 |
in Ashokan, Xavier, Suksathan, ... et Gowda, 2022. |
Highlights
• Hedychium originated in the Late Miocene, followed by Pleistocene diversification.
• Hedychium has a Northern Indo-Burmese origin with successive dispersal events to Southern Indo-Burma, Himalayas, Peninsular India, and the Malay Archipelago.
• Both Himalayan uplift as well as Asian monsoon might have shaped the diversification of Hedychium.
• Epiphytism evolved multiple times within the genus and is the dominant growth habit among the island species (Malay Archipelago).
• Vegetative dormancy was restricted to species from clades I and II (subtropical montane forests).
Abstract
The Indo-Malayan Realm is a biogeographic realm that extends from the Indian Subcontinent to the islands of Southeast Asia (Malay Archipelago). Despite being megadiverse, evolutionary hypotheses explaining taxonomic diversity in this region have been rare. Here, we investigate the role of geoclimatic events such as Himalayan orogeny and monsoon intensification in the diversification of the ginger lilies (Hedychium J.Koenig: Zingiberaceae). We first built a comprehensive, time-calibrated phylogeny of Hedychium with 75% taxonomic and geographic sampling. We found that Hedychium is a very young lineage that originated in Northern Indo-Burma, in the Late Miocene (c. 10.6 Ma). This was followed by a late Neogene and early Quaternary diversification, with multiple dispersal events to Southern Indo-Burma, Himalayas, Peninsular India, and the Malay Archipelago. The most speciose clade IV i.e., the predominantly Indo-Burmese clade also showed a higher diversification rate, suggesting its recent rapid radiation. Our divergence dating and GeoHiSSE results demonstrate that the diversification of Hedychium was shaped by both the intensifications in the Himalayan uplift as well as the Asian monsoon. Ancestral state reconstructions identified the occurrence of vegetative dormancy in both clades I and II, whereas the strictly epiphytic growth behavior, island dwarfism, lack of dormancy, and a distinct environmental niche was observed only in the predominantly island clade i.e., clade III. Finally, we show that the occurrence of epiphytism in clade III corresponds with submergence due to sea-level changes, suggesting it to be an adaptive trait. Our study highlights the role of recent geoclimatic events and environmental factors in the diversification of plants within the Indo-Malayan Realm and the need for collaborative work to understand biogeographic patterns within this understudied region. This study opens new perspectives for future biogeographic studies in this region and provides a framework to explain the taxonomic hyperdiversity of the Indo-Malayan Realm.
Keywords: Dormancy, Environmental niche analysis, Epiphytism, Historical biogeography, Island dwarfism, Malay Archipelago, Northeast India, Pleistocene
Ajith Ashokan, Aleena Xavier, Piyakaset Suksathan, Marlina Ardiyani, Jana Leong-Škorničková, Mark Newman, W. John Kress and Vinita Gowda. 2022. Himalayan Orogeny and Monsoon Intensification explain Species Diversification in An Endemic Ginger (Hedychium: Zingiberaceae) from the Indo-Malayan Realm. Molecular Phylogenetics and Evolution. 170; 107440. DOI: 10.1016/j.ympev.2022.107440
