4.2. Environmental variable contribution
Our approach allowed to identify six environmental variables correlated with the potential distribution ranges of the species and populations. Clearly, the rainfall wettest month, rainfall driest quarter and temperature seasonality were mostly involved in fitting the models. The ecological weight that precipitations may have in KG’s distribution is also supported by a recent ethnobotanical study where farmers identified drought and high moisture during the reproductive stage as main factors hindering the species production (Akohouéet al. 2019; Coulibaly et al. 2020). Tamini (1997) also showed that the different sowing dates and seasons with varied temperatures influenced KG growing cycle by delaying or accelerating the flowering time. In order to cope with these weather issues, farmers managed their cropping calendar by advancing (in June) or delaying (in August) the date of planting KG. The change in temperature and moisture levels are not only determined by climatic parameters but may also lead to a change in the absorption rate of water, fertilizers and other minerals in soils, which determine yield output (Padi & Ehlers 2008; Sileshi et al.2010; Yohannes 2015). Therefore, the consideration of both climate and soil type was essential to better predict the species and genetic groups’ distribution. The physical composition of soil such as bulk density of soil in kg / cubic-meter for 22.5 cm depth also had a relevant role in KG and populations distribution. Furthermore, based on variables importance shown by Jackknife measures, soil texture fractions clay and sand in percent, at 10 cm depth accounted for the potential distribution ranges of M. geocarpum and the genetic Pop1 while less for Pop2. Kouelo et al. (2012) reported that the soil texture and preparation (type of tillage) influenced the crop productivity in Benin. Although applying SDM to intraspecific genetic groups allowed the detection of environmental variables, a multidisciplinary approach involving agronomists and biologists would allow a clear understanding of the weight that each of these components may have on the crop growth and development.