Hernández-Velasco Javier, Hernández-Díaz José Ciro, Simental-Rodríguez Sergio Leonel, Jaramillo-Correa Juan P, Gernandt David S, Vargas-Hernández José Jesús, Porth Ilga, Goessen Roos, González-Elizondo M Socorro, Fladung Matthias, Sáenz-Romero Cuauhtémoc, Martínez-Ávalos José Guadalupe, Carrillo-Parra Artemio, Mendoza-Maya Eduardo, Blanco-García Arnulfo, Wehenkel Christian
Programa Institucional de Doctorado en Ciencias Agropecuarias y Forestales, Universidad Juárez del Estado de Durango, Constitución 404 sur. Zona Centro, C.P. 34000, Durango, Mexico.
Universidad Intercultural de Baja California (UIBC), San Quintín, Baja California, C.P. 22930, Mexico.
Plant Divers. 2024 Dec 31;47(3):415-428. doi: 10.1016/j.pld.2024.12.006. eCollection 2025 May.
The presence of heterozygous individuals in a population is crucial for maintaining genetic diversity, which can positively affect fitness and adaptability to environmental changes. While inbreeding generally reduces the proportion of heterozygous individuals in a population, polyploidy tends to increase the proportion. North American is one of the most widely distributed and ecologically important tree species in the Northern Hemisphere. However, genetic variation in Mexican populations of , including the genetic signatures of their adaptation to a variety of environments, remains largely uncharacterized. The aim of this study was to analyze how inbreeding coefficient ( ) and ploidy are associated with clonal richness, population cover, climate and soil traits in 91 marginal to small, isolated populations of this tree species throughout its entire distribution in Mexico. Genetic variables were determined using 36,810 filtered SNPs derived from genome re-sequencing. We found that was approximately between 0 and -1, indicating an extreme heterozygosity excess. One key contributor to the observed extreme heterozygosity excess was asexual reproduction, although ploidy levels cannot explain this excess. Analysis of all neutral SNPs showed that asexual reproduction was positively correlated with observed heterozygosity ( ) but negatively correlated with expected heterozygosity ( ). Analysis of outlier SNPs also showed that asexual reproduction was positively correlated with and negatively correlated with , although this latter correlation was not significant. These findings support the presence of a Meselson effect.
群体中杂合个体的存在对于维持遗传多样性至关重要，而遗传多样性可对适合度和环境变化适应性产生积极影响。虽然近亲繁殖通常会降低群体中杂合个体的比例，但多倍体往往会增加这一比例。北美乔松是北半球分布最广且具有重要生态意义的树种之一。然而，墨西哥种群中的北美乔松的遗传变异，包括其对各种环境适应的遗传特征，在很大程度上仍未得到描述。本研究的目的是分析在墨西哥整个分布范围内91个边缘至小型孤立种群中，近亲繁殖系数（ ）和倍性如何与克隆丰富度、种群覆盖度、气候和土壤性状相关联。使用从基因组重测序中获得的36,810个经过筛选的单核苷酸多态性（SNP）来确定遗传变量。我们发现 大约在0到 -1之间，表明存在极端的杂合子过剩。观察到的极端杂合子过剩的一个关键因素是无性繁殖，尽管倍性水平无法解释这种过剩现象。对所有中性SNP的分析表明，无性繁殖与观察到的杂合度（ ）呈正相关，但与预期杂合度（ ）呈负相关。对异常SNP的分析还表明，无性繁殖与 呈正相关，与 呈负相关，尽管后一种相关性不显著。这些发现支持了梅塞尔森效应的存在。
