Identification and characterization of shea morphotypes
Criteria used by farmers for shea morphotypes identification and classification
Overall, farmers identified 35 different traits based on sixteen primary criteria related to fruit, tree, and nut variants (Table 2). Eleven traits were mentioned based on fruit characteristics (size, shape, fruiting period, and yield) and five were identified primarily according to characteristics of the fruit pulp (e.g. taste and density). Ten traits were identified based on tree characteristics (bark colour, height, scales size, heartwood colour and trunk shape) and another five were identified based on shea nut traits (size, presence and number of seeds). Farmers also differentiated shea trees based on leaf colour which could be light or dark green. The top five classification criteria reported by farmers were fruit size (56.47%), tree fertility (15.67%), bark colour (10.70%), fruiting period (6.34%) and pulp taste (3.48%). Farmers reported 13 shea morphotypes traits across the phytogeographical zones in Benin. Some criteria were seldom used. Traits with a citation frequency lower than 1% were not further considered in the analyses.
Shea tree name in the sociolinguistic group of surveyed areas include Sombou (Bariba), Boulanga (Dendi), Tam (Yom), Wougo (Fon), Egui èmè (Tachabè), Kouli (Boko), and Mouta, Koacha, or Taou in Ditamari. Table 3 presents the local names of the most mentioned traits by farmers in the different zones. These names recorded across the shea parks of Benin were based on morphological and organoleptic traits. Shea tree traits according to local communities were mainly related to bark colour, fruiting period and fruit size; other traits were based on tree fertility and pulp taste. Farmers distinguished shea trees having white, black or red bark; they also differentiated early fruiting trees (that bear fruits before the beginning of the rainy season), trees that have normal fruiting time (they produce fruits during the rainy season) and the ones, which have late production (they fructify after the two previous ones). Some trees produce fruits with sweet or insipid pulp and others produce large, small or medium size fruits. Farmers also reported that there are male and female shea trees. Based on the fruiting ability of shea trees, local people distinguished two types of shea tree: the “female,” fruit-producing trees, and the “male” trees, which never produce fruits. However, in the Ditamari sociolinguistic group, early maturing genotypes were referred to as ‘’Nda’’ which means ‘’male’’ ; this comparison was borrowed according to them from the rule of male gametes during fecundation. In the Ditamari community, the production of fruit in shea trees is comparable to the conception of a child; the male seed gives fruit very early (whereas the female keeps pregnancy for several months before giving birth. That is why they equate this trait with a male.
Diversity of shea morphotypes traits in shea parks of Benin
Local knowledge on shea morphotypes traits diversity and Shannon index diversity varied from one zone to the another (Table 4). Based on the classification criteria used, different numbers of morphotypes traits were recorded across parks. Our results indicated that traits richness was greater in Bembèrèkè, Parakou, Kandi and Savè zones than in Bohicon shea parkland zone.
The pairwise analysis allows the identification of patterns of dissimilarity between zones based on Sorensen index. The Sorensen index values range from 13.0 to 88.3% (Figure 2), taking into account ten combinations of pairwise comparison : Bembèrèkè – Bohicon (BB-BH), Bembèrèkè – Kandi (BB-KD), Bembèrèkè – Parakou (BB-PK), Bembèrèkè – Savè (BB-SV), Bohicon – Kandi (BH-KD), Bohicon – Parakou (BH-PK), Bohicon – Savè (BH-SV), Kandi – Parakou (KD-PK), Kandi – Savè (KD-SV), Parakou – Savè (PK-SV). The dissimilarity in terms of shea traits natural variation between northern zones (Parakou, Bembèrèkè and Kandi) is rather low (<25%). In contrary, dissimilarity index values were higher between northern and southern (Bohicon) zones (60-88.3%). There is a big difference in local knowledge between the northern zones and southern zone.
In order to understand how the richness of the morphotypes traits varied according to the number of zones considered, we realized the cumulative curve of morphotypes richness (Figure 3). Which revealed that the morphotypes richness increases and then becomes stable when all five zones were explored.
Characterization of shea morphotypes’ traits performance
Respondents reported three different level of shea morphotypes’ abundance attribute such as ‘widespread’, ‘few’ and ‘scarce'. Trees fruit yield and butter yield after processing could be according to respondents ‘high’, ‘medium’ or ‘low’. Principal Component Analysis (PCA) performed on the perception scores of the distribution, the morphological and performance traits showed that the first two dimensions accounted for 79.96% of the observed variation (Figure 4). The first component is positively correlated with the variables medium and low yield (fruit yield), medium and low quantity of butter after processing (medium butter and low butter) and scarce and few distribution frequencies. The second component is negatively correlated with the variable null yield (no fruit production), and positively with the variables high yield, high butter and widespread.
According to the biplot of morphotypes and abundance, fruit yield and butter yield characteristics (Figure 4), it appears that, based on farmers’ perception, shea morphotypes having the trait Yanki (small fruit) are characterized by high fruit yield, a high amount of butter after nuts processing and are widespread. On the other hand, shea morphotypes with the trait Bakanou (large fruit) and are rare (scarce) or very little spread (few). They may have medium and low fruit production and the nuts inside their fruits produce an average amount of butter after processing. The morphotypes characterized by the trait Akô (male tree) do not have ability to produce fruit (null yield). All other morphotypes traits do not reveal any particular characteristics. No specific trend of these variables has been recorded for the other morphotypes traits.
Influence of occurence and sociocultural factors on local knowledge of shea morphotypes natural variation
The average number of traits cited by each respondent did not vary significantly (p> 0.05) regarding the parkland, age, gender, instruction level, and sociolinguistic group.
However, the relative frequency of citation of the 13 main local morphotypes varied very highly significantly regarding shea parklands zones (p< 0.001). Factorial correspondence analyses (FCA) plot (Figure 5) shows traits mostly mentioned by farmers in each zone. Morphotypes that have red bark (Soarou), large and small fruit size (Bakanou and Yanki) were more common in Parakou and Kandi zones. Local morphotypes identified based on the pulp taste such as sweet and insipid (Dourobou and Yeniyando) were mostly mentioned in Kandi park than in others. Morphotypes traits relative to the timing of production, medium fruit size (Saganin) and bark colour specifically morphotype having white and black bark, were common in Bembèrèkè shea parklands zone. On the other hand, the morphotypes traits Akô and Abô were mostly cited in the Savè and Bohicon zones.
With exception to gender (p = 0.218), all socio-demographic characteristics very significantly (p < 0.001) influence the relative frequency of the 13 main traits of shea morphotypes (Figure 6). Figure 6 shows the relative citation frequency (RCF) of traits according to age groups, gender, instruction level and sociolinguistic groups. All traits were known to the three age groups; however, local knowledge varied from an age group to another. The relative frequency of citation decreased from adult to old people passing by young for all traits except the trait “Dourobou” which was most reported by elders than young respondents.
General trend for the influence of instruction level is the decrease of local knowledge on morphotypes traits from illiterate to literate respondents. Morphotypes citation frequency were higher for illiterate (25 < RCF < 85%) and respondents with primary school level (1 < RCF < 80%) than those of respondents who attained secondary and university (0 < RCF < 25%). Relative citation frequency of traits citation varied also from a sociolinguistic group to another. All sociolinguistic groups cited the female trait Abô and except Dendi, all sociolinguistic groups recognised the trait Akô which is qualified as male by farmers. Bariba sociolinguistic group cited all traits mainly than those related to fruit size (Yanki, Saganin and Bakanou), bark colour (Kpika and Wonka) and pulp taste (Dourobou and Yeniyando) with RCF > 50%. The Fon sociolinguistic group mentioned only female and male traits. Shea morphotypes traits identified based on timing of the fruit production (Nina, Nda and Niendembou) were registered mostly within Ditamari sociolinguistic group (70 < RCF < 80%). The differentiation of morphotypes according to fruit size, pulp taste, bark colour criteria were almost common to Bariba, Dendi, Yom and Boko sociolinguistic groups located in the Northern part of the country.