The results are important for conservation of these species and are of general significance for conservation by assisted colonization. We conclude that our procedures for producing models and projecting the climate niches of Mexican spruces provide a way for handling other rare plants, which constitute the great bulk of the world's endangered and most vulnerable flora.

Weeping piñon (Pinus pinceana) has a restricted and fragmented range, trees are widely scattered within populations, and reproduction is limited. Nevertheless, genetic diversity was high; based on 27 isozyme loci in 18 enzyme systems, unbiased expected heterozygosity averaged 0.174. Differentiation also was high (F(ST) = 0.152), reflecting isolation between southern, central, and northern fragments of the range. Among populations in the northern fragment, F(ST) was only 0.056, and the number of migrants per generation (Nm) was 4.21, which should preclude fixation. Nm between central and southern populations or between them and populations in the northern fragment was lower, 0.99-1.66, indicating a degree of genetic isolation. Multilocus outcrossing rates (t(m)) ranged from 0.836 in the south to 0.897 in the north. Therefore, selfing is low but statistically significant. The equilibrium inbreeding coefficient (F(e)) calculated from t(m) was in good agreement with observed inbreeding coefficients, suggesting that weeping piñon may be near equilibrium with respect to inbreeding and selection against selfed trees. Weeping piñon was variable at all loci polymorphic in maxipiñon (Pinus maximartinezii) and, therefore, qualifies as a possible progenitor of maxipiñon. Because of the high level of diversity, reasonable levels of gene flow within the northern fragment of weeping piñon's range, high rates of outcrossing, and, perhaps, only weak selection against inbred trees, protection in reserves would be a viable option for conservation.

No abstract

Martínez spruce (Picea martínezii T.F. Patterson) is a conifer currently passing through a bottleneck, reduced to a few relict populations totaling less than 800 trees. We used isozyme markers to analyze the mating system and survey the level of genic diversity in two populations. The mating system was characterized by a high frequency of selfing. The multilocus outcrossing rates (tm) and 95% confidence intervals were only 0.399 (0.197 < tm < 0.601) for the smallest population and 0.589 (0.475 < tm < 0.703) or 0.685 (0.465 < tm < 0.905), depending on year, for the largest. These are among the lowest rates of outcrossing observed in conifers. The fixation indices for the two populations were -0.058 and 0.121, less than expected for such high levels of selfing. Expected heterozygosity, unbiased He, based on 22 loci in 13 enzyme systems, was 0.121 and 0.101 in the two populations. The proportion of the total genic diversity between populations, FST, was 2.4%. Nm, the number of migrants per generation, was about 1.00 or 10.17, depending on the method of estimation. The time since the two populations were isolated was estimated from Nei's genetic distance as only 150 to 15 000 years, which is consistent with a hypothesis of population collapse during late Pleistocene or Holocene warming. We discuss the implications for conservation.