The shores of Sub-Antarctic Marion Island foregather crustaceans with a greater capacity to tolerate temperature
variability compared to similar environments in South Africa.
Determining the extent to which organisms are able to tolerate and respond to climate change is important for
assessing species vulnerability and informing strategies for biodiversity management. Recent work has demonstrated that responses
to warming may be less variable and more predictable in marine than in terrestrial organisms. Variation in the upper limits of
temperature tolerance in terrestrial organisms has been showed and three rules have emerged given the patterns found for these
organisms across latitudes. First, according to Janzen’s rule, the range of temperature tolerated by organisms should increase
with latitude. Second, Vernberg’s rule states that the extent of acclimation of these organisms should increase with latitude;
that is, species in higher latitudes should be able to compensate to short-term temperature exposures more readily than species
at lower latitudes. Finally, Gause’s rule proposes that acclimation ability should be reduced in organisms that have the highest
initial (pre-exposure) or basal tolerance.
A paper published in Functional Ecology by C·I·B student Katelyn Faulkner, Dr Susana
Clusella-Trullas, Prof Lloyd Peck and Prof Steven Chown assessed the effect of rate of temperature change and acclimation on the
upper temperature tolerance of several crustacean populations along a latitudinal gradient to test these three rules.
The authors showed that for all intertidal populations sampled in the sub-Antarctic Marion Island and in South
Africa, slow rates of temperature change reduced temperature tolerance and compromised acclimation responses. Species from South
Africa had a smaller margin between the highest temperature that they could withstand and the maximum microhabitat temperature
compared to their sub-Antarctic counter-parts, supporting Janzen’s rule. In addition, Sub-Antarctic species had more plasticity
in the ability to change in the short-term compared to South African species, supporting Vernberg’s rule. This finding shows that
sub-Antarctic species pre-exposed to cold or warm spells could cope more optimally to subsequent climatic changes compared to
South African species. Finally, the Gause’s rule was also supported as species with highest initial tolerance had the lesser ability
to acclimate to short-term temperature exposures.
Overall, temperate populations of marine crustaceans had a lower ability to withstand or respond to increasing
temperatures than populations from the sub-Antarctic, even if populations used behavioural thermoregulation to escape extreme
temperatures. Thus the responses of marine organisms to warming may not be as coherent and predictable as previous work had
suggested. Rather variation in long-term responses may be a consequence of geographical variation in organismal traits, thermal
environments, acclimation capacity and evolutionary potential. Finally, this work highlights the importance of understanding the
microclimates experienced by crustaceans in the field and the extent to which lethal conditions may be avoided through behavioural
Examples of intertidal crustaceans examined in this study: the amphipod Hyale hirtipalma (left) and the isopod Exosphaeroma gigas (right).
Read the paper:
Faulkner, K.T., Clusella-Trullas, S.,
Peck, L.S. and Chown, S.L. 2013. Lack of coherence in the warming responses of marine crustaceans. Functional Ecology.
For more information, contact Susanna Clusella-Trullas at email@example.com