4.3. Niche overlapping
We found important geographic overlap among the projected distributions
of the species genetic populations. The clusters did not show strict
cluster-specific ecological niches. Our results did not support the view
that a given species could be considered as an assemblage of genetic
units differing in their spatial distribution
(Ikeda et al. 2016;
Marcer et al. 2016). Populations
of KG are both cultivated in the Northern-Guinean and the
Southern-Sudanian zones of Benin, characterized by a bimodal (rainfall ≤
1500mm) and unimodal (rainfall ≤ 1100mm) growing seasons, respectively.
However, the Pop 2 showed wide cultivable areas rather than the Pop1, as
it is also grown in the Northern-Sudanian zone, where rainfalls are
relatively low (rainfall ≤ 900mm). The null hypothesis was rejected as
climatic niches between the two populations were identical and similar
(niche identity test p < 0.01 and niche similarity p
< 0.05)), suggesting variation in their environmental niches
and adaptation to different climate conditions, as previously reported
by Wellenreuther et al. (2012) who
analyzed the ecological causes of the ranges limits and the coexistence
of two congeneric damselflies (Calopteryx splendens and C.
virgo ). In addition, Maxent’s outputs also revealed that climatic
niches of the two genetic populations of M. geocarpum are
relatively different in the distribution areas. This finding is in
accordance with other studies which reported environmental niche
dissimilarity at the intraspecific level
(Banerjee et al. 2019;
Gorel et al. 2019;
Ikeda et al. 2016;
Milanesi et al. 2018).