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An Ectotherm Tolerating More Heat than Once Thought Possible

Paper Reviewed
Polgar, G., Khang, T.F., Chua, T. and Marshall, D.J. 2015. Gross mismatch between thermal tolerances and environmental temperatures in a tropical freshwater snail: Climate warming and evolutionary implications. Journal of Thermal Biology 47: 99-108.

Writing in the Journal of Thermal Biology, Polgar et al. (2015) state that "the relationship between acute thermal tolerance and habitat temperature in ectotherm animals informs about their thermal adaptation and is used to assess thermal safety margins and sensitivity to climate warming." And, therefore, they decided to study this relationship in an equatorial freshwater snail (Clea nigricans), which belongs to a predominantly marine gastropod lineage."

In doing so, the four researchers discovered that "tolerance of heating and cooling exceeded average daily maximum and minimum temperatures, by roughly 20°C in each case." And because, quoting them, "habitat temperature is generally assumed to be the main selective factor acting on the fundamental thermal niche," they concluded that "the discordance between thermal tolerance and environmental temperature implies trait conservation following 'in situ' environmental change, or following novel colonization of a thermally less-variable habitat."

In discussing their findings, Polgar et al. thus conclude that (1) "the broad upper thermal safety margin (difference between heat tolerance and maximum environmental temperature) observed in this snail is grossly incompatible with the very narrow safety margins typically found in most terrestrial tropical ectotherms (insects and lizards)." And, hence, they suggest that (2) it is also grossly incompatible with "the emerging prediction that tropical ectotherms are especially vulnerable to environmental warming," implying that such is likely to be far from the truth.

Posted 20 May 2015