 In other words, areas on maps that demonstrate the same biological phenomenon or character will be connected by something that resembles a contour line.When mapping clines therefore, which follow a character gradation from one extreme to the other, isophenes will transect clinal lines at a right angle.Although the term “cline” was first officially coined by Huxley in 1938, gradients and geographic variations in the character states of species have been observed for centuries.