Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees

Abstract

Frontiers in Plant ScienceSpengler, Robert N., III (2019) Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees. Frontiers in Plant Science. 10(617):1-18.

Available open access

The apple (Malus domestica [Suckow] Borkh.) is one of the most economically and culturally significant fruits in the world today, and it is grown in all temperate zones.
With over a thousand landraces recognized, the modern apple provides a unique case
study for understanding plant evolution under human cultivation. Recent genomic and
archaeobotanical studies have illuminated parts of the process of domestication in the
Rosaceae family. Interestingly, these data seem to suggest that rosaceous arboreal
crops did not follow the same pathway toward domestication as other domesticated,
especially annual, plants. Unlike in cereal crops, tree domestication appears to have
been rapid and driven by hybridization. Apple domestication also calls into question
the concept of centers of domestication and human intentionality. Studies of arboreal
domestication also illustrate the importance of fully understanding the seed dispersal
processes in the wild progenitors when studying crop origins. Large fruits in Rosaceae
evolved as a seed-dispersal adaptation recruiting megafaunal mammals of the late
Miocene. Genetic studies illustrate that the increase in fruit size and changes in
morphology during evolution in the wild resulted from hybridization events and were
selected for by large seed dispersers. Humans over the past three millennia have fixed
larger-fruiting hybrids through grafting and cloning. Ultimately, the process of evolution
under human cultivation parallels the natural evolution of larger fruits in the clade as an
adaptive strategy, which resulted in mutualism with large mammalian seed dispersers
(disperser recruitment).