Complexity in the relationship between matrix composition and inter-patch distance in fragmented habitats
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The connectivity of fragmented landscapes is a function of the physical distance between suitable habitats and the characteristics of the habitat through which the animal is moving, i.e. the matrix. Experimental manipulations done to explain how spatial arrangement and composition of habitats affects biota remain scarce, particularly in marine systems. Holdfasts of the common kelp, Ecklonia radiata, are discrete units of habitat for small invertebrates (e.g. amphipods, isopods, molluscs, annelids) that can be isolated from other holdfasts by habitat, which may be less suitable (e.g. other species of algae or relatively bare space). We compared assemblages, which colonised defaunated holdfasts in experimentally created small-scale landscapes where patches of habitat (holdfasts) were distant versus close together and which had Sargassum spp. versus relatively bare space in the matrix. We also compared colonisation across matrices of crushed fucoid algae to assess whether the structural or chemical nature of algae in the matrix had the most influence on the colonisation. Assemblages in defaunted holdfasts differed between those that were close to and those that were distant from undisturbed holdfasts, where the matrix was devoid of vegetation. Where Sargassum spp. was present in the matrix, however, this difference disappeared and was possibly due to the chemical, rather than structural, characteristics of the fucoid matrix. The extent to which matrix habitat is a barrier to movement of invertebrates among holdfasts thus depends on not only how extensive it is but what type of habitat it contains. As within terrestrial systems, the nature of the matrix is also likely to be a fundamental component of the connectivity within marine systems.
KeywordsFragmented Landscape Bare Space Central Individual Fragmented Habitat Primary Habitat
We are very grateful to E. Vytopil, P. Anderson and K. Rouse for help with the painstaking fieldwork. Thanks to M. Thiel and anonymous reviewers for helpful comments that improved the manuscript. This research was supported by postgraduate awards to PJG and an Australian Research Council grant to SDC. The research complies with the current laws of Australia.
- Anderson MJ (2005) PERMANOVA: a FORTRAN computer program for permutational multivariate analysis of variance., Department of Statistics, University of Auckland, New ZealandGoogle Scholar
- Connell SD (2007) Water quality and the loss of coral reefs and kelp forests: alternative states and the influence of fishing. In: Connell SD, Gillanders BM (eds) Marine ecology, Oxford University Press, Melbourne, pp 556–568Google Scholar
- Fahrig L (2002) Effect of habitat fragmentation on the extinction threshold: a synthesis. Ecol Appl 12:346–353Google Scholar
- Gray JS, Aschan M, Carr MR, Clarke KR, Pearson TH, Rosenburg R, Warwick RM (1998) Analysis of community attributes of the benthic macrofauna of the Frierfjord/Langesundfjord and in a mesocosm experiment. Mar Ecol Prog Ser 46:285–299Google Scholar
- Goodsell PJ, Chapman MG, Underwood AJ (2008) Differences between biota in anthropogenically fragmented and in naturally patchy habitats. Mar Ecol Prog Ser (in press)Google Scholar
- MacArthur RH, Wilson E (1967) The equilibrium theory of island biogeography. Princeton University Press, PrincetonGoogle Scholar
- Poore AB, Steinberg PD (1999) Preference-performance relationships and effects of host plant choice in an herbivorous marine amphipod. Ecol Monogr 69:443–464Google Scholar
- Tischendorf L, Grez A, Zaviezo T, Fahrig L (2005) Mechanisms affecting population density in fragmented habitat. Ecol Soc 10:7 (online) URL: http://www.ecologyandsociety.org/vol10/iss11/art10/ Google Scholar
- Wiens JA (1992) Ecological flows across landscape boundaries: a conceptual overveiw. In: Hansen AJ, di Castro F (eds) Landscape boundaries: consequences for biotic dievrsity and ecological flows. Springer, New York, pp 217–235Google Scholar
- Witman JD, Dayton PK (2001) Rocky subtidal communities. In: Bertness MD, Gaines SD, Hay ME (eds) Marine community ecology. Sinauer Associates, Sunderland, pp 339–366Google Scholar