Australia: The Land Where Time Began

A biography of the Australian continent 

Ocean-Warming hotspot - Geographic Range Shifts Explained by Species Traits and Climate Velocity

According to Sunday et al. the ranges of species are shifting on a global scale in response to the warming climate, and there is substantial variability among taxa, even within regions. They suggest that particularly in the oceans, where the distribution of species is more directly shaped by temperature, relationships between range dynamics and intrinsic species traits may be more apparent. In this paper Sunday et al. test for a role in driving extension of ranges in the ocean-warming hotspot of southeast Australia of species traits and climate velocity. Some variation in the range shifts is explained by climate velocity, however when traits of species are included the degree of variation that is explained is more than doubled. Positive relationships with the rate of range extension include swimming ability, omnivory and latitudinal range size, which supports hypotheses that increased capacity for dispersal and ecological generalism promote range extensions. Sunday et al. say they found independent support for the hypothesis that species having a narrow latitudinal range are limited by non-climate factors. It is suggested by the findings of this study that species with a small range are in double jeopardy, having only limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances.

Conclusions

Support for using climate trajectories in the prediction of shifts of species and identifying the spatial patterns of the loss of species and their movement is provided by the mean variation of the extensions of range which is explained by temperature isotherm in the models of Sunday et al. There was substantial variability around the prediction of climate velocity (Pinsky et al., 2013; Polczanska et al., 2013) which was reduced greatly when species traits were included, as in previous analyses that incorporated climate. Sunday et al. say their most important findings were the positive relationships they found between the mobility of adults and the lateral range size on extension rate of range: i.e. species in which the adults have the ability to swim, and which are already distributed broadly, have moved more rapidly into thermal habitats that are newly available. A mechanism for the range size finding is provided by the analysis by Sunday et al. of potential and realised latitudinal ranges, which indicates that species that have smaller latitudinal ranges have a tendency to be out of equilibrium with the climate (Early & Sax, 2014). A greater risk of extinction is also faced by species that have narrow ranges due to metapopulation dynamics and extinctions that are localised from stochastic threats (Roberts & Hawkins, 1999; Purvis et al., 2000). As a result of this species with narrow ranges may face double jeopardy in an ocean that is warming, as they are intrinsically more vulnerable to extinction and have a lower ability to track their thermal preferences.

Sources & Further reading

1. Sunday, J. M., G. T. Pecl, S. Frusher, A. J. Hobday, N. Hill, N. J. Holbrook, G. J. Edgar, R. Stuart-Smith, N. Barrett, T. Wernberg, R. A. Watson, D. A. Smale, E. A. Fulton, D. Slawinski, M. Feng, B. T. Radford, P. A. Thompson and A. E. Bates (2015). "Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspot." Ecology Letters 18(9): 944-953.