John Pannell

University of Lausanne | UNIL · Department of Ecology and Evolution

Dioecious plants are frequently sexually dimorphic. Such dimorphism, which reflects responses to selection acting in opposite directions for male and female components of fitness, is commonly thought to emerge after separate sexes evolved from hermaphroditism. But associations between allocation to male and female function and traits under sexual c...

The many independent transitions from hermaphroditism to separate sexes (dioecy) in flowering plants and some animal clades must often have involved the emergence of a heterogametic sex-determining locus, the basis of XY and ZW sex determination (i.e., male and female heterogamety). Current estimates indicate that XY sex determination is much more...

Within‐flower self‐pollination should be the major source of self‐fertilization in mixed‐mating species that present single or few flowers simultaneously. It is also an often unmeasured source of selfing in species with many flowers open simultaneously. In self‐compatible species in which pistil and stamen numbers vary, the rate of within‐flower se...

Sex allocation theory successfully predicts sex-ratio variation among organisms with separate sexes, but it has been much less successful in explaining variation in sex allocation in hermaphrodites because the assumption of a direct tradeoff between male and female functions is often violated. Here, we show that sex-allocation theory can be applied...

Dioecious plants are frequently sexually dimorphic. Such dimorphism, which reflects responses to selection acting in opposite directions for male and female components of fitness, is commonly thought to emerge after separate sexes evolved from hermaphroditism. But associations between allocation to male and female function and traits under sexual c...

Pollen-mediated gene flow and spatial genetic structure have rarely been studied in alpine plants that are pollinated by dipteran insects. In particular, it is not clear how different floral traits, such as floral gender, phenology, and ancillary traits, may affect pollen dispersal distance within alpine plant populations. In this study, we conduct...

Pollen-mediated gene flow and spatial genetic structure have rarely been studied in alpine plants pollinated by Dipteran insects. Furthermore, it is not clear how different floral traits, such as floral gender, phenology, and ancillary traits, may affect pollen dispersal distance within a population. In this study, we conducted a paternity analysis...

In dioecious populations, males and females may evolve different trait values to increase fitness through their respective sexual functions. Because hermaphrodites express both sexual functions, resolving sexual conflict is potentially more difficult for them. Here, we show that hermaphrodite plants can partially resolve sexual conflict by expressi...

"When we view gender as an accomplishment, an achieved property of situated conduct, our attention shifts from matters internal to the individual and focuses on interactional and, ultimately, institutional arenas. In one sense, of course, it is individuals who 'do' gender. But it is a situated doing, carried out in the virtual or real presence of o...

The optimal life history and sex allocation of perennial hermaphrodites should depend on both their size and the relative costs and benefits of reproducing through male versus female functions. Theory predicts that insect-pollinated perennials should increase their allocation to female function with size, while the 'mating environment' hypothesis p...

The evolution of dioecy from hermaphroditism is not rare in plants. However, recent evidence shows that this transition is reversible, as was shown in the herb Mercurialis annua by the mean of evolution experiment. This herbaceous species exhibits a XY sex determination system. But the ability of its females to produce few male flowers can lead, in...

Premise: Floral stalk height is known to affect seed dispersal of wind-dispersed grassland species, but it may also affect the attractiveness of flowers and fruits of animal-pollinated and animal-dispersed plants. Stalk height may thus be responsive to selection via interactions with both mutualist pollinators and seed dispersers, but also antagon...

Premise of the study Floral stalk height is known to affect pollination and seed dispersal in wind-dispersed grassland species, but it may also affect the attractiveness of flowers and fruits in animal-pollinated and animal-dispersed plants. Stalk height may thus be responsive to selection via interactions with both mutualist pollinators and seed d...

It is commonly observed that plant species’ range margins are enriched for increased selfing rates and, in otherwise self‐incompatible species, for self‐compatibility (SC). This has often been attributed to a response to selection under mate and/or pollinator limitation. However, range expansion can also cause reduced inbreeding depression, and thi...

Because establishing a new population often depends critically on finding mates, individuals capable of uniparental reproduction may have a colonization advantage. Accordingly, there should be an over‐representation of colonizing species in which individuals can reproduce without a mate, particularly in isolated locales such as oceanic islands. Des...

Plant mimicry is used for two major purposes that benefit the mimic.

Colonization is likely to be more successful for species with an ability to self-fertilize and thus to establish new populations as single individuals. As a result, self-compatibility should be common among colonizing species. This idea, labelled ‘Baker's law’, has been influential in discussions of sexual-system and mating-system evolution. Howeve...

Flowers with only one sexual function typically result from the developmental suppression of the other. A recent study that shows how this is achieved has important implications for models of the evolution of separate sexes in plants.

I. II. III. IV. V. VI. VII. VIII. References SUMMARY: Baker's law refers to the tendency for species that establish on islands by long-distance dispersal to show an increased capacity for self-fertilization because of the advantage of self-compatibility when colonizing new habitat. Despite its intuitive appeal and broad empirical support, it has re...

The coexistence of hermaphrodites and female-sterile individuals, or androdioecy, has been documented in only a handful of plants and animals. This study reports its existence in the plant species Cardamine amara (Brassicaceae), in which female-sterile individuals have shorter pistils than seed-producing hermaphrodites. Morphological analysis, in s...

Colonization is likely to be more successful for species with an ability to self-fertilize and thus to establish new populations of its species as single individuals. As a result, we expect an enrichment of self-compatibility among colonising species. This idea, labelled 'Baker's law', has been influential in discussions of sexual-system and mating...

Many eucaryote organisms are polyploid. However, despite their importance, evolutionary inference of polyploid origins and modes of inheritance has been limited by a need for analyses of allele segregation at multiple loci using crosses. The increasing availability of sequence data for non-model species now allows the application of established app...

Separate sexes have evolved on numerous independent occasions from hermaphroditic ancestors in flowering plants. The mechanisms of sex determination is known for only a handful of such species, but, in those that have been investigated, it usually involves alleles segregating at a single locus, sometimes on heteromorphic sex chromosomes. In the gen...

Background / Purpose: Self-incompatibility (SI) is a crucial and effective mechanism to avoid self-fertilization in flowering plants. It helps to prevent the negative effects of inbreeding and it has evolved several times. Inbreeding depression is probably the main factor avoiding the invasion of self-compatibility (SC), given that selfers have a...

Plants are notoriously variable in gender, ranging in sex allocation from purely male through hermaphrodite to purely female. This variation can have both a genetic and an adaptive plastic component. In gynodioecious species, where females co-occur with hermaphrodites, hermaphrodites tend to shift their allocation towards greater maleness when grow...

In androdioecious metapopulations, where males co-occur with hermaphrodites, the absence of males from certain populations or regions may be explained by locally high selfing rates, high hermaphrodite outcross siring success (e.g. due to high pollen production by hermaphrodites), or to stochastic processes (e.g. the failure of males to invade popul...

Research into the evolution of subdivided plant populations has long involved the study of phenotypic variation across plant geographic ranges and the genetic details underlying that variation. Genetic polymorphism at different marker loci has also allowed us to infer the long- and short-term histories of gene flow within and among populations, inc...

1. Wind pollination is thought to have evolved in response to selection for mechanisms to promote pollination success, when animal pollinators become scarce or unreliable. We might thus expect wind-pollinated plants to be less prone to pollen limitation than their insect-pollinated counterparts. Yet, if pollen loads on stigmas of wind-pollinated sp...

The Mediterranean shrub Phillyrea angustifolia is one of the few plants that display androdioecy, a rare breeding system in which males co-occur with hermaphrodites. However, it has been difficult to account for male frequencies previously documented for this species, which have frequently been higher than 0.5. Here we present sex-ratio data from 1...

Many species exist as metapopulations in balance between local population extinction and recolonization, processes that may strongly affect the distribution of neutral genetic diversity within demes and in the metapopulation as a whole. In this paper we use both the infinite-alleles and the infinite-sites models to reframe Slatkin's propagule-pool...

Many species exist as metapopulations in balance between local population extinction and recolonization, processes that may strongly affect the distribution of neutral genetic diversity within demes and in the metapopulation as a whole. In this paper we use both the infinite-alleles and the infinite-sites models to reframe Slatkin's propagulepool a...

Baker's Law states that it is more likely for self-compatible than for self-incompatible individuals to establish sexually reproducing colonies after long-distance dispersal, because only the former can do so with a single individual. This hypothesis, proposed by H. G. Baker 40 years ago is based largely on the observation that self-compatibility i...

Baker's Law states that it is more likely for self-compatible than for self-incompatible individuals to establish sexually reproducing colonies after long-distance dispersal, because only the former can do so with a single individual. This hypothesis, proposed by H. G. Baker 40 years ago is based largely on the observation that self-compatibility i...

Males and females are at a selective disadvantage relative to hermaphrodites (cosexuals) in species with a colonizing habit, as only cosexuals are able to establish new colonies on their own. The implications of this disadvantage are assessed by means of a computer model of metapopulation dynamics, in which individual colonies are established throu...

1 Strong spatial heterogeneity in male frequencies and allocation to male and female function was found within and between androdioecious populations of the wind-pollinated ruderal Mercurialis annua in south-western Spain. 2 Sex determination is largely genetic and the constancy from year to year of the frequency of males in small quadrats suggests...

Males and females are at a selective disadvantage relative to hermaphrodites (cosexuals) in species with a colonizing habit, as only cosexuals are able to establish new colonies on their own. The implications of this disadvantage are assessed by means of a computer model of metapopulation dynamics, in which individual colonies are established throu...