Sexual Conflict and Sexually Antagonistic Coevolution in an Annual Plant

Abstract

BackgroundSexual conflict theory predicts sexually antagonistic coevolution of reproductive traits driven by conflicting evolutionary interests of two reproducing individuals. Most studies of the evolutionary consequences of sexual conflicts have, however, to date collectively investigated only a few species. In this study we used the annual herb Collinsia heterophylla to experimentally test the existence and evolutionary consequences of a potential sexual conflict over onset of stigma receptivity.Methodology/Principal FindingsWe conducted crosses within and between four greenhouse-grown populations originating from two regions. Our experimental setup allowed us to investigate male-female interactions at three levels of geographic distances between interacting individuals. Both recipient and pollen donor identity affected onset of stigma receptivity within populations, confirming previous results that some pollen donors can induce stigma receptivity. We also found that donors were generally better at inducing stigma receptivity following pollen deposition on stigmas of recipients from another population than their own, especially within a region. On the other hand, we found that donors did worse at inducing stigma receptivity in crosses between regions. Interestingly, recipient costs in terms of lowered seed number after early fertilisation followed the same pattern: the cost was apparent only if the pollen donor belonged to the same region as the recipient.Conclusion/SignificanceOur results indicate that recipients are released from the cost of interacting with local pollen donors when crossed with donors from a more distant location, a pattern consistent with a history of sexually antagonistic coevolution within populations. Accordingly, sexual conflicts may have important evolutionary consequences also in plants.

Sexually antagonistic evolution caused by male-male competition in the pistil

“…reallocation of resources), thereby increasing reproductive success of the sperm donor at the expense of the recipient fitness (Koene 2016). Moreover, stage-specific seed set in S was similar to that seen in a previous greenhouse study using the same original population (Madjidian and Lankinen 2009) and a survey of 12 natural populations showed that the majority of populations produced the most seeds at stages 3-4 (Madjidian and Lankinen 2009;Hersh et al 2015). We cannot exclude that the higher seed set in the unselected S was partly a consequence of loss of low-quality seeds during storage of S seeds during experimental evolution or resource allocation from the fewer flowers produced (Obeso 2004).…”

“…Studying a broader range of organisms (including plants where replication is resource and labour intensive) is, however, important for obtaining general knowledge (Kawecki et al 2012). We have found implications for sexual conflict within C. heterophylla as previous studies showed pollen influence on floral receptivity and reduced early seed set in 12 studied populations (Lankinen and Kiboi 2007;Madjidian and Lankinen 2009;Hersh et al 2015), and that early fertilization resulted in lowered seed set also following additional pollination at later stages (Madjidian et al 2012). It is though reasonable to assume that we could detect phenotypic changes imposed by sexual selection within a few generations as we previously showed that narrow sense heritability for the sexually selected pollen tube growth rate is 36% ).…”

Effects of soil resources on expression of a sexual conflict over timing of stigma receptivity in a mixed‐mating plant

“…). In accordance with previous results recipients showed a strong influence on this trait (Lankinen and Kiboi , Madjidian and Lankinen ). A previous study also found significant heritability for recipient‐based stage of first seed set (Madjidian et al ).…”

Sexual antagonism in the pistil varies among populations of a hermaphroditic mixed‐mating plant

“…In a recent investigation of Collinsia , only the timing of stigma receptivity was positively correlated with outcrossing rate among species (Kalisz et al ., ), suggesting that this trait is closely connected with the mating system. Collinsia heterophylla shows evidence of a sexual conflict over timing of stigma receptivity (Lankinen & Kiboi, ; Madjidian & Lankinen, ; Madjidian et al ., ). Delayed stigma receptivity favours female fitness under pollen competition between self‐pollen by reducing inbreeding depression (Lankinen & Armbruster, ) and between outcross pollen by increasing offspring quantity (Lankinen & Madjidian, ).…”

“…by germinating on partially receptive stigma or growing rapidly in the unripe pistil), which ensures high siring success but reduces seed set, both after single (Lankinen & Kiboi, ) and multiple pollinations (Madjidian et al ., ), indicating a direct female cost. Interestingly, in crosses within and among four populations from two regions, foreign donors induced stigma receptivity earlier than local donors, pointing to a history of antagonistic coevolution between pollen and pistil traits (Madjidian & Lankinen, ). However, it remains to be seen whether pollinators visit and successfully pollinate flowers at early developmental stages, a necessary condition for the expression of the conflict under natural conditions.…”