Impacts of seed-trees management on genetic diversity and spatial genetic structure of Eremanthus erythropappus (Asteraceae)

Abstract

Understanding the genetic diversity and spatial genetic structure of tree species, as well as knowing about ecological and environmental factors related to their development are essential steps for applying appropriate management strategies for the genetic conservation. The detection of any genetic discontinuity is essential for the improvement of current management systems applied to tree species and for the definition of the cutting cycle. The main objective of the present study is to analyze the effect of forest management under a silvicultural system of seed-trees on the genetic diversity and spatial genetic structure of Eremanthus erythropappus in Itamonte, Minas Gerais state. Specifically, we aim to: (a) develop and characterize nine microsatellite primers for E. erythropappus; (b) analyze the spatial genetic structure and the kinship structure of regenerating and adult individuals; (c) describe the levels of genetic diversity within and among managed and unmanaged stands. One of the main approaches used in this study is the detection of possible genetic discontinuity between managed and unmanaged stands. F irstly, for the development of the primers, we created an enriched microsatellite library for E erythropappus. Afterwards, leaf material was collected from 42 individuals distributed in two forest fragments located in the southern r egion of the state of Minas Gerais. We identified 16 primers where 9 were polymorphic and satisfactorily amplified, producing 38 alleles with a mean of 4.22 alleles per primer. The value of polymorphic information content (PIC) ranged from 0.438 to 0.943 and the observed (HO) and expected (HE) heterozygosity values ranged from 0.647 to 1.00; and 0.308 to 1.00; respectively. In general, these primers revealed as an efficient tool for studies about genetic conservation and forest breeding E. erythropappus. Subsequently, we used six SSR primers to quantify the genetic variability and spatial genetic structure of a stand under forest management and a natural stand. Besides, we collected leaf material of 275 adult and regenerating individuals in the managed (213) and unmanaged stands (62), 60 months after the management. Generally, we found a slight but not statistically significant increase on the mean values of genetic diversity parameters comparing the managed stand (HE = 0.410; A = 2.67) to the unmanaged stand (HE = 0.437; A = 2.33). However, regenerating individuals from the managed stand presented patterns of genetic coancestry (SGSMAX = 25), which was confirmed by low values of the kinship coefficient (Sp = 0.0070 ± 0.00354) and genetic similarity for individuals in the first distance class (F(1) = 0.00690; P < 0.05). Besides, this result indicates a possible correlation of genetic discontinuity on the spatial genetic structure of regenerating individuals caused by forest management. On the other hand, we also evidenced the potential of maintenance of the genetic diversity parameters on the first generations after management as well an efficient gene flow between the managed and unmanaged stands.