As seen in the Traits, Phenotypes and Genotypes post, genotype and environment both shape phenotype in many cases. Simplistically, G + E = P
Consider a farm. It has:
- a physical environment (altitude, soils, seasons, climate, water and pasture availability and quality)
- fixed resources (land size, workable area, labour)
- management policies
- economic inputs and outputs
The animals are the genotypic input, with the rest environmental inputs. All these parts interact and ultimately influence the end phenotypes.
When you have a group of parts interacting to create a whole, you have a system. Here, the farm is a system and the animals and environmental inputs are the parts of that system.
A breeder strives to improve phenotype by improving genotype. But for maximum genotypic improvement, a breeder must also consider his animals as part of a system, subject to the interactions of other parts, and make decisions accordingly. And these decisions could be different for different breeders, as their personal systems also are different.
For example, alpacas in Australia occupy a wide range of temperate climates, and management practices change to suit. Paralysis tick can be fatal on the east coast if not controlled for, but not in the drier inland where it doesn’t exist. Shearing and birthing are timed, for the most part, earlier with decreasing latitude. It was not uncommon for breeders located in the subtropical north in the early days of the industry to relocate to the temperate south, having lost valuable breeding stock (genotypes) and their young to ticks and the vagaries of hot humid weather that set them back several years.
Nowadays most alpacas are found in the traditional wool sheep regions of the country. The environments favourable to wool sheep genotypes would appear to also be favourable to alpaca genotypes. The next four posts will go more deeply into genotype-environment interactions, and how knowledge of these can improve breeding programmes.