However, several empirical studies have challenged the 'abundant center' view of species distribution [ 54], such as in the intertidal zone where localized variations in the thermal environment due to climatic and tidal interactions disrupt monotonic latitudinal temperature clines [ 54- 56].
In terms of seeking out genes under selection over a latitudinal gradient where rainfall and temperature clines are steep, genes related to water balance and response to drought are obvious candidates.
The different responses can be explained by different proximate mechanisms; Bergmann clines are mediated by temperature, while converse Bergmann clines are an adaptive response to time constraints by shorter growing seasons (Blanckenhorn and Demont 2004).
We, therefore, hypothesised that the geographic differentiation also involves adaptation to the local climate, namely to a north south cline in temperature.
For example, an amino acid substitution between two alleles that vary along a cline in temperature affects thermostability [ 8], and experimental studies have shown that this variation is involved in the adaptation of killifish to hypoxia [ 9, 10].
Therefore, we suspected similar differences in thermal tolerance would be associated with the more localized clines in temperature caused by urbanization.
Comparisons of related taxa in the Antarctic and in warmer waters could provide a powerful means of testing the idea that the impact of boundary-layer limitations to diffusive O2 transport – and corresponding selection for physiological, physical, or behavioral traits to minimize these limitations – vary on large scales, across global clines in temperature and O2 availability.
But at present it is unclear whether temperature alone drives the clines.
Also importantly, some parameters of the weevil - camellia interaction such as the severity of seed infestation showed clines along temperature, suggesting the effects of climate on the fine-scale geographic differentiation of the coevolutionary processes.
