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

Temperate pine species have unusually large, complex genomes which make gen omic 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 N icaragua, spanning latitudes 14 degrees -37 degrees N. These values were co mpared with previously reported LFC estimates for 17 subtropical and temper ate species. Genome sizes in this study were large, varying 1.6-fold from 1 994 to 31.76 pg/C. Genome size variation paralleled taxonomic classificatio n more closely than latitudinal origin. Genome sizes of subgenus Strobus (s oft 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 exce ption was hard pine subsection Macrocarpae which had larger genome sizes ra nging from 26.33 to 28.35. Intraspecific variation was substantial for trop ical hard pines P. oocarpa and P. tecunumanii yet negligible for tropical h ard pine P. patula. (C) 2000 Annals of Botany Company.