Comparison Of Pollen Research Articles

Comparison of pollen and conifer stomates as indicators of alpine treeline in northwestern Canadian lake sediments

We compare fossil pollen and stomate assemblages in 29 lake sediment surface samples from mountainous regions in northwestern Canada to characterize the relationship between modern vegetation, and ...

Evolution of Pollen Morphology

Over evolutionary time, the morphology of angiosperm pollen has evolved toward an increasing number of apertures, among other things. From a neo-Darwinian point of view, this means that (i) some polymorphism for aperture number must exist and (ii) there must be some fitness increase associated with increasing the aperture number. Pollen types with different aperture numbers often occur in the same species. Such is the case in Viola diversifolia. Comparison of pollen with three and four apertures in this species showed that four-apertured grains germinated faster than three-apertured ones but that the four-apertured ones experienced other disadvantages. These results obtained on the gametophyte can be interpreted in terms of strategies of the sporophyte.

Comparison of pollen and macrofossils in packrat ( Neotama) middens: A chronological sequence from the Waterman mountains of southern Arizona, U.S.A.

Pollen percentages in moss polsters and soil samples were compared with percent plant cover along 30-m transects in desertscrub vegetation, Waterman Mountains, Arizona, in the northeastern Sonoran Desert. These data were used to interpret pollen assemblages and associated plant macrofossils from 14 packrat ( Neotoma sp.) middens radiocarbon dated from 1320 to 22,450 yr B.P. A macrofossil: pollen index ( MPI) was used to compare the presence and relative abundances of pollen and macrofossils in midden samples. In general, pollen and macrofossils from Sonoran Desert middens reflect similar vegetation signals. Calculation of Sørensen's Similarity Index ( SI) comparing the presence of midden pollen and macrofossils indicates greater similarities for Sonoran desertscrub than pinyon-juniper woodland. SI values from the Waterman series are greater for all age samples, compared to samples from other desert locations, perhaps reflecting greater species richness and summer rainfall in the northeastern Sonoran Desert. The pollen and macrofossil assemblages reflect a middle and late Wisconsin (22,450-ca. 11,500 yr B.P.) pinyon-juniper woodland with sagebrush and Joshua tree on limestone slopes. A transitional early Holocene juniper woodland/chaparral was replaced by 8900 yr B.P. by a mesic Sonoran desertscrub of saguaro, catclaw acacia, blue paloverde and velvet mesquite. The presence of the latter three on exposed rocky locations, now restricted mostly to riparian washes, indicates moister conditions during the middle Holocene than today. Essentially modern vegetation developed by ca. 4000 yr B.P. Changes over the last ca. 1300 years suggest that modern climate is the most xeric in the entire record.

Comparison of pollen and macrofossil based reconstructions of Late Quaternary vegetation in western North America

In western North America, vegetation reconstructions based on separate palynological and packrat ( Neotoma spp.) midden studies can be compared to explore the strengths and weaknesses of each technique. Agreement between interpretations based on the different data appears to decrease with increasing distance from the pollen site. Likely sources of disagreement can be found in both the pollen and plant macrofossil studies. For pollen-based interpretations, these include the association of fossil pollen spectra with modern vegetation types and assumptions regarding the nature of vegetation zonation during the last glacial age. Factors in midden analysis that contribute to disagreement include the restriction of macrofossil data to rocky habitats and its sparse geographic coverage. Along with providing novel tests of palynological reconstructions, balanced comparisons of plant macrofossil and pollen data allow greater understanding of interpretive factors affecting our view of Late Quaternary vegetation.

Late pleistocene paleoenvironmental studies from the Rocky Mountain Region: A comparison of pollen and insect fossil records

AbstractA regional paleoenvironmental reconstruction is presented for a north‐south transect of late glacial pollen and insect fossil sites from the Rocky Mountain region. Altitudinal treelines were depressed by an average of 671 m and summer temperatures were an average of 5.4° lower. the interpretation of paleoenvironmental conditions based on insect fossil evidence tends to show stronger departures from modern parameters than that based on palynology. While clear evidence for late glacial occupation of the region by Paleoindians is scarce, montane conditions were not so severe as to preclude human occupation, at least on a seasonal basis. Newly discovered sites of early occupation would benefit greatly from inter‐disciplinary studies.

Late Pleistocene and early Holocene environmental history of southwestern Washington State, U.S.A.

A comparison of pollen records and associated plant remains from sites along a major precipitation gradient in southwestern Washington enables reconstruction of the late Quaternary environment during glacial and early Holocene time. During the Evans Creek Stade (25 000 – 17 000 years BP) little moisture reached lowlands east of the Olympic Mountains and as a result both the Puget Trough and the Columbia Basin featured a cold dry climate and parkland–tundra vegetation In glacial time, greatest aridity seems to have occurred between 19 000 and 17 000 years BP. After 17 000 years BP the development of mesophytic subalpine parkland suggests that maritime conditions extended farther east into the Puget Trough, and the Cascade Range became an important precipitation divide. Conditions warmer and (or) drier than today developed throughout western Washington between 10 000 and 8000–6000 years BP. Vegetation on opposite sides of the Cascade Range became dissimilar as early as 17 000 years BP, but this trend was accentuated in late glacial and early Holocene time.

Distinguishing allozymes and isozymes of phosphoglucoisomerases by electrophoretic comparisons of pollen and somatic tissues

The different electrophoretic patterns of dimeric phosphoglucoisomerases extracted from haploid pollen and diploid somatic tissues of plants may be used to distinguish allozymes and isozymes. The analysis depends on the presence of two alleles at each locus in somatic tissues but only one or the other allele in pollen grains. Consequently, in heterozygotes, heterodimeric allozymes can be identified because they are formed in stems and leaves but not in pollen. The procedure is described in enzymes extracted from the diploid annual plant Clarkia dudleyana, which possesses three gene loci for PGI subunits. Comparison of the electrophoretic patterns of stem and pollen extracts makes it possible in many cases to identify allelic state without breeding tests. The technique also is likely to be useful in the interpretation of zymograms of other multimeric enzymes coded by more than one gene locus.

Présence de pollen d'araliacées dans le paléogène anglais et français

Comparison of pollen from the Paleogene in south England, the Paris Basin and Alès Basin (Gard) with the present-day Araliaceae pollen allow us to establish the presence of the following genera: Acanthopanax, Aralia, Brassaiopsis, Scheffleropsis and Panax. Five new species which show a close affinity with present-day Asiatic species are described.