Island biogeography theory outweighs habitat amount hypothesis in predicting plant species richness in small grassland remnants

Jessica P Lindgren,Sara A O Cousins

doi:10.1007/s10980-017-0544-5

Abstract

ContextThe habitat amount hypothesis has rarely been tested on plant communities. It remains unclear how habitat amount affect species richness in habitat fragments compared to island effects such as isolation and patch size.ObjectivesHow do patch size and spatial distribution compared to habitat amount predict plant species richness and grassland specialist plant species in small grassland remnants? How does sampling area affect the prediction of spatial variables on species richness?MethodsWe recorded plant species density and richness on 131 midfield islets (small remnants of semi-natural grassland) situated in 27 landscapes in Sweden. Further, we tested how habitat amount, compared to focal patch size and distance to nearest neighbor predicted species density and richness of plants and of grassland specialists.ResultsA total of 381 plant species were recorded (including 85 grassland specialist species). A combination of patch size and isolation was better in predicting both density and richness of species compared to habitat amount. Almost 45% of species richness and 23% of specialist species were explained by island biogeography parameters compared to 19 and 11% by the amount of habitat. A scaled sampling method increased the explanation level of island biogeography parameters and habitat amount.ConclusionsHabitat amount as a concept is not as good as island biogeography to predict species richness in small habitats. Priority in landscape planning should be on larger patches rather than several small, even if they are close together. We recommend a sampling area scaled to patch size in small habitats.

Highlights

The importance of landscape structure on biodiversity and community composition has been highlighted within both theoretical and empirical ecological research (Lindenmayer and Fischer 2006; Mouquet et al 2006; McGill 2010; Lindenmayer et al 2015)
As small remnant habitats contribute to diversity within fragments they may help to enhance biodiversity at the regional scale (Ricketts et al 2001; Daily et al 2003; Jakobsson et al 2016) and mitigate negative effects caused by fragmentation and isolation in species-poor agricultural landscapes (Vandermeer and Perfecto 2007; Plue and Cousins 2013)
We found a relationship between species density and density of specialist species to the surrounding habitat amount

Summary

Introduction

The importance of landscape structure on biodiversity and community composition has been highlighted within both theoretical and empirical ecological research (Lindenmayer and Fischer 2006; Mouquet et al 2006; McGill 2010; Lindenmayer et al 2015). As small remnant habitats contribute to diversity within fragments they may help to enhance biodiversity at the regional scale (Ricketts et al 2001; Daily et al 2003; Jakobsson et al 2016) and mitigate negative effects caused by fragmentation and isolation in species-poor agricultural landscapes (Vandermeer and Perfecto 2007; Plue and Cousins 2013). In this context, small remnant habitats may fulfil important ecological functions for biodiversity, e.g. as stepping stones for dispersal (Honnay et al 1998), and they might increase the general permeability in the landscape for certain species (Jakobsson et al 2016)

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