Taxonomic studies on Malagasy Dalbergia (Fabaceae). III. Two new species from Southeastern Madagascar and an emended description of the rosewood species D. maritima

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.

马达加斯加黄檀属（Dalbergia）物种滨海黄檀（Dalbergia maritima）因其美观的酒红色心材，长期遭受过度采伐。按当前的分类界定，滨海黄檀在马达加斯加东部有着广泛的地理分布，且表现出显著的形态、生态和遗传变异，这表明该类群可能并非单一物种。对叶、花、花序（inflorescence）性状及生态地理特征的多变量分析（multivariate analyses）显示，存在多个形态界定清晰的类群，它们具有独特的生境偏好和/或地理分布范围，这与近期针对马达加斯加黄檀属的系统基因组学（phylogenomic）及种群基因组学（population genomic）研究结果一致。基于上述发现，我们对产自马达加斯加东南部、此前被归入滨海黄檀的类群进行修订，描述并图示了两个新物种：分别为具圆锥花序（paniculate inflorescences）、小叶小型、呈宽椭圆形至近圆形（orbicular）且无毛（glabrous）的假滨海黄檀（D. pseudomaritima），以及具总状花序（racemose inflorescences）、花较大、小叶狭卵形（narrowly ovate）至狭椭圆形（narrowly elliptic）且无毛（glabrous）的拉扎卡马拉黄檀（D. razakamalalae）。因此，滨海黄檀被重新界定为仅包含马达加斯加中东部的种群，该类群下我们识别出两个亚种：一是叶、花序轴及雌蕊群（gynoecia）均无毛、生于滨海林（littoral forest）生境的原亚种滨海黄檀（D. maritima subsp. maritima）；二是上述结构具毛被（indument）、生长于更内陆的常绿湿润林中的柔毛滨海黄檀（D. maritima subsp. pubescens）。所有类群均配有照片，两个新物种额外配有线条绘图。暂定的世界自然保护联盟红色名录（IUCN Red List）评估显示，这三个物种均被列为濒危：滨海黄檀与拉扎卡马拉黄檀濒危的主要原因是为优质心材贸易而进行的选择性采伐；假滨海黄檀濒危则主要源于为开展自给农业（subsistence agriculture）而进行的土地清理与焚烧导致的生境退化，上述结果对其保护与可持续管理具有重要意义。