Influence of connectivity on demography and dispersal in two contrasting habitats: an experimental approach

Authors

  • Katia Boudjemadi,

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, UMR 7625, Université de Paris VI, 7, Quai Saint Bernard, Bâtiment A 7ème étage, 75252 Paris Cedex 05, France; and
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  • Jane Lecomte,

    1. Laboratoire d’Ecologie, Systématique et Evolution, CNRS-URA 2154, Université de Paris XI, Bâtiment 362, 91405 Orsay Cedex, France
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  • Jean Clobert

    1. Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, UMR 7625, Université de Paris VI, 7, Quai Saint Bernard, Bâtiment A 7ème étage, 75252 Paris Cedex 05, France; and
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Jean Clobert, Laboratoire Fonctionnement et Evolution des Systèmes Ecologiques, UMR 7625, Université de Paris VI, 7, Quai Saint Bernard, Bâtiment A 7ème étage, 75252 Paris Cedex 05, France. Tel.: 33-1-44-27-25-45. Fax: 33-1-44-27-35-16. E-mail: jclobert@hall.snv.jussieu.fr

Summary

1. Habitat fragmentation is involved in the present extinction crisis and is known to influence many aspects of population dynamics. The level of connectivity between populations is one of its components. In an experimental study on the common lizard (Lacerta vivipara Jacquin), we analysed in two contrasting habitats the influence of connection on dispersal patterns, on differences between dispersing and philopatric individuals, on population size, survival rates, and reproduction.

2. The experimental design consisted of eight two-patch units. Half of them were connected by dispersal. We performed this treatment in a grassland and a wood clearance, two habitats with different resource availability (respectively called ‘rich’ and ‘poor’ habitat).

3. We expected that the loss of connection would modify juvenile dispersal patterns, have a different effect on dispersing and philopatric individuals, negatively affect survival rates and fecundity by modifying social interactions and would have different consequences in ‘rich’ habitats compared to ‘poor’ ones.

4. Connection modified dispersal patterns. Two dispersal periods occurred in unconnected units, but only one occurred in connected ones. Moreover, dispersers of the second dispersal period were morphologically similar to philopatric individuals. The loss of connection probably caused the late dispersal of individuals which would have remained philopatric in a connected context. Dispersers of the second period seemed to have lower winter survival rates than philopatric individuals, as expected if these individuals had been ‘forced’ to disperse.

5. We found that connection modified demography through juvenile winter survival rates and female reproduction depending on habitat type. Connection led to higher juvenile survival rates in ‘rich’ habitats, whereas it was not the case in ‘poor’ habitats. The loss of connection decreased female reproductive rate whatever the type of habitat.

6. This study suggests that connection can directly modify demographic parameters depending on habitat quality and involving behavioural mechanisms. It confirms that conservation management, like installation of dispersal corridors, must take into account habitat characteristics and behavioural features.

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