Rd. Semlitsch et al., Jumping performance and short-term repeatability of newly metamorphosed hybrid and parental leopard frogs (Rana sphenocephala and Rana blairi), CAN J ZOOL, 77(5), 1999, pp. 748-754
Citations number
37
Categorie Soggetti
Animal Sciences
Journal title
CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE
Differential fitness between hybrid and parental genotypes plays a critical
role in explaining the maintenance of natural hybrid zones as well as the
production of novel genetic variation that may lead to diversification. Bec
ause locomotor performance is a reliable and practical measure of potential
fitness related to morphological variation, we tested for differences in j
umping performance among parental and hybrid genotypes of newly metamorphos
ed leopard frogs (Rana sphenocephala and Rana blairi). Tadpoles of the pare
ntal species and primary and backcross hybrid tadpoles, generated from arti
ficial crosses (a total of five genotypes), were reared at two initial larv
al densities. Locomotor performance of newly metamorphosed frogs, as measur
ed by jumping ability, was tested three times over 6 days in the laboratory
at 24-25 degrees C. Maximum and average jump lengths were greater for meta
morphs reared at low larval density than for those reared at high density.
Regression analyses indicated that 70-79% of the variation in jump length w
as due to body mass. When reared at low density, metamorphs of two F-1 back
cross genotypes (HB and HS) and one primary hybrid genotype (SB) jumped sho
rter distances than either parental species. When reared at high density, h
ybrid performance was indistinguishable from that of the parentals, except
for one backcross hybrid (HB). Moderately high short-term repeatabilities (
0.47-0.66) of metamorphs reared at the high density indicate that measures
of performance in newly metamorphosed frogs can be predictive. We suggest t
hat, owing to poor jumping performance, some hybrid frogs would be at a sel
ective disadvantage relative to their parental species in the terrestrial e
nvironment and thus would partially reinforce mechanisms of reproductive is
olation in this leopard frog system. Yet equivalent performance of some hyb
rids relative to the parentals, at least when reared at low density, sugges
ts that hybrid lineages also have the potential to evolve independently in
some environments.