The Shapiro Study

Many of the lep listservs and discussion groups the past few weeks have spent a lot of bandwidth on discussing the recent paper in Proceedings of the National Academy of Sciences online about the effect of climate change and habitat destruction by Art Shapiro and colleagues.  The central thesis of the report is that, based on collecting (presumably by Art, for the most part) over 35 years in northern California’s Sierra Nevada mountains, species richness has declined dramatically at half the 10 study sites among the 159 species in the study.  For reference, here’s the abstract:

“Climate change and habitat destruction have been linked to global
declines in vertebrate biodiversity, including mammals, amphib-
ians, birds, and fishes. However, invertebrates make up the vast
majority of global species richness, and the combined effects of
climate change and land use on invertebrates remain poorly un-
derstood. Here we present 35 years of data on 159 species of
butterflies from 10 sites along an elevational gradient spanning 0–
2,775 m in a biodiversity hotspot, the Sierra Nevada Mountains of
Northern California. Species richness has declined at half of the
sites, with the most severe reductions at the lowest elevations,
where habitat destruction is greatest. At higher elevations, we
observed clear upward shifts in the elevational ranges of species,
consistent with the influence of global warming. Taken together,
these long-term data reveal the interacting negative effects of
human-induced changes on both the climate and habitat available
to butterfly species in California. Furthermore, the decline of rud-
eral, disturbance-associated species indicates that the traditional
focus of conservation efforts on more specialized and less disper-
sive species should be broadened to include entire faunas when
estimating and predicting the effects of pervasive stressors.”

Particularly on TILS-leps-talk, some of the commenters questioned whether the collecting schemes were robust enough to support the conclusions of the paper, and wondered why the data sets themselves weren’t publicly available (the online Supplemental Materials provided by PNAS discuss statistical methods, but don’t link to any actual collecting data). The collection data are, however, available on Art Shapiro’s web site — but you have to apply for access and be approved to look at them.

One of the more interesting discussions has to do with the authors’ introduction of the word “ruderal” to the entomological literature.  Botanists are well acquainted with ruderal, used to refer to plants of weedy or waste places.  In Shapiro’s parlance, however, ruderal species s tend to be generalists and good dis-
persers, whereas nonruderal species are specialists and poor dispersers.  Judging from the online listserv discussions, it might take a while before the natural history categories of ruderal vs nonruderal butterfly species catch on as common terms of reference. Here’s one excerpt from the discussion:

“The constant referral to ruderal and nonruderal species is also strange. Ruderal is not a common word in the English language and I have never seen it applied to anything other than plants before this. A person reading this paper and not familiar with entomological or lepidoptera oriented studies might think it is a common term in these fields. It is not.  In searching 21,599 posts to TILS-leps-talk (going back for nine years until November 2001) it has never been used until now. Somehow the Lepidoptera study species should have been cited with indications by the authors as to which they considered to be ruderal and which they considered as nonruderal species.”

Download the PDF at PNAS 2010 Shapiro et al

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