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Climate variability predicts thermal limits of aquatic insects across elevation and latitude
Author(s) -
Shah Alisha A.,
Gill Brian A.,
Encalada Andrea C.,
Flecker Alexander S.,
Funk W. Chris,
Guayasamin Juan M.,
Kondratieff Boris C.,
Poff N. LeRoy,
Thomas Steven A.,
Zamudio Kelly R.,
Ghalambor Cameron K.
Publication year - 2017
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/1365-2435.12906
Subject(s) - temperate climate , elevation (ballistics) , streams , latitude , ecology , biology , tropics , aquatic insect , tropical climate , atmospheric sciences , habitat , geography , geology , geometry , mathematics , geodesy , computer network , computer science
Janzen's extension of the climate variability hypothesis (CVH) posits that increased seasonal variation at high latitudes should result in greater temperature overlap across elevations, and favour wider thermal breadths in temperate organisms compared to their tropical counterparts. We tested these predictions by measuring stream temperatures and thermal breadths (i.e. the difference between the critical thermal maximum and minimum) of 62 aquatic insect species from temperate (Colorado, USA ) and tropical (Papallacta, Ecuador) streams spanning an elevation gradient of c . 2000 m. Temperate streams exhibited greater seasonal temperature variation and overlap across elevations than tropical streams, and as predicted, temperate aquatic insects exhibited broader thermal breadths than tropical insects. However, elevation had contrasting effects on patterns of thermal breadth. In temperate species, thermal breadth decreased with increasing elevation because CT MAX declined with elevation while CT MIN was similar across elevations. In tropical insects, by contrast, CT MAX declined less sharply than CT MIN with elevation, causing thermal breadth to increase with elevation. These macrophysiological patterns are consistent with the narrower elevation ranges found in other tropical organisms, and they extend Janzen's CVH to freshwater streams. Furthermore, because lowland tropical aquatic insects have the narrowest thermal breadths of any region, they may be particularly vulnerable to short‐term extreme changes in stream temperature. A plain language summary is available for this article.