Habitat characteristics contributing to local occupancy and habitat use in rock pool Daphnia metapopulations
2007
Pajunen, V Ilmari | Pajunen, Irmeli
The regional dynamics of Daphnia longispina, D. magna and D. pulex living in rock pools was studied over a period of 17 years in 507 pools. Rock pools and their catchment areas were characterized by 12 habitat variables. Stepwise discriminant analysis was carried out using as the grouping variable the species with longest occupancy. The species habitat preferences differed significantly. D. magna preferred rock pools with higher conductivity, higher calcium content and higher pH, whereas D. pulex tolerated water with low conductivity, low pH and high humic content. D. longispina occupied larger and more sheltered rock pools with low conductivity and high pH. However, the canonical scores of species groups overlapped widely and scores of unoccupied rock pools did not differ from those of occupied pools. The length of occupancy was analysed with multiple regression analysis using discriminant scores and with species-specific occupancy times as dependent variables. In both D. longispina and D. magna, long patch occupancy was associated with greater pool size, greater height above the sea and a less exposed position. Rock pools inhabited by D. pulex were smaller. Also, the sheltered position of pools and the low calcium content characterized rock pools with long-lived populations of this species. In spite of habitat segregation, all three species show metapopulation dynamics with frequent extinctions and recolonizations at approximate equilibrium.
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