PALYNOLOGICAL RECORD OF THE LAST 20 MILLION YEARS IN PANAMA (original) (raw)
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Data to Accompany: PALYNOLOGICAL RECORD OF THE LAST 20 MILLION YEARS IN PANAMA
Data to Accompany: PALYNOLOGICAL RECORD OF THE LAST 20 MILLION YEARS IN PANAMA
The Isthmus of Panama illustrates how the vegetation of a newly created landscape in a tropical setting evolves over time. It also allows us to investigate biological invasions, because the landscape was first connected to temperate North America, and later connected to tropical South America. Using a large number of outcrops newly exposed during the recent expansion of the Panama Canal, we were able to complement the extensive palynological research that Alan Graham conducted in Panama over the past 25 years. We analyzed the palynological record of the interval 19.5-1.2 Ma, represented by 282 samples containing 27,910 grains (pollen/spores) with 496 morphotypes. Further, a revision of the plant macrofossil literature of Panama and analysis of the carbon isotope content of 14 samples were carried out. Our results indicate that since the Early Miocene, Panamanian forests have been dominated by Gondwana-Amazonian taxa, suggesting that plants were able to cross the Central American Seaway much earlier than mammals. The landscape was dominated by tropical rainforest and lower montane to montane forest, contrary to the dry and open habitats that some previous studies have proposed. Plant diversity seems to have increased over the past 10 My, but it is unclear if this increase is due to a taphonomic bias. Further studies are needed to understand the relationships of the Early Miocene Panamanian mammals derived from North American temperate forest lineages as they faced new habitats in Panama dominated by South American-derived tropical rainforest.
Palynologycal recor of the last 20 million years in Panama
The Isthmus of Panama illustrates how the vegetation of a newly created landscape in a tropical setting evolves over time. It also allows us to investigate biological invasions, because the landscape was first connected to temperate North America, and later connected to tropical South America. Using a large number of outcrops newly exposed during the recent expansion of the Panama Canal, we were able to complement the extensive palynological research that Alan Graham conducted in Panama over the past 25 years. We analyzed the palynological record of the interval 19.5–1.2 Ma, represented by 282 samples containing 27,910 grains (pollen/spores) with 496 morphotypes. Further, a revision of the plant macrofossil literature of Panama and analysis of the carbon isotope content of 14 samples were carried out. Our results indicate that since the Early Miocene, Panamanian forests have been dominated by Gondwana-Amazonian taxa, suggesting that plants were able to cross the Central American Seaway much earlier than mammals. The landscape was dominated by tropical rainforest and lower montane to montane forest, contrary to the dry and open habitats that some previous studies have proposed. Plant diversity seems to have increased over the past 10 My, but it is unclear if this increase is due to a taphonomic bias. Further studies are needed to understand the relationships of the Early Miocene Panamanian mammals derived from North American temperate forest lineages as they faced new habitats in Panama dominated by South American–derived tropical rainforest. Key words: biogeography, GABI, Neogene, paleobotany, palynology.
Testing geological models of evolution of the Isthmus of Panama in a phylogenetic framework
Botanical Journal of the Linnean Society, 2013
The emergence and closure of the Isthmus of Panama had regional and global impacts that were rivalled by few other Cenozoic geological events. The closure of the Central American Seaway and the rise of the Isthmus had dramatic affects on climate and air and oceanic currents worldwide. Formation of the Isthmus also drove terrestrial biotic interchange, ending the isolation of South America by permitting the mixing of its biota with that of North and Central America. A dated phylogenetic tree of a well-sampled clade of palms in the tribe Trachycarpeae (Copernicia, Pritchardia and Washingtonia) was used to conduct biogeographical analyses. Examination of the timing of lineage dispersal from North into South America was performed and two contrasting temporal hypotheses of the Isthmus formation were tested: occurrence in the Pliocene (c. 5 Mya to the present) or in the Miocene (prior to c. 5 Mya). Copernicia is inferred to have dispersed through the Isthmus of Panama region into South America and subsequently into the Caribbean, where it underwent a rapid radiation. Consistent with a geologically older age for the Isthmus than previously understood, our results support recent geological and palaeobiological data that suggest an early Oligocene to early Miocene model of evolution of the Isthmus of Panama.
Middle Miocene global change and paleogeography of Panama
Palaios, 2007
Fossil leaves in the middle Miocene Cucaracha Formation along the Panama Canal are 10-15 cm long, thick, and entire-margined; fossil pollen is also dicot dominated, as expected for wet tropical forests. Fossil woods include palms and ring-porous dicots, with smooth bark as is found in weakly seasonal tropical climates. In contrast, late Hemingfordian to early Barstovian mammals of the Cucaracha Formation are the same as those found in Nebraska, Kansas, and Florida, where climate was drier and cooler and vegetation more open. Cucaracha paleosols reconcile these differences as evidence of a mosaic of swamps to mangal (mangrove forests) preserving plants and dry uplands preserving mammals. A dozen pedotypes represent as many vegetation types, including mangrove, fresh-water and marineinfluenced swamp, early successional riparian woodland, colonizing forest, dry tropical forest, and woodland. Many paleosols have calcareous nodules, and some have pedogenic barite nodules. Depth to carbonate and paleosol thickness with carbonate indicate mean annual precipitation of 573-916 ؎ 147 mm and mean annual range of precipitation of 27-65 ؎ 22 mm. Chemical analyses of paleosol Bt horizons confirm mean annual precipitation of 296-1142 mm and mean annual temperature of 15-16 ؎ 4.4؇C. Low precipitation and temperature estimates imply a rain shadow from a high (1400-4000 m) volcanic mountain range to the west, with continuous land connection to allow immigration of mammals from North America. Partial enclosure of the Caribbean Sea by a mountainous Panama peninsula, as well as by Antillean arcs, initiated high Caribbean marine temperature and salinity well before Pliocene isthmian closure.
PloS one, 2017
The late Miocene was an important time to understand the geological, climatic, and biotic evolution of the ancient New World tropics and the context for the Great American Biotic Interchange (GABI). Despite this importance, upper Miocene deposits containing diverse faunas and floras and their associated geological context are rare in Central America. We present an integrated study of the geological and paleontological context and age of a new locality from Lago Alajuela in northern Panama (Caribbean side) containing late Miocene marine and terrestrial fossils (plants, invertebrates, and vertebrates) from the Alajuela Formation. These taxa indicate predominantly estuarine and shallow marine paleoenvironments, along with terrestrial influences based on the occurrence of land mammals. Sr-isotope ratio analyses of in situ scallop shells indicate an age for the Alajuela Formation of 9.77 ± 0.22 Ma, which also equates to a latest Clarendonian (Cl3) North American Land Mammal Age. Along wi...
Biological evidence supports an early and complex emergence of the Isthmus of Panama
The linking of North and South America by the Isthmus of Panama had major impacts on global climate, oceanic and atmospheric currents, and biodiversity, yet the timing of this critical event remains contentious. The Isthmus is traditionally understood to have fully closed by ca. 3.5 million years ago (Ma), and this date has been used as a benchmark for oceanographic, climatic, and evolutionary research, but recent evidence suggests a more complex geological formation. Here, we analyze both molecular and fossil data to evaluate the tempo of biotic exchange across the Americas in light of geological evidence. We demonstrate significant waves of dispersal of terrestrial organisms at approximately ca. 20 and 6 Ma and corresponding events separating marine organisms in the Atlantic and Pacific oceans at ca. 23 and 7 Ma. The direction of dispersal and their rates were symmetrical until the last ca. 6 Ma, when northern migration of South American lineages increased significantly. Variability among taxa in their timing of dispersal or vicariance across the Isthmus is not explained by the ecological factors tested in these analyses, including biome type, dispersal ability, and elevation preference. Migration was therefore not generally regulated by intrinsic traits but more likely reflects the presence of emergent terrain several millions of years earlier than commonly assumed. These results indicate that the dramatic biotic turnover associated with the Great American Biotic Interchange was a long and complex process that began as early as the Oligocene-Miocene transition. biogeography | evolution | neotropics | fossil | migration
Paleoenvironments and human occupation in late-glacial Panama
Quaternary Research, 1990
The first pollen and phytolith data covering the entire Pleistocene/Holocene transition from the lowlands of the Central American isthmus indicate that the forests of late-glacial Panama at an altitude of 650 m resembled those currently found at ca. 1500–1800 m. A temperature depression of ca. 5°C and reduced precipitation/evaporation ratios in the late-glacial period are suggested. Forest composition from ca. 14,000 to 10,500 yr B.P., although primarily montane in character, contained a low biomass of species today segregated in lowland forests and, hence, a floral assemblage with no modern analog. The sudden appearance of carbon and burnt, weedy plant material at ca. 11,000 yr B.P. is attributed to the earliest human impact yet recorded from tropical America and may perhaps have been associated with the first human occupation of the region.
Palaeogeography Palaeoclimatology Palaeoecology
The Late Quaternary paleoenvironmental history from Pacific slopes of the western Andes is reconstructed by pollen analysis of 32 samples from two marine sediment cores from the Panama Basin, eastern equatorial Pacific: core ODP 677B (83844.2200V W, 1812.1440V N, 3473 m water depth) is 185 cm long and spans the last 39,410 years, core TR 163-38 (81.5838 W, 1.3378 N, 2200 m water depth) is 103 cm long and covers the last 17,380 years. Six ecological groups were established: mangrove, brackish and fresh water swamps, terra firma lowland forests, broad range taxa, Andean forests, and open vegetation. A good correspondence was found between the changes of these ecological groups in the two cores. The records evidence the continuous presence of all vegetation types during the last 39,410 years and specially the uninterrupted occurrence of tropical rain forest. They record a development from: (1) a cold and humid phase (39,410-28,120 yr cal BP) with moderately high sea levels, (2) the coldest and driest phase in the record (28,120-14,500 yr cal BP) accompanied by the lowest sea levels, (3) a transitional phase when sea level rose and humid conditions dominated, (4) a stage (11,300-5600 yr cal BP) of the highest sea levels and moisture conditions including a drier period~7000 yr BP, to (5) a final period (5600 yr cal BP-Present) when sea level reached its present height, humidity persisted, and indicators of disturbance expanded. Peaks in pollen and spore concentration, associated with high river discharge periods, indicate periods of higher precipitation around 33,500, 28,000 and 12,000-9000 yr cal BP. Although main vegetation responses seem to reflect rainfall and moisture variations, a good correspondence was found between y 18 O values and percentages of Andean and lowland pollen, suggesting that vegetation also responded to tempearture changes. D