Desiccation risk favours prevalence and diversity of tardigrade communities and influences their trophic structure in alpine ephemeral rock pools

Matteo Vecchi,Daniel Stec,Sara Calhim,Claudio Ferrari

doi:10.1007/s10750-022-04820-0

Abstract

Rock pools are ephemeral freshwater habitats characterized by their small size, well-defined boundaries, and periodic desiccation, making them ideal model systems to answer numerous ecological questions. Although there are numerous studies on rock pool fauna around the world, tardigrades have only rarely been recorded. We conducted the first tardigrade-focused study on rock pools by quantitatively extracting and classifying them from rock pools in the Italian Apennines. Rock pools were divided into three types, based on maximum duration of their inundation period. Following the patterns usually observed with rock pool invertebrates, we tested the hypothesis that desiccation has a negative effect on prevalence, abundance, and diversity of tardigrades, and thus could alter the trophic structure of their communities. In contrast to what is commonly found for other animal groups in the same type of habitat, we found that tardigrades were more diverse and prevalent in shallower, more desiccation prone, rock pools. Moreover, the trophic structure of tardigrade communities was different among the different pool types. Lastly, we also provide DNA barcodes of the most commonly found taxa. Ultimately, our study demonstrates that tardigrade communities in rock pools provide a valuable model system for the study of abiotic factors influencing meiofauna communities.

Highlights

Rock pools are eroded depressions that occur in a matrix of bedrock that accumulate a layer of unconsolidated bottom sediment by trapping material transported by runoff and wind (Brendonck et al, 2016)
In contrast to what is commonly found for other animal groups in the same type of habitat, we found that tardigrades were more diverse and prevalent in shallower, more desiccation prone, rock pools
Rock pools have been proposed as a model system in ecology and evolutionary studies (Srivastava et al, 2004; Brendonck et al, 2010) as they are small, pristine environments with clear boundaries; they can be subjected to experimental manipulations and generally host a simple community

Summary

Introduction

Rock pools are eroded depressions that occur in a matrix of bedrock that accumulate a layer of unconsolidated bottom sediment by trapping material transported by runoff and wind (Brendonck et al, 2016). Passive dispersers (for example tardigrades; Ptatscheck et al, 2018; Fontaneto, 2019) disperse mainly in a resting stage via wind and overflow of water between pools, and can be rock pool specialists. Active dispersers are those that can actively migrate (usually only during the adult stage) between different pools, have broad distributions and occur in a wide range of temporary habitats in addition to rock pools. Developmental constraints, such as development time, can prevent larger organisms and predators from occurring in pools with shorter hydroperiods, which, in turn, allows the proliferation of smaller and less competitive organisms like tardigrades adapted to ephemeral habitats (Tevis, 1966; Jeffries, 1994; Jocqué et al, 2007)

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