Animal viability under certain environmental conditions. This is

Animal development is regulated by biotic and abiotic factors. In this work we intend to focus on the environment as a source and inducer of genotypic and phenotypic variation and as an evolutionary agent. Thus, in this work we will talk about the concept of ecological evolutionary developmental biology, most commonly known as Eco-Evo-Devo. This field aims to uncover how the environment interacts with an organism’s genome and development (Landry and Aubin-Horth, 2014; Gilbert, Bosch and Ledón-Rettig, 2015). This term is a fusion of the already existing evolutionary developmental biology (Evo-Devo) with ecology, including other known developmental concepts, such as developmental plasticity, developmental symbiosis, polyphenisms, epigenetics, among others (Abouheif et al., 2014; Gilbert, Bosch and Ledón-Rettig, 2015).Organisms in their embryonic or larval stages can respond to environmental variations, changing their morphology, physiology and behaviour. This ability is called developmental plasticity, and it is in the origin of new traits that may cause organisms to change their form, physiology, or behaviour (West-Eberhard, 2005; Gilbert, Bosch and Ledón-Rettig, 2015), and potentially improve their viability under certain environmental conditions. This is the first process that leads to species differences under natural selection (West-Eberhard, 2005). The necessary reorganization of the phenotype, to produce new variants upon environmental or genomic stimuli is achieved through developmental recombination of the ancestral phenotype (West-Eberhard, 2003). New developmental variants, in the form of the regulation or formation of a new trait, establish themselves in populations and species due to genetic evolution, through selection of phenotypes, when there is a genetic component.According to West-Eberhard, developmental effect of new variations, like genomic mutations, or changes caused by the environment, such as a pathogen or a climate shift, only occurs if the pre-existing phenotype is responsive to it. So, without developmental plasticity, the bare genes and environmental demands would not cause any response on the phenotype, nor would they present an evolutive importance (West-Eberhard, 2005).  Another important process is developmental recombination, which occurs upon a new input. This input causes a reorganization of the phenotype, providing new material for natural selection to work on (West-Eberhard, 2005). The third and final process that contributes to intra-species variability is genetic accommodation. If the acquired phenotypic variations are heritable, in other words, when there is a genetic component, natural selection favors those alleles or allele combinations that have a fitness effect and allow the expression of the new trait. These new traits may, subsequently, be genetically assimilated into the lineage, and might even prosper, as a consequence of environmental changes, to the detriment of the preexisting characters (West-Eberhard, 2003; Gilbert, Bosch and Ledón-Rettig, 2015). In this way developmental plasticity are considered as a major force in adaptation, speciation and macroevolutionary change (Gilbert, Bosch and Ledón-Rettig, 2015).The concept of phenotypic plasticity is also important to understand Eco-Evo-Devo, and it should not be confused with developmental plasticity. Phenotypic plasticity represents the basis of the relationship between phenotypic variation and environmental influence on the development, that may eventually be mediated by natural selection. This plasticity includes environmental action on several stages of development, contrarily to developmental plasticity which refers to early phase only (Oliveira et al., 2016). Phenotypic plasticity can be divided in two main types: polyphenism and the reaction norm (Gilbert, 2000). Polyphenism occurs when two or more distinct phenotypes originate from the same genotype, based on environmental cues, such as the climate, or population density (Gilbert, 2000; Simpson, Sword and Lo, 2017). One example is the polyphenisms of the butterfly Araschnia levana that present different forms if the butterflies eclose in the spring or in summer; the spring morph is bright orange with black spots, while the summer form is mostly black with a white band (Gilbert, 2005). About the reaction norm, this term refers to the spectrum of potential phenotypes expressed by a genotype in different environmental conditions (Stearns, de Jong and Newman, 2017) – the most adaptive phenotype is selected by the environment, within genetically-determined limits specific to the gene itself (Gilbert, 2000). An example it is the study referred in (Gilbert, 2001) with wood frog, Rana sylvatica, that in presence of predatory larval dragonfly Anax grow smaller than those without predators. This is a reaction norm that depend of the number and type of predators. The addition of more predators leads to a continuously deeper tail fin and tail musculatureUnder the optics of phenotypic plasticity, new phenotypes could emerge from reaction norms present in the genetic variation already existing in the population, without necessarily have a new allele with phenotypic effects (Oliveira et al., 2016).Eco-Evo-Devo can also be combined with ecological genomics, for the investigation of development in its ecological context. This merge will increase the current knowledge of evolution, and of the genetic and regulatory mechanisms behind the expression of traits important to function, fitness, and ecological interactions in their environment (Abouheif et al., 2014).