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The habitat harshness hypothesis revised: life history of the isopod Excirolana braziliensis in sandy beaches with contrasting morphodynamics
Defeo, O.; Martínez, G. (2003). The habitat harshness hypothesis revised: life history of the isopod Excirolana braziliensis in sandy beaches with contrasting morphodynamics. J. Mar. Biol. Ass. U.K. 83(2): 331-340. dx.doi.org/10.1017/S0025315403007161h
In: Journal of the Marine Biological Association of the United Kingdom. Cambridge University Press/Marine Biological Association of the United Kingdom: Cambridge. ISSN 0025-3154, more
Peer reviewed article  

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Keywords
    Abundance; Animal morphology; Beaches; Biotic factors; Dynamics; Fauna; Intertidal environment; Life history; Excirolana braziliensis Richardson, 1912 [WoRMS]; Isopoda [WoRMS]; Marine

Authors  Top 
  • Defeo, O.
  • Martínez, G.

Abstract
    Demographic and life history characteristics of the intertidal isopod Excirolana braziliensis (Isopoda: Cirolanidae) were compared between populations of two exposed sandy beaches with contrasting morphodynamics (reflective vs dissipative) during 22 consecutive months. Most population processes and life history traits did not give support for the ‘habitat harshness hypothesis’ (HHH): abundance of males, females, ovigerous females and juveniles was significantly higher at the reflective beach population, which also presented higher growth rates in size and weight with respect to the dissipative beach population. No significant differences in weight-at-length were found between beaches. Among the compared parameters, only the lower natural mortality rates at the dissipative beach gave support for the HHH. The results were not consistent with a previous analysis of Excirolana braziliensis along Pan-American beaches, which showed that this isopod occurs almost invariably in fine sands of tropical and temperate beaches. The results give strong support to recent findings that show that in macrofauna species capable of sustaining large populations across a wide spectrum of physical conditions, such as Excirolana braziliensis, beach morphodynamics should not be considered the primary factor affecting abundance and life history traits. Instead, our results reinforce the view that sandy beach populations are controlled by the intertwined forces of biotic and abiotic factors operating together.

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