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  • 1
    Electronic Resource
    Electronic Resource
    Magnitude of within-patch variation in seagrass Halophila ovalis growth affected by adjacent Thalassia hemprichii vegetation (2000)
    Springer
    Ecological research 15 (2000), S. 415-424 
    Details
    ISSN: 1440-1703
    Keywords: growth ; interspecific interactions ; patch structure ; seagrass ; Thailand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Seagrass beds in South-east Asia sometimes consist of a mosaic of different species in monospecific patches. We examined whether the magnitude of within-patch variation in the seagrass Halophila ovalis is affected by the presence or absence of surrounding vegetation consisting of another seagrass species Thalassia hemprichii in an intertidal flat in Thailand waters. We measured biomass and growth rates of H. ovalis at the edges and centers of two different types of patches: (i) H. ovalis patches adjoining T. hemprichii vegetation (HT patches), and (ii) H. ovalis patches adjoining unvegetated sand flats (HS patches). Furthermore, we examined the possible effects of interspecific interactions on the growth of H. ovalis by experimentally removing adjoining T. hemprichii at the edges of HT patches. The biomass of H. ovalis was greater at the patch centre than the patch edge in both types of patches. For the growth rate of H. ovalis, significant interactions were detected between patch types and positions in patches. The difference in growth was significant and more than 4-fold between edges and centers of the HS patches, whereas the growth was not significantly different between edges and centers of the HT patches. The removal of T. hemprichii did not significantly affect the growth rate of H. ovalis at the edge of the HT patches. These findings demonstrate that the magnitude of within-patch variation in H. ovalis growth is affected by the conditions of adjoining habitats. However, any effects of local competition with T. hemprichii on H. ovalis growth were not evident in this short-term manipulative experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00362.x
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  • 2
    Electronic Resource
    Electronic Resource
    Optimal resource allocation of the marine bivalve Yoldia notabilis: The effects of size-limited reproductive capacity and size-dependent mortality (1998)
    Springer
    Evolutionary ecology 12 (1998), S. 347-361 
    Details
    ISSN: 1573-8477
    Keywords: life history ; reproductive effort ; resource allocation ; size at maturity ; state variable model ; Yoldia notabilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the morphological constraint of maximum reproductive output (reproductive capacity) and the size at which individuals can avoid heavy mortality (refuge size) on the resource allocation pattern between growth and reproduction are investigated using a dynamic modelling approach for a population of Yoldia notabilis (Mollusca: Bivalvia) in Otsuchi Bay, northeastern Japan. A state variable model is developed using field data on shell length, somatic weight, production, survivorship and reproductive capacity of the bivalve. The optimal allocation pattern is characterized by sudden switching from growth to reproduction without the assumption of reproductive capacity, while simultaneous investment in growth and reproduction becomes optimal when maximum reproductive output is limited by reproductive capacity. Size-specific reproductive effort, size at maturity and the growth curve predicted by the latter model fit more closely to the field data, suggesting that size-limited reproductive capacity can play an important role in the evolution of the observed resource allocation pattern. The mortality pattern affects optimal size at maturity, but not size-specific reproductive effort after maturity. When refuge size is fixed, optimal size at maturity increases with survivorship above refuge size. Optimal size at maturity changes in a more complex way with changes in refuge size. Size at maturity remains constant when refuge size is small, increases when it is intermediate, and decreases when it is large. The results suggest that refuge size is an important factor in the evolution of size at maturity, although its contribution varies depending on the values of other factors, such as size-dependent production and survivorship above refuge size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006556301655
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