Conclusion
By comparing distribution patterns for plants families of Malesia, this
study offers valuable insights on the mechanisms underlying elevational
range-sizes of flora on tropical mountains and their potential response
to changing environments. The synthesis of our findings is that
long-term climate stability, in the sense of both centers of richness
within lowland tropical forests as well as the consistently equatorial
position of landmasses over millions of years, is linked to how much
average range-sizes increase with elevation (ERR slope). Positive ERR
slopes may indicate changes in ecological strategies, such as a shift
from communities driven by biotic competition at lower elevations to
ones that are more tolerant of abiotic stressors with increasing
elevation. In contrast neutral, or even negative, ERR slopes may
indicate directional expansion out of habitats with high abiotic
variation, such as transitioning downward from montane habitats into
lowland forests, or tectonic movement of landmasses towards the equator.
Our findings indicate that lowland endemics of landmasses with
consistent positioning near the equator (e.g. Sundaland) may be
disproportionately at a higher risk of extinction as environmental
conditions change and become more variable.