Emergence and extinction of Dipterocarpaceae in western India with reference to climate change: Fossil wood evidences

Abstract

Climate has played a crucial role in assigning a different kind of topography to Rajasthan and Gujarat since the Cenozoic time. Evidently, three genera, namely, Dipterocarpus Gaert. f., Hopea Roxb. and Shorea Roxb. of the Dipterocarpaceae are described from the Neogene sediments of western India (Rajasthan and Gujarat). These taxa are marked by their complete absence in the region today. The presence of Dipterocarpaceae in western India has been noticed from the Early Eocene up to the Plio-Pleistocene in deep time. The family is usually a dominant component of the humid tropical and subtropical flora of the Indo-Malayan region and its discovery, along with earlier described fossils from western India indicates existence of ancient tropical rain forests in western India. A change in the climate affected warm and humid conditions occurring there during the Cenozoic resulting in arid to semi-arid climate at present which is responsible for the ultimate extinction of Dipterocarpaceae in the region. In addition, the palaeobiogeography of Dipterocarpaceae is reviewed.

Leaf Physiological Responses to Drought Stress and Community Assembly in an Asian Savanna

“…The deciduous dipterocarp species in the present study are four of only six deciduous species of the Dipterocarpaceae family [18,45], which includes 520 species mainly occurring across the tropics of continental and insular Southeast Asia [46]. Our data suggest that the Ψ tlp of the deciduous Dipterocarpus (−1.7 MPa) and Shorea (−2.6 MPa) species were substantially more negative than the values reported for evergreen dipterocarp species from aseasonal tropical forests (range: −1 to −1.4 MPa) [7].…”

Origins and Assembly of Malesian Rainforests

“…The early Eocene Cambay amber deposit in Gujarat, India, includes resins, wood, and pollen with what are described as strong morphological affinities to Dipterocarpaceae (Rust et al 2010, Dutta et al 2011). However, Shukla et al (2013) cautioned that the wood characters were potentially misinterpreted and that Lauraceae cannot be excluded as a possibility; additional experts whom we recently queried confirmed this opinion (E. Wheeler & C. Williams, personal communication, 2018). More generally, reference to dipterocarps based on resin (amber) spectroscopy, if not supported by direct fossil evidence, may require closer scrutiny because bicadinanes are now known to come from sources other than Dipterocarpaceae (see the sidebar titled Bicadinane Biomarkers) (van Aarssen et al 1994, Coward et al 2018.…”

A tropical forest of the middle Miocene of Fujian (SE China) reveals Sino-Indian biogeographic affinities

“…However, the megafossils of Dipterocarpaceae that were reported in the Neogene sediments of India and Nepal (e.g. Awasthi and Prasad, 1990;Prasad, 1990Prasad, , 1994Prakash et al, 1994;Khan et al, 2011) are absent from the Paleogene of India but present in the Paleogene of South-East Asia (Bande and Prakash, 1986;Srivastava and Mehrotra, 2010;Shukla et al, 2013). The occurrence of Dipterocarpaceae from the middle Miocene of China raises the question of the route of exchange between Chinese and Indian palaeofloras.…”