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Distinct Units (distinct + unit)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Are species,area relationships from entire archipelagos congruent with those of their constituent islands?

GLOBAL ECOLOGY, Issue 4 2010
Ana M. C. Santos
ABSTRACT Aim, To establish the extent to which archipelagos follow the same species,area relationship as their constituent islands and to explore the factors that may explain departures from the relationship. Location, Thirty-eight archipelagos distributed worldwide. Methods, We used ninety-seven published datasets to create island species,area relationships (ISARs) using the Arrhenius logarithmic form of the power model. Observed and predicted species richness of an archipelago and of each of its islands were used to calculate two indices that determined whether the archipelago followed the ISAR. Archipelagic residuals (ArcRes) were calculated as the residual of the prediction provided by the ISAR using the total area of the archipelago, standardized by the total richness observed in the archipelago. We also tested whether any characteristic of the archipelago (geological origin and isolation) and/or taxon accounts for whether an archipelago fits into the ISAR or not. Finally, we explored the relationship between ArcRes and two metrics of nestedness. Results, The archipelago was close to the ISAR of its constituent islands in most of the cases analysed. Exceptions arose for archipelagos where (i) the slopes of the ISAR are low, (ii) observed species richness is higher than expected by the ISAR and/or (iii) distance to the mainland is small. The archipelago's geological origin was also important; a higher percentage of oceanic archipelagos fit into their ISAR than continental ones. ArcRes indicated that the ISAR underpredicts archipelagic richness in the least isolated archipelagos. Different types of taxon showed no differences in ArcRes. Nestedness and ArcRes appear to be related, although the form of the relationship varies between metrics. Main conclusions, Archipelagos, as a rule, follow the same ISAR as their constituent islands. Therefore, they can be used as distinct units themselves in large-scale biogeographical and macroecological studies. Departure from the ISAR can be used as a crude indicator of richness-ordered nestedness, responsive to factors such as isolation, environmental heterogeneity, number and age of islands. [source]

Dual-Mode Luminescent Colloidal Spheres from Monodisperse Rare-Earth Fluoride Nanocrystals

ADVANCED MATERIALS, Issue 19 2009
Peng Li
Monodisperse rare-earth fluoride nanocrystals are synthesized and used as building blocks to fabricate dual-mode luminescent colloidal spheres, which are composed of two distinct units, one offering down-converting luminescence under UV excitation and the other providing up-converting luminescent emission when excited with a 980,nm laser, and have potential applications in multiplexed and highly sensitive bioassays. [source]

Two genetically distinct units of Sinomanglietia glauca (Magnoliaceae) detected by chloroplast PCR-SSCP

JOURNAL OF SYSTEMATICS EVOLUTION, Issue 2 2009
Zhi-Rong ZHANG
Abstract Sinomanglietia glauca is a critically endangered species described from Jiangxi Province in the 1990s. Recently two populations were discovered from Yongshun County of west Hunan Province, about 450 km away from those in Jiangxi. Because of the new findings and the poor reproducibility inherent to RAPD and ISSR markers of previous studies, the population structure of this rare species was reanalyzed with chloroplast PCR-SSCP (single-stranded conformation polymorphism), including all of four recorded populations. The results showed that two distinct haplotypes characterized Jiangxi and Hunan populations separately, with no genetic variation occurring within regions. We postulated that this surprising pattern might result from habitat fragmentation and demographic bottlenecks during and/or after the Quaternary glaciation. On the basis of the pronounced genetic structure, two evolutionarily significant units (ESUs) were recommended for effective conservation of S. glauca. [source]

Phylogeography of the Angolan black and white colobus monkey, Colobus angolesnsis palliatus, in Kenya and Tanzania

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 8 2010
Monica M. McDonald
Abstract Little is known about genetic variation in the 6,8 subspecies of Colobus angolensis, currently distinguished by pelage differences. We present a comparative genetic analysis of one of these subspecies, C. a. palliatus, in Kenya and Tanzania that assesses evolutionary relationships and patterns of mitochondrial genetic diversity in 103 individuals across its geographic range. Fecal samples from approximately 156 individuals were collected in four localities: (1) Diani Forest, Kenya; (2) Shimoni, Kenya; (3) Udzungwa Mountains National Park, Eastern Arc Mountains, Tanzania; and (4) Mount Rungwe, Southern Highlands, Tanzania. These samples represent at least six groups, with 5,15 samples from each. Comparative sequence analysis of a 1,795 base pair mtDNA fragment revealed 19 unique haplotypes in four populations. Phylogenetic analyses suggest that sampled Kenyan haplotypes are paraphyletic, with one Kenyan haplotype basal to all other sampled haplotypes. Analysis of molecular variance (AMOVA) suggests high levels of genetic variation among populations (,ST 0.72, P<0.001). Genetic data are concordant with a subspecies level differentiation between C. a. palliatus populations in Kenya and those in Central and southern Tanzania, as earlier suggested based on pelage differences. This study highlights the evolutionary distinctiveness of Kenyan populations of C. a. palliatus relative to Tanzanian populations. Although C. a. palliatus habitat in Tanzania is currently better protected than in Kenya, our results suggest Kenyan and Tanzanian populations should be considered distinct units, and the protection of C. a. palliatus habitat in Kenya, as well as habitat connectivity between Kenyan populations, should be prioritized for conservation and management. Am. J. Primatol. 72:715,724, 2010. © 2010 Wiley-Liss, Inc. [source]