Isoflor

Isoflor maps do not show actual species distributions, but each line is a contour delimiting a greater or lesser concentration of species. The species distributions for each species is plotted onto one sectional map, then contours are drawn around areas of similar species concentration. The isoflor maps are intended to indicate patterns of distribution concentration, rather than actual distributional patterns.

But by drawing lines known as isoflors we may approximate the positions of Eocene isotherms. These lines connect floras of the same general composition, which are assumed to indicate, as do similar floras to-day, essentially the same climatic background. The isoflor connecting the localities where subtropical floras have been recorded, as shown by Fig. 9, swings up the west coast of Europe into England, then turns southward into France and trends in a southeasterly direction, with a bulge north over the Black Sea […]