Collevatti Rosane Garcia, Dos Santos Juliana Silveira, Rosa Fernanda Fraga, Amaral Tatiana S, Chaves Lazaro José, Ribeiro Milton Cezar
Laboratório de Genética & Biodiversidade, ICB, Universidade Federal de Goiás, Goiânia, Brazil.
Laboratório de Ecologia Espacial e Conservação (LEEC), Departamento de Biodiversidade, Universidade Estadual Paulista Júlio de Mesquita Filho, Rio Claro, Brazil.
Front Genet. 2020 Mar 25;11:259. doi: 10.3389/fgene.2020.00259. eCollection 2020.
Changes in landscape structure can affect essential population ecological features, such as dispersal and recruitment, and thus genetic processes. Here, we analyze the effects of landscape metrics on adaptive quantitative traits variation, evolutionary potential, and on neutral genetic diversity in populations of the Neotropical savanna tree . Using a multi-scale approach, we sampled five landscapes with two sites of savanna in each. To obtain neutral genetic variation, we genotyped 60 adult individuals from each site using 10 microsatellite loci. We measured seed size and mass. Seeds were grown in nursery in completely randomized experimental design and 17 traits were measured in seedlings to obtain the average, additive genetic variance ( ) and coefficient of variation ( %), which measures evolvability, for each trait. We found that habitat loss increased genetic diversity () and allelic richness (), and decreased genetic differentiation among populations ( ), most likely due to longer dispersal distance of pollen in landscapes with lower density of flowering individuals. Habitat amount positively influenced seed size. Seeds of are wind-dispersed and larger seeds may be dispersed to short distance, increasing genetic differentiation and decreasing genetic diversity and allelic richness. Evolvability ( %) in root length decreased with habitat amount. Savanna trees have higher root than shoot growth rate in the initial stages, allowing seedlings to obtain water from water tables. Landscapes with lower habitat amount may be more stressful for plant species, due to the lower plant density, edge effects and the negative impacts of agroecosystems. In these landscapes, larger roots may provide higher ability to obtain water, increasing survival and avoiding dying back because of fire. Despite the very recent agriculture expansion in Central Brazil, landscape changes are affecting neutral and adaptive variation in . Several populations have low additive genetic variation for some traits and thus, may have limited evolvability, which may jeopardize species long-term persistence. The effect of habitat loss on highly variable neutral loci may only be detected after a certain threshold of population size is attained, that could become dangerously small masking important losses of heterozygosity endangering species conservation.
景观结构的变化会影响种群的基本生态特征，如扩散和补充，进而影响遗传过程。在此，我们分析了景观指标对新热带稀树草原树木种群中适应性数量性状变异、进化潜力以及中性遗传多样性的影响。我们采用多尺度方法，对五个景观进行了采样，每个景观中有两个稀树草原地点。为了获得中性遗传变异，我们使用10个微卫星位点对每个地点的60个成年个体进行了基因分型。我们测量了种子的大小和质量。种子在苗圃中采用完全随机实验设计进行培育，并对幼苗测量了17个性状，以获得每个性状的平均值、加性遗传方差（ ）和变异系数（ %），变异系数用于衡量进化能力。我们发现，栖息地丧失增加了遗传多样性（ ）和等位基因丰富度（ ），并降低了种群间的遗传分化（ ），这很可能是由于在开花个体密度较低的景观中花粉的扩散距离更长。栖息地面积对种子大小有积极影响。 的种子靠风力传播，较大的种子可能传播距离较短，从而增加遗传分化，降低遗传多样性和等位基因丰富度。根长的进化能力（ %）随栖息地面积的减少而降低。稀树草原树木在初始阶段根系生长速度高于地上部分，使幼苗能够从地下水位获取水分。栖息地面积较小的景观对植物物种可能压力更大，这是由于植物密度较低、边缘效应以及农业生态系统的负面影响。在这些景观中，较大的根系可能具有更高的获取水分的能力，从而提高存活率并避免因火灾而死亡。尽管巴西中部最近农业扩张迅速，但景观变化正在影响 的中性和适应性变异。一些种群某些性状的加性遗传变异较低，因此进化能力可能有限，这可能危及物种的长期存续。栖息地丧失对高度可变的中性位点的影响可能只有在达到一定的种群大小阈值后才能检测到，而这个阈值可能会变得危险地小，掩盖杂合性的重要损失，危及物种保护。
