Fire-prone Rhamnaceae with South African affinities in Cretaceous Myanmar amber

Abstract

Background: Flowering plants (angiosperms) dominate most global ecosystems today, but their rapid Cretaceous diversi cation has remained poorly understood ever since Darwin referred to it as an 'abominable mystery'. Although numerous Cretaceous fossil owers have been discovered in recent years, most are represented by incomplete charcoali ed fragments that do not preserve delicate structures such as complete petals and surface textures, which means that their similarity to living forms is often di cult to discern. The scarcity of information about the ecology of early angiosperms makes it di cult to test hypotheses about the drivers of their diversi cation. Among other factors, frequent res in the Cretaceous have been postulated as having possibly facilitated the rise of angiosperms. However, to date no early fossil angiosperms displaying re-adapted traits have been known, making the role of re in shaping Cretaceous oras uncertain.Results: We report the discovery of two exquisitely preserved fossil ower species, one identical to the in orescences of the extant crown eudicot genus Phylica and the other recovered as a sister group to Phylica, both preserved as inclusions in Cretaceous amber from northern Myanmar (~99 Ma). These specialized ower structures, named Phylica piloburmensis sp. nov. and Eophylica priscastellata gen. et sp. nov., were adapted to surviving frequent wild res, providing the earliest evidence of re-resistance in angiosperms. The fossils suggest that re was a signi cant selective force in Cretaceous angiosperm oras and that adaptations to re resistance in some eudicot clades have been conserved for at least 99 Ma. This morphological stasis encompasses a range of oral characters, including the production of 'pseudo-owers', and characteristic fruit and pollen architecture. Given its morphological distinctiveness,

Fire‐released seed dormancy ‐ a global synthesis

“…Is it consistent with dormancy as a fire adaptation? We propose that fire‐released dormancy must be ancient within the evolutionary history of flowering plants because ( i ) the capacity for seed dormancy was present among their earliest ancestors [at least 130 million years ago (Ma); Willis et al ., 2014; Friis et al ., 2015], ( ii ) fire is an ancient process on Earth (from 420 Ma; Scott, 2018), ( iii ) fireprone ecosystems have been common at least since the mid‐Cretaceous (100 Ma) when flowering plants first became prominent (Shi et al ., 2022), ( iv ) many other fire‐adapted traits appeared during the Cretaceous and proliferated during the Paleogene–Neogene (Lamont et al ., 2019a), and ( v ) fire‐released dormancy provides strong fitness benefits to plants (as shown in previous sections).…”

“…7). Recent research shows that a 99‐million‐year‐old fossil Phylica (Rhamnaceae) from a fireprone ecosystem exhibited floral and leaf traits identical to modern Phylica (Shi et al ., 2022). Since the modern taxa also inhabit fireprone ecosystems (fynbos) and have hard and arillate (ant‐dispersed) seeds, it indicates that these traits have been maintained for at least 99 million years (My) in Rhamnaceae.…”

A New Subgenus and Species of Priochirus from Mid-Cretaceous Kachin Amber (Coleoptera: Staphylinidae: Osoriinae)

“…The amber specimen studied herein was found in the Hukawng Valley, Kachin State, northern Myanmar (26°21′33.41″ N, 96°43′11.88″ E) [ 13 ]. The age of Kachin amber has been dated to 98.79 ± 0.62 Ma based on U-Pb zircons (earliest Cenomanian) [ 14 ].…”

Ancient Rhamnaceae flowers impute an origin for flowering plants exceeding 250-million-years ago

“…A case in point are the flowering plants (Angiosperms) whose origin has gradually been taken from the mid-Cretaceous, as favored just a few years ago, to the Jurassic, then the Triassic and now possibly even into the Permian ( Li et al., 2019 ; Silvestro et al., 2021 ). In this regard, the study of Shi et al. (2022) is a huge step forward as they provide convincing evidence for the presence of intact flowering shoots belonging to the Phylica clade (family Rhamnaceae, subfamily Ziziphoideae) in Burmese amber.…”

“…But how did Phylica get to Myanmar if it is essentially a South African clade? Of the possible routes, Shi et al., 2022 prefer the attachment of the West Burma plate (corresponding to present-day Myanmar) to the northeast corner of Greater India. Once the Indian plate, together with Madagascar and Sri Lanka, severed its link with Africa at ∼115 Ma, it rapidly drifted north to collide with outheast Asia at 60−50 Ma ( Reeves, 2018 ).…”