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  • Coefficient Ri  (1)
  • Evolution  (1)
  • Litterfall  (1)
  • Springer  (3)
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  • Springer  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Maternal factors and the evolution of developmental mode: Evolution of oogenesis in Heliocidaris erythrogramma (1999)
    Springer
    Development genes and evolution 209 (1999), S. 275-283 
    Details
    ISSN: 1432-041X
    Keywords: Key words Echinoid ; Oogenesis ; Development ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Evolutionary change in developmental mode in sea urchins is closely tied to an increase in maternal provisioning. We examined the oogenic modifications involved in production of a large egg by comparison of oogenesis in congeneric sea urchins with markedly different sized oocytes and divergent modes of development. Heliocidaris tuberculata has small eggs (95 µm diameter) and the ancestral mode of development through feeding larvae, whereas H. erythrogramma has large eggs (430 µm diameter) and highly modified non-feeding lecithotrophic larvae. Production of a large egg in H. erythrogramma involved both conserved and divergent mechanisms. The pattern and level of vitellogenin gene expression is similar in the two species. Vitellogenin processing is also similar with the gonads of both species incorporating yolk protein from coelomic and hemal stores into nutritive cells with subsequent transfer of this protein into yolk granules in the developing vitellogenic oocyte. Immunocytology of the eggs of both Heliocidaris species indicates they incorporate similar levels of yolk protein. However, H. erythrogramma has evolved a highly divergent second phase of oogenesis characterised by massive deposition of non-vitellogenic material including additional maternal protein and lipid. Maternal provisioning in H. erythrogramma exhibits recapitulation of the ancestral vitellogenic program followed by a novel oogenic phase with hypertrophy of the lipogenic program being a major contributor to the increase in egg size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050253
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  • 2
    Electronic Resource
    Electronic Resource
    Coeficient of relationship (RI) within and between four black venezuelan populations (1997)
    Springer
    International journal of anthropology 12 (1997), S. 55-62 
    Details
    ISSN: 1824-3096
    Keywords: Coefficient Ri ; Isonymy ; Population Structure ; Venezuelan populations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The coefficient of relationship by isonymy Ri was obteined using paternal and maternal surnames of individuals in four black Venezuelan populations. The analysis of eight Ri values obtained from different combinations of surnames within each population and between population in two periods of time (1900–1920 and 1944–1967) show that: 1) Higher values of Ri are those that include combinations of maternal surnames, 2) Ri values of the second period are higher than those shown in the first, 3) No correlation was observed between Ri values and geographic distance. These results indicate that there is a tendency towards matrilocal behavior and show agreement with the degree of isolation of each population. The use of four surnames for estimating the coefficient of relationship by isonymy Ri, permits better comparisons of the relationship between and within groups and gives detailed information of the population structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02447897
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogen in litterfall and precipitation and its release during litter decomposition in the Chilean piedmont matorral (1982)
    Springer
    Plant and soil 67 (1982), S. 359-365 
    Details
    ISSN: 1573-5036
    Keywords: Chile ; Lithraea caustica ; Litterfall ; N-cycling ; Piedmont-matorral ; Quillaja saponaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen En el matorral premontano de Chile se estudiaron algunas partes del ciclo de nitrógeno de dos de sus dominantes (Lithraea caustica y Quillaria saponaria) durante 15 meses. Los análisis mostraron que los ingresos de nitrógeno por lluvia y deposición seca fueron de 8,5 kg N ha−1 año−1; este valor podría ser mayor si se considera el ingreso adicional por impactación de compuestos nitrogenados sobre la vegetación (no medido). Debido a su mayor cobertura porcentual,L. caustica contribuyó con mas hojarasca queQ. saponaria obteniendose valores de 1089 y 737 kg ha−1 materia seca año−1 respectivamente. Sin embargo, al considerar el area bajo los individuos,Q. saponaria produjo mas hojarasca queL. caustica (640vs 350 g materia seca m−2 año−1. Durante la descomposición de la hojarasca,L. caustica liberó 2,61 g N kg−1 hojarasca seca año mientras queQ. saponaria liberó 0,60 g N kg−1 hojarasca seca año−1.
    Notes: Abstract Parts of the nitrogen cycle involving two dominants (Lithraea caustica andQuillaja saponaria) in the Chilean piedmont matorral have been studied over a 15-month period. Analyses showed that 8.2 kg N ha−1 yr−1 entered the system in rainfall and dry deposition, though impaction of N-containing compounds on vegetation (not measured) may elevate this value.L. caustica, by virtue of its greater percent cover, contributed more leaf litter than didQ. saponaria to the system (1089,vs 737 kg dry matter ha−1 yr−1, respectively), although on an individual basisQ. saponaria produced more litter (640,vs 350 g dry leaf litter m−2 yr−1 rL. caustica). This plus the greater nitrogen release ofL. caustica leaf litter during decomposition (2.61,vs 0.60 g N kg dry litter−1 yr−1 forQ. saponaria) andQ. saponaria's higher N-content of dropped leaves (0.54,vs 0.37% N forL. caustica) may indicate a more external cycling of nitrogen inQ. saponaria relative to that inL. caustica. These two species may therefore represent two different strategies of individual nitrogen cycling, external and internal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182783
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