Biogeographical patterns of grasses (Poaceae) indigenous to South Africa, Lesotho and Eswatini

Abstract

The grass family, Poaceae (Gramineae) is considered the most valuable plant family in food production worldwide. In addition to its importance as a grain crop (e.g. maize, wheat and rice), its tolerance to grazing, fire and drought, makes grasses a significant component of livestock feed, mainly sourced from rangeland and/or planted pastures. Soreng et al. (2017) recognised at least 11 506 grass species worldwide of which approximately 685 species are indigenous to southern Africa (Trytsman et al. 2020).Considering that in southern Africa only eight indigenous grass species were extensively researched in the past century (Truter et al. 2015), the wealth of grass genetic resources, indigenous to the subcontinent, still needs to be prioritised, conserved and developed for forage production.The classification and distribution of southern African grasses that included Botswana, Namibia, South Africa, Lesotho and Swaziland were described by Gibbs Russell et al. (1990) and was updated by Fish et al. (2015). Studies on the biogeographical patterns of grasses in relation to southern African vegetation types are, however, limited. Then again, there are numerous phytogeographical studies on the southern African flora, which include those by

Harnessing Ecosystem Services from Invasive Alien Grass and Rush Species to Suppress their Aggressive Expansion in South Africa

“…The Poaceae family was found to be the most important botanical family with 94.7% (n = 18) useful invasive grass species, whereas Juncaceae contains only 5.3% (n = 1) rush species. High species richness within the family Poaceae demonstrates species diversity within this family [48,[69][70][71][72][73]. The findings of this review are not unique, but serve as confirmation of similar findings in studies done by Schubert et al [74] and Díaz and Jorquera [75].…”

A Phytogeographical Classification and Survey of the Indigenous Browse Flora of South Africa, Lesotho, and Eswatini

“…The statistical software PC-Ord, version 5.31 [26] was used to perform the cluster analysis, applying the Euclidean distance for dissimilarity and Ward's linkage. Previous studies with southern African grasses and legumes showed that, although PC-Ord formed disjointed groups, it was more accurate in placing QDGCs in the resulting phytochoria compared to using XLSTAT 1 Jun 2010 Software (Addinsoft to MS Excel) [24]. The geographical distribution of the clusters resulting from the AHC was compared with existing maps of well supported phytogeographical regions in the study area, especially those depicting biomes and bioregions [27] of southern Africa.…”

“…The QDGCs assigned to ecotones (where two or more biomes or bioregions converge in a QDGC) were not included in the dataset where the key biomes and bioregions of browse-choria are defined. Similar to previous studies [22,24], the total number of occurrences (records) in a browse-chorion was calculated, and 20 key species with the highest occurrences were selected to identify species with presumably wide ecological tolerance in a particular browse-chorion. The collection intensity (expressed as the number of browsed species per QDGC collected as herbarium specimens) was calculated and mapped on the biome and bioregion maps of South Africa, Lesotho, and Eswatini [28].…”

“…The result of the AHC is shown as a dendrogram in Figure 1. As in previous biogeographical studies by Trytsman et al [22,24], smaller clusters were distinguished from the dendrogram, mapped, and examined for meaningful ecologically interpretable groups. A total of 25 coherent clusters with clear phytographical boundaries were identified (Supplementary Material Figure S1) and grouped into seven distinct browse-choria as shown in Table 1.…”

“…In this study, browse is defined as a woody shrublet, dwarf shrub, shrub, or tree known to be utilised as food by livestock and game, both by ruminants and/or non-ruminants. The term browse-choria describes the phytochoria based on assemblages of distinctly woody species utilised by herbivores, similar to leguminochoria (assemblages of Leguminosae) and grasschoria (assemblages of Poaceae) referred to in previous studies [22][23][24]. The phytogeographical patterns and significance of the browse-choria (from this study), as well as the previously recognised leguminochoria and grasschoria, will assist in formulating a collection, conservation, screening, and characterisation strategy for indigenous genetic resources with pasture and or soil conservation potential for the South African National Forage Genebank.…”