Evolution and biogeography of Memecylon

Abstract

Premise The woody plant group Memecylon (Melastomataceae) is a large clade occupying diverse forest habitats in the Old World tropics and exhibiting high regional endemism. Its phylogenetic relationships have been previously studied using ribosomal DNA with extensive sampling from Africa and Madagascar. However, divergence times, biogeography, and character evolution of Memecylon remain uninvestigated. We present a phylogenomic analysis of Memecylon to provide a broad evolutionary perspective of this clade. Methods One hundred supercontigs of 67 Memecylon taxa were harvested from target enrichment. The data were subjected to coalescent and concatenated phylogenetic analyses. A timeline was provided for Memecylon evolution using fossils and secondary calibration. The calibrated Memecylon phylogeny was used to elucidate its biogeography and ancestral character states. Results Relationships recovered by the phylogenomic analyses are strongly supported in both maximum likelihood and coalescent‐based species trees. Memecylon is inferred to have originated in Africa in the Eocene and subsequently dispersed predominantly eastward via long‐distance dispersal (LDD), although a reverse dispersal from South Asia westward to the Seychelles was postulated. Morphological data exhibited high levels of homoplasy, but also showed that several vegetative and reproductive characters were phylogenetically informative. Conclusions The current distribution of Memecylon appears to be the result of multiple ancestral LDD events. Our results demonstrate the importance of the combined effect of geographic and paleoclimatic factors in shaping the distribution of this group in the Old World tropics. Memecylon includes a number of evolutionarily derived morphological features that contribute to diversity within the clade.

Niche dynamics of Memecylon in Sri Lanka: Distribution patterns, climate change effects, and conservation priorities

“…Moreover, examining these niche differences in the context of phylogenetic relationships may help us understand the factors that have led to the diversification of Memecylon within the island and to infer ancestral niches. However, Sri Lankan Memecylon is not monophyletic; instead, it includes Memecylon from India, Andaman, and the Seychelles (Amarasinghe, Joshi, et al, 2021 ). To understand the ancestral niches of Sri Lankan Memecylon , niche models should be generated from all these geographical regions in South Asia where Memecylon occurs and analyzed in a phylogenetic framework.…”

“…Maroon circles show the field collection sites identifications of some herbarium specimens were found to be erroneous: ~15% of specimens in GBIF, ~13% deposited at the PDA, ~2% at the SING, ~5% at the US Herbaria. The likely reason for the misidentification of Memecylon specimens is due to many specimens being sterile because of seasonal and/or rarity of flowering events (Amarasinghe, Joshi, et al, 2021). Therefore, we corrected all misidentified specimens stored in the PDA, SING, and US herbaria by carefully studying the type specimens and taxonomic descriptions during the visits to these herbaria.…”

“…To date, research on Memecylon has mainly focused on its taxonomy, ethnobotany, and evolution (e.g., Amarasinghe, Joshi, et al, 2021;Bremer, 1988;Sivu et al, 2013) (Loarie et al, 2008;Manes et al, 2021;Thuiller et al, 2006) due to occupying specialized niches, limited dispersal capabilities, and reduced adaptive capacities when compared to nonendemic species (Chichorro et al, 2019;Staude et al, 2020). Further, organisms that have more restricted geographical ranges are at greater risk (Elsen & Tingley, 2015;Stubbs et al, 2018) compared to species with large geographical ranges, which may find refugia in parts of their range (Lucas et al, 2019).…”

“…To date, research on Memecylon has mainly focused on its taxonomy, ethnobotany, and evolution (e.g., Amarasinghe, Joshi, et al, 2021 ; Bremer, 1988 ; Sivu et al, 2013 ) and studies to examine how climate change potentially impacts its distribution are completely lacking. In this study, we compiled occurrences of Memecylon from diverse sources and bioclimatic data associated with various climate scenarios to address three key questions: (1) What are the patterns of distribution of Sri Lankan Memecylon under current climate conditions?…”

Diversification and divergence of rainforest woody plants in South India and Madagascar relate to geomorphological history

“…Studies based on genetic data have highlighted the recurrent role of long-distance dispersal on the diversification and distribution of organisms (Cook & Crisp, 2005;De Queiroz, 2005). Furthermore, other lineages, such as the Memecylon genus in Melastomataceae with divergence times that are inconsistent with geographical separation events (Amarasinghe et al, 2021;Renner, 2004), emphasize the need to consider transoceanic migration events in elucidating the biogeographical history of these regions.…”