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.