Comparative genetic structure in pines: evolutionary and conservation consequences

Abstract

Pines have been the focus of several studies that estimate population genetic parameters using both allozymes and chloroplast single sequence repeats (SSRs). Also, the genus has also been recently studied using molecular systematics so that we now have a more clear understanding of their evolutionary history. With this background we studied comparatively the genetic structure in pines. Expected heterozygosity is particularly constant with a 99 % confidence interval between 0.19 and 0.23 in species that have been studied until now using allozymes. There is a significant proportion of species (9/41) that show high population differentiation estimates (F ST = or larger than 0.15) and five of these have large and wingless seeds probably associated with low densities, bird dispersal mechanisms and resistance to water stress. These species include the North American pinyon pines. Outcrossing rates are also constant among species from both subgenus Pinus and subgenus Strobus, which probably reflects a selective limit to the amount of deleterious alleles that can be maintained in pine species and this also affects inbreeding levels. We also explored the data published using microsatellites in pines and conclude that these markers uncover a higher proportion of variation and genetic differentiation as expected and that the evolutionary models that are used to derive the population genetic structure estimators should take into account other sources of mutation (point mutations, larger insertions and or deletions and duplications) to better understand the comparative applications of these molecular markers.

Genetic diversity and structure of natural and managed populations of Cedrus atlantica (Pinaceae) assessed using random amplified polymorphic DNA

“…Our estimate of intrapopulation variability was, however, higher than that based on AFLP markers (0.11) in a Moroccan population (Bou Dagher-Kharrat et al, 2001b). Furthermore, our H values are within the 99% confidence limits for expected heterozygosity (0.189-0.227) in 50 pine species (Ledig, 1998;Delgado et al, 2002). The Bayesian (H B ) and Shannon's index estimates of intraspecific genetic diversity within C. atlantica were slightly higher (0.239 and 0.270, respectively).…”

“…However, our estimates of the fixation indices for the Moroccan populations (⌽ ST ϭ 0.309; B ϭ 0.304; Gst-B ϭ 0.276) are significantly higher than those reported for other conifers and cannot be explained with the theoretical predictions regarding isolation by distance. Similarly, the mean genetic diversity among populations in 50 pine species, as measured by allozymes, was 0.129 (Ledig, 1998;Delgado et al, 2002). Similarly, the mean genetic diversity among populations in 50 pine species, as measured by allozymes, was 0.129 (Ledig, 1998;Delgado et al, 2002).…”

Long‐distance colonization, isolation by distance, and historical demography in a relictual Mexican pinyon pine (Pinus nelsoniiShaw) as revealed by paternally inherited genetic markers (cpSSRs)

“…1999, 2001; Molina et al . 2001), Pinus nelsonii is not genetically depauperate, but shows a moderate amount of chloroplast genetic diversity, similar to that found for other pine species with a wider geographical distribution (reviewed in Delgado et al . 2002; Marshall et al .…”

Genetic diversity and differentiation of Chilean plantations of Pinus radiata D. Don using microsatellite DNA markers

“…We reported an overall F ST value of 0.04, which indicates that 4 % of the genetic variation present in radiata pine in Chile is partitioned among sites, indicating they are poorly differentiated. Most forest tree species have estimated F ST between 0.01 to 0.17 (DELGADO et al, 2002), which suggests extensive gene flow (SLAVOV et al, 2004). This pattern of genetic structure is common in conifers with large distributional ranges (e.g., GAPARE et al, 2005) and it is in agreement with other studies that used molecular markers for radiata pine (ARREGUI et al, 1999;VOGL et al, 2002) and other conifers (HAMRICK et al, 1992).…”