THE PLANT SPECIES IN RELATION TO HABITAT AND CLIMATE

Abstract

In a previous paper (TURESSON 1922) I endeavoured to show that the I mass of genetically different biotypes which make up the Linnean species do not distribute themselves indiscriminately over an area comprising different types of localities. The biotypes, on the contrary, are found in nature to be grouped into different types, each confined to a definite habitat. I also produced facts which went to show that these habitat types, or ecotypes in my own terminology, do not origi- nate through sporadic variation preserved by chance isolation; they are, on the contrary, to be considered as products arising through the sorting and controlling effect of the habitat factors upon the heterogeneous specie?-population. In the further consideration of these findings special attention was paid to the bearing upon the species problem and systematism which these studies implied, as well as upon ecology. The latter point was further developed in a sub- sequent publication (TURESSON 1923), where the importance of the distinction between modifications and heredritary variations in the field of ecology was emphasised, and the foundation of a new line of ecologic inquiry, viz. genecology, was proposed. The material dealt with in my previous publications on this topic comprised mainly different species of the genus Atriplex, Sedum maximum (L.) SUTER, Armeria vulgaris WILLD., and Hieracium um- beZZatum L. It is my object in the following pages to present addi- tional material in support of the conclusions already arrived at, as well as to raise some new problems which have become worth noting during the progress of the investigation. I shall also have occasion to discuss certain points in the works of some of those investigators who have in some way or other made use of the results set forth in my previous publications, e. g. CLAUSEN (1922), Du RIETZ (1923), HALL and CLEMENTS (1923), and HAUCH (1924). ffercdltas 1’1. 11 148 GaTE TURESSON A few introductory words should be said as to the material and cultures employed in this work. As stated before (TURESSON 1928) species with extended and uninterrupted distribution through regions climatically and edaphically dissimilar are best suited for investiga- tions of this kind. Such species have thus been most extensively employed. The number of transplants made from various regions of such species and now in culture in the experimental fields of this Insti- tute exceeds 10000. As regards methods of collecting and cultivating reference should be made to the paper cited above. Besides the cultiva- tion on a large scale and under the same conditions of as many indivi- duals as possible of different species breeding experiments are also in progress. It has not been thought wise, however, to postpone the publication of the work till these breeding experiments have been brought to an end as the evidence accumulated from the cultural experiments, as well' as from the behaviour of the different types in their natural localities is sufficient to show the nature of the types dealt with in the following. Before going further I wish to acknowledge my indebtedness to Professor H. NILSSON-EHLE for his generous efforts to provide ne- cessary space at this Institute to the increasing mass of cultivated material. I also wish to express my deep gratitude to Langmctnska kdturfonden, who has made it possible for me to collect material from such an extended area by granting me pecuniary support. The photographs published in this paper have been taken by Messrs. K. B. KRISTOFFERSON and J. H. LEHMANN, to whom due acknowledgement is made.