Conifer Podocarpus Research Articles

The last glacial termination in northwestern Patagonia viewed from the Lago Fonk (∼40°S) record

The anatomy of the Last Glacial Termination (T1) in the southern mid-latitudes, and its relationship with changes in the Southern Westerly Winds (SWW), offers empirical constraints for understanding the mechanisms involved in the transition from the Last Glacial Maximum into the current interglacial. Northwestern Patagonia (40°-44°S) is a sensitive region for monitoring past changes in the SWW, the Patagonian Ice Sheet, terrestrial ecosystems, and fire regimes through T1. Here we present results from Lago Fonk (∼40°S) to examine the structure of T1 based on the palynological, macroscopic charcoal, elemental, and isotopic composition of organic lake sediments.We observe an instantaneous establishment of Nothofagus-dominated forests at the onset of T1, followed by a diversification and densification trend that culminated with the establishment of thermophilous, Myrtaceae-dominated North Patagonian rainforests between ∼15.6–14.7 cal ka BP. The expansion of the conifer Podocarpus nubigena marks a shift to cool-temperate and hyperhumid conditions, coeval with high lake levels and enhanced algal productivity between ∼14.7–11.9 cal ka BP. Stand-replacing fires, driven by enhanced seasonality or high-frequency rainfall variability, started at ∼12.4 cal ka BP and catalyzed the rapid spread of Weinmannia trichosperma. Subsequent warming and a decline in precipitation at ∼11.4 cal ka BP led to intense fire activity, lake-level lowering, and establishment of the Valdivian rainforest trees Eucryphia/Caldcluvia. Our results suggest a coherent linkage between changes documented in the amphi south Pacific region and Antarctic ice cores during T1. This implies a zonal and hemispheric response to changes in the position/intensity of the SWW that emphasizes their central role as a key driver of the hemispheric and global climate evolution through T1.

The fossil flora of the Dead Sea region, Jordan – A late Permian Garden of Delights

The Umm Irna Formation, Jordan, holds one of the most peculiar late Permian plant–fossil assemblages worldwide. Over the last decades of field work, several localities close to the eastern shore of the Dead Sea have yielded a highly diverse ‘mixed flora’ of mesic to xeric environments encompassing elements that are typical either for different floral realms or for different time periods of Earth History. Taxa typical for particular floral realms include, e.g. Cathaysian gigantopterids and Lobatannularia, Euramerican conifers such as Otovicia hypnoides, or the characteristic Gondwanan seed ferns Glossopteris and Dicroidium. Moreover, most taxa are typical for the Permian, some assemblages have also yielded precocious occurrences of taxa that have so far been considered typical for the Mesozoic, such as Umkomasiaceae, Bennettitales, and podocarp conifers. In most cases, fossils from the Umm Irna Formation show well–preserved cuticles that allow sound systematic placement and contribute to the reconstruction of dispersed plant parts into whole–plant–taxa. Altogether, the Umm Irna Formation provides an exceptional window into depositional environments and vegetation types that are rarely preserved in the fossil record but that are crucial for our understanding of plant evolution.

Bark Anatomy of Podocarpus elongatus (Ait) L.Herit and Screening of Phytochemical Constituents with Antimicrobial Potential

Background: Conifer Podocarpus elongatus belongs to the family Podocarpaceae and some species of Podocarpus are used in traditional medicine. The present study was undertaken to study the anatomical features of the bark of Podocarpus elongatus (Ait) L.Herit. The study was also focused on the antimicrobial activity and phytochemicals present in the bark extract. Methods: The bark was collected from the P. elongatus from Nilgiri Hills of Ooty, Tamil Nadu. The anatomical structures of the bark were elucidated macroscopically and microscopically by using the sectioning techniques. The phytochemical examination was done to confirm the presence of phytochemical components in the methanol extract. The antimicrobial activity was also studied based on the zone of inhibition. Result: The surface of the bark was highly distinguished from other related species, in the pattern of colour, stripes and thickness. Microscopical study envisaged that periderm is characterised by well distinct, continuous structures of the branchy sclereids with thick undulate, continuous segments that have been originated from a deeper cortex. TLS and RLS of the bark view elucidated that the phloem component appeared to be a vertical plane in the fibres. Phloem rays were found as uniseriate with wide sieve cells. Furthermore, antimicrobial activities of the bark exhibited potential effects against examined bacterial and fungal strains.

Fortuna Forest Reserve, Panama

The Fortuna Forest Reserve and adjacent upland areas of the Palo Seco Reserve in western Panama support some of the most extensively studied lower and premontane tropical forests in the world. The forests of Fortuna are among the most diverse in Central America and are therefore of exceptional significance for the preservation of regional biodiversity. This volume brings together more than 50 years of research on the climate, geology, soils, and major plant groups of Fortuna. Spanning the Continental Divide at around 1,000 m above sea level, some parts of the reserve receive more than 6,000 mm of annual rainfall, although there is considerable variation in cloud cover and seasonality. Soil fertility also varies markedly, reflecting the complex regional volcanic geology. The resulting gradients of climate and fertility across the reserve shape the composition, structure, and diversity of plant communities. A network of 12 one-hectare plots at Fortuna contains more than 400 species of trees greater than 5 cm diameter at breast height and reveals extensive compositional turnover across the reserve. One tree species, Oreomunnea mexicana, forms monodominant stands in otherwise species-rich forests, while forests on extremely infertile soils are dominated by the canopy palm Colpothrinax aphanopetala and include the tropical conifer Podocarpus oleifolius. There are also almost 400 species of bryophytes, almost 300 species of ferns and lycophytes, 31 species of palms, 80 species of bromeliads, and more than 200 species of orchids. Many species of ectomycorrhizal fungi identified from fruiting bodies are new to science. Overall, results from Fortuna highlight the remarkable diversity of plants that occur in montane forests and the extent to which their communities are structured by gradients of climate and soil fertility. The chapters in this volume provide a foundation for further research and exploration in this fascinating region.

A 15,400-year long record of vegetation, fire-regime, and climate changes from the northern Patagonian Andes

Paleoecological studies from the northern Patagonian Andes (40–44°S) have identified past changes in vegetation, fire regimes and paleoclimate since the last glaciation, including variations in strength and position of the Southern Westerly Winds (SWW). The extent to which records west and east of the Andes provide a congruent paleoclimatic history, however, has not been explored in detail in the literature. Physical and biological contrasts are evident between these regions today and are to be expected in paleoclimate reconstructions. In this context, we present pollen and charcoal records from sediment cores collected in Lago Espejo, a small closed-basin lake located in the core sector of the northern Patagonian Andes that spans uninterrupted the last ∼15,400 years. Following glacier withdrawal, the vegetation surrounding Lago Espejo features scattered Nothofagus woodlands, including relatively thermophilous rainforest trees between ∼15,400 and 14,400 cal yr BP. The disappearance of these trees and an abrupt rise in Nothofagus at ∼14,400 cal yr BP mark the establishment of closed-canopy forests during the Antarctic Cold Reversal, followed by increases in the cold-tolerant hygrophilous conifer Podocarpus nubigena during the Younger Dryas (∼12,700–11,500 cal yr BP). The Holocene vegetation consists of Nothofagus-dominated forests with modest variation in composition and structure until the present, attesting to the resilience of these forest communities to climate change and natural disturbance regimes. Rapid deforestation, anthropogenic fires and the establishment of artificial meadows with exotic herbs introduced by Europeans at ∼150 cal yr BP, triggered a rapid, large-magnitude landscape transformation unprecedented in the last 14,000 years. The timing and structure of vegetation changes revealed by the Lago Espejo record suggest that changes in the SWW were the main driver of vegetation and fire regimes in the Andes of northern Patagonia over the last 15,400 years. Comparison between multiple reconstructions from northern Patagonia reveals overall coherent vegetation and fire regime changes in the western and Andean sectors, and a spatially variable and more divergent behaviour in sites located further east. This spatial patter is akin to the present-day correlation between precipitation and SWW in this region.

Terrestrial and marine floral response to latest Eocene and Oligocene events on the Antarctic Peninsula

ABSTRACTPalynological results from opposite sides of the northernmost Antarctic Peninsula provide insight on terrestrial vegetation and sea-surface conditions immediately before the Eocene–Oligocene transition (EOT), through Early Oligocene glacial conditions and the subsequent Late Oligocene interglacial interval. A latest Eocene sample set from the uppermost La Meseta Formation on Seymour Island, James Ross (back-arc) Basin, records a low-diversity Nothofagus (southern beech)-dominated vegetation with some podocarp conifers similar to Valdivian-type forest found today in Chile and Argentina. Marine organic-walled phytoplankton include leiospheres and Eocene dinoflagellate cysts such as Vozzhennikovia rotunda, V. apertura, Senegalinium asymmetricum and Spinidinium macmurdoense. Immediately before the EOT near the top of the section the decrease in terrestrial palynomorphs, increase in reworked specimens, disappearance of key dinocysts, and overwhelming numbers of sea-ice-indicative leiospheres plus the small dinoflagellate cyst Impletosphaeridium signal the onset of glacial conditions in a subpolar climate. Early to Late Oligocene samples from the Polonez Cove and Boy Point formations on King George Island, South Shetland Islands (magmatic arc), yielded an extremely depauperate terrestrial flora, likely resulting in part from poor vegetation cover during the Polonez Glaciation but also because of destruction of vegetation due to continued regional volcanism. The prevalence of sea-ice-indicative leiospheres in the marine palynomorph component is consistent with polar to subpolar conditions during and following the Polonez Glaciation.

The last glacial termination on the eastern flank of the central Patagonian Andes (47 ° S)

Abstract. Few studies have examined in detail the sequence of events during the last glacial termination (T1) in the core sector of the Patagonian Ice Sheet (PIS), the largest ice mass in the Southern Hemisphere outside of Antarctica. Here we report results from Lago Edita (47°8′ S, 72°25′ W, 570 m a.s.l.), a small closed-basin lake located in a valley overridden by eastward-flowing Andean glaciers during the Last Glacial Maximum (LGM). The Lago Edita record shows glaciolacustrine sedimentation until 19 400 yr BP, followed by organic sedimentation in a closed-basin lake and a mosaic of cold-resistant hygrophilous conifers and rainforest trees, along with alpine herbs between 19 400 and 11 000 yr BP. Our data suggest that the PIS retreated at least ∼ 90 km from its LGM limit between ∼ 21 000 and 19 400 yr BP and that scattered, low-density populations of cold-resistant hygrophilous conifers, rainforest trees, high-Andean and steppe herbs thrived east of the Andes during the LGM and T1, implying high precipitation levels and southern westerly wind (SWW) influence at 47° S. The conifer Podocarpus nubigena increased between 14 500 and 13 000 yr BP, suggesting even stronger SWW influence during the Antarctic Cold Reversal, after which it declined and persisted until 11 000 yr BP. Large increases in arboreal pollen at ∼ 13 000 and ∼ 11 000 yr BP led to the establishment of forests near Lago Edita between 10 000 and 9000 yr BP, suggesting a rise in the regional tree line along the eastern Andean slopes driven by warming pulses at ∼ 13 000 and ∼ 11 000 yr BP and a subsequent decline in SWW influence at ∼ 11 000 yr BP. We propose that the PIS imposed a regional cooling signal along its eastern, downwind margin through T1 that lasted until the separation of the northern and southern Patagonian ice fields along the Andes during the Younger Dryas period. We posit that the withdrawal of glacial and associated glaciolacustrine environments through T1 provided a route for the dispersal of hygrophilous trees and herbs from the eastern flank of the central Patagonian Andes, contributing to the afforestation of the western Andean slopes and pacific coasts of central Patagonia during T1.

Glutathione and abscisic acid supplementation influences somatic embryo maturation and hormone endogenous levels during somatic embryogenesis in Podocarpus lambertii Klotzsch ex Endl.

Here we propose a protocol for embryogenic cultures induction, proliferation and maturation for the Brazilian conifer Podocarpus lambertii, and investigated the effect of abscisic acid (ABA) and glutathione (GSH) supplementation on the maturation phase. ABA, zeatin (Z) and salicylic acid (SA) endogenous levels were quantified. Number of somatic embryos obtained in ABA-supplemented treatment was significant higher than in ABA-free treatment, showing the relevance of ABA supplementation during somatic embryos maturation. Histological analysis showed the stereotyped sequence of developmental stages in conifer somatic embryos, reaching the late torpedo-staged embryo. GSH supplementation in maturation culture medium improved the somatic embryos number and morphological features. GSH 0mM and GSH 0.1mM treatments correlated with a decreased ABA endogenous level during maturation, while GSH 0.5mM treatment showed constant levels. All treatments resulted in decreased Z endogenous levels, supporting the concept that cytokinins are important during the initial cell division but not for the later stages of embryo development. The lowest SA levels found in GSH 0.5mM treatment were coincident with early embryonic development, and this treatment resulted in the highest development of somatic embryos. Thus, a correlation between lower SA levels and improved somatic embryo formation can be hypothesized.

A new species of Protophyllocladoxylon from the Upper Cretaceous (Cenomanian–Turonian) portion of the Winton Formation, central-western Queensland, Australia

Leaf floras in fluvial–lacustrine sediments of the Upper Cretaceous (Cenomanian–Turonian) portion of the Winton Formation suggest a community with co-dominance of angiosperms, conifers, ginkgo and other seed plants. To date wood floras associated with the Winton Formation have not been examined in detail. Winton Formation wood has been presumed to comprise araucarian, podocarp and taxodiaceous components, but this has been based largely on the identification of other plant macro and microfossils. Here we describe a new species of podocarp fossil wood from the genus Protophyllocladoxylon based on eleven specimens of silicified wood found as surface material at two broadly coeval sites in the Cenomanian–Turonian portion of the Winton Formation: QM L311 and Bladensburg National Park. The new species is characterised by the presence of araucaroid tracheid pitting and phyllocladoid oopores, the absence of oculipores, and the paired arrangement of the oopores within the crossfields. The recognition of Protophyllocladoxylon in the Winton Formation supports previous palynological frequency counts that suggest a dominance of podocarp conifers.

Palaeodistribution modelling and genetic evidence highlight differential post‐glacial range shifts of a rain forest conifer distributed across a latitudinal gradient

AbstractAim We examine the range expansion/contraction dynamics during the last glacial cycle of the late‐successional tropical rain forest conifer Podocarpus elatus using a combination of modelling and molecular marker analyses. Specifically, we test whether distributional changes predicted by environmental niche modelling are in agreement with (1) the glacial maximum contractions inferred from the southern fossil record, and (2) population genetic‐based estimates of range disjunctions and demographic dynamics. In addition, we test whether northern and southern ranges are likely to have experienced similar expansion/contraction dynamics.Location Eastern Australian tropical and subtropical rain forests.Methods Environmental niche modelling was completed for three time periods during the last glacial cycle and was interpreted in light of the known palynology. We collected 109 samples from 32 populations across the entire range of P. elatus. Six microsatellite loci and Bayesian coalescence analysis were used to infer population expansion/contraction dynamics, and five sequenced loci (one plastid and four nuclear) were used to quantify genetic structure/diversity.Results Environmental niche modelling suggested that the northern and southern ranges of P. elatus experienced different expansion/contraction dynamics. In the northern range, the habitat suitable for P. elatus persisted in a small refugial area during the Last Glacial Maximum (LGM, 21 ka) and then expanded during the post‐glacial period. Conversely, in the south suitable habitat was widespread during the LGM but subsequently contracted. These differential dynamics were supported by Bayesian analyses of the population genetic data (northern dispersal) and are consistent with the greater genetic diversity in the south compared with the north. A contact zone between the two genetically divergent groups (corresponding to the Macleay Overlap Zone) was supported by environmental niche modelling and molecular analyses.Main conclusions The climatic fluctuations of the Quaternary have differentially impacted the northern and southern ranges of a broadly distributed rain forest tree in Australia. Recurrent contraction/expansion cycles contributed to the genetic distinction between northern and southern distributions of P. elatus. By combining molecular and environmental niche modelling evidence, this unique study undermines the general assumption that broadly distributed species respond in a uniform way to climate change.

Shrinking Forests under Warming: Evidence of Podocarpus parlatorei (pino del cerro) from the Subtropical Andes

Phylogeography in combination with ecological niche modeling (ENM) is a robust tool to analyze hypotheses on range shifts under changing climates particularly of taxa and areas with scant fossil records. We combined phylogeographic analysis and ENM techniques to study the effects of alternate cold and warm (i.e., glacial and interglacial) periods on the subtropical montane cold-tolerant conifer Podocarpus parlatorei from Yungas forests of the central Andes. Twenty-one populations, comprising 208 individuals, were analyzed by sequences of the trnL -trnF cpDNA region, and 78 sites were included in the ENM. Eight haplotypes were detected, most of which were widespread while 3 of them were exclusive of latitudinally marginal areas. Haplotype diversity was mostly even throughout the latitudinal range. Two distribution models based on 8 bioclimatic variables indicate a rather continuous distribution during cooling, while under warming remained within stable, yet increasingly fragmented, areas. Although no major range shifts are expected with warming, long-lasting persistence of cold-hardy taxa inhabiting subtropical mountains may include in situ and ex situ conservation actions particularly toward southern (colder) areas.

A palynological investigation of plesiosaur-bearing rocks from the Upper Cretaceous Tahora Formation, Mangahouanga, New Zealand

High-palaeolatitude plesiosaur, mosasaur and, more rarely, dinosaur fossils are well known from the Maungataniwha Sandstone Member of the Tahora Formation in Mangahouanga Stream, Hawkes Bay, New Zealand. A palynological investigation of strata exposed along Mangahouanga Stream and of transported boulders hosting vertebrate fossils reveals well-preserved assemblages dominated by terrestrial pollen and spores but also including marine dinoflagellate cysts in some samples. The palynofacies are strongly dominated by wood fragments including charcoal; one outcrop sample and the sample taken from a boulder hosting plesiosaur vertebrae contain entirely terrestrially derived palynoassemblages, suggesting a freshwater habitat for at least some of the plesiosaurs. The host unit spans the Santonian to lowermost Maastrichtian, while the key pollen taxa Nothofagidites senectus and Tricolpites lilliei, together with the dinocyst Isabelidinium pellucidum and the megaspore Grapnelispora evansii, indicate a late Campanian to early Maastrichtian age for the fossiliferous boulders. The palynoflora indicates a mixed local vegetation dominated by podocarp conifers and angiosperms with a significant tree-fern subcanopy. The presence of taxa with modern temperate distributions, such as Nothofagus (southern beech), Proteaceae and Cyatheaceae (tree-ferns), indicates a mild-temperate climate and lack of severe winter freezing during the latest Cretaceous, providing an ecosystem that most probably made it possible for polar dinosaurs to overwinter in this part of the world.

Cretaceous plant fossils of Pitt Island, the Chatham group, New Zealand

Pitt Island, a part of the Chathams Islands group, lies 700 km east of New Zealand. Its geology includes the Tupuangi Formation, dated as Motuan to Teratan (late Albian to Santonian) on the basis of palynology. Samples of Tupuangi Formation mudstone yielded leaf cuticle assemblages dominated by araucarian and podocarp conifers and locally by angiosperms. The 12 distinguishable conifer taxa include a new species of Araucaria, A. rangiauriaensis, and the extinct genera Eromangia, Kakahuia (both Podocarpaceae), Otwayia (Cheirolepidiaceae), Paahake (Taxodiaceae or Taxaceae) and possibly Katikia (Podocarpaceae). Ginkgo and two types of dicotyledonous angiosperm cuticle are present. Based on the absence of bennettitaleans and rarity of Ginkgo, a Turonian or slightly younger age is inferred, making the Pitt Island assemblage the first Turonian plant macrofossils documented from New Zealand. The fossils provide a window into southern high-latitude (polar) vegetation of the mid-Cretaceous. Conifer charcoal (probably of Podocarpaceae) is locally abundant and suggests that fire was an important part of the ecosystem. A broad analogy with modern boreal conifer-deciduous angiosperm forests is suggested although clearly with warmer temperatures.

Role reversal in the stand dynamics of an angiosperm–conifer forest: Colonising angiosperms precede a shade-tolerant conifer in Afrotemperate forest

In mixed angiosperm–conifer forests worldwide, infrequent landscape-level catastrophic disturbances create a mosaic of persistent and different aged forest stands in the landscape with varying levels of dominance by the conifer component. In the ‘temporal stand replacement model’ (TSRM), disturbance creates conditions favouring a colonising cohort that is replaced by a suite of relatively shade-tolerant canopy species, which establish following the synchronous senescence of the pioneer canopy. In most southern hemisphere mixed angiosperm–conifer forests, with the exception of those in southern Africa, the establishing cohort is usually a large and very long-lived (550–650 years) conifer that is gradually replaced by angiosperms. As an explanation of the apparent dominance of the conifer Podocarpus latifolius, we examine the efficacy of the TSRM in mixed Afrotemperate forests where the establishing cohort is not a conifer. Forest succession in Afrotemperate forests was deterministic with the successive replacement of species determined first by their establishment success in shaded environments, and second, by their relative longevity. Several angiosperm species that were common canopy dominants established a pioneer cohort but were gradually replaced by P. latifolius, a shade-tolerant species. Continuous regeneration beneath the angiosperm canopy by P. latifolius eliminates synchronous canopy senescence, a key feature of the TSRM, as a mechanism driving the temporal replacement of canopy species. Senescing angiosperms created canopy gaps that were colonised by grasses and ferns, which suppressed canopy tree regeneration. In contrast, with continuous regeneration beneath the shaded canopy, P. latifolius gains a critical advantage over angiosperms at gap formation. Thus, in the absence of fairly large-scale natural disturbances, conifers come to dominate Afrotemperate forests. Commensurate with the latter, conifers in Podocarpus-forest were dated to approximately 320 years, more than 100 years older than the oldest P. latifolius in angiosperm-dominated forest. Tree life-history differences (shade tolerance, longevity) and the time since disturbance drive successional change from an angiosperm-dominated system to a stage dominated by P. latifolius. In general, the TSRM is a plausible explanation for the observed canopy tree structure and dynamics in mixed Afrotemperate forests. South African Afrotemperate forest is unusual among other southern hemisphere mixed angiosperm–conifer forests in that a suite of angiosperm canopy species, rather than a single conifer species, forms the colonising cohort.

Environmental controls and patterns of cumulative radial increment of evergreen tree species in montane, temperate rainforests of Chiloé Island, southern Chile

AbstractWe investigated the local environmental controls on daily fluctuations of cumulative radial increment and cambial hydration of three dominant, evergreen tree species from montane, Coastal rainforests of Chiloé Island, Chile (42° 22′ S). During 2 years (1997–1998 and 1998–1999) we recorded hourly cumulative radial increments using electronic band dendrometers in the long‐lived conifer Fitzroya cupressoides (Cupressaceae), the evergreen broad‐leaved Nothofagus nitida (Nothofagaceae), and the narrow‐leaved conifer Podocarpus nubigena (Podocarpaceae). We also measured soil and cambial tissue hydration using capacitance sensors, together with air and soil temperature and rainfall during the period of the study. In addition, we collected cores of these tree species to evaluate how dendrometer measurements reflect annual tree ring width. One‐year long daily time series of cumulative radial increments suggests that radial growth of Fitzroya cupressoides was initiated slowly in early spring, with a maximum in early summer. Multiple regressions showed positive relations between daily precipitation and radial index (i.e. the difference in cumulative radial increment of two consecutive days) in the three species. According to path analysis there was a significant direct effect of changes in tree hydration on radial index of the three focal species. In emergent, pioneer species such as Nothofagus and Fitzroya, radial index was negatively affected by changes in maximum air temperature and photosynthetically active radiation, probably because of high evapotranspiration demand on warm sunny days. The shade‐tolerant species Podocarpus nubigena was positively affected by photosynthetically active radiation. Our diel scale findings support the use of tree ring widths for reconstructing past climate in these southern temperate forests and provide evidence that rainforest trees may be highly sensitive to future declines in rainfall and temperature increases during summer.

In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection

Sauropod dinosaurs, the dominant herbivores throughout the Jurassic, challenge general rules of large vertebrate herbivory. With body weights surpassing those of any other megaherbivore, they relied almost exclusively on pre-angiosperm plants such as gymnosperms, ferns and fern allies as food sources, plant groups that are generally believed to be of very low nutritional quality. However, the nutritive value of these taxa is virtually unknown, despite their importance in the reconstruction of the ecology of Mesozoic herbivores. Using a feed evaluation test for extant herbivores, we show that the energy content of horsetails and of certain conifers and ferns is at a level comparable to extant browse. Based on our experimental results, plants such as Equisetum, Araucaria, Ginkgo and Angiopteris would have formed a major part of sauropod diets, while cycads, tree ferns and podocarp conifers would have been poor sources of energy. Energy-rich but slow-fermenting Araucaria, which was globally distributed in the Jurassic, was probably targeted by giant, high-browsing sauropods with their presumably very long ingesta retention times. Our data make possible a more realistic calculation of the daily food intake of an individual sauropod and improve our understanding of how large herbivorous dinosaurs could have flourished in pre-angiosperm ecosystems.

Regional assessment of the impact of climatic change on the distribution of a tropical conifer in the lowlands of South America

AbstractFor decades, palynologists working in tropical South America are using the genus Podocarpus as a climate indicator although without referring to any modern data concerning its distribution and limiting factors. With the aim to characterize the modern and past distribution of the southern conifer Podocarpus in Brazil and to obtain new information on the distribution of the Atlantic rainforest during the Quaternary, we examined herbarium data to locate the populations of three Brazilian endemic Podocarpus species: P. sellowii, P. lambertii, and P. brasiliensis, and extracted DNA from fresh leaves from 26 populations. Our conclusions are drawn in the light of the combination of these three disciplines: botany, palynology, and genetics. We find that the modern distribution of endemic Podocarpus populations shows that they are widely dispersed in eastern Brazil, from north to south and reveals that the expansion of Podocarpus recorded in single Amazonian pollen records may have come from either western or eastern populations. Genetic analysis enabled us to delimit regional expansion: between 5° and 15° S grouping northern and central populations of P. sellowii expanded c. 16,000 years ago; between 15° and 23° S populations of either P. lambertii or sellowii expanded at different times since at least the last glaciation; and between 23° and 30° S, P. lambertii appeared during the recent expansion of the Araucaria forest. The combination of botany, pollen, and molecular analysis proved to be a rapid tool for inferring distribution borders for sparse populations and their regional evolution within tropical ecosystems. Today the refugia of rainforest communities we identified are crucial hotspots to allow the Atlantic forest to survive under unfavourable climatic conditions and, as such, offer the only possible opportunity for this type of forest to expand in the event of a future climate change.

Millennial‐scale climate variability in northwest Patagonia over the last 15 000 yr

AbstractA pollen record from Lago Condorito (41°45'S, 73°07'W) shows prominent vegetation and climate changes at millennial time‐scales, superimposed on multimillennial trends in temperature and westerly activity in northwest Patagonia during the past 15 000 yr. The record shows that evergreen temperate rainforests have dominated the landscape over this interval, with floristic changes ranging from cold‐resistant North Patagonian forests with podocarp conifers to Valdivian forests with thermophilous, summer‐drought resistant species. The long‐term trend shows that cool‐temperate and humid conditions prevailed between 15 000 and 11 000 cal. yr BP, followed by an extreme warm and dry phase between 11 000 and 7600 cal. yr BP, and subsequent cooling events and increase in precipitation that peaked at ca. 5000 cal. yr BP, when Southern Hemisphere alpine glaciers achieved their first Neoglacial maximum. Modern conditions were established at ca. 1800 cal. yr BP, following a warm and dry phase between ca. 2900 and 1800 cal. yr BP. These results suggest that millennial‐scale climate variability during deglacial and post‐glacial times also affected the mid‐latitude region of the South Pacific, supporting the idea that changes in the tropical Pacific might be a key factor in the initiation and/or propagation of millennial‐scale climate variability at regional, hemispheric and global scales. Copyright © 2004 John Wiley & Sons, Ltd.

Terrestrial Paleoecology of the Cretaceous (Early Aptian) Cerro Negro Formation, South Shetlands Islands, Antarctica: A Record of Polar Vegetation in a Volcanic Arc Environment

Nothing is known about the community-scale plant ecology of early Cretaceous volcanic environments in the southern high latitudes. The paleoecology of the early Aptian (119–120 Ma) volcaniclastic Cerro Negro Formation of South Shetland Islands, Antarctica, has been investigated to improve understanding of these enigmatic ecosystems. This unit was deposited in an intra-arc setting at the edge of the paleo-polar circle (66°S). Taphonomic analysis of megaflora in seven volcanic facies indicates the existence of a spatially complex vegetation mosaic co-dominated by conifers, bennettites, and ferns. A lower stratigraphic unit was deposited by high-magnitude, low-frequency silicic eruptions, partially reworked by fluvial processes. Following ash falls, shrubby communities of ferns and bennettites dominated for short periods in low-altitude paleovalleys before being replaced by araucarian-podocarp-fern conifer forests. Forests of podocarp conifers and bennettites covered adjacent mid-altitude slopes of active volcanic cones. These were destroyed periodically by hot pyroclastic flows, and their charred remains washed down into paleovalley fluvial systems. Analysis of architectural and phenological data from both major forest communities indicates the predominance of evergreen trees with a canopy height of c. 20–30 m. Growth-ring analysis indicates that, despite occasional catastrophic eruptions, growing conditions were mostly favorable and uniform, although in riparian paleovalley niches flooding locally produced more stressful growing conditions. An upper stratigraphic unit was deposited by low-magnitude, high-frequency basaltic eruptions. Shrubby, fern and bennettite-dominated vegetation, together with local conifer stands, colonized this environment. Growth of more widespread arborescent vegetation in the upper unit was inhibited by high-frequency volcanic disturbances. Bennettites are much more abundant and diverse in the Cerro Negro Formation compared with coeval, non-volcanic sites in the southern high latitudes, indicating that this group may have favored volcanic environments.

GENETIC VARIATION IN WILD CHILEAN AND CULTIVATED BRITISH POPULATIONS OF PODOCARPUS SALIGNUS D. DON (PODOCARPACEAE)

The threatened Chilean conifer Podocarpus salignus D. Don is currently the focus of ex situ conservation eorts being undertaken by the Conifer Conservation Programme of the Royal Botanic Garden Edinburgh. To assess variation within in and ex situ populations of the species, leaf material collected from four wild populations was analysed by random amplified polymorphic DNA (RAPD). Amova of RAPD profiles indicated that 93% of the variation occurred within, rather than between, populations. Intraspecific genetic diversity, estimated using percentage polymorphic loci, Shannon's diversity index, and Nei's gene diversity, was relatively high (47%, 0.692 and 0.314, respectively). To assess genetic diversity in ex situ populations within the UK, RAPD analysis of parents and progeny at two Cornish arboreta was undertaken. The results provided evidence of novel hybridization with suspected paternal trees (P. hallii Kirk and P. totara G. Benn. ex D. Don) endemic to New Zealand. RAPD was found to be an effective tool for assessing the genetic structure of P. salignus, for providing a guide to future germplasm-sampling strategies, and for hybrid identification. Implications for genetic conservation of the species and the role of ex situ approaches are discussed.