﻿A natural hybrid of Sindora (Fabaceae, Detarioideae) from Singapore.

Le Min Choo,Adrian Hock Beng Loo,Kenneth Boon Hwee Er,Wee Foong Ang

doi:10.3897/phytokeys.190.79185

Abstract

Sindora×changiensis L.M.Choo, Loo, W.F.Ang & K.Er is a new hybrid from the subfamily Detarioideae in Fabaceae. This is the first reported instance of natural hybridisation in Sindora. Based on population genetics analyses using ddRAD and morphological observations, this taxon represents a fertile hybrid between Sindoracoriacea and Sindoraechinocalyx. This new hybrid is so far only known to occur naturally from Changi at the north-eastern coast of Singapore. It has pods that are sparsely spiny. This is intermediate between the smooth, non-spiny pods of S.coriacea, and the densely spiny pods of S.echinocalyx. The calyx is smooth and unarmed, resembling S.coriacea. Last but not least, the ovary is entirely pubescent, different from S.coriacea and S.echinocalyx. The ovary of S.coriacea has a glabrous patch in the middle, while that of S.echinocalyx has minute spines protruding from the dense pubescence. A taxonomic description and an updated key to the Sindora of Singapore and Peninsular Malaysia are also provided.

Highlights

Sindora Miq. is a genus of the legume family (Fabaceae: Detarioideae) and consists of 20–22 species
The Neighbour-Net analysis in SPLITSTREE (Fig. 1) showed all three individuals of S. × changiensis to be located between S. coriacea and S. echinocalyx in the plot, which indicated that S. × changiensis was likely the result of hybridisation between the two parent species
The STRUCTURE analysis of the subsample of 10,000 single nucleotide polymorphism (SNP) showed similar results at K = 2, where individuals of S. coriacea and S. echinocalyx were assigned to separate genetically distinct populations, and individuals of S. × changiensis were shown to be admixed between the two parents, as shown in Fig. 2, where the genetic composition of S. × changiensis is a mix of S. coriacea and S. echinocalyx

Summary

Introduction

Sindora Miq. is a genus of the legume family (Fabaceae: Detarioideae) and consists of 20–22 species. It has a paleotropical distribution, with one species from West Central Africa, and the rest from Asia, which are distributed from Southern China to Southeast Asia, and to as far west as the Philippines (de Wit 1949; Chen et al 2010; Choo and Ngo 2020). Four species, Sindora coriacea, S. echinocalyx, S. velutina and S. wallichii are present in both Singapore and Peninsular Malaysia, while S. siamensis is found only in northern Peninsular Malaysia, Thailand, Cambodia, Laos and Vietnam, and is only present as a cultivated tree in Singapore. Recent field observations of mature Sindora trees in Singapore revealed a particular 27 m-tall mature tree from Changi at the north-eastern coast of the island, which could not be satisfactorily identified to species using the taxonomic key in Choo and Ngo (2020)

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Conclusion