ECR Feature: Maria Sporbert on relating local abundance to broad-scale distributions

Maria has just recently submitted her PhD thesis at Martin-Luther-University Halle-Wittenberg. She is a vascular plant ecologist with an interest in macroecolgoical patterns and processes. Maria shares her recent work of highly debated theories on the relationship between species local abundances and their broad-scale distributions.

Maria Sporbert. (Photo credit: Philipp Schinschke)

Personal links. ResearchGate | Twitter

Institute. Department of Geobotany and Botanical Garden, Martin-Luther-University Halle-Wittenberg, Germany

Academic life stage. PhD student (thesis submitted in November 2020!)

Major research themes. Macroecology, Biogeography, Vegetation science, Spatial scaling

Current study system. I am a plant ecologist. Since my undergraduate studies I have been fascinated by vascular plants. Currently, my main focus is on herbaceous species, but also dwarf shrub and shrub species that have large parts of their distribution, or even their whole distribution, across Europe. About half of the plant species on Earth are herbaceous, contributing substantially to global biodiversity and providing important ecosystem services. I have two major research themes. Firstly, general patterns in species distribution at the broad scale, and secondly, abundance, a measure of individual species performance, at more local scales.

Recent paper in JBI. Sporbert, M. et al. (2020). Testing macroecological abundance patterns: The relationship between local abundance and range size, range position and climatic suitability among European vascular plants. Journal of Biogeography47(10), 2210-2222. doi: 10.1111/jbi.13926.

Motivation behind this paper. Species can be rare or common within a local plant community. Similarly, some species have restricted distribution ranges while other species are widely distributed. Several macroecological theories relate species’ local abundance with their broad-scale distributions in geographic and climatic space. In this paper we focused on three major theories that are highly debated, namely the abundance-range size relationship, the abundance-range centre relationship and the abundance-suitability relationship. So far, the hypothesized relationships have seen mixed empirical support and most studies that have investigated these relationships have focused on (1) popular taxa, or (2) functional species groups like trees or amphibians, or (3) were restricted to specific geographic regions. Therefore, we wanted to investigate support for these theories with reduced bias by sampling many species across their entire range.

Maria working at her tidied-up desk at the Martin-Luther University Halle, Germany. Typical setting of a macro ecologist: analysing data and creating colourful maps. (Picture credit: Carolin Plos)

Key methodologies. We extracted species distribution maps from the Chorological Database Halle to derive information on the geographic range size for the plant species. The estimated local species abundances were based on about 800,000 vegetation plots from the European Vegetation Archive. We related the species’ broad-scale distribution with species’ mean abundance based on all vegetation plots in which a species occurred, to test for the interspecific abundance-range size relationship We calculated the distance between the vegetation plot locations and the centroid of each species range, which allowed us to test for the abundance-range centre relationship. Furthermore, we applied Species Distribution Models to calculate the climatic suitability of the location of the abundance observation and with this we were able to test for the abundance-suitability relationship. The opportunity to bring two large datasets together enabled us to study macroecological abundance patterns throughout the entire Eurasian distribution ranges of our study species.

A snap shot of the work involved when transferring information on species distribution from maps and notes to a digital format. Work of many years: expert-drawn range maps were compiled for 5,583 taxa national and floristic databases and maps from floristic literature. For 1,200 European vascular plant species, geographical information for the distribution ranges is available in electronic format. (Picture credit: Erik Welk)

Any challenges you and your co-authors faced along the way? One might expect that it’s “low hanging fruits” when you are working with secondary data from biodiversity databases. Nevertheless, bringing together large datasets from different sources can be challenging as it includes carefully matching and synchronizing taxonomy information and coping with spatial uncertainty in the different data sources. Due to spatial uncertainty we decided to raster all of the used data to a 2.5-min cell resolution, which corresponds to grid cells that cover approximately 15 km² across Central Europe, to overcome this potential bias from spatial uncertainty. With this coarsening of resolution, we did also reduce the effect of spatial autocorrelation and pseudo-replication that might arise from very high densities of vegetation plots in highly sampled regions.

Major results. In this study, we found no clear support for any of the three macroecological hypotheses linking local abundance to species’ broad scale distribution. This is an important finding and it highlights the complexity of factors that determine species abundance throughout their geographic range. This complexity can strongly influence predictions about habitat conservation. Most conservation strategies are implemented at the local scale but follow guidelines based on predictions that were made at the global or regional scale. Therefore, it remains crucial to understand whether a species’ local abundance follows the same pattern as the species’ broad-scale distribution. We therefore advocate for including information on microclimatic conditions that are available at fine spatial resolution to improve predictions of species’ local abundance based on broad-scale occurrence data.

An insight into the collection of the Chorological Database Halle that stores information on species distribution ranges for more than 17,000 vascular plant taxa. (Picture credit: Erik Welk)

Next steps in this research. Species’ functional traits are used as proxies for species’ dispersal abilities, tolerance of environmental conditions and competitiveness and have been linked to species’ commonness and rarity on both local and large geographic scale. However, no single trait can completely describe a species’ ecological strategy. Therefore, we are interested to understand whether species’ local abundance and broad-scale distribution can be predicted by single functional traits and sets of traits. The manuscript is on its way so stay tuned for some interesting results in the near future!

If you could study any organisms on Earth, what would it be? I am fascinated by vascular plants which are so manifold in their forms and functions, so I think I am already studying my favourite “species group”. Nevertheless, especially the interaction between plants and their pollinators have raised my interest and I am keen to learn more on these important relationships and the abiotic factors that are influencing them.

Published by jbiogeography

Contributing to the growth and societal relevance of the discipline of biogeography through dissemination of biogeographical research.

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