Patterns in the alien flora of the Democratic Republic of the Congo: a comparison of Asteraceae and Fabaceae

Abstract

Background and aims – This work provides the first pattern analysis of the alien flora of the Democratic Republic of the Congo (D.R. Congo), using Asteraceae and Fabaceae as a case study. Methods – Based on herbarium collections, existing databases, and literature data, a database of 38 alien species of Asteraceae and 79 alien species of Fabaceae has been assembled. Patterns in the introduction pathway, phylogeny, life form, morpho-functional traits, geographic origin, and occurrence in D.R. Congo are explored. Key results – America is the main source continent in both families, but Asia is also an important donor of Fabaceae. Taxonomic spectrum discrepancies between the alien and the native flora reflect the continent of origin. Sixty-six percent of alien Asteraceae have been accidentally introduced, most of which being annual weeds of disturbed soil. In contrast, 90% of alien Fabaceae have been deliberately introduced for forestry, agriculture, or environmental purposes, most of which being phanerophytes. Traits were compared between pairs of congeneric alien and native species. For Asteraceae, a sharp discrepancy was found in the life form spectrum (aliens: mostly therophytes; natives: phanerophytes). For Fabaceae, alien species had larger leaves and larger pods compared to their native congeners. The number of specimens in collections was positively correlated with the time since the date of first collection for both families. The GuineoCongolian region has the highest number of alien Fabaceae, while alien Asteraceae are overrepresented in the Zambezian region. Conclusions – Contrasting patterns between alien Asteraceae and Fabaceae in the flora of D.R. Congo in terms of life forms, trait divergence compared to the native flora, and occurrence, reflect the divergent biological attributes and relations to humans of the two families. The striking discrepancies between the two families call for analyses of patterns of alien flora at family level and warn against global generalisations.