4.4. Predicting evolutionary change based on genetic variation
We assumed that KG species will conserve its cultivated areas over space
and time. Our results however, found evidence of variability in the
species response to future environmental conditions. This corroborates
many other studies which showed the impact of future climatic conditions
on crops production, such as cereals, legumes, vegetables
(Burke et al. 2009;
Pironon et al. 2019;
Ramirez-Cabral et al. 2017;
Ramirez-Cabral et al. 2016;
Syfert et al. 2016).
We also combined genetic information to ENM to test hypothesis that
genetic divergent groups differ in their adaptive potential to respond
to environmental change. The projection under future climatic scenarios
RCP4.5 and RCP8.5 clearly indicate that the response of Kersting’s
groundnut and genetic groups varied significantly across agroclimatic
zones. Our results confirmed the idea that different genetic clusters
potentially showed adaptive variation to different abiotic conditions
within the geographical range of the species
(Hancock et al. 2011). Globally,
although Central Benin is presumed to be a centre of origin for the
crop, we observed a loss in suitable areas for the species production in
the Southern-Sudanian zone of the country. The genetic Pop 1 is the
mostly concerned by the negative impact of environmental evolution as it
was generally found in these regions of the country. Similarly,
Ikeda et al. (2016) tested and
demonstrated the hypothesis that species locally adapted to current
environments are likely to become maladapted in the future. The same
trends were reported on other cereals such as maize, wheat, sorghum and
barley which tend to decrease their area of suitability in their centres
of origin (Bellon & van Etten 2014;
Lane & Jarvis 2007). In the context of
an inevitable agricultural reduction in these agroclimatic zones, the
earlier the mitigation actions are taken, more successful will be the
collection and conservation efforts of KG’ resources. On the other hand,
severe environmental conditions (RCP8.5) of the Northern-Guinean zone in
Southern Benin and Togo remain, even become more favorable to the
species cultivation (Pop2). Likewise, the Southern-Sudanian zone of
Ghana, Burkina Faso, Togo and Northern Benin, and Northern-Sudanian zone
increased in cultivable areas of Pop2. Out of the 361 individuals
included in this study, 101 belong to the genetic Pop2, distributed
mostly in the Southern-Sudanian zone and counts all the landraces grown
- diversity based on seed coat color -
(Akohoué et al. 2019;
Coulibaly et al. 2020). Such
diversity in this population may explain the adaptive response of the
Pop2 to climate variation. This is supported by the conclusion of
Vigouroux et al. (2011) who
described the evolution and adaptation of pearl millet in West-Africa.
However, the cultivable area of this genetic Pop2 is predicted to
decline in the Southern-Sudanian zone of Central Benin. With regards to
these results, significant headway can be made by creating more
favorable policy environments. Two strategies proposed by
Ramirez-Cabral et al. (2016) can
be used in order to mitigate loss in KG resources and diversity: first,
the use of all the resources of Pop2 in regions where the stress of
climate conditions become unsuitable for the species production.
Examples of this is the Southern-Sudanian zone of Central Benin, where
the use of KG is more important than other regions. And the second
option was to address future loss of suitability by shifting the current
cultivation areas of Pop1 to new regions, where the future climatic
conditions is projected to become more cultivable for KG, the
Northern-Guinean zone of Southern Benin, the southern-Sudanian and
northern-Sudanian zones.