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Mitchell, Edward

Nom
Mitchell, Edward
Affiliation principale
Site web
Fonction
Professeur ordinaire
Email
edward.mitchell@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/357
_
0000-0003-0358-506X

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  • Publication
    Accès libre
    Checklist, diversity and distribution of testate amoebae in Chile
    Fernández, Leonardo D
    ;
    Lara, Enrique 
    ;
    Mitchell, Edward 
    Bringing together more than 170 years of data, this study represents the first attempt to construct a species checklist and analyze the diversity and distribution of testate amoebae in Chile, a country that encompasses the southwestern region of South America, countless islands and part of the Antarctic. In Chile, known diversity includes 416 testate amoeba taxa (64 genera, 352 infrageneric taxa), 24 of which are here reported for the first time. Species−accumulation plots show that in Chile, the number of testate amoeba species reported has been continually increasing since the mid-19th century without leveling off. Testate amoebae have been recorded in 37 different habitats, though they are more diverse in peatlands and rainforest soils. Only 11% of species are widespread in continental Chile, while the remaining 89% of the species exhibit medium or short latitudinal distribution ranges. Also, species composition of insular Chile and the Chilean Antarctic territory is a depauperated subset of that found in continental Chile. Nearly, the 10% of the species reported here are endemic to Chile and many of them are distributed only within the so-called Chilean biodiversity hotspot (ca. 25°S-47°S). These findings are here thoroughly discussed in a biogeographical and evolutionary context.
  • Publication
    Accès libre
    Towards a Holarctic synthesis of peatland testate amoeba ecology: Development of a new continental-scale palaeohydrological transfer function for North America and comparison to European data
    Amesbury, Matthew J
    ;
    Booth, Robert K
    ;
    Roland, Thomas P
    ;
    Bunbury, Joan
    ;
    Clifford, Michael J
    ;
    Charman, Dan J
    ;
    Elliot, Suzanne
    ;
    Finkelstein, Sarah
    ;
    Garneau, Michelle
    ;
    Hughes, Paul D.M
    ;
    Lamarre, Alexandre
    ;
    Loisel, Julie
    ;
    Mackay, Helen
    ;
    Magnan, Gabriel
    ;
    Markel, Erin R
    ;
    Mitchell, Edward 
    ;
    Payne, Richard J
    ;
    Pelletier, Nicolas
    ;
    Roe, Helen
    ;
    Sullivan, Maura E
    ;
    Swindles, Graeme T
    ;
    Talbot, Julie
    ;
    van Bellen, Simon
    ;
    Warner, Barry G
    Fossil testate amoeba assemblages have been used to reconstruct peatland palaeohydrology for more than two decades. While transfer function training sets are typically of local-to regional-scale in extent, combining those data to cover broad ecohydrological gradients, from the regional-to continental- and hemispheric-scales, is useful to assess if ecological optima of species vary geographically and therefore may have also varied over time. Continental-scale transfer functions can also maximise modern analogue quality without losing reconstructive skill, providing the opportunity to contextualise understanding of purely statistical outputs with greater insight into the biogeography of organisms. Here, we compiled, at moderate taxonomic resolution, a dataset of nearly 2000 modern surface peatland testate amoeba samples from 137 peatlands throughout North America. We developed transfer functions using four model types, tested them statistically and applied them to independent palaeoenvironmental data. By subdividing the dataset into eco-regions, we examined biogeographical patterns of hydrological optima and species distribution across North America. We combined our new dataset with data from Europe to create a combined transfer function. The performance of our North-American transfer function was equivalent to published models and reconstructions were comparable to those developed using regional training sets. The new model can therefore be used as an effective tool to reconstruct peatland palaeohydrology throughout the North American continent. Some eco-regions exhibited lower taxonomic diversity and some key indicator taxa had restricted ranges. However, these patterns occurred against a background of general cosmopolitanism, at the moderate taxonomic resolution used. Likely biogeographical patterns at higher taxonomic resolution therefore do not affect transfer function performance. Output from the combined North American and European model suggested that any geographical limit of scale beyond which further compilation of peatland testate amoeba data would not be valid has not yet been reached, therefore advocating the potential for a Holarctic synthesis of peatland testate amoeba data. Extending data synthesis to the tropics and the Southern Hemisphere would be more challenging due to higher regional endemism in those areas.