Special Issue "Advances in Legume Systematics 14. Classification of subfamily Caesalpinioideae (Leguminosae)"

Open for submissionSubmission deadline: 15 December 2021

Special Issue Editors

Colin E. Hughes, Luciano de Queiroz, Gwilym Lewis

Special Issue Information

Caesalpinioideae is the second largest subfamily in the legume family with ca. 150 genera and ca. 4,400 species, 75% of which are placed in the Mimosoid clade (formerly subfamily Mimosoideae). The subfamily has a pantropical distribution and is diverse and abundant in all three major lowland tropical biomes – savannas, seasonally dry tropical forests and rain forests. The subfamily is almost entirely woody and made up of trees, shrubs, lianas and geoxyles, and includes a number of prominent and well-known genera such as Acacia, Mimosa, Inga, Prosopis, Caesalpinia and Cassia.

While the classification of the legumes into six subfamiles is now widely accepted (Legume Phylogeny Working Group in Taxon, 2017, 66: 44-77), the classification within subfamily Caesalpinioideae has remained unresolved due to a lack of phylogenetic resolution across the large paraphyletic grade subtending the mimosoid clade. Furthermore, the generic classification of this subfamily and especially the Mimosoid clade (with c. 88 genera) remains in a state of considerable flux due to lack of effective pantropical integration and widespread homoplasy of almost all morphological characters that have been used to delimit genera.

Recent phylogenetic work using a large phylogenomic DNA sequence dataset of 997 nuclear genes is now providing a much more robust backbone phylogeny that can be used to establish a new tribal classification of the subfamily. This new phylogeny also shows that 25% of the genera in the Mimosoid clade are non-monophyletic and that a new generic system is needed. A recently published version of this new phylogeny that included 120 taxa (Koenen et al. in American Journal of Botany, 2020, 107: 1710-1735) has now been expanded to include 422 species and 145 of the 150 genera, providing an excellent base for a landmark volume that would provide a significant advance in the classification of Caesalpinioideae.

This Special Issue of PhytoKeys aims to present and publish: (i) this new phylogeny demonstrating the extent of generic non-monophyly; (ii) a new tribal / clade-based classification of subfamily Caesalpinioideae; (iii) a series of papers that focus on generic re-delimitation of particular clades to deal with the majority of the genera that are currently non-monophyletic, including publication of new names and combinations as far as possible.


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