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Ejaculate evolution in external fertilizers: Influenced by sperm competition or sperm limitation?


Liao, Wen Bo; Huang, Yan; Zeng, Yu; Zhong, Mao Jun; Luo, Yi; Lüpold, Stefan (2018). Ejaculate evolution in external fertilizers: Influenced by sperm competition or sperm limitation? Evolution, 72(1):4-17.

Abstract

The evolution of sperm quality and quantity is shaped by various selective processes, with sperm competition generally considered the primary selective agent. Particularly in external fertilizers, however, sperm limitation through gamete dispersal can also influence gamete investments, but empirical data examining this effect are limited. Here, we studied the relative importance of sperm competition and the spawning conditions in explaining the macroevolutionary patterns of sperm size and number within two taxa with external fertilization but differences in their reproductive biology. In frogs, sperm swim slowly but for up to hours as they penetrate the gelatinous egg coating, whereas fish sperm typically swim fast, are very short-lived (seconds to minutes), and often face a relatively higher risk of being moved away from the ova by currents. Our phylogenetic models and path analyses revealed different trajectories of ejaculate evolution in these two taxa. Sperm size and number responded primarily to variation in sperm competition in the anurans, but more strongly to egg number and water turbulence in the fishes. Whereas the results across anurans align with the general expectation that sexual selection is the main driver of ejaculate evolution, our findings across the fishes suggest that sperm limitation has been underappreciated.

Abstract

The evolution of sperm quality and quantity is shaped by various selective processes, with sperm competition generally considered the primary selective agent. Particularly in external fertilizers, however, sperm limitation through gamete dispersal can also influence gamete investments, but empirical data examining this effect are limited. Here, we studied the relative importance of sperm competition and the spawning conditions in explaining the macroevolutionary patterns of sperm size and number within two taxa with external fertilization but differences in their reproductive biology. In frogs, sperm swim slowly but for up to hours as they penetrate the gelatinous egg coating, whereas fish sperm typically swim fast, are very short-lived (seconds to minutes), and often face a relatively higher risk of being moved away from the ova by currents. Our phylogenetic models and path analyses revealed different trajectories of ejaculate evolution in these two taxa. Sperm size and number responded primarily to variation in sperm competition in the anurans, but more strongly to egg number and water turbulence in the fishes. Whereas the results across anurans align with the general expectation that sexual selection is the main driver of ejaculate evolution, our findings across the fishes suggest that sperm limitation has been underappreciated.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:Anurans, fishes, reproductive investment, sperm number, sperm length, sperm size–number trade-off
Language:English
Date:9 January 2018
Deposited On:15 Feb 2018 10:57
Last Modified:18 Apr 2018 11:49
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0014-3820
Funders:National Natural Sciences Foundation of China, Sichuan Province Outstanding Youth Academic Technology Leaders Program, Sichuan Province Department of Education Innovation Team Project, Swiss National Science Foundation
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/evo.13372
Official URL:http://onlinelibrary.wiley.com/wol1/doi/10.1111/evo.13372/abstract
PubMed ID:28975611
Project Information:
  • : Funder
  • : Grant ID
  • : Project TitleNational Natural Sciences Foundation of China
  • : Funder
  • : Grant ID
  • : Project TitleSichuan Province Outstanding Youth Academic Technology Leaders Program
  • : Funder
  • : Grant ID
  • : Project TitleSichuan Province Department of Education Innovation Team Project
  • : FunderSNSF
  • : Grant ID
  • : Project TitleSwiss National Science Foundation

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