Testing for intraspecific postzygotic isolation between cryptic lineages of Pseudacris crucifer
Article first published online: 23 OCT 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 3, Issue 14, pages 4621–4630, November 2013
How to Cite
Ecology and Evolution 2013; 3(14): 4621–4630
- Issue published online: 25 NOV 2013
- Article first published online: 23 OCT 2013
- Manuscript Accepted: 17 SEP 2013
- Manuscript Revised: 14 SEP 2013
- Manuscript Received: 18 JUN 2013
- Natural Sciences and Engineering Research Council of Canada
- SSE Rosemary
- Ontario Ministry of Natural Resources
- Queen's University – University Animal Care Committee. Grant Number: 2008-059-R3
- University of Guelph Animal Utilization Protocol. Grant Number: 05R054
- cryptic diversity;
- intraspecific divergence;
- reproductive isolation
Phenotypically cryptic lineages appear common in nature, yet little is known about the mechanisms that initiate and/or maintain barriers to gene flow, or how secondary contact between them might influence evolutionary trajectories. The consequences of such contact between diverging lineages depend on hybrid fitness, highlighting the potential for postzygotic isolating barriers to play a role in the origins of biological species. Previous research shows that two cryptic, deeply diverged intraspecific mitochondrial lineages of a North American chorus frog, the spring peeper (Pseudacris crucifer), meet in secondary contact in Southwestern Ontario, Canada. Our study quantified hatching success, tadpole survival, size at metamorphosis, and development time for experimentally generated pure lineage and hybrid tadpoles. Results suggest that lineages differ in tadpole survival and that F1 hybrids may have equal fitness and higher than average mass at metamorphosis compared with pure parental crosses. These findings imply hybrid early life viability may not be the pivotal reproductive isolation barrier helping to maintain lineage boundaries. However, we observed instances of tadpole gigantism, failure to metamorphose, and bent tails in some tadpoles from hybrid families. We also speculate and provide some evidence that apparent advantages or similarities of hybrids compared with pure lineage tadpoles may disappear when tadpoles are raised with competitors of different genetic makeup. This pilot study implies that ecological context and consideration of extrinsic factors may be a key to revealing mechanisms causing negative hybrid fitness during early life stages, a provocative avenue for future investigations on barriers to gene flow among these intraspecific lineages.