Preprints
https://doi.org/10.5194/bg-2021-107
https://doi.org/10.5194/bg-2021-107

  05 May 2021

05 May 2021

Review status: this preprint is currently under review for the journal BG.

Geodiversity and biodiversity on a volcanic island: The role of scattered phonolites for plant diversity and reproductive fitness

David Kienle1,, Anna Walentowitz1,, Leyla Sungur1,, Alessandro Chiarucci2, Severin D. H. Irl3, Anke Jentsch4,5, Ole R. Veetas6, Richard Field7, and Carl Beierkuhnlein1,5,8 David Kienle et al.
  • 1Biogeography, University of Bayreuth, Bayreuth, 95440, Germany
  • 2BIOME Lab, Department of Biological, Geological and Environmental Sciences, Alma Mater Studiorum, University of Bologna, Bologna, 40126, Italy
  • 3Biogeography and Biodiversity Lab, Institute of Physical Geography, Goethe-University Frankfurt, Frankfurt, 60438, Germany
  • 4Disturbance Ecology, University of Bayreuth, Bayreuth, 95440, Germany
  • 5Bayreuth Center of Ecology and Environmental Research BayCEER, University of Bayreuth, Bayreuth, 95440, Germany
  • 6Department of Geography, University of Bergen, Bergen, 5020, Norway
  • 7School of Geography, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
  • 8Geographical Institute Bayreuth, GIB, University of Bayreuth, Bayreuth, 95440, Germany
  • These authors contributed equally to this work.

Abstract. Oceanic islands are cradles of endemism, contributing substantially to global biodiversity. A similarity in magmatic origin translates into high global comparability of substrates of volcanic islands on the oceanic crust. In some places, the petrography of magmatic rocks is differentiated chemically or physically. Phonolites are examples of rare localities with intermediate chemical traits between felsic and mafic and with diverse textures. They contribute to habitat heterogeneity and offer specific growth conditions in a significantly different matrix of basaltic substrates. The explicit contribution of geodiversity to island biodiversity has been little studied, despite accumulating evidence of its importance on continents. On the island of La Palma, Canary Islands, isolated phonolitic rocks are conspicuous by their light colour and specific shape. Although these outcrops only cover small areas, their unique form and composition increase within-island geodiversity. To investigate how this affects biodiversity on La Palma, we sampled all vascular plant species in 120 plots on four sets of paired sites, comparing phonolitic with basaltic rocks, to test whether phonolitic rocks increase overall plant species richness and promote the reproductive fitness of plants. We recorded species number and abundance, individual plant height, and diameter as proxies for aboveground resource allocation and tested for differences in vegetation cover and species composition between the bedrock types. We found higher species richness and abundance on phonolites than neighbouring basaltic substrates, and individuals of the same species were larger (in height and diameter) on phonolites compared to neighbouring basalt. An endemic woody species with two distinct varieties even appears almost exclusively on the small surfaces of phonolitic rock. Despite extremely limited spatial extent, phonolitic rocks can play an important role for plant biodiversity on islands.

David Kienle et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-107', Anonymous Referee #1, 15 Jun 2021
    • AC1: 'Reply on RC1', Anna Walentowitz, 14 Sep 2021
  • RC2: 'Comment on bg-2021-107', Anonymous Referee #2, 05 Aug 2021
    • AC2: 'Reply on RC2', Anna Walentowitz, 14 Sep 2021

David Kienle et al.

David Kienle et al.

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Short summary
Volcanic islands consist mainly of basaltic rocks. Additionally, there are often occurrences of small phonolite rocks differing in color and surface. On the Canary Island of La Palma, phonolites appear to be more suitable for plants than the omnipresent basalts. Therefore, we expected phonolites to be species-rich with larger plant individuals compared to the surrounding basaltic areas. Indeed, as expected, we found more species on phonolites and larger plant individuals in general.
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