Extreme Environments Facilitate Hybrid Superiority - The Story of a Successful Daphnia galeata × longispina Hybrid Clone.

Johanna Griebel,Amanda Navas Faria,Mingbo Yin,Monika Poxleitner,Sabine Gießler,Justyna Wolinska,Diego Fontaneto

doi:10.1371/journal.pone.0140275

Abstract

Hybridization within the animal kingdom has long been underestimated. Hybrids have often been considered less fit than their parental species. In the present study, we observed that the Daphnia community of a small lake was dominated by a single D. galeata × D. longispina hybrid clone, during two consecutive years. Notably, in artificial community set-ups consisting of several clones representing parental species and other hybrids, this hybrid clone took over within about ten generations. Neither the fitness assay conducted under different temperatures, or under crowded and non-crowded environments, nor the carrying capacity test revealed any outstanding life history parameters of this hybrid clone. However, under simulated winter conditions (i.e. low temperature, food and light), the hybrid clone eventually showed a higher survival probability and higher fecundity compared to parental species. Hybrid superiority in cold-adapted traits leading to an advantage of overwintering as parthenogenetic lineages might consequently explain the establishment of successful hybrids in natural communities of the D. longispina complex. In extreme cases, like the one reported here, a superior hybrid genotype might be the only clone alive after cold winters. Overall, superiority traits, such as enhanced overwintering here, might explain hybrid dominance in nature, especially in extreme and rapidly changing environments. Although any favoured gene complex in cyclic parthenogens could be frozen in successful clones independent of hybridization, we did not find similarly successful clones among parental species. We conclude that the emergence of the observed trait is linked to the production of novel recombined hybrid genotypes.

Highlights

The role of hybridization in evolutionary and ecological processes in the animal kingdom has long been disregarded
We traced the development of the “successful hybrid” in this lake by analysing zooplankton samples collected in the spring of six years (April to early June, until the first occurrence of Daphnia individuals, see S1 Fig), between 2008 and 2013
Daphnia were detected in the Feldmochinger See in spring samples of all studied years (2008– 2013) and in four additional samples from the monthly collections performed during the years 2011–2013 (S1 Fig)

Summary

Introduction

The role of hybridization in evolutionary and ecological processes in the animal kingdom has long been disregarded. Genotypes of the parental species have been evolving under prolonged selective pressure and are highly adapted to their environment. By contrast, recombined hybrid genomes might experience a breakdown of co-adapted gene complexes and, as a result, be less competitive in the same environment (reviewed in [3]). Hybrids are sometimes observed to have a higher fitness than their parental species [8, 12, 13]. All of these aspects challenge conventional views of the evolutionary outcome of hybridization [4, 14, 15]

Methods

Results

Conclusion