Evolutionary dynamics of vegetative agriculture in the Ethiopian Highlands

Integrating archaeobotanical and genomic science to address food security and climate change.

A long row of bunched up enset plants in Ethiopia

Almost half of food plants are vegetatively propagated including four of the ten most economically important species worldwide.

Currently, we know very little about vegetative crop history - for example, how long they have been cultivated, and where – because vegetative tissues rarely preserve in the archaeological record. Ethiopia is potentially Africa's most important centre of crop diversity, characterised by both the evolution and domestication of multiple vegetative species.

This project focuses especially on the major food security crop enset, or Ethiopian "false banana" (Ensete ventricosum), a tree-like perennial banana relative, building on extensive existing research on this crop at Kew.

Enset supports some of the densest populations in sub-Saharan Africa and is the staple for 20 million people. It is cultivated over a wide elevational range and ecological gradients, exists at very high biomass densities, and has a deep cultural association with multiple ethnic groups. As such enset offers an ideal model for studying long-term adaptation, diversification, and interaction with culture.

Our interdisciplinary approach will integrate archaeological, ethnohistoric, genomic and biogeographical information to reveal the long term development and diversification of enset. We also have a multi-layered temporal approach, that will connect modern diversity, recent changes, and the deep time antiquity of enset cultivation.

Our main objective is to test whether landrace patterning is primarily evolved through - (i) Environmental adaptation - meaning that crop diversity is generated through adaptation to environmental diversity such as cooler and drier locations; (ii) Cultural mechanisms - for example management traditions and variety preferences such as taste, or (iii) The antiquity of exploitation - in other words, enset could be most diverse where it has been cultivated the longest.

Long-term evidence for enset in agriculture will come from key archaeological sequences, collected across a series of sites in the Ethiopian Highlands, and being processed by partners in Ethiopia, USA and Germany. The PI Dorian Fuller, and team will develop new methods to refine the methods to interpret these remains by undertaking a comparative study of phytoliths (silica microfossils that can exist within certain plant cells) considered against phylogenetic position and potential plasticity due to growth environment. This will also be complemented by analysis of charred food remains recovered from macrobotanical assemblages using methods developed at UCL.

At Kew, we will develop additional lines of evidence by building a dated phylogenetic tree using DNA data from ~ 900 contemporary landraces.

These data will provide new hypotheses to explore archaeologically in terms of the cultural and adaptational history of this crop. Ethnobotanical fieldwork across different cultural regions in the southwestern highlands will query the extent to which agricultural and cultural changes in recent decades have altered patterns of local landrace diversity, uses and relative importance. Accounting for these changes aims to help us distinguish the influence of recent agricultural and cultural changes from long term historical patterns.

This research addresses key issues at the interface of indigenous agrobiodiversity and its role in future resilience to climate change, through better understanding rates of knowledge and landrace loss, as well as drivers of change.

The project will create a better understanding of both the past development and future potential of vegeculture from a global perspective. Vegetative species are amongst the least studied 'orphan crops', with major knowledge gaps about their biology, cultivation, processing and domestication.

The project will specifically contribute to debates concerning food security and climate change resilience in the Ethiopian highland centre of diversity.

Natural Environment Research Council (NERC)