecological and historical factors may have shaped the distribution of the groundwater crustacean copepods at a regional spatial scale in the Lessinian unsaturated karst. We collected 33 species belonging to the orders Harpacticoida and Cyclopoida. Species richness estimators and related species accumulation curves suggest an exhaustive sampling effort. A hydrologic analysis performed in a Geographic Information System environment divided the study area in three distinct drainage basins: Eastern Lessini, Lessinian Core, and Western Lessini. Regression analyses indicated that richness of non-stygobitic copepods (i.e., surface-water species which exploit groundwater for different purposes) was mainly driven by inter-basin differences. Richness of stygobitic copepods (i.e., obligate groundwater dwellers) was instead strongly related to lithological features and responded negatively to surface thermal variability. Next, we used a kernel density estimation to spatially explore diversity patterns in the area. The highest density of stygobitic harpacticoids was identified in the Eastern Lessinian basin, which is lithologically more heterogeneous and surrounded by practically non-aquiferous igneous rocks that may limit dispersal. Conversely, the Western Lessinian basin hosted a high density of stygobitic cyclopoid species. This spatial pattern suggests different colonization pathways for the two taxa, with a strong effect of igneous rocks in hampering dispersal of most harpacticoids. Lithological barriers seemingly did not affect non-stygobitic copepods, which were found across the whole area. Altogether, these results emphasize the key role played by the interaction of hydrological features, climate, and lithology in determining different copepod biodiversity patterns in the unsaturated karst.

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Section: Discussionsupporting

confidence: 57%

Environmental factors shaping copepod distributions in cave waters of the Lessinian unsaturated karst (NE-Italy)

et al. 2023

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“…In the case of communities at northern latitudes (greater than 48-50°N), this pattern might also reflect Pleistocene local extirpation of faunas, and the subsequent post-glacial dispersal limitation [51]. However, at this analytical scale, the influence of the distance from LGM glaciers in our models was negligible-a variable often found to be highly significant to explain the distribution of European subterranean arachnids at smaller scales [41,52]. The most important environmental gradient explaining dissimilarity in troglophile communities was mean annual temperature.…”

Section: Discussionmentioning

confidence: 79%

“…To consider the possible effects related to the biogeographical history, we further included the distance from the last glacial maximum (LGM) glacier as an additional broad-scale predictor. We constructed this raster by buffering the shapefile of LGM glaciers with distance rings of 5 km [41]. Furthermore, a shapefile of carbonate extent for the study area was obtained from the World Map of Carbonate Rock Outcrops (v.3.0).…”

Section: (B) Spider Composition and Environmental Gradientsmentioning

confidence: 99%

Local- versus broad-scale environmental drivers of continental β -diversity patterns in subterranean spider communities across Europe

et al. 2019

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Macroecologists seek to identify drivers of community turnover ( β -diversity) through broad spatial scales. However, the influence of local habitat features in driving broad-scale β -diversity patterns remains largely untested, owing to the objective challenges of associating local-scale variables to continental-framed datasets. We examined the relative contribution of local- versus broad-scale drivers of continental β -diversity patterns, using a uniquely suited dataset of cave-dwelling spider communities across Europe (35–70° latitude). Generalized dissimilarity modelling showed that geographical distance, mean annual temperature and size of the karst area in which caves occurred drove most of β -diversity, with differential contributions of each factor according to the level of subterranean specialization. Highly specialized communities were mostly influenced by geographical distance, while less specialized communities were mostly driven by mean annual temperature. Conversely, local-scale habitat features turned out to be meaningless predictors of community change, which emphasizes the idea of caves as the human accessible fraction of the extended network of fissures that more properly represents the elective habitat of the subterranean fauna. To the extent that the effect of local features turned to be inconspicuous, caves emerge as experimental model systems in which to study broad biological patterns without the confounding effect of local habitat features.

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“…Finally, we derived the distance of each cave from the Last Glacial Maximum glacier from reconstructions by Ehlers et al (2011). We interpreted this as a proxy for the influence of past glacial cycles on the current distribution of subterranean species (Assmann et al, 2010;Mammola, Schönhofer, et al, 2019).…”

Section: Environmental and Geographical Gradientsmentioning

confidence: 99%

Functional convergence underground? The scale‐dependency of community assembly processes in European cave spiders

Mammola,

Graco‐Roza,

Ballarin

et al. 2024

Global Ecol Biogeogr

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AimQuantifying the relative contribution of environmental filtering versus limiting similarity in shaping communities is challenging because these processes often act simultaneously and their effect is scale‐dependent. Focusing on caves, island‐like natural laboratories with limited environmental variability and species diversity, we tested: (i) the relative contribution of environmental filtering and limiting similarity in determining community assembly in caves; (ii) how the relative contribution of these driving forces changes along environmental gradients.LocationEurope.Time periodPresent.Major taxa studiedSubterranean spiders.MethodsWe used data on distribution and traits for European cave spiders (n = 475 communities). We estimated the trait space of each community using probabilistic hypervolumes, and obtained estimations of functional richness independent of the species richness of each community via null modelling. We model functional diversity change along environmental gradients using generalized dissimilarity modelling.ResultsSixty‐three percent of subterranean spider communities exhibited a prevalence of trait underdispersion. However, most communities displayed trait dispersion that did not depart significantly from random, suggesting that environmental filtering and limiting similarity were both exerting equally weak or strong, yet opposing influences. Overdispersed communities were primarily concentrated in southern latitudes, particularly in the Dinaric karst, where there is greater subterranean habitat availability. Pairwise comparisons of functional richness across caves revealed these effects to be strongly scale‐dependent, largely varying across gradients of cave development, elevation, precipitation, entrance size and annual temperature range. Conversely, geographical distance weakly affected trait composition, suggesting convergence in traits among communities that are far apart.Main conclusionsEven systems with stringent environmental conditions maintain the potential for trait differentiation, especially in areas of greater habitat availability. Yet, the relative influence of environmental filtering and limiting similarity change with scale, along clear environmental gradients. The interplay of these processes may explain the assembly of species‐poor subterranean communities displaying high functional specialization.

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Tracking the ice: Subterranean harvestmen distribution matches ancient glacier margins

Cited by 9 publications

References 37 publications

Environmental factors shaping copepod distributions in cave waters of the Lessinian unsaturated karst (NE-Italy)

Environmental factors shaping copepod distributions in cave waters of the Lessinian unsaturated karst (NE-Italy)

Local- versus broad-scale environmental drivers of continental β -diversity patterns in subterranean spider communities across Europe

Functional convergence underground? The scale‐dependency of community assembly processes in European cave spiders

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