Thursday, 31 March 2011

March Review for F1000

 This month we found something addressing the ongoing debate about the relationship between invasibility and diversity of native species; however, this study takes a new angle and looks at the relationship through time rather than across space.  Our biggest disappointment with this paper was that it makes a large assumption that abundance of a single species = diversity, which is not necessarily the case.  Therefore to really prove the conclusions of this study about this general hypothesis, the authors need to either test this assumption thoroughly or undertake a study focusing directly on invasive species diversity in relation to native diversity. 

Our Review:
Parry H, Lonsdale M: 2011. 

This is the first study of note that attempts to examine the relationship between invasibility and native species diversity across temporal scales. The diversity-invasibility relationship has intrigued researchers interested in invasion ecology because a paradox has arisen, as the relationship appears to flip at different spatial scales.

Elton {1} first proposed that a high richness of native species protects sites against invasion, where fewer invasive species are able to colonise areas with high native diversity, due to a lack of available resources. At small spatial scales, a negative relationship between native and exotic diversity has been found, in many studies, including Elton's, to support this hypothesis. However, at large spatial scales, there has been less agreement and the inverse has proved true {2}. Clarke and Johnston refer to this as the 'invasion paradox'. Although this relationship has been examined in detail in many studies, at multiple spatial scales, there have been very few, if any, studies of how this relationship might change over time.

This study goes some way to examining how this relationship might vary over time, as a possible explanation of the invasion paradox. The study shows that the diversity-invasibility relationship can vary through time when mediated by disturbance. It is found that disturbance favours colonization, but not persistence, of the invader; thus, the inverse relationship found between native diversity and disturbance indicates that diversity may favour persistence of the invader, but not colonization.

The authors make a key assumption in their experiment; that the abundance of a single invader species is a surrogate for invader diversity - this needs further testing. 

NB – I am listed as an author on ref {2}.
{1} Elton CS, "The ecology of invasions by animals and plants." Methuen and Co Ltd: London, 1958 [ISBN:978-0412114304].
{2} Lonsdale WM, Ecology 1999, 80:1522-36 [DOI:10.1890/0012-9658(1999)080[1522:GPOPIA]2.0.CO;2].
Competing interests: None declared

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