Evol Ecol Res 8: 1049-1059 (2006)     Full PDF if your library subscribes.

Bergmann’s rule and the terrestrial caecilian Schistometopum thomense (Amphibia: Gymnophiona: Caeciliidae)

G. John Measey* and Stefan Van Dongen

Laboratory of Animal Ecology, Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium

Author to whom all correspondence should be addressed.
e-mail: johnmeasey@hotmail.com


Question: Do caecilians follow Bergmann’s rule?

Hypothesis: Bergmann’s rule explains the wide variation in body sizes found among populations of the terrestrial caecilian Schistometopum thomense.

Field site: This is a range-wide study incorporating most terrestrial habitats throughout the island of São Tomé in the Gulf of Guinea.

Methods: We performed morphological measurements on 95 museum specimens and 187 field-collected individuals and compared them with site data from 13 separate localities on the island.

Conclusions: This is the first example of a caecilian amphibian that follows Bergmann’s rule. Total body mass doubles and length increases by nearly 50% up to 1050 m of altitude. This result is surprising as it occurs virtually on the equator, over a very small spatial scale (< 16 km horizontal), and within a relatively small temperature range (< 10°C).

Keywords: altitude, Bergmann’s rule, burrowing, Gymnophiona.

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