Billy West
GEO 4300
Lit Review 6
Good
10/10
Lyras, G.A., van der Geer, A. A. E., and Rook, L. (2010), Body size of insular
carnivores: evidence from the fossil record. Journal of Biogeography, 37: 1007–
1021.
Lyras is affiliated with the Museum of Paleontology and Geology at the University of
Athens, Panepistimiopolis, in Zografos, Greece. Van der Geer is with the Netherlands
Centre for Biodiversity Naturalis in Leiden, and Rook is part of the Earth Sciences
Department at the University of Florence in Italy.
2) Research Question/Problem
To explore the issue of insular dwarfism and insular gigantism by
determining the extent of the pattern in fossil carnivores, by offering hypotheses for
explaining the pattern and exceptions thereto, and by determining at what rate the
process occurred.
3) General Background Knowledge for the Study
The degree to which the “island rule” applies to extinct (pre-Holocene)
members of the Mammalian order Carnivora has been largely unexplored; most
modern island carnivores have been insufficiently isolated for significant
differentiation from mainland populations to have occurred. Otters constituted the
largest insular taxon for the obvious reason that otters have the greatest capacity
among the selected species to reach isolated locations.
4) Methods
Fossil species of carnivores from eight islands (including but not limited to
Sardinia, Java, Cyprus, and Kyushu) with worldwide distribution were established
as the dataset: canids, a hyena, otters, martens, and a genet. Body size estimates
were made both by comparing the insular species to their mainland counterparts
and by estimating body size more quantitatively based on molar size. Only one
species (the canid Cynotherium sardous) was able to be evaluated for its rate of body
mass change, which was estimated by comparing the ages of various fossil
specimens through radioactive dating.
5) Results of the Study
Decreases in body mass due to insularity were generally more common than
increases in body mass; body mass changes were only so drastic in two canid
species to constitute dwarfism, and no species exhibited technical gigantism. In five
otter species, three martens, and the genet, there was negligible change in body
mass due to insularity. The rate of evolutionary body mass change for C. sardous was
relatively slow.
6) Weaknesses of the Study
The estimation of body mass from teeth has been criticized because insular
mammals are not proportionally scaled models of their mainland counterparts. The
estimation of the rate of evolutionary change was admitted to require older fossil
specimens for validation.
7) What we learned new from the study
We learned that evolutionary reductions in body mass do not always occur
simply due to population insularity; constraining factors, such as availability of prey
species appropriate for smaller carnivores, must also be taken into account.