Flow cytometric analysis of DNA content for tropical and temperate New World pines

Temperate pine species have unusually large, complex genomes which make genomic analysis problematic; it has been suggested that tropical pines might have smaller genome sizes than temperate pines. Laser flow cytometry (LFC) was used to measure genome sizes of 11 species from Mexico, Guatemala and Nicaragua, spanning latitudes 14 degrees -37 degrees N. These values were compared with previously reported LFC estimates for 17 subtropical and temperate species. Genome sizes in this study were large, varying 1.6-fold from 1994 to 31.76 pg/C. Genome size variation paralleled taxonomic classification more closely than latitudinal origin. Genome sizes of subgenus Strobus (soft pines) were larger, ranging from 27.36 to 31.76 pg/C; those of subgenus Pinus (hard pines) were smaller, ranging from 1994 to 24.91 pg/C. The exception was hard pine subsection Macrocarpae which had larger genome sizes ranging from 26.33 to 28.35. Intraspecific variation was substantial for tropical hard pines P. oocarpa and P. tecunumanii yet negligible for tropical hard pine P. patula. (C) 2000 Annals of Botany Company.