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).