Microsatellite markers and mtDNA data indicate two distinct groups in dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae), a threatened freshwater fish from south-eastern Australia

Galaxiella pusilla is a small, non-migratory freshwater fish, endemic to south-eastern Australia and considered nationally threatened. To assist in the conservation of the species, microsatellite markers were developed and used to characterize genetic variation in 20 geographically distinct populations across its range. Substantial genetic differentiation was found between an eastern (Victoria east of the Otway Ranges and Tasmania) and western (South Australia and Victoria west of, and including, the Otway Ranges) region. This major separation was also observed in data from a mitochondrial gene and supports a previously proposed split. Populations from the eastern region had overall lower genetic diversity for both the microsatellite and mtDNA markers. There was substantial genetic differentiation between populations within the two regions, suggesting that gene flow is limited by the isolation of freshwater streams. Genetic structure, consistent with an isolation-by-distance model, was also evident in both regions. Patterns of genetic variation in this threatened species are compared to those obtained for other taxa across the same region. The need to consider separate conservation strategies for the two sets of populations is emphasized.     

Palaeo‐ecology of the Gap and Coturaundee Ranges,western New South Wales,using stick‐nest rat (Leporillus spp.) (Muridae) middens

Pollen, plant and animal macrofossils recovered from nine Leporillus spp. (Muridae) middens found in the Gap and Coturaundee Ranges, western New South Wales were examined. By comparing current vegetation, pollen from modern surface samples and pollen from midden samples, general vegetation characteristics over the last 6500 years BP were reconstructed. Evidence shows that a greater shrub cover was apparent between 6500 and 5200 BP , while other aspects of the vegetation cover were similar to present. An increase in tree pollen, possibly indicating greater tree cover, occurred around 3400–2600 BP , while vegetation in the last 1300 years was similar to present. These interpretations, particularly from the older samples, are tentative due to spatial and temporal limitations. Animal macrofossils from the middens indicate that several mammal species now extinct or uncommon in western New South Wales have occurred in the area in the past 3000 years. This study also confirms that reconstruction of vegetation from Leporillus spp. midden evidence should be seen as separate ‘snapshots’, rather than continuous records over a stratigraphically defined timescale.     

Vegetational stability and rare species from Early Holocene Lewis

Summary

Strata of complex geomorphological origin at Skigersta in the northeast of the Isle of Lewis include organic sediments which have provided a detailed pollen profile and two Early Holocene radiocarbon dates. These two sources of evidence suggest that a stable, pre-woodland, species-rich grass and sedge landscape may have existed for at least one thousand radiocarbon years (10,250 to 9250 BP). Included in the pollen taxa are Koenigia islandica and Polemonium caeruleum, neither of which is now native to Lewis. The former was present in the Middle Devensian (c. 30 kyr BP), perhaps hinting at survival in a local refugium during the Late Devensian glaciation.     

Pollen and macroscopic analyses of sediments from two lakes in the High Tatra mountains, Slovakia

The paper presents the results of investigations concerning the accumulation processes, sediment composition, pollen and macroscopic analyses of sediments from the lakes Popradské pleso (1513 m) and Štrbské pleso (1345 m) in the High Tatra mountains, western Carpathians, Slovakia. While Popradské pleso is undoubtedly of glacial origin with silts in the Lateglacial layers and algal gyttja in the Holocene layers, Štrbské pleso or its greater part originated recently between the 16th and the beginning of the 18th centuries when the previous bog of Atlantic or early Subboreal age was flooded with water after the dispersed outflow from the bog depression was blocked. Our pollen and macrofossil analyses indicate mountain tundra in the Lateglacial and a continuous presence of coniferous forest with Picea abies with admixture of Pinus cembra, Larix decidua, Juniperus communis and Pinus cf. mugo in the uppermost elevations at the alpine forest limit since the very beginning of the Holocene. No noticeable oscillation of the forest line can be interpreted from our pollen analyses. It seems probable that its position was controlled by geomorphological and edaphic conditions rather than by the Holocene climatic changes. Spruce forests dominated at elevations between ca. 1000–1400 m during the whole Holocene.     

Holocene vegetation and water level history in two bogs of the Cordillera de Talamanca, Costa Rica

Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG     

A short pollen diagram from rainforest in highland eastern Victoria

Pollen data from the Rooty Breaks swamp – a Sphagnum bog surrounded by Atherosperma-Elaeocarpus rainforest – in the eastern Victorian highlands appears to reflect changes in the mode of pollen and spore deposition at the study site, from the time sediments began accumulating at about 5500 BP until the present day. In the lower half of the deposit, pollen of rainforest taxa is more common than it is in the top half, while Eucalyptus pollen reflects the reverse situation. Although the pollen changes may reflect climatic change it is suggested that most of the pollen and spores in the lower sediment were stream-borne. Later the stream moved away from the site and the records became more representative of atmospheric pollenrain. Throughout the period covered by the pollen diagram the Rooty Breaks swamp itself was dominated by Leptospermum grandifolium. The pollen record shows that the association of important taxa in rainforests of the highlands of eastern Victoria was established by at least 5500 BP. The presence of sparse old eucalypts throughout the area dominated by rainforest suggests that sclerophyll forest was replaced by rainforest in the recent past. However, this change is not evidenced in the pollen diagram.     

The Early Holocene treeline in the southern French Alps: new evidence from travertine formations

Aims The present paper concerns the analysis of macro‐remains (plant imprints) from high altitude travertine deposits dating back to the early Holocene (9800 BP ). Our results allow us to discuss treeline location and ecology, and to supplement previous data based on pollen from natural sediments and charcoal from natural soil. Location The travertine under study is located in the Queyras massif, in the southern French Alps, along the Italian border. The site is situated on a south‐facing slope. Methods The travertine deposit has been dated by ²³⁰Th/²³⁴U. Taxonomic identification of plant imprints was achieved by comparison of the morphology of fossil specimens with extant material. Results Imprints of Pinus uncinata (cones and needles), broad‐leaved trees (Betula cf. pubescens, Populus tremula and Salix spp.), and unidentified trunks have been found. The plant assemblage records the existence at a high altitude (2200 m) of shade‐intolerant vegetation at around 9800 BP. Our data indicate that the treeline limit was at least 100 m higher than previously thought. The morphological features of the travertine, the plant assemblage and trunk diameters indicate that during the travertinization process, vegetation around the site was probably dense with tall upright trees. Main conclusions Our data show that Pinus uncinata and broad‐leaved trees developed at 2200 m, while regional pollen analyses locate the treeline at lower altitudes. Different research methods appear to provide different results. Around 9800 BP tree regeneration and growth were made possible up to at least 2200 m a.s.l., probably as a result of warmer and wetter summers. Warmer conditions are inferred from the predicted increase in incoming solar radiation based on calculated orbital variations, and wetter conditions are inferred from the build‐up of the travertine.     

Population genetic structure of the ectomycorrhizal fungus Laccaria sp. A resembles that of its host tree Nothofagus cunninghamii

The ectomycorrhizal fungus Laccaria sp. A is restricted to temperate rainforest of southeast Australia, associated with its host tree Nothofagus cunninghamii. Eight mitochondrial microsatellite markers were used to investigate the population genetic structure of L. sp. A across its distribution in Tasmania and Victoria. The highest allelic diversity was found in Tasmania, which appeared to contain a panmictic population, whereas the more fragmented Victorian populations were characterized by low allelic diversity and differentiation between east and west. There is evidence of glacial refugia in the west and the northeast of Tasmania, and in Victoria in the Otway Ranges and Central Highlands, with postglacial migration into the Strzelecki Ranges. Narrow host-specificity may have contributed to the presence of population structure in this fungus. Allelic diversity patterns in L. sp. A are largely congruent with diversity patterns already established in populations of its host, N. cunninghamii.     

Modelling of fossil and contemporary data suggest the Broad-toothed rat (Mastacomys fuscus) currently occupies a small part of its available climatic niche: Implications of paleontological data for conservation of a threatened species

We use fossil, sub-fossil and contemporary records of the Broad-toothed rat, Mastacomys fuscus, to model changes in its range over the last 21 thousand years. Mastacomys fuscus was exposed to, and flourished in, a much broader range of environmental conditions in the recent past than it occupies today. It also currently occupies a much smaller range than it did in the Late Pleistocene. Apart from a weak response to sea-level rise in the Holocene, the decline of M. fuscus does not correlate with known climate change. Instead, the contraction of the species' distribution on mainland Australia to high-elevation areas occurred recently and rapidly. Small changes in the 1000 year BP and present-day projected distributions imply some contraction of the area of suitable climate to higher elevations of the mainland subspecies M. f. mordicus, up to 2200 m above sea level. However, M. f. mordicus also persists near sea level at Cape Otway (southwestern Victoria) and from sea level to 1500 m above sea level at Barrington Tops (eastern New South Wales, Australia). This suggests suitable habitat may still exist in coastal Victoria and the central Tablelands/Blue Mountains areas. This research highlights the importance and value of using sub-fossil data to understand changes in the distribution and niche occupation of threatened species as the basis for conservation planning.     

Late Quaternary grassland (Campos), gallery forest,fire and climate dynamics,studied by pollen,charcoal and multivariate analysis of the São Francisco de Assis core in western Rio Grande do Sul (southern Brazil)

We present a detailed pollen and charcoal record of a 368-cm-long sediment core from the lowland Campos (grassland) region near the city of São Francisco de Assis in the western Rio Grande do Sul State in southern Brazil. Based on four AMS radiocarbon dates, the record represents the last about 22,000 cal yr BP. The region was naturally covered by Campos throughout the recorded glacial and Holocene period under cold and relatively dry and warm and dry condition, respectively. Initial expansion of gallery forest after 5170 cal yr BP indicates a change to wetter climatic conditions. Maximum extent of gallery forest after 1550 cal yr BP reflects the wettest recorded period. There is some evidence of plant migration from the eastern Atlantic coastal lowland reaching the western lowland, first after mid Holocene times by Cecropia and, possibly, species of Myrsine and Moraceae and later, after about 1000 cal yr BP, by species of Alchornea and Acalypha. Multivariate analysis revealed that the long-term pollen composition dynamics is a two-phase process, with random, chaotic changes characterizing some periods when climate conditions were likely more stable, and directional compositional changes (phase transitions) in periods coincide with major climate and/or anthropogenic changes. Natural fires were rare during full- and lateglacial periods, but became frequent at the beginning of the Holocene, suggesting the beginning of human occupation of the western lowland at that time. Highest fire frequency is found during the wet late Holocene period, suggesting an increase of indigenous populations in the São Francisco de Assis region.     

Palynology of the Venezuelan Andes

The results of palynological analyses from the Mérida Andes, Venezuela, from seven stratigraphic sections covering the last 13,000 years are discussed. An interpretation of the climate and vegetation for this time interval shows that the composition of the high montane vegetation and its altitudinal position was not constant during the Late Quaternary, the climate changed at the end of the Pleistocene and there were small oscillations during the Holocene.

The representation and abundance of arboreal pollen and spores in the old sediments as compared with modern deposition indicates the presence of: I. families and genera with high pollen or spore production and dispersion (Podocarpus, Alnus, Hedyosmum, and Cyatheaceae); 2. families with low pollen dispersion power, among them the Moraceae and Myrtaceae; 3. one genus among the Compositae (Coespeletia) which is probably anemophilous; 4. one species of montane Gramineae (Pariana stenolemma) which is probably not anemophilous, presenting the first case of insect-pollinated grasses in the tropics of South America.     

The vegetational history of the northern Apennines, Italy: information from three new sequences and a review of Regional vegetational change

Abstract. The results of pollen analysis and radiocarbon dating are presented from three northern Apennine sequences; Lago Padule in northern Tuscany and Lago Pratignano and Ospitale in the Emilia-Romagnan Apennines. This is the first detailed pollen stratigraphic information from sites in Emilia-Romagna and north Tuscany and extends eastwards the area from which information on vegetational history is available. The sequence from Lago Padule is one of the most complete Holocene records known from the northern Apennine region. Lago Pratignano has the deepest sequence of organic sediments (1544 cm) and the fastest rates of sediment accumulation (up to 28 cm per 100 years) providing the highest resolution record for the mid to late Holocene periods in the region. High rates of sedimentation have also occurred at Ospitale where organic sediments are 780 cm deep and began to form at approximately 5500 bp. The record from Lago Padule is compared with Holocene records from two nearby sites and a series of Regional Pollen Assemblage Zones is defined for the eastern area of the northern Apennines. The main features of vegetational change identified are: (i) a‘pioneer’phase of rapid forest development during the early Holocene followed by the establishment of an upper forest belt dominated by Abies, and a belt of mixed deciduous forest at lower altitudes; (ii) the appearance and rapid expansion of Fagus between approximately 5200 bp and 2900 bp forming a mixed Abies-Fagus association in the upper forest belt; and (iii) the overall reduction of forest cover, and dominance of Fagus in the arboreal vegetation from around 2900 bp. The scheme of Regional PAZs for the eastern area is used as a framework for the review of pollen stratigraphic information and radiocarbon dates from other sites in the northern Apennine region. Characteristics of pollen records which can be identified in sequences from across the region are identified and the chronology of similar changes in pollen stratigraphy is examined. The scheme of four regional PAZs for the Holocene period is shown to be valid for the entire northern Apennine region. The examination of a series of pollen records shows that Fagus appeared earlier in the western than the eastern part of the region during the mid Holocene and became dominant in the northern Apennine forests post 3000 bp. The impact of anthropogenic activity and climatic change on the spread and development of Fagus are discussed. The palynological evidence which is now available from the northern Apennines is compared with information for the region shown in the‘European pollen maps’of Huntley & Birks (1983). This study provides an updated review of the representation of different tree taxa in Holocene pollen records from the northern Apennines and illustrates the role of the northern Apennines as a refugium for trees during the Wurmian Lateglacial.     

Distinguishing fossil Betula nana and B. pubescens using their wingless fruits: implications for the late-glacial vegetational history of western Norway

Principal components analysis of 7 size and shape variables measured on 154 modern fruit bodies of Betula species and hybrids shows that B. pubescens and B. nana can be distinguished from each other on the basis of their fruit bodies, and that B. pubescens ssp. tortuosa and hybrids either fall within the range of B. pubescens or have an intermediate position on PCA axes 1 and 2. Passive positioning on the modern PCA axes of fossil fruit bodies from late-glacial sediments at Eigebakken, south-west Norway, shows that only B. nana was locally present in the Allerød. This contradicts earlier inferences from pollen analyses alone of birch woodland development in the Allerød in south-west Norway. There is no macrofossil evidence for tree-birches in the Allerød near Eigebakken. The relatively large amounts of Betula pollen, including B. pubescens, at Eigebakken are thus probably derived by long-distance transport from tree-birches in Denmark, south Sweden, and Britain, whose presence is proved there by macrofossils. Consequently, earlier estimates of mean July temperature during the Allerød in southwestern Norway should be reduced to around 7.5–10°C. In contrast, the PCA shows that fruit bodies from Holocene sediments at Eigebakken and at Kråkenes, western Norway, are mostly derived from B. pubescens. Birch trees were able to spread quickly and effectively across Norway in the early Holocene.     

A mid-Holocene vegetational and anthropogenic record in the Guanabara Bay region,Rio de Janeiro State,SE Brazil,assessed by palynological and charcoal data

Palynological and charcoal fragment analyses of Guanabara Bay sediments, as well as radiocarbon dating, were carried out on one 220 cm long sedimentary core collected from the northeast sector of the bay, near the São Gonçalo coast. This study aims at recognising and explaining the environmental history of this region during the mid-Holocene, and to identify the anthropogenic influences on it. The palynological data indicate the predominance of ombrophilous forest vegetation in the Guanabara Bay Hydrographic Basin at c. 6500 calendar years bp. During this period (pollen zone 1), the concentrations of pollen grains and spores may still have been controlled by the Holocene Maximum Transgressive Event. After a phase of low concentrations of palynomorphs, there was a considerable increase in the accumulation patterns of pollen and spore grains (pollen zone 2). This increase can probably be related to the retreat of the sea level event after the Holocene Maximum Transgressive Event. The 75 cm of the core top (pollen zone 3) provide clear evidence of human influence in the area, which is inferred from the significant reduction in ombrophilous forest pollen grains, the significant increase in herbaceous pollen grains, the presence of exotic pollen types (Eucalyptus and Pinus), and high concentration of carbonaceous particles.     

Temporal dynamics of invertebrate community assembly in Lake Victoria since the late Pleistocene based on chitinous remains

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Climatic and human effects on the post-glacial dynamics of <Emphasis Type="Italic">Fagus</Emphasis> <Emphasis Type="Italic">sylvatica</Emphasis> L. in NW Iberia

Our aim is to determine the population dynamics of Fagus sylvatica L. during the last 4,000 cal. BP in NW Iberia and the causes of its spatial and temporal patterns, previous palaeoecological studies having shown that between the Upper Pleistocene and the recent Holocene Fagus survived in this region. A number of pollen sites have allowed a reconstruction of the regional dynamics of Fagus from the Last Glaciation to the present. Specifically, two high-resolution pollen sequences located in both extremes of the Cantabrian region were analysed to discuss the beech forest dynamics during the last four millennia. Beech pollen percentages increased progressively to dominant species levels in eastern Cantabria, but only brief, minor increases are recorded in the west, where they never exceeded 2%. The expansion in the east shows three well-defined stages: an initial increase that lasted up to about 2,500 cal. BP, coinciding with a general increase in total tree pollen throughout the Cantabrian Mountains; a stage lasting between 2,500 and 1,500 cal. BP, in which Fagus pollen levels fluctuated while total tree pollen percentages began to decline and Ericaceae to increase; and a final further increase peaking around 1,250 cal. BP. The first stage (ca. 4,000–2,500 cal. BP) probably formed part of the final ascent of the tree line at the end of the mid-Holocene as the consequence of climatic improvement. Its maintenance during the second stage, while other tree species began to recede under unstable environmental conditions, is attributable to displacement of other genera such as Corylus and Quercus. Its final peak may have been facilitated by human disturbance of woodland, Fagus being a competitive species readily able to take advantage of such disturbances. That no such process occurred in the western Cantabrian area may be due to both the direct biological influence of harsher climatic conditions, and the lack of interest by human populations in settling highlands, which is attributable both to this climatic factor and to the fact that, compared with the east, this area has a greater extent of lowland and wide flat valleys where settlements were concentrated.     

Late Quaternary pollen records from the middle Caquetá river basin in central Colombian Amazon

Three pollen records are presented from the Pantano de Monica region (0°42′S, 72°04′W, 160 m elevation) on the lower terrace of Rio Caquetá of the central Colombian Amazonas. Ten radiocarbon dates from three cores indicate that the deposits are of Holocene age, but the pollen data suggest that the record may also contain the Late Glacial. The core Pantano de Monica 1 covers the time interval from 11,150 BP (extrapolated) to 4730 BP. During the Late Glacial and early Holocene this swamp was smaller in size and waters were more shallow than today, with abundant Mauritia palm trees. This indicates that the lower terrace of the Caquetá River was better drained than today, which might be related to changes in the drainage system and/or drier conditions during that time. Late Glacial and early Holocene vegetational changes in the rain forests surrounding the swamp Pantano de Monica indicate successional stages, probably related to changes in the drainage system and/or climate changes. Presence of Podocarpus pollen grains up to 2.6% of the total sum (and influx of 78 grains cm⁻² yr⁻¹) point to the regional presence of Podocarpus at the beginning of the Holocene. Evidence of Podocarpus during glacial times in other pollen records from the Amazon basin has been taken as indicative of cooling. Core Pantano de Monica 2 was taken in a small swamp (1000 m distance to Pantano de Monica 1) and starts at 4000 BP when this location was well drained. Several changes in the composition of the rain forest are documented, such as increase in disturbance (increase of Cecropia) followed by a quick recovery (increase of Psychotria). Protium and Caryocar tree taxa were frequent, suggesting that the lower terrace area was well drained until 3080 BP, after which small swamps developed. Core Pantano de Monica 3 is from the wet forest in between the two swamps and represents the period since 3260 BP. Pollen data show a continuously increasing presence of palms, probably Euterpe, suggesting either a transition from well-drained to less drained conditions in the lower terrace during the late Holocene, and/or a more intensive human impact of the rain forest on the lower terraces of Rio Caquetá. The three records from the lower terrace of Rio Caquetá show different forest compositions in the past and indicate that the rain forest environments were not stable during Late Glacial and Holocene times. Comparison with other data from lowland records of northwestern South America suggest that climate change is a major factor for environmental change in central Colombian Amazon.     

Late Quaternary foraminiferal assemblages from western Ross Sea (Antarctica) in relation to the main glacial and marine lithofacies

Investigations on foraminifers from Upper Pleistocene–Holocene sediments were carried out on twelve cores from the western Ross Sea continental margin (Drygalski, Joides, North Victoria Land Basins) as part of a “Progetto Nazionale di Ricerche in Antartide” (P.N.R.A.) multidisciplinary project. Data on the foraminiferal frequency, species diversity, tests abundance and their state of preservation were presented as a synthesis of 404 core samples to establish their relationships with the main glacial and marine lithofacies of this area. A total of 126 benthic species, pertaining to 73 genera have been identified; just few taxa, such as Cibicides spp., Globocassidulina spp., Trifarina angulosa and Miliammina spp. being the most ubiquitous and in some cases the dominant species of these paleoenvironments. Two variants of Neogloboquadrina pachyderma, including thin and thick-shelled forms have been recovered. We propose to use these results to provide the degree of glacial control during the Last Glacial Maximum and the following Holocene retreat of the ice sheets. High test fragmentation, low diversity and density tests reflect higher glacial influence of the ice sheet in the Drygalski Basin, whereas the decreasing percentage of fragmentation and a relative increase of density and diversity in Drygalski, Joides and North Victoria Land Basins indicate the paleoenvironmental passage from the ice sheet to the ice shelf condition. The ice shelf retreat is well evidenced in the Joides Basin by a succession of levels barren of foraminifers alternating with high-density levels, rich in T. angulosa, followed by a total disappearance of the calcareous foraminifers. Open-marine settings indicative of lower glacial influence and increased corrosiveness of the water masses is testified by the Miliammina foraminiferal assemblage during the Holocene in Drygalski and Joides Basins cores. On the contrary, rich and abundant benthic and planktonic assemblages characterize the Holocene paleoenvironment of the North Victoria Land area, indicating that the water masses were less corrosive with respect to the other areas. In addition to the glacial reworking of the tests, and the dissolution due to the corrosive water mass conditions, the volcaniclastic sediments recovered in the North Victoria Land Basin cores also affected the condition of test preservation. In volcaniclastic sediments, older than about 20 ka BP, the foraminifers concentration tends to zero and, when present, their tests are highly damaged or completely broken.     

Holocene environmental history of Lake Vuolep Njakajaure (Abisko National Park, northern Sweden) reconstructed using biological proxy indicators

Holocene environmental and climatic changes are reconstructed using analyses of biological proxies in lake sediments from Vuolep Njakajaure, a lake located near the altitudinal treeline in northern Sweden (68°20′ N, 18°47′ E). We analysed biological proxy indicators from both aquatic and terrestrial ecosystems, including diatoms, pollen and chironomid head capsules, in order to reconstruct regional Holocene climate and the development of the lake and its catchment. During the early Holocene and after 2500 cal b.p., Fragilaria taxa dominated the diatom assemblages, whereas planktonic Cyclotella taxa prevailed during the major part of the Holocene (7800–2300 cal b.p.), indicating the importance of the pelagic habitat for diatom assemblage composition. The planktonic diatoms appeared at the same time as Alnus became established in the catchment, probably altering nutrient availability and catchment stability. The pollen record is dominated by mountain birch (Betula pubescens ssp. tortuosa) pollen throughout the Holocene, but high percentage abundances of Scots pine (Pinus sylvestris) pollen suggest the presence of a mixed pine-birch forest during the mid-Holocene (6800–2300 cal b.p.). Head capsules of Tanytarsini and Psectrocladius dominated the chironomid assemblage composition throughout the Holocene, in combination with Corynocera ambigua after 2300 cal b.p. A quantitative, diatom-based reconstruction of mean July air temperature indicated a relatively cold temperature during the early Holocene (9000–8000 cal b.p.) and after ca. 2300 cal b.p., whereas the mid-Holocene period is characterised by stable and warm temperatures. The overall patterns of Holocene climate and environmental conditions are similarly described by all biological proxy-indicators, suggesting relatively warm conditions during the mid-Holocene (ca. 7800–2300 cal b.p.), with a subsequent colder climate after 2300 cal b.p. However, the onset and magnitude of the inferred changes differ slightly among the proxies, illustrating different responses to lake development phases, land-uplift, and climate forcing (e.g., insolation patterns) during the Holocene in northern Sweden.     

History of Late Holocene vegetation at Quintana Roo,Caribbean coast of Mexico

A pollen record of a Late Holocene sediment core from the Mexican Caribbean coast (Quintana Roo) shows the development and changes of a mangrove system. Humid conditions seem to have persisted for the period approximately 2500–1500 ¹⁴C yr BP (pollen zone I), and mangrove Rhizophora mangle dominated with a good representation of elements from the nearby semi-evergreen tropical forest. During the period approximately 1500–1200 ¹⁴C yr BP (pollen zone II) the mangrove Conocarpus erecta dominated. R. mangle almost disappeared and other taxa appeared, suggesting drier climatic conditions and generally more open vegetation. This dry period coincided with the period of the Maya cultural decline. The following period (pollen zone III, approximately 1200–1000 ¹⁴C yr BP) was characterized by the recovery of R. mangle, indicating more humid conditions than in the preceding pollen zone. Pollen zone IV (approximately 1000 ¹⁴C yr BP till present) suggests a drier period reoccuring with C. erecta; this marks the transition to present day conditions.