Low-altitude mountain ranges provide refugia for two narrow endemics

A small change in altitude can make a big difference in the right place.

Low-altitude mountains are important centres of diversity in landscapes with little topographic variation. Topographic variables and biotic factors (soil depth and vegetation) were important in predicting current distributions of Ornduffia calthifolia and O. marchantii in the low-altitude Porongorup Range region of the Southwest Australian Floristic Region biodiversity hotspot.

Ornduffia species and habitat in the Porongurup Range, south-western Australia.
Ornduffia species and habitat in the Porongurup Range, south-western Australia. (A) Habitat of Ornduffia calthifolia (yellow-flowered plants in granite rock crevices) at 640m elevation. (B) Single plant of O. calthifolia. (C) Flowers of O. calthifolia. (D) Karri (Eucalyptus diversicolor) forest habitat of O. marchantii at 330m elevation. The karri trees are approx. 50m high and the site had been burnt by high-intensity fire 5 years previously (2008). (E) Ornduffia marchantii along disturbed firebreak in karri forest at 330m elevation. (F) Intermediate form along walk track in bullich (E. megacarpa) forest at 450m elevation. (G) Bullich forest habitat of intermediate form of Ornduffia at 450m elevation. The bullich trees are approx. 10m high. Photo credits: A, Klaus Braun; B–G, Grant Wardell-Johnson.

Keppel et al. deduce from species distribution modelling approaches that both species are likely to severely contract under a milder RCP2.6 climatic projection (2 °C of warming), but are unlikely to persist if warming is more severe (RCP4.5). The Porongurup mountain range constitutes an important refugium for O. calthifolia and O. marchantii, but this valuable and protective site of endemic richness may be severely threatened if global warming exceeds 2 °C.

Endemism Hotspots Cover

This article is part of the AoB Special Issue on Endemism Hotspots as Climate Change Refugia, which is free access for a couple of months, then behind the paywall for a while before being free access after February 2017.

Reference List

Keppel, G., Robinson, T. P., Wardell-Johnson, G. W., Yates, C. J., Van Niel, K. P., Byrne, M., & Schut, A. G. T. (2016). A low-altitude mountain range as an important refugium for two narrow endemics in the Southwest Australian Floristic Region biodiversity hotspot. Annals of Botany, 119(2), 289–300. https://doi.org/10.1093/aob/mcw182