International Journal of Molecular Evolution and Biodiversity, 2025, Vol.15, No.1, 29-39 http://ecoevopublisher.com/index.php/ijmeb 30 2 Taxonomy and Domestication History of Geese 2.1 Wild progenitors of domestic geese Domestic geese mainly come from the two wild geese, Greylag goose (Anser anser) and Swan goose (Anser cygnoides). The Greylag goose was domesticated in Europe, while the Swan goose was mainly domesticated in East Asia, especially in China. They are the ancestors of most domestic goose breeds worldwide. Greylag goose mainly developed into various European domestic goose breeds. Swan goose is the ancestor of Chinese goose and African goose breeds. Both archaeological and genetic studies support that these two domestication processes occurred independently. The domestication of Greylag goose began approximately around 4 000 BC, while that of Swan goose was around 2 000 BC (Heikkinen et al., 2015; Honka et al., 2018; Kozák, 2019; Eda et al., 2022). 2.2 Domesticated goose lineages and breed diversity More than 180 species of domestic geese have been bred from these two wild ancestors, and they vary greatly in appearance and behavior. In China, most domestic geese, except for the Yili goose, share a common ancestor. However, geese from different regions have become significantly differentiated in terms of body size and traits. The origin of European domestic geese is more complex, and some breeds have even undergone genetic hybridization with Chinese geese. During the domestication process, domestic geese have undergone significant changes in many aspects, such as weight, feather color, and egg production. Geese like Toulouse and African geese weigh much more than their wild ancestors. Some domestic geese lay about 12 times more eggs than wild geese. Wild geese are generally monogamous, while domestic geese have transformed into a breeding method where one male goose gives birth to multiple female geese (Kozák, 2019; Chen et al., 2023; Zhang et al., 2023). 2.3 Challenges in phylogenetic resolution Heikkinen et al. (2015) and Honka et al. (2018) found that there has always been gene exchange between wild geese and domestic geese, as well as among different domestic goose strains, which makes the genetic relationship very complex. The genomes of many European domestic geese contain a large amount of genetic components from Chinese domestic geese, indicating that they have undergone multiple hybridization. Heikkinen et al. (2020) demonstrated that the genetic diversity of domestic geese is not high, with most individuals carrying only a small amount of mitochondrial haplotypes, which affects the resolution of phylogenetic analysis. Heikkinen et al. (2020) and Chen et al. (2023) hold that wild geese and domestic geese are difficult to distinguish clearly in archaeological research because they look very similar and there are not many ancient DNA samples. 3 Evolutionary Features of Mitochondrial Genomes in Geese 3.1 Structural and evolutionary characteristics of mtDNA The mitochondrial genome structure of geese is stable, generally consisting of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and 1 control region. This arrangement is very similar to that of other Anseriformes. The research conducted by Liu et al. (2013), Colom and O’Brien (2024) demonstrated that most protein-coding genes use ATG as the start codon, and there are also some conserved sequences in the control region that are crucial for DNA replication and transcription. In the mitochondrial tRNA genes of geese, tRNA^Ser (AGY) and tRNA^Leu (CUN) often lack DHU arms, which is a common feature in the mitochondria of birds. The differentiation rate of mitochondrial DNA in geese is approximately 2% per million years, which is similar to that of mammals. Liu et al. (2013) also found that the genetic sequence difference between the genera Anser and Branta was approximately 9%. Although different species of the genus geese show significant differences in appearance and behavior, their genetic differences are not significant, generally ranging from 0.9% to 5.5%. This indicates that they underwent rapid differentiation and the formation of new species during the late Pliocene to Pleistocene periods. 3.2 Phylogeographic patterns and haplotype diversity There are many different types of mitochondrial DNA in geese, and their distribution is also rather complex. Research on the lesser snow geese has found that their mitochondrial DNA can be divided into two major categories, with a difference of approximately 6.7% between them. This difference might have been caused by geographical separation during the Pleistocene. Among these two categories, some are closely related to geographical locations, while others do not have obvious geographical distribution characteristics, indicating that
RkJQdWJsaXNoZXIy MjQ4ODYzNA==