Departamento de Ecologia, Instituto de Biociências, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil.
INRAE, Univ. Bordeaux, Biogeco, Cestas, France.
Heredity (Edinb). 2021 Aug;127(2):203-218. doi: 10.1038/s41437-021-00442-9. Epub 2021 May 5.
Both genetic drift and divergent selection are predicted to be drivers of population differentiation across patchy habitats, but the extent to which these forces act on natural populations to shape traits is strongly affected by species' ecological features. In this study, we infer the genomic structure of Pitcairnia lanuginosa, a widespread herbaceous perennial plant with a patchy distribution. We sampled populations in the Brazilian Cerrado and the Central Andean Yungas and discovered and genotyped SNP markers using double-digest restriction-site associated DNA sequencing. In addition, we analyzed ecophysiological traits obtained from a common garden experiment and compared patterns of phenotypic and genetic divergence (P-F comparisons) in a subset of populations from the Cerrado. Our results from molecular analyses pointed to extremely low genetic diversity and a remarkable population differentiation, supporting a major role of genetic drift. Approximately 0.3% of genotyped SNPs were flagged as differentiation outliers by at least two distinct methods, and Bayesian generalized linear mixed models revealed a signature of isolation by environment in addition to isolation by distance for high-differentiation outlier SNPs among the Cerrado populations. P-F comparisons suggested divergent selection on two ecophysiological traits linked to drought tolerance. We showed that these traits vary among populations, although without any particular macro-spatial pattern, suggesting local adaptation to differences in micro-habitats. Our study shows that selection might be a relevant force, particularly for traits involved in drought stress, even for populations experiencing strong drift, which improves our knowledge on eco-evolutionary processes acting on non-continuously distributed species.
遗传漂变和分歧选择都被预测为导致斑块状栖息地种群分化的驱动因素，但这些力量对自然种群塑造特征的程度受到物种生态特征的强烈影响。在这项研究中，我们推断了广泛分布的草本多年生植物 Pitcairnia lanuginosa 的基因组结构，其分布具有斑块状特征。我们在巴西塞拉多和安第斯中央约尼加采样，并使用双消化限制位点相关 DNA 测序发现和基因分型 SNP 标记。此外，我们分析了来自共同花园实验的生态生理特征，并在塞拉多的一部分种群中比较了表型和遗传分歧（P-F 比较）的模式。我们的分子分析结果表明，遗传多样性极低，种群分化显著，支持遗传漂变的主要作用。至少有两种不同的方法将约 0.3%的基因分型 SNP 标记为分化异常，贝叶斯广义线性混合模型除了距离隔离外，还揭示了塞拉多种群中高分化异常 SNP 的环境隔离特征。P-F 比较表明，两个与耐旱性相关的生态生理特征存在分歧选择。我们表明，这些特征在不同的种群之间存在差异，尽管没有任何特定的宏观空间模式，这表明对微生境差异的局部适应。我们的研究表明，选择可能是一种相关的力量，特别是对于涉及干旱胁迫的特征，即使是在经历强烈漂变的种群中，这提高了我们对作用于非连续分布物种的生态进化过程的认识。
