Island theory is still relevant to alpine biogeography

Area, environmental heterogeneity, scale and the conservation of alpine diversity.

Above: Phyteuma hemisphericum from the Sierra de Villabandín, Cantabrian Mountains, Spain;
photograph by Borja Jiménez-Alfaro

This project was an extension of our work on the relative importance of geographic distance and environmental difference to the beta diversity of alpine plant communities (Malanson et al. 2022). We developed a simulation of all 23 of the mountain ranges in southern and central Europe based on data from 18,000 plot surveys. However, we decided that we could learn more by simulating each range independently. Further, we recognized that additional quantification of environmental heterogeneity within ranges could complement our earlier work (Jimenez-Alfaro et al. 2021). This concurrence led us to the key problem description by Udy et al. (2021) and the simulation model by Ben-Hur (2020) that was similar to what we had developed. Together, these reinvigorated our longstanding interest in the current relevance of island theory to alpine biogeography and the combination of field data and simulation results allowed us to assess the types of environments in which area per se becomes important in the maintenance of species diversity.

Areas of alpine vegetation are found in 23 mountain ranges in southern and central Europe from the Baetic System in the southwest, in an arc through the central Alps, shown here, to the Hellenides in the southeast (photograph courtesy of Harald Pauli).

Cover article: (Open Access)
Malanson, G. P., Testolin, R., Pansing, E. R., & Jiménez-Alfaro, B. (2023). Area, environmental heterogeneity, scale and the conservation of alpine diversity. Journal of Biogeography, 50, 743– 754.

Beyond the interest to reread MacArthur and Wilson and realize how blithely they dealt with heterogeneity, thinking about the relevance of area per se was motivating. The degree to which the complex topography, and thus heterogeneity, of mountains will provide microrefugia for current alpine species depends on that effect. While our empirical analysis of the 23 ranges is too coarse to address microrefugia, our virtual microcosms show that area per se will, indeed, be important – and this can be seen intuitively in the basic species-area curve upon which MacArthur and Wilson built their theory. The conservation of heterogeneity in microrefugia is no panacea for the impacts of climate change on alpine species diversity.

In local areas, extents can be quite small, as here in the Sierra de Villabandín, Cantabrian Mountains Spain. Fragmentation within the 23 ranges was included in the simulations (photo: Borja Jiménez-Alfaro).

In the process of developing the simulation, the question of the Heterogeneity – Effective-Area Tradeoff (HEAT) emerged. Its significance was driven home in conversation with Kostas Triantis at the International Biogeography Society meeting in Vancouver. Our simulation did not produce this pattern in our basic runs, but additional modifications allowed HEAT to evolve more often when our simulation grid had greater discrete steps of environment in space. While this indicated that HEAT could be induced as a model artifact, it also tells that real landscapes, which often are not continuous, could generate HEAT.

Teaming with others in AlpVeg (, next we will pursue questions of microrefugia using finer scale data. These studies may extend globally and would use the GLOBALP database (

Extension to finer scale analyses will rely in part on legacy data from worldwide plots (here, Glacier National Park, USA) in the GLOBALP database (photo: Calypso Ecological LLC, used by contract).

Written by:
George P Malanson
Coleman-Miller Professor Emeritus, The University of Iowa

Additional information:

Ben-Hur, E. & Kadmon, R. 2020. Heterogeneity–diversity relationships in sessile organisms: A unified framework. Ecology Letters 23, 193–207
Jiménez-Alfaro, B., Abdulhak S, Attorre, Bergamini A, Carranza ML, Chiarucci, A., Ćušterevska R, Dullinger S, Gavilán RG, Giusso del Galdo G, Kuzmanov N, Laiolo P, Loidi J, Malanson GP, Marcenó C, Milanović D, Pansing ER, Roces-Díaz JV, Ruprecht E, Šibik J, Stanisci A, Testolin R, Theurillat J-P, Vassilev K, Willner W, Winkler M. 2021. Postglacial determinants of regional species pools in alpine grasslands. Global Ecology & Biogeography 30, 1101-1115.
Malanson, G. P., Pansing, E. R., Testolin, R., Abdulhak, S., Bergamini, A., Ćušterevska, R., Marcenò, C., Kuzmanović, N., Milanović, Đ., Ruprecht, E., Šibík, J., Vassilev, K., Willner, W., & Jiménez-Alfaro, B. 2022. Explanation of beta-diversity in European alpine grasslands changes with scale. Ecosphere 13, e4066
Udy, K., Fritsch, M., Meyer, K. M., Grass, I., Hanß, S., Hartig, F., Kneib, T., Kreft, H., Kukunda, C. B., Pe’er, G., & Reininghaus, H. 2021. Environmental heterogeneity predicts global species richness patterns better than area. Global Ecology & Biogeography 30, 842–851

Published by jbiogeography

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