bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heritability and heterochrony of polychromatism in a Lake Victoria Cichlid fish: stepping stones for speciation?
Authors: Maan Martine E. , Haesler Marcel P. , Seehausen Ole , Van Alphen Jacques J.M. 
Published: December 2005

AbstractIn many haplochromine cichlid fish, male nuptial coloration is subject to female mate choice and plays a central role in the evolution of reproductive isolation between incipient species. Intraspecific variation in male coloration may serve as a target for diversifying sexual selection and provide a starting point for species divergence. Here, we investigated a polychromatism in Neochromis omnicaeruleus, a haplochromine from Lake Victoria, East‐Africa. In this species, male coloration ranges from skyblue to yellow‐red and females are grey‐blue to yellow. We found that both genetic and environmental factors influence the expression of these colours during individual development. In a natural population, we found that male colour was associated with size and sexual maturity: yellow males were smaller than blue males and tended to be sexually immature. In females, size and maturity did not differ between colour types. Laboratory crosses revealed that there is a heritable component to the observed colour variation: yellow parents produced more yellow offspring than blue parents. Together with repeated aquarium observations of yellow individuals that gradually become blue, these data suggest that yellow males change to blue as they approach sexual maturity, and that the occurrence and timing of this transition is influenced by both environmental and genetic effects. The significance of this mechanism of colour expression as a possible target for divergent selection remains to be evaluated. J. Exp. Zool. (Mol. Dev. Evol.) 306B, 2006. © 2005 Wiley‐Liss, Inc.
Neural crest cells and patterning of the mammalian dentition
Authors: Cobourne Martyn T. , Mitsiadis Thimios 
Published: December 2005

AbstractThe mammalian dentition is composed of serial groups of teeth, each with a distinctive crown and root morphology, highly adapted to its particular masticatory function. In the embryo, generation of individual teeth within the jaws relies upon interactions between ectoderm of the first branchial arch and the neural crest‐derived ectomesenchymal cells that migrate into this region from their site of origin along the neural axis. Classic tissue recombination experiments have provided evidence of an essential role of the ectoderm in initiating tooth development; however, the underlying ectomesenchyme rapidly acquires dominance in establishing shape. A key question is how these cells acquire this positional information. One theory suggests that ectomesenchymal cells are pre‐patterned with respect to shape generation. Alternatively, this cell population acquires positional information within the first branchial arch itself, following migration. Recent molecular evidence suggests a high degree of plasticity within these ectomesenchymal cells. In particular, signalling molecules within the ectoderm exert a time‐dependent influence upon the ectomesenchyme by establishing specific domains of homeobox gene expression. Initially, these ectomesenchymal cells are plastic and able to respond to signalling from the ectoderm, however, this plasticity is rapidly lost and pattern information becomes fixed. Therefore, in the first branchial arch, local regulation between the ectoderm and neural crest‐derived ectomesenchyme is crucial in establishing the appropriate tooth shape in the correct region of the jaw. J. Exp. Zool. (Mol. Dev. Evol.) 306B, 2006. © 2005 Wiley‐Liss, Inc.
Evolutionary genetics of vertebrate tissue mineralization: the origin and evolution of the secretory calcium‐binding phosphoprotein family
Authors: Kawasaki Kazuhiko , Weiss Kenneth M. 
Published: December 2005

AbstractThree principal mineralized tissues are present in teeth; a highly mineralized surface layer (enamel or enameloid), body dentin, and basal bone. Similar tissues have been identified in the dermal skeleton of Paleozoic jawless vertebrates, suggesting their ancient origin. These dental tissues form on protein matrix and their mineralization is controlled by distinctive proteins. We have shown that many secretory calcium‐binding phosphoproteins (SCPPs) are involved in tetrapod tissue mineralization. These SCPPs all originated from the common ancestral geneSPARCL1(secreted protein, acidic, cysteine‐rich like 1) that initially arose fromSPARC. The SCPP family also includes a bird eggshell matrix protein, mammalian milk casein, and salivary proteins. The eggshell SCPP plays crucial roles in rigid eggshell production, milk SCPPs in efficient lactation and in the evolution of complex dentition, and salivary SCPPs in maintaining tooth integrity. A comparative analysis of the mammalian, avian, and amphibian genomes revealed a tandem duplication history of the SCPP genes in tetrapods. Although these tetrapod SCPP genes are fewer in teleost genomes, independent parallel duplication has created distinct SCPP genes in this lineage. These teleost SCPPs are also used for enameloid and dentin mineralization, implying essential roles of SCPPs for dental tissue mineralization in osteichthyans. However, the SCPPs used for tetrapod enamel and teleost enameloid, as well as tetrapod dentin and teleost dentin, are all different. Thus, the evolution of vertebrate mineralized tissues seems to be explained by phenogenetic drift: while mineralized tissues are retained during vertebrate evolution, the underlying genetic basis has extensively drifted.J. Exp. Zool. (Mol. Dev. Evol.) 306B, 2006. © 2005 Wiley‐Liss, Inc.
The last excluded case of Dirac's map‐color theorem for choosability
Authors: Král' Daniel , S̆krekovski Riste 
Published: December 2005

AbstractIn 1890, Heawood established the upper bound $H ( \varepsilon )= \left \lfloor 7+\sqrt {24\varepsilon +1}/{2}\right \rfloor$ on the chromatic number of every graph embedded on a surface of Euler genus ε ≥ 1. Almost 80 years later, the bound was shown to be tight by Ringel and Youngs. These two results have became known under the name of the Map‐Color Theorem. In 1956, Dirac refined this by showing that the upper bound H(ε) is obtained only if a graph G contains KHε as a subgraph except for three surfaces. Albertson and Hutchinson settled these excluded cases in 1979. This result is nowadays known as Dirac's Map‐Color Theorem. Böhme, Mohar, and Stiebitz extended Dirac's Map‐Color Theorem to the case of choosability by showing that G is (H(ε) − 1)‐choosable unless G contains KH(ε) as a subgraph for ε ≥ 1 and ε ≠ 3. In the present paper, we settle the excluded case of ε = 3. © 2005 Wiley Periodicals, Inc. J Graph Theory 51: 319–354, 2006
Tropical ice core records: evidence for asynchronous glaciation on Milankovitch timescales
Authors: Thompson Lonnie G. , Davis Mary E. , Mosley‐Thompson Ellen , Lin Ping‐Nan , Henderson Keith A. , Mashiotta Tracy A. 
Published: December 2005

AbstractOver the last 28 years ice core records have been systematically recovered from ten high‐elevation ice fields, nine of which are located in the low latitudes. Each core has provided new information about the regional climate and environmental change, and together their records challenge existing paradigms about the Earth's climate system. When viewed collectively, these ice core histories provide compelling evidence that the growth (glaciation) and decay (deglaciation) of large ice fields in the lower latitudes are often asynchronous, both between the hemispheres and with high latitude glaciation that occurs on Milankovitch timescales. Although stable isotopic records suggest that global‐scale cooling occurred during the Last Glacial Stage (LGS), we contend that precipitation is the primary driver of glaciation in the low latitudes. This is consistent with the time‐transgressive nature of precession‐driven changes in insolation (and hence precipitation) such that glaciers advance/retreat in the tropics north of the equator while glaciers retreat/advance in the tropics south of the equator. Thus, the coeval inter‐hemispheric retreat of glaciers in the 20th century and the beginning of the 21st century is atypical. Copyright © 2005 John Wiley & Sons, Ltd.
Late Quaternary deglacial history of the Mérida Andes, Venezuela
Authors: Stansell Nathan D. , Abbott Mark B. , Polissar Pratigya J. , Wolfe Alexander P. , Bezada Maximiliano , Rull Valentí 
Published: December 2005

AbstractRadiocarbon‐dated sediment cores from seven lakes and two bogs spanning the Cordillera de Mérida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22 750 and 19 960 cal. yr BP. On the wetter southeastern side of the Cordillera de Mérida, glaciers had significantly retreated by 15 700 cal. yr BP, followed by several minor glacial advances and retreats between 14 850 and 13 830 cal. yr BP. At least one major glacial readvance occurred between 13 830 and 10 000 cal. yr BP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Mérida records initial glacial retreat by 14 240 cal. yr BP. Multiple sites on both sides of the Mérida Andes record a further phase of extensive deglaciation approximately 10 000 cal. yr BP. However, the north‐northwest facing Mucubají catchment remained partially glaciated until ca. 6000 cal. yr BP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter‐hemispheric deglacial lag in the northern tropics of the order of two thousand years. Copyright © 2005 John Wiley & Sons, Ltd.
Reconstruction of glacier equilibrium‐line altitudes for the Last Glacial Maximum on the High Plain of Bogotá, Eastern Cordillera, Colombia: climatic and topographic implications
Authors: Mark Bryan G. , Helmens Karin F. 
Published: December 2005

AbstractThe High Plain of Bogotá in the Andes of Colombia provides an exceptionally detailed record of glaciation. A two‐stage Last Glacial Maximum (LGM) is noted in Bogotá; the older stage (max) presents an opportunity to reconstruct individual valley glaciers and explore spatial patterns. Well‐mapped geomorphic features on topographic base maps permit the reconstruction of 23 palaeoglacier surfaces. Glacier extent varies across the region, with lower altitudes reached farther to the east. Equilibrium line altitudes (ELAs) are reconstructed using the area–altitude balance ratio (AABR) method, with BRs in three groups reflecting the W–E gradient in glacier extent and selected by minimising variation from group means. Average LGM ELA for all palaeoglaciers is 3488 m with a standard deviation of 182 m. The average lowering in ELA from LGM to modern of ca. 1300 m is best explained by a considerable drop in temperature. Significant intra‐regional variance in LGM ELA can be ascribed to topography and its influence on precipitation and/or glacier form, with lower headwall elevations being correlated to larger accumulation areas. Copyright © 2005 John Wiley & Sons, Ltd.
Delta progradation and Neoglaciation, Laguna Parón, Cordillera Blanca, Peru
Authors: Seltzer Geoffrey O. , Rodbell Donald T. 
Published: December 2005

AbstractThe history of Holocene glaciation serves as an important record of glacier mass balance and, therefore, of climatic change. The moraine record of Holocene glaciation in the tropical Andes, however, is fragmentary and poorly dated. In contrast, increases in the rate of accumulation of inorganic sediment in glacier‐fed lakes have been linked to periods of Neoglaciation in many mountain regions. The interpretation of such a record of Neoglaciation from sediment cores in glacier‐fed lakes in the tropical Andes can provide the continuity and chronologic control that is lacking in the existing moraine record. Unusual exposures of glacial lacustrine sediment in the Cordillera Blanca, Peru, provide a rare opportunity to assess the link between climatic change, glaciation, and lacustrine sedimentation.Intentional lowering of water levels in Laguna Parón (9°S, 77°44′ W, 4200 m a.s.l.) in 1985 resulted in the incision and exposure of at least 20 m of deltaic deposits at the eastern end of the lake. Three deltaic units can be identified: horizontal topset beds, steeply dipping and deformed foreset beds, and horizontally laminated fine‐grained sediment. Six radiocarbon ages ranging from 1800 ± 210 to 465 ± 95 14C yr BP on wood indicate that the average rate of delta progradation in the late Holocene has been approximately 290 m per 1000 yr. The lake formed during deglaciation at least 10 000 yr ago and if such a rate of progradation of the delta had prevailed over the entire Holocene, then the delta would be at least three times as extensive as it is today. Thus the rate of delta progradation has varied significantly over the Holocene. We suggest that the rate of delta progradation was at least three times greater when glaciers were in advanced positions. These positions are clearly delimited by Neoglacial moraines, which are within 1–2 km of the exposures studied and within 1 km of modern ice limits. The most recent increase in the rate of delta progradation is evidenced by an increase in sedimentation rate ca. 575 ± 90 14C yr BP, coincident with the onset of the Little Ice Age. Copyright © 2005 John Wiley & Sons, Ltd.
The Last Glacial Maximum: stability and change in a western Amazonian cloud forest
Authors: Urrego Dunia H. , Silman Miles R. , Bush Mark B. 
Published: December 2005

AbstractThe climatic and vegetation history of a western Amazonian cloud forest is documented in a continuous pollen record spanning the full last glacial period between 43.5 and 22k  cal. yr BP. The chronology for this record is based on eight radiocarbon dates yielding a low‐resolution pollen analysis for the region. A bioclimatic envelope model was generated on the basis of modern altitudinal distributions and the pollen data, which produced a glacial palaeotemperature estimate of ca. −5°C relative to present. Palaeoecological evidence of continuous moist cloud forest cover in the basin indicates that western Amazonian forests were not fragmented during the LGM. This evidence supports wet conditions in western Amazonia at the LGM and further refutes hypotheses of Amazonian aridity during the last ca. 44k cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd.
Contrasting pollen histories of MIS 5e and the Holocene from Lake Titicaca (Bolivia/Peru)
Authors: Hanselman Jennifer A. , Gosling William D. , Paduano Gina M. , Bush Mark B. 
Published: December 2005

AbstractTwo long sediment records (cores LTO1‐2B and LT01‐3B) from Lake Titicaca, Bolivia/Peru, are compared with a previously analysed Holocene record from this lake (core NE98‐1PC). The Holocene records of LT01‐2B and NE98‐1PC are similar. There are striking differences, however, between the MIS 5e sections of the long cores and the Holocene records. In these records, temperature is probably the dominant parameter that determines the total fossil pollen concentration and is used to time the onset and termination of deglaciation. In contrast, the relative and absolute abundance of specific taxa (e.g. Polylepis/Acaena, Chenopodiaceae) are indicators of relative moisture availability. Although the Holocene contains a period of aridity between ca. 8000 cal. yr BP and 4300 cal. yr BP, it is a minor event compared with the more extreme aridity of MIS 5e. Core LT01‐3B showed similar trends during MIS 5e when compared to LT01‐2B, as did NE98‐1PC when comparing Holocene records. MIS 5e and the Holocene are markedly different interglacials, depicted by shifts in pollen concentration and taxa representation over time. Copyright © 2005 John Wiley & Sons, Ltd.
Equilibrium‐line altitudes during the Last Glacial Maximum across the Brooks Range, Alaska
Authors: Balascio Nicholas L. , Kaufman Darrell S. , Manley William F. 
Published: December 2005

AbstractEquilibrium‐line altitudes (ELAs) were estimated for 383 reconstructed glaciers across the Brooks Range, northern Alaska, to investigate their regional pattern during the Last Glacial Maximum (LGM). Glacier outlines were delimited based on published field mapping and the original interpretations of aerial photographs. Glacier margins were digitised from 1:63 360‐scale maps into a geographic information system (GIS) with a digital elevation model on a 60‐m grid. ELAs were calculated for each reconstructed glacier using the accumulation area ratio method (AAR = 0.58). The analysis was restricted to relatively simple cirque and valley glaciers that deposited clearly identifiable LGM moraines, and that did not merge with the complex transection glacier ice that filled most troughs of the range. The glaciers used in this analysis had areas ranging from 0.14 to 120 km2. Their ELAs rose from 470 m a.s.l. in the western Brooks Range to 1860 m a.s.l. in the east, over a distance of 1000 km. The ELAs were fitted with a third‐order polynomial trend surface to model their distribution across the range, and to investigate the source of local‐scale variations. The trend surface lowers toward the west and south, similar to previously derived trends based on glaciation thresholds. In addition, ELAs in the northeastern part of the range lower northward toward the Beaufort Sea, which has not been reported as strongly in other studies. Modern glacier ELAs also lower toward the southwest. The depression of LGM ELAs from modern glacier ELAs is greatest in the central Brooks Range (a maximum of 700 m), and decreases to the east (200 m). The regional pattern of LGM ELAs points to the primary source of moisture from the North Pacific, as it is today. The unexpected trend of LGM ELAs in the northeast part of the range is supported by recent field mapping, where anomalous ice distribution and ELAs reflect complicated LGM climate patterns and possibly late Quaternary tectonism. Copyright © 2005 John Wiley & Sons, Ltd.
Moraine preservation and boulder erosion in the tropical Andes: interpreting old surface exposure ages in glaciated valleys
Authors: Smith Jacqueline A. , Finkel Robert C. , Farber Daniel L. , Rodbell Donald T. , Seltzer Geoffrey O. 
Published: December 2005

AbstractCosmogenic dating provides a long‐awaited means of directly dating glacial deposits that pre‐date the last glacial cycle. Although the potential benefits of longer chronologies are obvious, the greater uncertainty associated with older cosmogenic ages may be less readily apparent. We illustrate the challenges of developing and interpreting a long chronology using our data from the Peruvian Andes. We used surface exposure dating with cosmogenic radionuclides (CRNs; 10Be and 26Al) to date 140 boulders on moraines in valleys bordering the Junin Plain (11° S, 76° W) in central Peru. Our chronology spans multiple glacial cycles and includes exposure ages greater than 1 million years, which indicate that long‐term rates of boulder erosion have been very low. Interpreting the chronology of moraines for glaciations that predate the last glacial cycle is complicated by the need to consider boulder erosion and exhumation, surface uplift, and inheritance of CRNs from previous exposure intervals. As an example, we recalculate exposure ages using our boulder erosion rates (0.3–0.5 metres per million years) and estimated surface uplift rates to emphasise both the challenges involved in interpreting old surface exposure ages and the value of chronological data, even with large uncertainties, when reconstructing the palaeoclimate of a region. Copyright © 2005 John Wiley & Sons, Ltd.
Comparing reconstructed Pleistocene equilibrium‐line altitudes in the tropical Andes of central Peru
Authors: Ramage Joan M. , Smith Jacqueline A. , Rodbell Donald T. , Seltzer Geoffrey O. 
Published: December 2005

AbstractGlacier equilibrium‐line altitude (ELA), and the difference between modern and palaeo‐ELA can be interpreted as a proxy for climate change. One issue in ELA reconstruction is that different methods of ΔELA reconstruction may produce a range of results for the same palaeoglacier. When a range of methods is used to reconstruct ELAs across a region, resulting variations may be related to the method rather than the past climate. Palaeoclimatic interpretation of ELAs that were reconstructed by different methods may prompt spurious inferences if the ELA range is the result of methodological differences rather than climatic variation. We address the relationship and degree of variation between methods by comparing terminus‐to‐headwall‐altitude ratio (THAR), accumulation–area ratio (AAR), and accumulation‐area balance ratio (AABR) methods for palaeoglaciers in four valleys in the tropical Andes. Valleys in the eastern cordillera of the Peruvian Andes bordering the Junin Plain (11° S, 76° W, ca. 4100 m a.s.l.) are presently ice‐free but were glaciated repeatedly during the Pleistocene. We use a combination of 90‐m shuttle radar topography mission (SRTM) data, 15‐m Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, and 1:25 000 topographic maps to reconstruct ELAs. Within each of three groups of moraines, map‐based THAR and AABR estimates of ELA tend to be highest, followed by DEM‐derived THAR ELAs, with AAR‐reconstructed ELAs somewhat lower in this region. ELA estimates for the local Last Glacial Maximum (LLGM) range from ca. 4250 to 4570 m a.s.l., with ΔELAs of ca. −220 to −550 m (depending on valley and method used). Within individual valleys, ΔELAs for the same palaeoglaciers calculated by different methods vary by ± 100 m. ELAs of the LLGM glaciers and those of the largest glaciers to occupy the Junin valleys (> 65 ka) are not markedly different from each other, regardless of the method used in their calculation, which is largely a reflection of the valley hypsometry in the region. Our analysis suggests relatively low decreases in temperature during glacial periods in the region (ca. 2.5± 1°C). Copyright © 2005 John Wiley & Sons, Ltd.
Contrasts in the Quaternary of mid‐North America and mid‐Eurasia: notes on Quaternary landscapes of western Siberia
Authors: Wright H. E. 
Published: December 2005

AbstractThe West Siberian Plain was formed by marine deposits that extended from the Mediterranean basin to the arctic. Tectonic action later produced a striking series of long straight NE–SW grabens in the southern part of the plain. Pleistocene advance of the Kara ice sheet onto the continent resulted in blockage of the Ob and Yenisey rivers to form huge proglacial lakes that drained through these grabens south via the Turgay Pass and the Aral, Caspian, Black and Mediterranean seas to the North Atlantic Ocean, but during the Last Glacial Maximum (late Weichselian, isotope stage 2), the Kara ice sheet did not advance onto the continent in northwestern Siberia. The Altai Mountains, which bound the West Siberian Plain on the south, contained large deep intermontane ice‐dammed lakes, which drained catastrophically when the ice dams broke, forming giant ripples on the basin floors. Pollen studies of glacial lakes indicate that the Lateglacial steppe vegetation and dry climatic conditions continued into the early Holocene as summer insolation maintained high levels. Permafrost development on a drained lake floor in the western Altai Mountains resulted in the formation of groups of small pingos. In North America the growth and wastage of the huge Laurentide ice sheet had an indirect role in the climatic history of western Siberia during the Glacial and Lateglacial periods, after which the climate was more affected directly by insolation changes, whereas in North America in the early Holocene the insolation factor was coupled with the climatic effects of the slow wastage of the ice sheet, and the time of maximum dryness was postponed until the mid‐Holocene. Copyright © 2005 John Wiley & Sons, Ltd.