Long-distance dispersal of aquatic invertebrates by ducks increases with propagule size

 

Migratory ducks are key dispersal agents for aquatic organisms. Some groups are, however, particularly understudied. Despite consistent evidence of the potential  role of waterbird-mediated dispersal for aquatic invertebrates, and the key role of this group in the functioning of aquatic ecosystems, most evidencece remains anecdotal - or it is restricted to the collection of viable propagule in waterbird faces collected in the wild

In the article 'Evidence that long-distance dispersal of aquatic invertebrates by ducks increases with propagule size', which got published yesterday in Freswater Biology, researchers from the Doñana Biological Station and the Netherlands Institute of Ecology (NIOO-KNAW) teamed up to explore the potential for short- and long-distance dispersal of aquatic invertebrates, using a combinsation of experimental evidence and process-based modelling .

Using seven species of aquatic invertebrates and a duck species known to feed on them in the wild (the northern shoveler) as a model system, we evaluated whether their potential for endozoochorous dispersal varies among species, and the role of propagule size and morphology (e.g., the number of protective layers) in explaining such variation.  We also tested the expectation of a lower dispersal potential for invertebrate propagules, as compared to plant seeds; and evaluated whether intra-specific variation (in particular, sexual dimorphism) influences the potential of waterbirds as dispersal vectors.

Results showed that endozoochory of invertebrate propagules by waterbirds results in frequent dispersal among wetlands (tens of km) and regular dispersal at regional scale (over a hundred km). Increasing propagule size had two contrasting effects on invertebrate dispersal potential, decreasing the frequency of dispersal (fewer seeds dispersed) but increasing the potential for long-distance dispersal.

Habitat heterogeneity increases wild ungulate resilience to climatic variation

 

Mediterranean environments are characterized by strong fluctuations in plant primary production. These fluctuations can regulate the carrying capacity of ungulate populations, but their effects may vary across spatial and temporal scales. In particular, habitat heterogeneity may allow wild ungulates to mitigate temporal fluctuations in plant production by using different resources along the year. 

In the article Landscape heterogeneity increases the stability of wild ungulate populations facing climatic variability in Mediterranean ecosystems, published last week in STOTEN, J.M. Giralt and L. Santamaría use a 15-years dataset (including remote-sensing data and ungulate population counts) to assess how temporal variability in plant primary production and livestock abundance influence the population dynamics of two wild ungulates: native red deer and introduced fallow deer. 

Results show that temporal alternation in the phenology of the four different vegetation types increased  food availability for ungulates within each year; and  complementarity in the responses of different vegetation types  increased the predictability of food availability across different years.

Domestic ungulates had positive effects on wild ungulate density at low to intermediate abundances, but high livestock densities decreased ungulate density and constrained the stability of the plant-ungulate system in response to the impact of climatic variation, particularly under climate change.

World heritage wetland site threatened by strawberry farming

 Flamencos al atardecer en la Laguna Dulce (Parque Nacional de Doñana). / Jorge Monje

 The artcile 'How Europe’s most iconic wetland could be finished off by a strawberry farming bill' has been published today  in Nature Water.

In the article, Luis Santamaría (EBD-CSIIC) and Julia Martín Ortega, a Professor in Environmental Economics from the University of Leeds, say that urgent protection is needed for the fragile Doñana wetlands, as the result of the bill which sanctions illegal strawberry production in its immediate vicinity.

Here you can see the press release prepared by University of Leeds:

World heritage wetland site threatened by strawberry farming

Los herbívoros se mueven, pero sus recursos no

 

(See English version below)

El pasado 30 de setiembre, el equipo del Grupo de Ecología Espacial estuvo presente en la Noche Europea de los Investigadores celebrada en Sevilla, desarrollando la actividad Los herbívoros se mueven, pero sus recursos no: ¿Podemos proteger la vegetación de Doñana ante el cambio climático?

Esta actividad, basada en el trabajo que desarrollamos actualmente dentro del proyecto SUMHAL-WP3 y en los resultados de otros proyectos previos (como el proyecto GRAZE), buscaba familiarizar a los participantes con los ungulados del Parque Nacional de Doñana; presentaba varios ejemplos practicos de las metodologías que usamos para investigar su comportamiento trófico, uso del espacio e interacciones con la vegetación; y mostraba algunos ejemplos de las actuaciones de gestión realizadas para reducir el impacto que genera la sobreherbivoría en este espacio protegido.

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Last September 30th, a team of the Spatial Ecology Group was present during the European Researcherers' Night in Sevilla. The presented the activity Herbivores move, but their food resources don't: Will we be able to protect Doñana's vegetation against climate change? 

The activity was based on the corrent research undertook by the SUMHAL-WP3 project, as well as in the results of previous research project such as GRAZE. It aimed at familiarizing participants with Doñana's ungulates; presenting the methodologies used to investigate their trophic behaviour, space use and their interactions with the vegetation; and showed several examples of the management measures used to reduce their impact on the vegetation of this iconic protected area.

Extending the seed dispersal effectiveness framework across the mutualism–antagonism continuum

 

The seed dispersal effectiveness (SDE) framework provides a mechanistic approach to evaluate evolutionary and ecological characteristics of animal-mediated seed dispersal, by synthesising the quantity and the quality of the dispersal that a plant species receives from each of its animal dispersers. However, the application of the SDE framework has been largely restricted to plant–frugivore interactions, whereas animal-mediated seed dispersal results from plant–disperser interactions that cover a continuum from pure mutualisms to antagonisms.

In the article "A seed dispersal effectiveness framework across the mutualism–antagonism continuum", recently published in Oikos, an international team of researchers (including Nacho Villar and Luis Santamaría from the SEG) propose an extended SDE framework aiming at including plant–disperser interactions in the full mutualism–antagonism continuum, ranging from pure mutualisms (frugivores) to conditional mutualisms (scatter-hoarding granivores and folivores) and antagonisms (pure granivores).

Examples used to illustrate how it can be applied to compare effectiveness among plant–disperser interaction types indicate that vertebrate species differ more in the number of seeds they deposit away from the mother plant (quantity), than in the effects such dispersal processes have on seed fate (quality). Scatter-hoarding granivores provide the most effective dispersal due to high removal rates, closely followed by frugivores due to high deposition rates. Folivores and pure granivores provide low quantity dispersal, but of high and moderate quality, respectively. These early comparative insights illustrate the necessity and usefulness of more standardized data collection protocols, for which we provide recommendations. 

Applying the eSDE framework can reveal broad-scale patterns across and within plant–disperser interaction types, which will advance our evolutionary understanding of plant–animal interactions. This will provide new insights into the consequence of anthropogenic impacts on vertebrate-mediated seed dispersal in a world in which plant–animal interactions are increasingly threatened.

Reference: van Leeuwen, C.H.A., Villar, N., Mendoza Sagrera, I., Green, A.J., Bakker, E.S., Soons, M.B., Galetti, M., Jansen, P.A., Nolet, B.A. and Santamaría, L. (2022), A seed dispersal effectiveness framework across the mutualism–antagonism continuum. Oikos e09254. https://doi.org/10.1111/oik.09254

Functional and phenological complementarity among vegetation types increase ecosystem resilience to climate change and grazing

 

In environments with high climatic variability such as the Mediterranean region, plant primary production shows strong seasonal and inter-annual fluctuations, which both drive and interplay with herbivore grazing. Knowledge on the responses of different vegetation types to the variability in both rainfall and grazing pressure by wild and domestic ungulates is a necessary starting point for the sustainable management of these ecosystems.

We combined a 15 year series of remote sensing data on plant production (NDVI) with meteorological (daily precipitation data) and ungulate abundance (annual counts of four species of wild and domestic ungulates: red deer, fallow deer, cattle, and horses) in an iconic protected area (the Doñana National Park, SW Spain) to  estimate the impact of intra- and inter-annual variation in rainfall and herbivore pressure on primary production, for each of four main vegetation types. 

Our results showed that, although the density of domestic ungulates shows a linear, negative effect on the primary production of three of the four vegetation types, differences in primary production and phenology among vegetation types increase ecosystem resilience to both climatological variability and grazing pressure. Such resilience may be reduced under the conditions predicted by climate change models, if the reduction in rainfall levels is not accompanied by reductions in the densities of domestic ungulates - potentially leading to no-return degradation levels. New management strategies taking advantage of habitat heterogeneity and phenological alternation, more flexible stocking rates, and the redistribution of management units should be considered to mitigate these effects.

This work, belonging to the PhD Project of Juan Miguel Giralt (the leadind author), just got published in the paper: Complementary Differences in Primary Production and Phenology among Vegetation Types Increase Ecosystem Resilience to Climate Change and Grazing Pressure in an Iconic Mediterranean Ecosystem