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in all four lizard populations over the 18-year study period, with snout-vent length expanding
by roughly 28%. This increase in body size occurred in all age classes and, as they describe it,
“appeared related to a concomitant increase in temperature experienced during the first
month of life (August).” As a result, they found that “adult female body size increased
markedly, and, as fecundity is strongly dependent on female body size, clutch size and total
reproductive output also increased.” In addition, for a population where capture-recapture
data were available, they learned that “adult survival was positively related to May
temperature.”
In summarizing their findings, the French researchers stated that since all fitness components
investigated responded positively to the increase in temperature, “it might be concluded that
the common lizard has been advantaged by the shift in temperature.” This finding, in their
words, stands in stark contrast to the “habitat-based prediction that these populations located
close to mountain tops on the southern margin of the species range should be unable to cope
with the alteration of their habitat.” Hence, they concluded that “to achieve a better prediction
of a species persistence, one will probably need to combine both habitat and individual-based
approaches,” noting, however, that individual responses, such as those documented in their
study (which were all positive), represent “the ultimate driver of a species response to climate
change.”
Out in the watery realm of the world’s oceans, Rombouts et al. (2008) developed the first
global description of geographical variation in the diversity of marine copepods in relation to
ten environmental variables; and in doing so, they found that “ocean temperature was the
most important explanatory factor among all environmental variables tested, accounting for 54
percent of the variation in diversity.” Hence, it was not surprising, as they described it, that
“diversity peaked at subtropical latitudes in the Northern Hemisphere and showed a plateau in
the Southern Hemisphere where diversity remained high from the Equator to the beginning of
the temperate regions,” which pattern, in their words, “is consistent with latitudinal variations
found for some other marine taxa, e.g. foraminifera (Rutherford et al., 1999), tintinnids (Dolan
et al., 2006) and fish (Worm et al., 2005; Boyce et al., 2008), and also in the terrestrial
environment, e.g. aphids, sawflies and birds (Gaston and Blackburn, 2000).”
“Given the strong positive correlation between diversity and temperature,” the six scientists
went on to say that “local copepod diversity, especially in extra-tropical regions, is likely to
increase with climate change as their large-scale distributions respond to climate warming.”
This state of affairs is much the same as what has typically been found on land for birds,
butterflies and several other terrestrial lifeforms, as their ranges expand and overlap in
response to global warming. And with more territory thus available to them, their “foothold”
on the planet becomes ever stronger, fortifying them against forces (many of them humaninduced)
that might otherwise lead to their extinction.
Millar and Westfall (2010) studied American pikas: small generalist herbivores that are relatives
of rabbits and hares that inhabit patchily-distributed rocky slopes of western North American
mountains and are good at tolerating cold. And as a result of that fact, it is not surprising that
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