Evolution of LUPINS and ContinentalDrift

Wegener's theory of continental drift suggests a hypothesis aboutstage-by-stage division of continents in the past two hundred andfifty to fifty million years. Similar plant and animal fossilsare found around different continent shores, suggesting that theywere once joined.

According to this hypothesis the unified primary centre offormation for most ancient ancestors of lupin probably existed inthe Cretaceous and subsequent periods on Laurasia. Further on, asa result of subsequent division of the continents, thedevelopment of remote ancestors of lupin continued independentlyon the divided parts. It was homologous but not identical,pursuant to the Vavilov’s law of homological series.

Evolution of ancient ancestors of Lupins in the couse of drift of continents

Fast development and seizure of new biotic spaces byangiospermous vegetation started in the Cretaceous period. Therewere many families of angiospermous plants at that time,including the genus Lupinus. Proceeding from this thesis, it ispossible to surmise, that a considerable proportion of ancientprogenitors of lupins appeared also in the Cretaceous period inLaurasia, and predominantly, in its western part, whichsubsequently turned into North America. It is confirmed bytoday’s presence on the American continent of a large number ofspecies. Further distribution of lupins, or their progenitors,from the north to the south, in particular from North Americainto Central and even South America and from Northern Europe intothe countries of the Mediterranean and Africa, could have beenprovoked by periodically recurring changes of climate, chill andthaw, seismic activity or oscillations of the magnetic field.

The origin and development of Live

When the continents drifted apart, however, lupin ancestors foundthemselves in isolated environments and started their independentdevelopment. The species of lupin currently existing in bothhemispheres, already emerged after the splitting of thecontinents. It explains the existence of two absolutely isolatedlupin groups differing in morphological characters, developmentcycles, sets of chromosomes and having a genetic barrier againstcrossing.

American lupin forms are somewhat less specialized thanMediterranean ones. They are characterized by a more primitivemonopodial type of branching and by the cross-pollination habit(with the help of insects). Their plants are heterozygous andeasily generate all possible mutations. Seeds are small,the embryo is gently differentiated, it is insufficient inendosperm and located close to the seed cover, with a lengthenedhypocotyl. Rather specialized Mediterranean lupin forms arecharacterized by a more advanced type of branching (sympodial);

for them, self-pollination is dominating. Seeds are larger,the embryo is well-formed, with two sedentary leaves or a veryshort hypocotyl.

Lupins from the Mediterranean region and those from America arealso contrasting in storage proteins, each of the groups havingdeterminants specific for their native hemisphere. Thesedistinctions between lupins of the two continents have induced usto search for a more accurate definition of their systematicposition in the generic system.

Considering the essential morphological differences betweenlupins of the two hemispheres, we made revision of two subgenerain Lupinus L., according to geographic principle. Thegenus LupinusL. and, in particular, its North-American species,were divided by Watson (in 1873) into threeparts:Lupinus, Platycarpos and Lupinnelus. Differences in habit and inthe number of ovules were accepted as the basis for thisclassification. The majority of perennial and annual species from

the American continent described by Watson was referredto Lupinus.

To the Platycarpos section were attributed some annual species withtwo ovules in the ovary, and two seeds in the pod (L. densiflorus , L.micricarpus).

Section Lupinnelus consisted of one species (L. uncialis), withaxillary and solitary flowers, and also with two ovules in theovary. Presently, the existence of such species seems doubtful.

This principle of classification was extended by Ascherson andGraebner to all lupins from the eastern and western hemispheres.The genus Lupinus was for the first time subdivided into twosubgenera: A. Eulupinus and B. Platycarpos. Quantity of ovules (seedbuds) in the ovary and seeds in the pod was also accepted as thecriterion for this division. Majority of the described speciesfrom the eastern and western hemispheres were referred tosubgenus A. Eulupinus. Subgenus B.Platycarpos included several annualspecies from the eastern hemisphere with two seedbuds and seedsin the bean. (The same species, as the one specified by Watson).

These works were a starting point for our researches.

In connection with definition of two secondary centres of formation for different species of lupin in the eastern and western hemispheres, and with the essential morphological differences between lupins of the two hemispheres (Table), we managed to revise the volumes of two subgenera in the genus Lupinus according to the geographic principle, however in view of the findings of the previous writers (Kurlovich, 1989).

Doctor Nikolai  Kuptsov (the Belarus Institute of Agriculture)  andlupin (Lupinus nootkatensis)  in Iceland, 2002.

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