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Recent evolution of large offspring size and post-fertilization nutrient provisioning in swordtails
Cheyenne Y Payne1,2,3,4, Derek Ly5, Rebecca A Rodriguez-Soto1
1Department of Biology, Stanford University, Stanford, CA, USA.
Proceedings. Biological Sciences
|February 10, 2026
Summary
Swordtail fish (Xiphophorus) exhibit distinct reproductive strategies. Xiphophorus malinche evolves larger, more resilient offspring, suggesting adaptation to harsh environments and unique maternal nutrient provisioning.
Area of Science:
- Evolutionary biology
- Reproductive strategies
- Comparative genomics
Background:
- Organisms employ diverse reproductive strategies influencing offspring survival.
- Swordtail fish (Xiphophorus) exhibit internal fertilization and live birth.
- Understanding reproductive divergence is key to evolutionary insights.
Purpose of the Study:
- To investigate reproductive strategy divergence between Xiphophorus malinche and Xiphophorus birchmanni.
- To explore the genetic and environmental factors influencing offspring size and survival.
- To document maternal nutrient provisioning in Xiphophorus.
Main Methods:
- Morphological measurements of embryos and fry.
- Gene expression analysis in maternal tissues.
- Hybrid crosses between X. malinche and X. birchmanni.
Main Results:
- X. malinche produces larger, more starvation-resilient offspring than X. birchmanni.
- Evidence of maternal nutrient provisioning during embryonic development in X. malinche.
- Offspring size is genetically determined, with asymmetric hybrid incompatibility observed.
Conclusions:
- Large offspring size in X. malinche may be an adaptation to challenging environments.
- Maternal nutrient provisioning is a documented reproductive strategy in Xiphophorus.
- Reproductive strategy influences hybrid incompatibilities in swordtail fish.
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