Molecular identification of natural hybridization betweenMelastoma malabathricumandMelastoama beccarianumin Sarawak, Malaysia

Abstract

Hybridization is very common in flowering plants and it plays a significant role in plant evolution and adaptation. Melastoma L. (Melastomataceae) comprises about 80–90 species in tropical Asia and Oceania, among which 41 species occur in Borneo. Natural hybridization is frequently reported in Melastoma in China, but so far there have been no confirmed cases of hybridization in Southeast Asia (including Borneo), where most species occur. Here, we identified a case of natural hybridization between Melastoma malabathricum L. and Melastoma beccarianum Cogn. in Sarawak, Malaysia, by using sequence data of three nuclear genes and one chloroplast intergenic spacer. Melastoma malabathricum is the most widespread species of this genus, occurring in almost the whole range of this genus, while M. beccarianum is a local species endemic to northern Borneo. Our results showed that natural hybridization and introgression occur between M. malabathricum and M. beccarianum, and the introgression was asymmetrical, mainly from M. malabathricum to M. beccarianum. As adaptive traits can be transferred by introgression, our study suggests that natural hybridization should be a significant mechanism for the evolution and adaptation of Melastoma in Southeast Asia. However, introgression from the common species M. malabathricum to the relatively rare species M. beccarianum may cause the decline of M. beccarianum, incurring conservation concern. With a large number of species of Melastoma and almost year‐around flowering in Southeast Asia, more cases of natural hybridization are expected to be found and identified in near future.

Flower-visiting insects of genus Melastoma (Myrtales: Melastomataceae) at the Fushan Botanical Garden, Taiwan

“…While reproduction biology is recognised as an essential part of plant conservation, identifying key pollinators and pollination mechanisms becomes fundamental ( Havens et al 2006 , Moza and Bhatnagar 2007 ). Without such information, cultivation of closely-related species with high hybridisation potential, as observed in Melastoma ( Dai et al 2012 , Liu et al 2014 , Wu et al 2019 ) in ex situ collection sites, may increase chances of genetic introgression ( Lozada-Gobilard et al 2020 ). The hybridisation risk in ex situ collections might be more severe for sanctuaries in the tropics as most countries in the tropical regions usually have mega-diverse flora, but often grow high numbers of species in a confined area due to lack of sufficient infrastructure.…”

“…To date, only one study on the pollination biology of one Melastoma species, M. candidum , in Taiwan has been published ( Liu et al 2008 ). Noteworthy, interspecific hybridisation in this genus is often observed in both wild and cultivated plants in China and Southeast Asia ( Cai et al 2019 , Wu et al 2019 , Zhou et al 2017 ). Although genetic introgression has not been reported from Taiwan, co-occurrence of congeners, including the endangered and endemic M. kudoi , is common in Taiwan (C.J.…”

Species richness, lineages, geography, and the forest matrix: Borneo’s ‘Middle Sarawak’ phenomenon

“…Indeed, there is now molecular demonstration of bidirectional introgression between Melastoma malabathricum L. and M. beccarianum Cogn. from Sarawak (Wu et al, 2019). Incomplete reproductive isolation following rapid diversification, such as possible in the case of Melastoma (Renner & Meyer, 2001), as well as shared pollinators and overlapping distribution (Wu et al, 2019), should also be important factors.…”

“…from Sarawak (Wu et al, 2019). Incomplete reproductive isolation following rapid diversification, such as possible in the case of Melastoma (Renner & Meyer, 2001), as well as shared pollinators and overlapping distribution (Wu et al, 2019), should also be important factors. Expectedly, smaller seed mass concomitant with high selfing rates, such as in the canopy dipterocarp Neobalanocarpus heimii (King) P.S.Ashton, ties in with lower survival of selfed progeny from seeds to established seedlings, indicating inbreeding depression (Naito et al, 2005).…”

Natural hybridization between two butterfly bushes in Tibet: dominance of F1 hybrids promotes strong reproductive isolation

“…Natural hybridization in plants is a common phenomenon, and is thought to play an important role in plant diversity and speciation [1][2][3][4]. Many empirical studies have focused on the onset of natural hybridization and have examined issues including reproductive barriers [5,6], backcrossing and introgression which are sometimes involved in transference of adaptation [7][8][9] or acceleration of extinction by genetic swamping [10][11][12]. A phenomenon previously assumed to be rare but recently found to be common, is the presence of hybrids consisting mainly of F 1 s [13][14][15][16][17], due to intrinsic incompatibilities including F 1 hybrid sterility and/or inviability [4,13,18], and extrinsic selection, with other genotypes of hybrids being outcompeted due to strong habitat selection [13,14,19,20].…”