Taxonomic Studies on Malagasy Dalbergia (Fabaceae). III. Two New Species from Southeastern Madagascar and an Emended Description of the Rosewood Species Dalbergia maritima

Abstract

Abstract The Malagasy rosewood species Dalbergia maritima has a long history of unsustainable exploitation for its beautiful, burgundy-colored heartwood. As currently circumscribed, D. maritima has a wide geographic distribution in eastern Madagascar and exhibits significant morphological, ecological, and genetic variation, suggesting it may comprise more than a single entity. Multivariate analyses of leaf, flower, and inflorescence characters as well as eco-geographic features reveal several morphologically well delimited entities with distinct habitat preferences and/or geographic ranges, which are consistent with results from recent phylogenomic and population genomic studies of Malagasy Dalbergia. Based on these findings, we describe and illustrate two new species from southeastern Madagascar comprising material previously assigned to D. maritima, viz. D. pseudomaritima, characterized by paniculate inflorescences and small, broadly elliptic to orbicular, glabrous leaflets, and D. razakamalalae, distinguished by racemose inflorescences with large flowers, and narrowly ovate to narrowly elliptic, glabrous leaflets. Dalbergia maritima is consequently re-circumscribed to include only populations from east-central Madagascar, within which we recognize two subspecies, D. maritima subsp. maritima, with glabrous leaves, inflorescence axes, and gynoecia, occurring in littoral forest habitats, and D. maritima subsp. pubescens, with indument on these structures, and growing in evergreen humid forest farther inland. Photos are provided for each taxon, along with line drawings for the two new species. Provisional IUCN Red List assessments indicate that all three species are Endangered, D. maritima and D. razakamalalae mainly because of selective logging for trade in their high-quality heartwood, and D. pseudomaritima primarily because of habitat degradation due to land clearing and fire for subsistence agriculture, which has important implications for their conservation and sustainable management.