Species-environment relationships and diversity of liverworts in Israel
2002
Bischler-Causse, Hélène
A data set comprising 275 sampling plots of Israeli liverworts, each consisting of a coded list of twenty environmental variables and a species list, was investigated with multivariate analyses. A factorial map summarizes the data and provides a survey of the main ecological preferences of the Israeli liverwort species. The species proved to be linked to specific biotopes. Their distribution in the factorial space depends predominantly on climate, altitude, vegetation, and shelter of habitats. Life history traits are discussed to explain which ecological conditions are best for survival and dispersal. Floristic richness is low compared with the whole Mediterranean region. Species richness and size of sampling plots correlate with the climatic gradient, lowest in the arid, highest in the Mediterranean zones of Israel. The species able to survive in the arid zone also grow under less severe climatic conditions, whereas many species common in the Mediterranean zone are absent from the arid zone. The Israeli liverworts have wide geographical distributions, not only in the whole Mediterranean region, but also in other continents. Endemics are absent. Species with present-day tropical chorotypes are most common. The liverwort flora appears as a mixture of predominantly tropical and a few northern colonizers that did not differentiate after their settlement. The genetic structure of liverwort populations is discussed in order to explain the scarcity of endemics.
显示更多 [+] 显示较少 [-]