Background
The authors write that "because of climate unpredictability, species have evolved a certain amount of tolerance to various abiotic climate-related factors in their responses to warming and cooling events," noting that such responses may have been driven by natural selection, "in which case," as they continue, "genetic traits that provide a higher fitness under the new climate regime are selected, or they may be phenotypically plastic, where the organism can adjust its phenotype without any genotypic change," as described by West-Eberhard (2003).

What was done
Very simply, in the words of Schilthuizen and Kellermann, they conducted "a review on evolutionary adaptation and phenotypic plasticity of temperature-related traits in terrestrial invertebrates."

What was learned
The two researchers say their review of the subject indicates that the findings of laboratory studies suggest that responses of terrestrial invertebrates to climate change will be both evolutionary and plastic in nature, and that the evidence for adaptive evolution in melanization is especially good.

What it means
In light of what they learned from their careful review of the pertinent scientific literature, Schilthuizen and Kellermann conclude that, "overall, depending on the species, both genetic and plastic responses exist in phenology and other life-history traits," and they add that it is clear that "these traits are changing in response to climate."

Reference
West-Eberhard, M.J. 2003. Developmental Plasticity and Evolution. Oxford University Press, Oxford, United Kingdom.