The professional activity of João Costa e Silva (JCS) as a researcher has been focused on Forest Genetics, within the major domain of Forest Science. In this context, relevant fields have covered Quantitative Genetics, Population Genetics, Ecological Genetics, Evolutionary Genetics and Applied Statistics, with a special emphasis placed on the management and sustainable use of forest genetic resources. An important component of JCS's activities has entailed studying the genetic variation in tree phenotypes for being able to evaluate the response of forest tree populations to either artificial or natural selection. In this sense, until 2017, JCS's activities have involved dissecting the genetic architecture of quantitative traits within the framework of tree genetics and breeding; from 2018, JCS's work has comprised the fields of Ecological Genetics and Evolutionary Biology for studying the adaptive significance of variation in functional traits, in order to be able to understand and predict how forest tree populations will respond to global environmental change. In addition, molecular genetic studies in JCS's work with forest trees have included measuring genetic diversity, assessing deviations from Hardy-Weinberg and linkage equilibrium, estimating relatedness between individual genotypes (e.g. a coancestry matrix), and analyzing population genetic differentiation and structure. In summary, documented work pursued by JCS within the field of Forest Genetics has dealt with multiple areas such as (starting from the most recent activities): natural selection and contemporary evolution; the genetic basis of interactions among conspecifics (i.e. indirect genetic effects, and comprising in particular competition for growth, and disease infection); intra-specific hybridization and heterosis; inter-specific hybrid inviability and outbreeding depression; inbreeding and its consequences on mean performance and genetic variation; magnitude and drivers of genotype by environment interaction, and its relevance for delineation of breeding and/or deployment zones; effects of propagule type (i.e. clones versus seedlings) on genetic evaluation, in order to optimize tree deployment strategies; importance of additive relative to non-additive (dominance and epistasis) genetic effects, as well as relative to maternal reciprocal and non-reciprocal effects; prediction of genetic responses under single- and/or multiple-trait selection methods, and their impact on the delineation of tree breeding strategies; and estimation of genetic parameters and breeding values, while modelling several sources of variation within (e.g. spatial variability) and across (e.g. heterogeneous genetic and environmental variances) field experiments at a given age and over time. Following the conclusion of his Ph.D. degree in 1997, JCS’s work experience has involved the development of a scientific collaborative network with colleagues at Portuguese institutions, as well as at the international level (e.g. with researchers from Australia, Canada, Denmark, Holland, New Zealand and USA).