Jumping performance and short-term repeatability of newly metamorphosed hybrid and parental leopard frogs (Rana sphenocephala and Rana blairi)

Citation
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
ISSN journal
00084301 → ACNP
Volume
77
Issue
5
Year of publication
1999
Pages
748 - 754
Database
ISI
SICI code
0008-4301(199905)77:5<748:JPASRO>2.0.ZU;2-6
Abstract
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.