Your orange juice exists because of climate change in the Himalayas millions of years ago, according to a new study that investigated how the citrus fruit evolved and then spread across the world to be enjoyed by each and every one of us today .
Oranges, mandarins, clementines, lemons, lime, and grapefruit. Where do all citrus fruits come from? An international research team has found out in a large genetic survey that included 60 different citrus plants.
We see an incredible variety of citrus fruits available today and the researchers behind this new study aimed to show how these fruits are related to each other, and that turned out to be no simple relation.
Even before humans began to process citrus fruits, there were already many different citrus species hybridized in the wild and that is why the citrus fruit history has been so hard to understand.
The new research study published Nature is the results of a comparison of the genetic diversity of 60 different species. The genetic data show that all of today’s citrus plants all stem from ten wild citrus ancestors.
According to this study, citrus fruits originate in and around the Chinese province of Yunnan, China, about six to eight million years ago. They then spread rapidly across Asia and eventually also down to Australia.
The rapid spread may be due to the fact that the monsoon rainfall became less extensive over a period, according to the researchers behind the study. The much drier climate made it easier for the citrus fruit to spread, the researchers argue.
About 8 to 10 millions years ago, ancestral citrus forests grew at the foot of the Himalayas, but then something changed. Over a period of hundreds of thousands of years, the monsoons weakened, triggering a migration of plants and animals out of the area. Out of this mass migration, over time, at least 10 ancestral citrus species emerged.
One of these ten citrus ancestors has been found in the form of a citrus leaf fossil, discovered in southwestern China. It shows that a common ancestor existed in the area about 8 million years ago. This grandparent of all citruses then spread and diversified to give rise to today’s many varieties we see today.
The research team also identified 6 genes that may be general hotspots of natural genetic variation in Citrus. Advantageous mutations for adaptation were detected in 4 of these genes, matK, ndhF, ycf1 and ccsA. In particular, matK and ndhF were thought to help the Australian varieties adapt to hotter and drier climates while ccsA represents the emergence of mandarins.
Another recent study examined the spread of lemons in ancient times when it became a luxury good in the Roman Empire, The lemon was a high-status luxury good in the Roman Empire.
Guohong Albert Wu et al. Genomics and phylogenetic analyzes of Citrus origins and evolution. Nature February 7, 2017. DOI: 10.1038 / nature25447