Basic reproductive strategies of glossopterids: supraidioadaptive divergence from the viewpoint of a non–Gondwana palaeobotanist

Abstract

The paper deals with two main tendencies in the reproductive adaptations of the glossopterids (order Glossopteridales Pant, 1982, class Glossopteridopsida Banerjee, 1984). The life conditions in densely inhabited communities compelled the glossopterids to use two considerably different reproductive strategies. The glossopterids with the ovuliferous reproductive organs similar to Scutum Plumstead, i.e the large number of closely related genera, such as Bifariala Prevec et al., Dictyopteridium Feistmantel ex Zeiller, Hirsutum Plumstead, Homevaleia Nishida et al., Lanceolatus Plumstead, Ottokaria Zeiller emend. Pant & Nautiyal, Pluma Plumstead, Plumsteadia (= Cystella) Rigby, Plumsteadiostrobus Chandra & Surange, Venustostrobus Chandra & Surange, etc, were barochorous and produced very many small unwinged seeds. The seeds of that type of glossopterid fructifications fell down due to gravitation nearby the parent plant, after they detached from the reproductive organ. The chance for successful germination was minimal for these plants because of high density of plant population, and it was compensated by large amount of the produced seeds. The plants with the female reproductive organs of the genus Partha Surange & Chandra and similar genera Denkania Surange & Chandra, Lidgettonia Thomas, Rusangea Lacey et al. produced small numbers of relatively large seeds with well–developed wings. These plants were anemochorous. Their seeds were dispersed by wind over long distances, far away from the parent plant, and because of this the chance for successful germination of those plants was much higher. The direct result of this was the reduction of seed numbers on the fructifications of the second type. Such diversification of reproductive strategies expressed in different styles of propagate dissemination (i.e. type of seed dispersal) was characteristic of glossopterids in all the Gondwana regions. This process agrees well with the concept of supraidioadaptive effects proposed by the present author.