Comment on Lyons et al finally published

After many months, our comment on Lyons et al is finally published [link should give free access].

Lyons et al looked at many community  data sets from the last 300 million years and tested for pairs of species that are more aggregated (co-occur) or segregated than expected by chance. They found that in modern data sets, there are more segregated than aggregated species pairs, and the opposite pattern in fossil data sets, with a breakpoint about 6000 years ago, suggesting a severe impact from early agriculture. This was a surprising finding, especially given the presence-absence data used by the authors.

We argue that Lyons et al result is a product of

  • poor data set selection (some of which were addressed by a corrigendum)
  • artefacts in the breakpoint analysis
  • data-set size related artefacts in the identification of segregated and aggregated species pairs

Together, these problems mean that the results of Lyons et al cannot be substantiated.

Lyons and co-authors, predictable, disagree with our conclusion.

Once I get back to Bergen from Makerere, I plan to write something about the reply, and some of our findings that we didn’t have space for in our comment.


About richard telford

Ecologist with interests in quantitative methods and palaeoenvironments
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