Open AccessExogenous selection rather than cytonuclear incompatibilities shapes asymmetrical fitness of reciprocal A rabidopsis hybrids
Author(s) -
Muir Graham,
RuizDuarte Paola,
Hohmann Nora,
Mable Barbara K.,
Novikova Polina,
Schmickl Roswitha,
Guggisberg Alessia,
Koch Marcus A.
Publication year - 2015
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.1474
Subject(s) - biology , reproductive isolation , hybrid , evolutionary biology , reciprocal cross , selection (genetic algorithm) , genetics , arabidopsis , natural selection , pollen , adaptation (eye) , botany , gene , population , demography , artificial intelligence , neuroscience , sociology , computer science , mutant
Reciprocal crosses between species often display an asymmetry in the fitness of F 1 hybrids. This pattern, referred to as isolation asymmetry or Darwin's corollary to Haldane's rule, is a general feature of reproductive isolation in plants, yet factors determining its magnitude and direction remain unclear. We evaluated reciprocal species crosses between two naturally hybridizing diploid species of A rabidopsis to assess the degree of isolation asymmetry at different postmating life stages. We found that pollen from A rabidopsis arenosa will usually fertilize ovules from Arabidopsis lyrata ; the reverse receptivity being less complete. Maternal A . lyrata parents set more F 1 hybrid seed, but germinate at lower frequency, reversing the asymmetry. As predicted by theory, A . lyrata (the maternal parent with lower seed viability in crosses) exhibited accelerated chloroplast evolution, indicating that cytonuclear incompatibilities may play a role in reproductive isolation. However, this direction of asymmetrical reproductive isolation is not replicated in natural suture zones, where delayed hybrid breakdown of fertility at later developmental stages, or later‐acting selection against A . arenosa maternal hybrids (unrelated to hybrid fertility, e.g., substrate adaptation) may be responsible for an excess of A . lyrata maternal hybrids. Exogenous selection rather than cytonuclear incompatibilities thus shapes the asymmetrical postmating isolation in nature.