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Geography, topography, and history affect realized to potential tree species richness patterns in Europe.
Ecography. 2010; 33:1070-1080
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23 Mar 2011
Technical Advance
DOI: 10.3410/f.9188956.9780054
This study introduces a new way to look at species richness, the realized/potential (R/P) species ratio. In other words, how many species are present locally compared to the number that could potentially be present, and what environmental factors limit the realized species richness at a given location?
R/P...Continue reading
R/P...Continue reading
This study introduces a new way to look at species richness, the realized/potential (R/P) species ratio. In other words, how many species are present locally compared to the number that could potentially be present, and what environmental factors limit the realized species richness at a given location?
R/P species richness ratios were examined for the European tree flora in 50x50km cells across the continent; this flora is well known and mapped, and was therefore used to illustrate the new method while simultaneously providing new insight into the pattern of tree species richness in Europe.
Because estimating potential species richness is somewhat hazardous, the authors used three different methods to estimate how many species could potentially be present in a given 50x50km cell. Briefly, these were two approaches based on species distribution modeling in which distributions were modeled for each tree species individually and the number of species predicted to occur in each cell was summed. These models included predictive variables such as growing degree days, minimum temperature, and water balance (one model including only those and the second, more complex, model had a number of additional climate and soil variables). The third method to estimate potential species richness was based on quantile regression, where the relationship between species richness and environmental variables was modeled and the potential species richness per cell was taken to be the 95% quantile of the regression model, given the environmental conditions that exist in the cell.
The key finding of the study was that local tree assemblages in Europe often do not include all the species from the environmentally relevant regional species pool. The most important influences on realized richness were accessibility as regulated by barriers to migrations, such as sea straits and mountain ranges (which had a negative influence), and local topographic diversity (which had a positive influence). There was limited support for distance from glacial refugia as a factor negatively influencing local species richness. It is important to note that the three methods of modeling potential species richness produced variable results in some parts of Europe. Although all three models were consistent in showing that R/P tree species richness was very high in parts of Eastern Europe such as Poland, and low in the Iberian Peninsula (the latter presumably due to the migration barrier posed by the Pyrenees Mountains). However, results for Scandinavia, the British Isles, and lowland areas along the southern and eastern shores of the North Sea varied substantially among the three models. This may indicate that we still don't know the optimum way to measure potential species richness, or perhaps that one measure will not work in all regions.
It took an impressive amount of work to carry out this study in a part of the world and for a growth form with relatively few species that are extremely well known and mapped. It is hard to imagine how much effort would be required to do a similar analysis for other taxonomic groups and regions of the world with more numerous species and sparse data sets. Nevertheless, the insights gained from applying the R/P species ratio are considerable, and this sets a challenge for ecologists.
R/P species richness ratios were examined for the European tree flora in 50x50km cells across the continent; this flora is well known and mapped, and was therefore used to illustrate the new method while simultaneously providing new insight into the pattern of tree species richness in Europe.
Because estimating potential species richness is somewhat hazardous, the authors used three different methods to estimate how many species could potentially be present in a given 50x50km cell. Briefly, these were two approaches based on species distribution modeling in which distributions were modeled for each tree species individually and the number of species predicted to occur in each cell was summed. These models included predictive variables such as growing degree days, minimum temperature, and water balance (one model including only those and the second, more complex, model had a number of additional climate and soil variables). The third method to estimate potential species richness was based on quantile regression, where the relationship between species richness and environmental variables was modeled and the potential species richness per cell was taken to be the 95% quantile of the regression model, given the environmental conditions that exist in the cell.
The key finding of the study was that local tree assemblages in Europe often do not include all the species from the environmentally relevant regional species pool. The most important influences on realized richness were accessibility as regulated by barriers to migrations, such as sea straits and mountain ranges (which had a negative influence), and local topographic diversity (which had a positive influence). There was limited support for distance from glacial refugia as a factor negatively influencing local species richness. It is important to note that the three methods of modeling potential species richness produced variable results in some parts of Europe. Although all three models were consistent in showing that R/P tree species richness was very high in parts of Eastern Europe such as Poland, and low in the Iberian Peninsula (the latter presumably due to the migration barrier posed by the Pyrenees Mountains). However, results for Scandinavia, the British Isles, and lowland areas along the southern and eastern shores of the North Sea varied substantially among the three models. This may indicate that we still don't know the optimum way to measure potential species richness, or perhaps that one measure will not work in all regions.
It took an impressive amount of work to carry out this study in a part of the world and for a growth form with relatively few species that are extremely well known and mapped. It is hard to imagine how much effort would be required to do a similar analysis for other taxonomic groups and regions of the world with more numerous species and sparse data sets. Nevertheless, the insights gained from applying the R/P species ratio are considerable, and this sets a challenge for ecologists.
Disclosures
None declared
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Frelich L: F1000Prime Recommendation of [Svenning JC et al., Ecography 2010, 33:1070-1080]. In F1000Prime, 23 Mar 2011; DOI: 10.3410/f.9188956.9780054. F1000Prime.com/9188956#eval9780054
F1000Prime Recommendations, Dissents and Comments for [Svenning JC et al., Ecography 2010, 33:1070-1080]. In F1000Prime, 23 May 2013; F1000Prime.com/9188956
