Botanical-geographic orientation of citrus fruits with reference to their historical background

Abstract

The progress of citrus taxonomy has been greatly delayed from various reasons, primarily due to the misapplication of specific names to classify obvious unit species. From the time of LINNAEUS, a num-ber of definite unit species of Citrus have been passes into two major groups symbolized by Citrus Medica and C. Aurantium, under which good unit species are placed in either one of them with the status of lower categories such as their subspecies, subvarieties and so on. HOOKER, and later ENGLER, followed the same erraneous scheme in using these specific names to group existing units which are quite independent from each other having definite characteristics with type materials, geographic dis-tribution and historical careers together with au-thentic descriptions and valid names worthy of bo-tanical species. C. Medica, for instance, is an unit species, representing the Turunj type of citron, known in India from the Sanskrit time under the name Matulunga, and in China from CHI-Han's period (A. D. 290_??_307) under Kou yuan. By simple resembrance, it cannot involve C. Limon (the lemon), C. Limonia (Canton lemon) and the lime (C. aurantifolia) of different taxonomic status and geographical independence. All of them are equally separate species of different origin and C. Medica cannot stand at an upper taxon to group them all. From this principle, every one of citrus units is to be handled equally to hold species rank so far as it represents valid specific status with definite geo-graphical background and historical bearing to prove its concrete existence. Higher taxa, such as sub-genus, section, subsection, etc., are to be created to systematize these unit species, which should not be in the shape of specific taxon, as these great authors unjustly misapplied against the present day type-concept. Minor difficulties blocking so far the smooth pathway of the taxonomic development of citrus fruits, are misidentification based upon graphical and historical absurdity, repeated abues of non-valid specific names, too frequent negligence of valid species by the lack of critical investi-gations, and the random use of obscure non-specific botanical units without proper justification. Citrus taxonomy, therefore, must proceed with the secure mapping of independent specific units authorized by taxonomic-geographical proof with historical endorsement if possible, then followed by their sys-tematic arrangement properly classified keeping the evolutionary sequence in sight.