Conservation of temporary streams: The relevance of spatiotemporal variation in beta diversity

Abstract

Temporary streams are affected by increasing human alterations, and this situation is expected to worsen under global change. Understanding biodiversity trends and the contribution of sites and species to β‐diversity is of high importance in establishing conservation priorities at a regional scale. This paper focuses on aquatic macroinvertebrate biodiversity in temporary streams on the island of Mallorca, using a space–time framework. Differences in α‐diversity, spatial–temporal fluctuations of β‐diversity, local contribution to β‐diversity (LCBD) and species contribution to β‐diversity (SCBD) were examined. Data analysis shows that only the space–time approach to β‐diversity can capture the full variation of macroinvertebrate composition in temporary streams. This confirmed our hypothesis that β‐diversity patterns are better explained by incorporating the temporal dimension to the space–time approach. Regarding β‐diversity components, species replacement components always dominate over richness difference. These results imply that β‐diversity variability is mainly caused by differences in species composition, while the relative difference in richness among sites has a minor role. Consequently, the optimal conservation strategy requires the protection of several undisturbed sites. Although the LCBD analysis did not detect any keystone sites, it helped to identify those sites that should be prioritized for restoration efforts (sites with high LCBD values and low α‐diversity). We also concluded that SCBD analysis should be interpreted carefully, as rare endemic species had low SCBD values. This study demonstrated the need for incorporating temporal variability in the analysis of biodiversity patterns in highly dynamic ecosystems, such as temporary streams. It also revealed the urgency of preserving a spatial network of temporary streams under non‐impaired conditions that can act as dispersal point sources to other streams for biodiversity conservation. These insights are relevant for Mallorca and other Mediterranean islands, and for the protection of temporary rivers elsewhere.

Integrating spatiotemporal hydrological connectivity into conservation planning to protect temporary rivers

“…Concordantly, we found a very strong relationship between species occupancy and abundance with SCBD for diatoms and macroinvertebrates. This suggests that SCBD alone is not a suitable metric to assess the conservation value of a given taxa, since it is strongly driven by locally abundant and regionally common species, rather than rare or endemic species with high conservation value (Rodríguez‐Lozano et al, 2023). For example, the genus Tyrrhenoleuctra , a specialist taxon of ephemeral rivers, whose nymphal presence only occurs in winter and early spring, did not strongly contribute to SCBD in our study.…”

“…Despite some efforts have been done in some parts of the world (e.g., partial recognition in the EU Water Framework Directive and Habitats Directive; Fritz et al, 2017), they still remain neglected by policy‐makers (Datry et al, 2023; Leigh et al, 2015), and conservation plans have largely ignored them (Bruno et al, 2022). The few existing studies on the conservation of TRs argue that priority sites for conservation can vary over time in these ecosystems (Rodríguez‐Lozano et al, 2023; Ruhí et al, 2017). For example, when present, disconnected pools might play a vital role as biodiversity refugia during the dry season (e.g., fish or amphibians) (Bonada et al, 2020; Hermoso et al, 2013), or can be used as stepping‐stones habitats, favouring connections across the disconnected river network (Datry, Boulton, et al, 2017; Sánchez‐Montoya et al, 2022).…”

“…Usually, species with high SCBD values have a large, or moderate, occupancy across sites and high abundance, resulting in the most important species contributing to the uniqueness (LCBD) of the different sites (Heino & Grönroos, 2017). These beta partitioning approaches have increasingly been used for identifying conservation sites based on different organisms, such as diatoms and macroinvertebrates (Heino & Grönroos, 2017; Rodríguez‐Lozano et al, 2023; Vilmi et al, 2017), fish (Xia et al, 2022), terrestrial arthropods (Sánchez‐Montoya et al, 2020), and terrestrial plants (Kirk et al, 2021).…”