Correlation between higher altitudes and endemic plant species

Abstract

Plant species do not have an even distribution or species richness over the earth. This can be influenced by many factors, like topography. Especially tropical areas have a high species diversity presumably correlating with the high temperatures and high humidity. Some species are widespread (non-endemics) others only occur very locally (endemics). Could there be a correlation with altitude? This was done by comparing the altitudes of non-endemic and endemic plant species of the islands New Guinea and Borneo. On both islands a trend between altitude and non-endemic or endemic species was found. The number of non-endemic species decreases with increasing altitude. The endemic species of New Guinea have a positive correlation with the altitude; they are relatively more abundant on higher altitudes. The endemic species of Borneo have a negative correlation with the altitude, but compared with the non-endemic species they are more present on higher altitudes, their decrease is far less with increasing altitude. If endemic species are the result of recent speciation, then mountains, by whatever mechanism, catalyse speciation.