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Location of the Laguna del Hunco (LH2) locality, Chubut Province, Patagonia, Argentina. MEF = Museo Paleontológico Egidio Feruglio, Trelew City, Chubut Province, the repository of all fossil specimens reported here.
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PREMISE: Fossils provide fundamental evidence of the evolutionary processes that crafted today’s biodiversity and consequently for understanding life on Earth. We report the finding of Myrtaceidites eucalyptoides pollen grains preserved within the anthers of a 52-million-year-old Eucalyptus flower collected at Laguna del Hunco locality of Argentine...
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Context 1
... more than pollen grains Maria C. Zamaloa 1,3 , Maria A. Gandolfo 2 , and Kevin C. Nixon 2 a diverse and beautifully preserved suite of fossils belonging to the iconic Australian genus Eucalyptus. The fossils were collected at the early Eocene (~52 mya) sediments that outcrop at Laguna del Hunco locality, Chubut Province, Patagonia, Argentina (Fig. 1). The fossil Eucalyptus remains include leaves and infructescences, as well as isolated capsules, flower buds, and two flowers preserved at different developmental stages. Although none of the fossils were preserved in organic connection, each one has synapomorphies that independently support their assignment to Eucalyptus sensu ...
Context 2
... fossil flower was collected at quarry LH2 ( Gandolfo et al., 2011;Hermsen et al., 2012) of the Laguna del Hunco locality, Huitrera Formation, that outcrops in Chubut Province, Patagonia, Argentina (Fig. 1). The Laguna del Hunco flora was deposited in sandstones and tuffaceous mudstones representing a lacustrine-caldera unit of the Chubut River volcanic-pyroclastic complex (Aragón and Romero, 1984;Aragón and Mazzoni, 1997). The age of the LH2 quarry was calculated as Ypresian, early Eocene (52.22 ± 0.22 Ma) by sanidine dating ( Wilf et ...
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Citations
... Deposits of the early Eocene Tufolitas Laguna del Hunco at Laguna del Hunco, Chubut Province, Argentina (Fig. 1) offer a unique, high-resolution snapshot of late-Gondwanan rainforests and the paleoecology and paleogeography of the Southern Hemisphere. The Laguna del Hunco deposits host a world-class, highly diverse fossil assemblage that has provided key data constraining how Gondwanan plant lineages-of which many living relative genera now inhabit West Pacific tropical rainforests-evolved and migrated in relation to the southern super-continent's breakup (e.g., Romero and Hickey 1976;Romero 1986;Wilf et al. 2003Wilf et al. , 2013Wilf et al. , 2017Wilf et al. , 2019Wilf et al. , 2023Zamaloa et al. 2006Zamaloa et al. , 2020Gandolfo et al. 2011;Kooyman et al. 2014;Deanna et al. 2020;Matel et al. 2022;Giraldo et al. 2024;Siegert et al. 2024). The flora is renowned for its extremely delicate plant reproductive structures such as flowers, fruits, and whole infructescences, and no explanation has previously emerged for this exceptional preservation. ...
... Paleontological studies of fossil plants, insects, and vertebrates from Laguna del Hunco began in the 1920s (e.g., Berry 1925;Dolgopol de Sáez 1941;Casamiquela 1961;Romero and Hickey 1976;Fidalgo and Smith 1987) and have accelerated through intensive collection and study over the past 25 years. Some notable recent discoveries from the fossil flora of over 200 species, among many examples Barreda et al. 2020), include the oldest and first non- Australian Eucalyptus fossils (Gandolfo et al. 2011;Zamaloa et al. 2020); the first Western Hemisphere fossils of the giant West Pacific kauri conifer, Agathis ; the first Southern Hemisphere fossils of the beech family Fagaceae, assigned to the Asian chinkapin genus Castanopsis ; and the first fossil fruits and oldest fossils of the nightshade family Solanaceae, assigned to the living tomatillo genus Physalis Deanna et al. 2020). ...
Caldera lake sediments of the early Eocene Tufolitas Laguna del Hunco (Chubut Province, Argentina) host one of the world's best-preserved and most diverse fossil plant assemblages, but the exceptional quality of preservation remains unexplained. The fossils have singular importance because they include numerous oldest and unique occurrences in South America of genera that today are restricted to the West Pacific region, where many of them are now vulnerable to extinction. Lacustrine depositional settings are often considered optimal for preservation as passive receptors of suspended sediment delivered, often seasonally, from lakeshores. However, caldera lakes can be influenced by a broader range of physical and chemical processes that enhance or decrease fossil preservation potential. Here, we use Laguna del Hunco to provide a new perspective on paleoenvironmental controls on plant fossil preservation in tectonically active settings. We establish a refined geochronological framework for the Laguna del Hunco deposits and present a detailed history of processes active during~200,000 years of lake filling from 52.217 6 0.014 Ma to 51.988 6 0.035 Ma, the time interval that encompasses nearly all fossil deposition. Detailed facies analysis shows that productive fossil localities reside within high-deposition-rate beds associated with high-energy density flows and wave-reworked lake-floor sediments, challenging traditional views that low-energy environments are required for well-preserved plant fossils. These results demonstrate that even delicate fossil components like fruits and flowers can survive high-energy transport, underscoring the importance of rapid burial as a primary control on fossil preservation. Short, steep sediment-transport networks may facilitate terrestrial fossil preservation by limiting opportunities for biochemical degradation on land and providing relatively frequent, high-energy depositional events, which quickly transport and bury organic material following events such as landslides from steep, wet, surrounding slopes. Our new model for plant taphonomy opens a path toward finding and understanding other exceptional biotas in environments once considered unlikely for preservation.
... The iconic genus Eucalyptus (gum trees, Myrtaceae) provides a rare opportunity to explore how insect herbivores assembled on a plant host through geologic time, due to its high extant diversity (> 700 species ;Hill et al., 2016), ecological dominance in the Australian landscape (Wrigley & Fagg, 2010), and long fossil history starting in Patagonia during the early Eocene (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). The extant diversity of Eucalyptus is heavily concentrated in Australia, although some species are naturally distributed in Papua New Guinea, East Timor, Indonesia, and the Philippine island of Mindanao (Pryor & Johnson, 1981;Williams & Woinarski, 1997;Ladiges et al., 2003). ...
... However, the oldest, most complete, and abundant fossil Eucalyptus material was described from the early Eocene (52 million years ago (Ma)) Laguna del Hunco (LH) caldera-lake locality in northwestern Chubut, Argentinean Patagonia, which preserves one of the most diverse Eocene floras world-wide (Wilf et al., 2003;Gandolfo et al., 2011). The Eucalyptus fossilsconsisting of leafy branches and isolated leaves with abundant and diverse insect herbivore damage; a flower with in situ pollen, flower buds, infructescences, and dispersed capsulesare confidently placed within crown group Eucalyptus based on many distinctive features, including leaf architecture, oil glands, operculate flower buds, infructescence structure, and valvate capsulate fruits (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). The presence of a transverse scar on the flower buds most likely indicates that the fossils belong to the large subgenus Symphyomyrtus (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). ...
... The Eucalyptus fossilsconsisting of leafy branches and isolated leaves with abundant and diverse insect herbivore damage; a flower with in situ pollen, flower buds, infructescences, and dispersed capsulesare confidently placed within crown group Eucalyptus based on many distinctive features, including leaf architecture, oil glands, operculate flower buds, infructescence structure, and valvate capsulate fruits (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). The presence of a transverse scar on the flower buds most likely indicates that the fossils belong to the large subgenus Symphyomyrtus (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). No insect damage has been reported on Eucalyptus (or Eucalyptus-related) foliage from the Cenozoic of Australia and New Zealand (McCoy, 1876;Ettingshausen, 1895;Holmes et al., 1982;Pole, 1993Pole, , 1994Pole, , 2019Pole et al., 1993). ...
Fossilized plant–insect herbivore associations provide fundamental information about the assembly of terrestrial communities through geologic time. However, fossil evidence of associations originating in deep time and persisting to the modern day is scarce.
We studied the insect herbivore damage found on 284 Eucalyptus frenguelliana leaves from the early Eocene Laguna del Hunco rainforest locality in Argentinean Patagonia and compared damage patterns with those observed on extant, rainforest‐associated Eucalyptus species from Australasia (> 10 000 herbarium sheets reviewed).
In the fossil material, we identified 28 insect herbivory damage types, including 12 types of external feeding, one of piercing‐and‐sucking, five of galls, and 10 of mines. All 28 damage types were observed in the herbarium specimens.
The finding of all the fossil damage types on extant Eucalyptus specimens suggests long‐standing associations between multiple insect herbivore lineages and their host genus spanning 52 million years across the Southern Hemisphere. This long‐term persistence, probably enabled through niche conservatism in wet eucalypt forests, demonstrates the imprint of fossil history on the composition of extant insect herbivore assemblages. Although the identities of most insect culprits remain unknown, we provide a list of Eucalyptus species and specific population locations to facilitate their discovery, highlighting the relevance of fossils in discovering extant biodiversity.
... This situation changed with the recent discovery of the oldest and best-preserved Eucalyptus fossils at the early Eocene (52 Ma) Laguna del Hunco fossil lake site in Chubut, Patagonian Argentina ( Fig. 2). Fossil Eucalyptus frenguelliana leaves are preserved there in great abundance (Fig. 3), along with extraordinary additional evidence for the genus from complete infructescences, flower buds, and a flower with in situ pollen ( Fig. 2; Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). The combined evidence is sufficient to place the fossils in the Eucalyptus crown group, and they preserve diagnostic features of the large subgenus Symphyomyrtus. ...
... Early Eocene Eucalyptus fossils from Laguna del Hunco, Chubut, Argentina (star on the map inset; seeGandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). From left, E. frenguelliana holotype, MPEF-Pb 2329 (quarry LH4), Bar, 1 cm; E. caldericola holotype (infructescence), MPEF-Pb 5021, and E. frenguelliana leaf (quarry LH25), Bar, 1 cm; holotype of E. xoshemium (flower) with in situ Myrtaceidites eucalyptoides pollen, MPEF-Pb 5022 (quarry LH2), Bar, 5 mm. ...
The tall eucalypt forests (TEFs) of the Australian tropics are often portrayed as threatened by ‘invasive’ neighboring rainforests, requiring ‘protective’ burning. This framing overlooks that Australian rainforests have suffered twice the historical losses of TEFs and ignores the ecological and paleobiological significance of rainforest margins. Early Eocene fossils from Argentina show that biodiverse rainforests with abundant Eucalyptus existed > 50 million years ago (Ma) in West Gondwana, shaped by nonfire disturbance factors such as landslides and volcanic flows. Humid volcanic environments with eucalypts were also present in eastern Australia over much of the Cenozoic. The dominance of fire‐adapted eucalypts appears to be geologically recent and is linked to Neogene C4 grassland expansion, Pleistocene climate cycles, and human activity. We suggest that characterizing TEFs and rainforests as adversarial results from misinterpreting the evolutionary history and expansion‐contraction dynamics of a single humid forest system, whose features are now heavily modified by human activities. The resulting management practices damage the outstanding World Heritage values and carbon storage of affected areas and thus have impacts far beyond Australia. The fossil evidence shows that rainforest margins preserve ancient, still evolving, and globally significant forest interactions that should be prioritized for restoration and research.
... Fossils of the eucalypt clade are well known in Neogene and Paleogene floras of Argentina (Frenguelli, 1953;Wilf et al., 2003;Gandolfo et al., 2011;Zamaloa et al., 2020), Australia (Lange, 1978(Lange, , 1982Ambrose et al., 1979;Holmes et al., 1982;White, 1994;Rozefelds, 1996;Ladiges, 1997;Basinger et al., 2007;Carpenter et al., 2011), New Zealand (Pole, 1993(Pole, , 1994, China (Chen et al., 1983), and India (Bande et al., 1986;Shukla et al., 2012Shukla et al., , 2014b (Table 1). These records include isolated leaves, flower buds, flowers, capsules, and wood (Table 1). ...
... The South Australian middle Eocene flower species Tristaniandra alleyi Wilson and Basinger differs by having perigynous types and quite larger lengths (3 cm) of flowers (Basinger et al., 2007) unlike the epigynous type and quite smaller length (0.23 cm) of flower in the present specimen. The early Eocene Argentinian flower species Eucalyptus xoshemium Gandolfo and Zamaloa is easily distinguished by having obconic to campanulate-shaped hypanthium (Zamaloa et al., 2020) in contrast to the cup-shaped hypanthium of the present specimen. ...
Eucalypt fossils were widely reported from the Cenozoic deposits across the Southern Hemisphere (Australia, New Zealand, and Argentina). However, no attached reproductive and vegetative fossil remains of this myrtaceous clade have been discovered till now. We report and describe for the first time a fossil eucalypt twig with attached foliage, flower buds, and mature flowers from the early Eocene (~55-52 Ma) sediments (Palana Formation) of Rajasthan, western India. As both vegetative and reproductive organs are in organic connection, they clearly represent the same species. In addition, here we also introduce fossil materials of isolated leaves, flower buds, inflorescence, and flowers recovered from the same stratigraphic level. Our Eocene fossils and extant members of the eucalypt clade are related morphologically by means of robust, thick petiolate lanceolate-shaped leaves with intramarginal secondary veins; operculate flower buds consisting of imbricate petals with discernable margins; solitary inflorescence with three flowers per umbellaster, epigynous and bisexual flowers. Based upon combined characteristics of leaf, flower, and bud morphology, these fossils conform to the Eucalypt clade and are recognized as a new fossil genus and species: Hindeucalyptus eocenicus Patel, R.F. Almeida, Ali et Khan, gen. nov. et sp. nov. We also compare it with extant and extinct eucalypts using morphological phylogeny and character mapping analyses. In addition, we briefly discuss its phytogeographic and paleoclimatic implications regarding the distribution and habitat of fossil and modern eucalypts.
... Most dominant plant species in the flora have been revised. For example, the second most abundant leaf species by field-census leaf counts, initially identified to the family Myrtaceae (Wilf et al., 2005a), is now resolved in Eucalyptus and is associated with infructescences and flowers bearing in situ pollen of that genus (Gandolfo et al., 2011;Hermsen et al., 2012;Zamaloa et al., 2020). The third most common, "Tetracera" patagonica leaves with putative affinities to Dilleniaceae (berry, 1925), are fagaceous, now placed in Castaneophyllum, and associated with Castanopsis infructescences and dispersed castaneoid pollen barreda et al., 2020). ...
The most common macrofossils in the highly diverse flora from Laguna del Hunco (early Eocene of Chubut, Argentina) are "Celtis" ameghinoi leaves, whose true affinities have remained enigmatic for a century. The species accounts for 14% of all plant fossils in unbiased field counts and bears diverse insect-feeding damage, suggesting its high biomass and paleoecological importance. The leaves have well-preserved architecture but lack cuticles or reproductive attachments. We find that the fossils only superficially resemble Celtis and comparable taxa in Cannabaceae, Ulmaceae, Rhamnaceae, Malvaceae, and many other families. However, the distinctive foliar morphology conforms in detail to Dobinea (Anacardiaceae), a genus with two species of shrubs and large herbs ranging from India's Far East and Tibet to Myanmar and central China, and we propose Dobineaites ameghinoi (E.W. Berry) gen et. comb. nov. for the fossils. This discovery strengthens the extensive biogeographic links between Eocene Patagonia and mainland Asia, provides the first fossil record related to Dobinea, and represents a rare Gondwanan macrofossil occurrence of Anacardiaceae, which was widespread and diversified in the Northern Hemisphere at the time. The diverse leaf architecture of Anacardiaceae includes several patterns usually associated with other taxa, and many other leaf fossils in this family may remain misidentified.
... Eucalyptus spp., be long to Myrtaceae are trees variety recognized for its remarkable traits including rapid growth and superior wood quality [1]. Them have cultivated spanning over 20 million hectares across more than 90 nations, with focal points situated predominantly in Brazil (covering 5.7 million hectares), India (spanning 3.9 million hectares), and China (encompassing 4.5 million hectares) [2]. Its status as one of the most widely cultivated hardwood trees globally remains prominent. ...
Eucalyptus is one of the important plant species for paper pulp, fuel wood, and timber. In this study, a hybrid Eucalyptus, U16 line, was investigated for rapid in vitro propagation. The apical and adventitious shoots served as initial explants. These were free-disease symptoms that were collected for surface sterilization. Different disinfectants including mercuric and Javel solutions at different concentrations and treated times were performed. The results showed that explants were cleaned under taping water with soap, rinsed in 70 o EtOH for 1 minute, and then immersed in 10% Javen solution for 15 minutes and 0.1% HgCl2 for 10 minutes gave the highest disinfection rate that was 46.5%. The modified MS medium included basal MS, 30 g/L sucrose, and 7 g/L agar supplemented with 20 ml/L of coconut water (MS medium*) was the most suitable for the rapid multiplication of Eucalyptus lines U16, the shoot multiplication coefficient reached 1.56. In vitro multiplication of eucalyptus U16 was carried out by culturing disinfected shoot segments on the MS* medium supplemented with BAP 1.5 mg/L and kinetin 1.0 mg/L which gave the highest shoot multiplication coefficient (3.24 shoot per explant). The in vitro rooting medium of the U16 line was basal MS supplemented with 1.0 mg NAA/L, the rooting rate was 90.49%, the number of roots was 8.3, and the roots expressed strong growth.
... Since the beginning of palaeobotanical research and the first report of in situ pollen in flowers/inflorescences by Göppert (1841), the extraction and identification of pollen from compressed fossil angiosperm flowers have rarely been reported. Only in the last years a few studies on this topic have been made, see Lee et al. (2010Lee et al. ( , 2013, Jud et al. (2018), Zamaloa et al. (2020), Uhl et al. (2021), and Wilde et al. (2021). The reason for this is probably not the lack of suitable material. ...
... Still, some researchers successfully found, extracted, and prepared in situ pollen from compression fossils using different methods and tools. These procedures involved among others, breaking off pieces from flowers or anthers (later chemically treated; e.g., Uhl et al., 2021), applying adhesive cellulose tape and acetate sheet for surface layer removal (e.g., Zamaloa et al., 2020) followed by LM and scanning electron microscopy (SEM) study, or to directly extract pollen (clumps) using various needles or paintbrushes (e.g., Lee et al., 2010;Conran et al., 2014;Uhl et al., 2021). Since a first overview on the application of epifluorescence to investigate fossil pollen by Friedrich and Schaarschmidt (1977), only few palaeobotanists have picked up on the idea and started using epifluorescence to pinpoint the presence of pollen in fossil flowers (e.g., Schaarschmidt, 1984;Jud et al., 2018;Wilde et al., 2021). ...
Fossilised compressed angiosperm flowers that can be determined in a botanically/systematically meaningful sense are rare in the fossil record. The main reason for this might be the preservation state, i.e., such fossils are in many cases strongly compacted, and can lack diagnostic features essential for proper identification and assignment to extant or (natural) extinct taxa. Since pollen morphology can be very conservative and of diagnostic significance at family and/or genus level from the Upper Cretaceous to modern times, analysis of in situ pollen is a crucial tool in identifying flowers. Unfortunately, despite its potential taxonomic value already addressed nearly 200 years ago by Heinrich Göppert, fossil in situ pollen from compressed flowers has not yet become a “standard” research subject in modern-day palaeobotany. Possible reasons for this may be due to the effort and complexity related to the detection and extraction of said in situ pollen. The method described herein fills this gap and makes it easy for everyone (students and professionals) to screen flower compression fossils and to extract in situ or adhered pollen from the flowers. It also provides a fast and practical way to process fossil pollen prior to photography with light- and scanning electron microscopy for future taxonomic work.
... Early Eocene sedimentation includes restricted regions with calderalake systems (for geographic and stratigraphic details see Gosses et al., 2021) that preserved diverse floras (e.g. Romero and Hickey, 1976;Gandolfo et al., 1988Gandolfo et al., , 2011Gandolfo and Hermsen, 2017;Wilf et al., 2005Wilf et al., , 2009Wilf, 2012;Zamaloa et al., 2006Zamaloa et al., , 2020Jud et al., 2018). Mid-late Eocene Atlantic incursions recorded mainly in southern Patagonia include shallow marine and highly fossiliferous sediments that have been constrained to the middle to late Eocene ages (Griffin, 1991;Malumián andCaramés, 1997,2000a;Camacho et al., 1998Camacho et al., , 2000aMalumián, 1999;Olivero and Malumián, 1999;Olivero et al., 2020;Guerstein and Junciel, 2001;Guerstein et al., 2014;González Estebenet et al., 2016;del Río, 2021). ...
The fossil record from Cenozoic sediments provides a great deal of information that has direct bearing on the early assembling of modern Patagonian ecosystems. In this synthesis, we revise selected fossil marine and terrestrial records from the last 66 Ma with the aim of understanding major shifts of Patagonian biotas. From the Paleocene to the mid Eocene this region supported outstandingly diverse terrestrial assemblages that show strong connections to modern-day Australasia (e.g. gum trees, casuarinas, monotremes). Nearshore marine biotas confirm peak warmth conditions, with tropical species with Tethyan affinities. The late Eocene and early Oligocene marks the onset of a period of overall regional cooling, drying, and increasingly variable ecological conditions. The rise of palm-dominated flammable biomes in hinterlands and the prevalence of Gondwanan gallery forest (e.g. southern beeches and podocarps) along river-sides supported the existence of mosaic habitats maintained by edaphic and regional climatic conditions. This shift in landscapes reflects the evolution of a wide range of herbivorous mammals (e.g. Notoungulata, Litopterna, and Astrapotheria). The late Oligocene and early-to-mid Miocene witnessed a dramatic modification of landscapes including the incursion of high sea-level episodes, the emergence of specialized coastal (i.e. salt-marsh) plant taxa and the expansion of large herbivorous mammals with predominantly high-crowned teeth (e.g. Notoungulata: Hegetotheriidae, Interatheriidae, and Mesotheriidae). The cooling trend of this interval was interrupted by a mid-Miocene transient warming event, with the dispersion of terrestrial (e.g. platyrrhine monkeys, palms) and marine (e.g. Tuberculodinium vancampoae) elements with tropical affinity into southernmost South American regions. Seasonally-dry conditions increased towards the end of the Miocene, yet subtropical species persisted either in terrestrial (e.g. malpighs, passion vines, capybaras), and marine (e.g. Subtropical and Caribbean molluscs) environments. The increasing aridity caused by the Andean uplift wiped out most of the forest species and promoted the diversification of open-habitat species; the emergence of the current grass-dominated Patagonian Steppe occurred later on, probably during the Quaternary.
Premise
Araliaceae comprise a moderately diverse, predominantly tropical angiosperm family with a limited fossil record. Gondwanan history of Araliaceae is hypothesized in the literature, but no fossils have previously been reported from the former supercontinent.
Methods
I describe large (to macrophyll size), palmately compound-lobed leaf fossils and an isolated umbellate infructescence from the early Eocene (52 Ma), late-Gondwanan paleorainforest flora at Laguna del Hunco in Argentine Patagonia.
Results
The leaf fossils are assigned to Caffapanax canessae gen. et sp. nov. (Araliaceae). Comparable living species belong to five genera that are primarily distributed from Malesia to South China. The most similar genus is Osmoxylon, which is centered in east Malesia and includes numerous threatened species. The infructescence is assigned to Davidsaralia christophae gen. et sp. nov. (Araliaceae) and is also comparable to Osmoxylon.
Conclusions
The Caffapanax leaves and Davidsaralia infructescence, potentially representing the same source taxon, are the oldest araliaceous macrofossils and provide direct evidence of Gondwanan history in the family. The new fossils and their large leaves enrich the well-established biogeographic and climatic affinities of the fossil assemblage with imperiled Indo-Pacific, everwet tropical rainforests. The fossils most likely represent shrubs or small trees, adding to the rich record of understory vegetation recovered from Laguna del Hunco.
The Myrtaceae is the ninth largest angiosperm family with c . 6000 species, and it diverged from its closest relative the Vochysiaceae c . 100 Ma in southern Gondwana before the final separation of South America and Australia from Antarctica. The family has trees and shrubs and a few viny epiphytes but no herbs and mainly occurs in the tropics and in temperate regions with a Mediterranean climate. Numerous fleshy-fruited species and dry-fruited species have evolved in moist and seasonally dry (fire-prone) regions, respectively. Five kinds of fully developed embryos are found in Myrtaceae seeds, and at maturity seeds are either nondormant (ND) or have physiological dormancy, regardless of embryo morphology, kind of fruit produced, life form, habitat/vegetation region or tribe. Dormant seeds of fleshy-fruited species in wet habitats become ND and germinate at high temperatures. Dormant seeds of dry-fruited species in seasonally dry habitats become ND during the hot, dry season and germinate with the onset of the wet season; seeds germinate only at high temperatures or over a range of low to high temperatures, depending on the species. Seeds of fleshy-fruited species are animal-dispersed, and some Myrteae and Syzygieae are desiccation-sensitive and/or exhibit totipotency. Relatively few species form a persistent soil seed bank, but many dry-fruited species in fire-prone habitats form an aerial seed bank (serotiny). Heat and smoke from fires have a negative, neutral or positive effect on germination, depending on the species. Challenges for maintaining the high species richness of Myrtaceae include habitat destruction/fragmentation, pathogenic fungi and climate change, especially patterns of precipitation.
