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1.
New Phytol ; 234(3): 1075-1087, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35147224

RESUMO

Morphological diversity (disparity) is a key component of biodiversity and increasingly a focus of botanical research. Despite the wide range of morphologies represented by pollen grains, to date there are few studies focused on the controls on pollen disparity and morphospace occupation, and fewer still considering these parameters in a phylogenetic framework. Here, we analyse morphospace occupation, disparity and rates of morphological evolution in Asterales pollen, in a phylogenetic context. We use a dataset comprising 113 taxa from across the Asterales phylogeny, with pollen morphology described using 28 discrete characters. The Asterales pollen morphospace is phylogenetically structured around groups of related taxa, consistent with punctuated bursts of morphological evolution at key points in the Asterales phylogeny. There is no substantial difference in disparity among these groups of taxa, despite large differences in species richness and biogeographic range. There is also mixed evidence for whole-genome duplication as a driver of Asterales pollen morphological evolution. Our results highlight the importance of evolutionary history for structuring pollen morphospace. Our study is consistent with others that have shown a decoupling of biodiversity parameters, and reinforces the need to focus on disparity as a key botanical metric in its own right.


Assuntos
Magnoliopsida , Biodiversidade , Evolução Biológica , Magnoliopsida/genética , Ocupações , Filogenia , Pólen/anatomia & histologia
2.
Nat Commun ; 13(1): 293, 2022 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-35022396

RESUMO

Grasslands are predicted to experience a major biodiversity change by the year 2100. A better understanding of how grasslands have responded to past environmental changes will help predict the outcome of current and future environmental changes. Here, we explore the relationship between past atmospheric CO2 and temperature fluctuations and the shifts in diversification rate of Poaceae (grasses) and Asteraceae (daisies), two exceptionally species-rich grassland families (~11,000 and ~23,000 species, respectively). To this end, we develop a Bayesian approach that simultaneously estimates diversification rates through time from time-calibrated phylogenies and correlations between environmental variables and diversification rates. Additionally, we present a statistical approach that incorporates the information of the distribution of missing species in the phylogeny. We find strong evidence supporting a simultaneous increase in diversification rates for grasses and daisies after the most significant reduction of atmospheric CO2 in the Cenozoic (~34 Mya). The fluctuations of paleo-temperatures, however, appear not to have had a significant relationship with the diversification of these grassland families. Overall, our results shed new light on our understanding of the origin of grasslands in the context of past environmental changes.


Assuntos
Dióxido de Carbono , Pradaria , Asteraceae , Teorema de Bayes , Biodiversidade , Evolução Biológica , Simulação por Computador , Ecossistema , Modelos Biológicos , Filogenia , Poaceae
3.
Commun Biol ; 4(1): 176, 2021 02 09.
Artigo em Inglês | MEDLINE | ID: mdl-33564110

RESUMO

A major climate shift took place about 40 Myr ago-the Middle Eocene Climatic Optimum or MECO-triggered by a significant rise of atmospheric CO2 concentrations. The biotic response to this MECO is well documented in the marine realm, but poorly explored in adjacent landmasses. Here, we quantify the response of the floras from America's southernmost latitudes based on the analysis of terrestrially derived spores and pollen grains from the mid-late Eocene (~46-34 Myr) of southern Patagonia. Robust nonparametric estimators indicate that floras in southern Patagonia were in average ~40% more diverse during the MECO than pre-MECO and post-MECO intervals. The high atmospheric CO2 and increasing temperatures may have favored the combination of neotropical migrants with Gondwanan species, explaining in part the high diversity that we observed during the MECO. Our reconstructed biota reflects a greenhouse world and offers a climatic and ecological deep time scenario of an ice-free sub-Antarctic realm.


Assuntos
Dinoflagelados , Fósseis , Sedimentos Geológicos/análise , Aquecimento Global , Efeito Estufa , Plantas , Pólen , Esporos , Biota , Dióxido de Carbono/análise , Gases de Efeito Estufa/análise , América do Sul , Fatores de Tempo
4.
New Phytol ; 223(2): 1023-1030, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30924945

RESUMO

The replacement of seed-free plants and gymnosperms by flowering plants during the Cretaceous is one of the most important biotic events in the evolution of life. However, the magnitude of this global turnover remains largely unknown. Here we present sampling-standardized diversity estimates from a high resolution palynological record of the Late Cretaceous (85-66 Ma) from Antarctica, in the context of the past climatic events. Our fossil evidence reveals the occurrence of a rich Campanian flora peaking at c. 80 Ma, with angiosperms as the most diverse group of plants for the first time in Antarctica. This peak of diversity was followed by a period of a stepwise deterioration; 60% of ferns and 40% of gymnosperms became locally extinct from the early/mid-Campanian to the late Maastrichtian. Although angiosperms also faced several extinctions - 25% became extinct - they were far less affected than nonangiosperms. The onset of deterioration of the greenhouse conditions at the end of the Cretaceous - low CO2 and global cooling trends - would have led to our observed pattern of change. Overall, our study reveals the beginning of a profound floristic turnover in the highest southern latitudes that pre-dates the major extinction event of the end of the Cretaceous by 15 Myr.


Assuntos
Fósseis , Magnoliopsida/fisiologia , Pólen/fisiologia , Regiões Antárticas , Geografia , Paleontologia
6.
Proc Natl Acad Sci U S A ; 112(35): 10989-94, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26261324

RESUMO

The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general.


Assuntos
Asteraceae/genética , Evolução Biológica , Regiões Antárticas , Asteraceae/classificação , Fósseis , Filogenia
7.
Am J Bot ; 101(12): 2121-35, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25480709

RESUMO

UNLABELLED: • PREMISE OF STUDY: Have Gondwanan rainforest floral associations survived? Where do they occur today? Have they survived continuously in particular locations? How significant is their living floristic signal? We revisit these classic questions in light of significant recent increases in relevant paleobotanical data.• METHODS: We traced the extinction and persistence of lineages and associations through the past across four now separated regions-Australia, New Zealand, Patagonia, and Antarctica-using fossil occurrence data from 63 well-dated Gondwanan rainforest sites and 396 constituent taxa. Fossil sites were allocated to four age groups: Cretaceous, Paleocene-Eocene, Neogene plus Oligocene, and Pleistocene. We compared the modern and ancient distributions of lineages represented in the fossil record to see if dissimilarity increased with time. We quantified similarity-dissimilarity of composition and taxonomic structure among fossil assemblages, and between fossil and modern assemblages.• KEY RESULTS: Strong similarities between ancient Patagonia and Australia confirmed shared Gondwanan rainforest history, but more of the lineages persisted in Australia. Samples of ancient Australia grouped with the extant floras of Australia, New Guinea, New Caledonia, Fiji, and Mt. Kinabalu. Decreasing similarity through time among the regional floras of Antarctica, Patagonia, New Zealand, and southern Australia reflects multiple extinction events.• CONCLUSIONS: Gondwanan rainforest lineages contribute significantly to modern rainforest community assembly and often co-occur in widely separated assemblages far from their early fossil records. Understanding how and where lineages from ancient Gondwanan assemblages co-occur today has implications for the conservation of global rainforest vegetation, including in the Old World tropics.


Assuntos
Evolução Biológica , Fósseis , Filogenia , Plantas/genética , Floresta Úmida , Clima Tropical , Regiões Antárticas , Australásia , Filogeografia
8.
PLoS One ; 7(12): e52455, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23285049

RESUMO

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.


Assuntos
Biodiversidade , Cycadopsida/crescimento & desenvolvimento , Extinção Biológica , Flores/crescimento & desenvolvimento , Argentina , Geografia , Pólen , Esporos , Fatores de Tempo
9.
Ann Bot ; 109(1): 127-34, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22179952

RESUMO

BACKGROUND AND AIMS: Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although palaeontological studies on this continent failed to reveal conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. & sp. nov., an exceptionally well preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina. METHODS: The fossil was collected from the 47·5 million-year-old Huitrera Formation at the Estancia Don Hipólito locality, Río Negro Province, Argentina. KEY RESULTS: The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate-imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of Asteraceae, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato) and Dicomeae and Oldenburgieae (Carduoideae), today endemic to or mainly distributed in South America and Africa, respectively. CONCLUSIONS: This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the ancestor of Mutisioideae-Carduoideae. It might have evolved in southern South America some time during the early Palaeogene and subsequently entered Africa, before the biogeographical isolation of these continents became much more pronounced. The new fossil represents the first reliable point for calibration, favouring an earlier date to the split between Barnadesioideae and the rest of Asteraceae than previously thought, which can be traced back at least 47·5 million years. This is the oldest well dated member of Asteraceae and perhaps the earliest indirect evidence for bird pollination in the family.


Assuntos
Asteraceae/anatomia & histologia , Asteraceae/classificação , Asteraceae/genética , África , Argentina , Evolução Biológica , Flores/anatomia & histologia , Flores/genética , Fósseis , Filogenia , Filogeografia , América do Sul
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