Abstract

In order to contribute to our understanding of the evolution of forest trees, the major structural life form of some of the most diverse ecosystems of the world, I conducted studies on (a) the genetic structure of Jack Pine ( Pious banksiana ) and (b) the phylogeny of the tropical tree family Dipterocarpaceae. Jack pine is one of the most widely distributed pine species in Canada and a valuable natural resource. The purpose of the present study was to examine the range-wide genetic diversity, population differentiation, inter-population migration, and genetic distances within Canada. The maritime populations were genetically distinct from the mainland populations. Genetic distance values for maritime populations ranged from 0.0504 to 0.0812 as compared to 0.0386 across all populations. The overall range-wide genetic structure of this species likely resulted from multiple refugia events. The members of the pantropical tree family Dipterocarpaceae dominate Asian rainforests, and are considered an excellent model to study the evolution of high tree species diversity characteristic of tropical rainforests. The objective of my study was to decipher the evolutionary relationships among dipterocarps using the partial sequences from the gene that codes nuclear 18S ribosomal RNA (N18S) sequence to determine the phylogenetic relationships within the Dipterocarpaceae. Although the level of polymorphism detected was relatively low, the overall phylogenetic relationships inferred from the N18S data were congruent with chromosome number of each group, where chromosome 7 is the derived state, and consistent with historical biogeographical events