Izquierdo-Munoz, A. | bioRxiv Science

bioRxiv2021

Meiofauna is an important, yet neglected, component of biodiversity of Posidonia oceanica

Posidonia oceanica meadows are biodiversity reservoirs and provide many ecosystem services in coastal Mediterranean regions. Marine meiofauna, on the other hand, not only represents a major component of regional marine biodiversity, but also a useful tool to address both theoretical and applied questions in ecology, evolution, and conservation. We review the meiofaunal diversity in the P. oceanica ecosystem combining a literature review and a case study. First, we gathered records of 664 species from 69 published studies as well as unpublished sources, including few species exclusive from this ecosystem. Eighteen of those studies quantified the spatial and temporal changes of species composition, highlighting habitat-specific assemblages that fluctuate following the annual changes experienced by P. oceanica. Hydrodynamics, habitat complexity, and food availability, all three inherently linked to the seagrass phenology, are recognised as the main factors at shaping the complex distribution patterns of meiofauna in the meadows. These drivers have been identified mainly from Copepoda and Nematoda, and depend ultimately on species-specific preferences. Second, we tested the generality of these observations using marine mites as a model group, showing that the same processes might be in place also for other less abundant meiofaunal groups. Overall, our study highlights an outstanding diversity of meiofauna in P. oceanica and shows its potential for future research, not only focused on exploring and describing new species of neglected meiofaunal organisms, but also providing a more complete understanding on the functioning of the iconic Mediterranean ecosystem created by P. oceanica.

ecology↗

bioRxiv2020

Habitat differences filter functional diversity of low dispersive microscopic animals

O_LIWhereas the study of patterns of distribution of microscopic animals has long been dominated by the ubiquity paradigm, we are starting to appreciate that microscopic animals are not as widespread as previously thought and that habitat preferences may have a strong role in structuring their patterns of occurrence. However, we still ignore to what extent and through which mechanisms the environment selects for specific communities or traits in microscopic animals. This gap is partly due to the lack of data on the relevant traits of many species, and partly because measuring environmental variables at an appropriate resolution may be problematic. C_LIO_LIWe here overcome both issues by analysing the functional space of marine mite communities living in a sea-grass (Posidonia oceanica) meadow across two habitats: the leaves and the matte. The strictly benthic lifestyle and the conserved morphology of mites allow for unambiguous characterization of their functional traits, while the discrete nature of the two habitats alleviates the uncertainty in their ecological characterization. C_LIO_LIOur results show that habitat filters the distribution of certain traits favouring a higher diversity, dispersion, and evenness of functional traits in the matte than in the leaves. We further observed temporal variations in the functional diversity of communities, potentially following the seasonal renovation and decay of seagrass leaves. However, in spite of the stark ecological differences between the two habitats and across seasons, the filtering effect is partial and affects mostly relative species abundances. C_LIO_LIWe conclude that in other microscopic organisms, habitat filtering might appear even more subtle especially if they are capable of long distance dispersal or occur in ecological systems where environmental variables vary continuously or fluctuate through time. Our study therefore emphasises the need of moving from a merely taxonomical toward a functional view of ecological studies of microscopic organisms if we want to achieve a mechanistic understanding of their habitat and distribution patterns. C_LI Data availability statementRaw data and R script to generate the analyses will be deposited in a public repository upon acceptance.

ecology↗