Size-dependent sex allocation in Solanum lycocarpum St. Hil. (Solanaceae)

Resource allocation to reproduction can change depending on size, as predicted by the size-dependent sex allocation. This theory is based on the fact that small individuals will invest in the allocation of sex with lower cost of production, usually male gender. In plants, there are some andromonoecy species, presence of hermaphrodite and male flowers in the same individual. Andromonoecy provides a strategy to optimally allocate resources to male and female function, evolving a reproductive energy-saving strategy. Thus, our objective was to investigate the size-dependent sex allocation in Solanum lycocarpum St. Hil. We tested the hypothesis that plants with larger size will invest in the production of hermaphrodite flowers, because higher individuals have greater availability of resources to invest in more complex structures involving greater energy expenditure. The studied species was S. lycocarpum, an andromonoecious species. From June 2016 to March 2017 the data were collected in 38 individuals, divided in two groups: the larger plant group (n=18; height=3-5 m) and the smaller plant group (n=20; height=1-2 m).Our data show that there was effect of plant size on the flower production and the sexual gender allocation. The larger plants showed more flowers and higher production of hermaphrodite flowers. Furthermore, in the flower scale, we observed allometric relationship among the flower’s traits with proportional investments in biomass, anther size and gynoecium size. Our results are in agreement with size-dependent sex allocation theory and andromonoecy hypothesis related to mechanisms for optimal resource allocation to male and female function.

Epigenetic mechanisms in sex determination and in the evolutionary transitions between sexual systems

The hypothesis that epigenetic mechanisms of gene expression regulation have two main roles in vertebrate sex is presented. First, and within a given generation, by contributing to the acquisition and maintenance of (i) the male or female function once during the lifetime in individuals of gonochoristic species; and (ii) the male and female function in the same individual, either at the same time in simultaneous hermaphrodites, or first as one sex and then as the other in sequential hermaphrodites. Second, if environmental conditions change, epigenetic mechanisms may have also a role across generations, by providing the necessary phenotypic plasticity to facilitate the transition: (i) from one sexual system to another, or (ii) from one sex-determining mechanism to another. Furthermore, if the environmental change lasts enough time, epimutations could facilitate assimilation into genetic changes that stabilize the new sexual system or sex-determining mechanism. Examples supporting these assertions are presented, caveats or difficulties and knowledge gaps identified, and possible ways to test this hypothesis suggested. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.

Theoretical and Empirical Research of the Impact of Psychological Context Effects on Participants of Short-term Business Negotiations

В статье излагается впервые предпринятая попытка подойти к исследованию психологических особенностей процесса ведения переговоров с позиций контекстного подхода и смыслообразующей категории «контекст». Дается описание теоретико-эмпирической модели изучения смыслообразующего психологического контекста деятельности участников краткосрочных деловых переговоров, которая состоит из системы индивидуально-психологических характеристик, участвующих в формировании смысла и значения аспектов переговорной деятельности и переговорной ситуации в целом, позволяющих с большей вероятностью добиваться или не добиваться успеха в переговорах. В качестве таких характеристик рассматриваются эмоциональный интеллект, уровень рефлексивности, социальные ценности и переговорная ориентация. В процессе анализа результатов 52 переговоров, в которых участвовали 104 опытных переговорщика, с применением методов анкетирования было установлено, что успешные переговорщики обладают более широким смыслообразующим психологическим контекстом, то есть могут вовлекать в свое семантическое поле большую психологическую информацию, касающуюся своего оппонента по переговорам; лучше понимают эмоции другого человека и управляют этими эмоциями, ориентируются на ценность «любовь», имеют больше корреляций между уровнем рефлексивности, ценностями и эмоциональным интеллектом. Это проявляется в процессе переговоров в поведении, направленном не только на себя, но и на собеседника и обеспечивает успех в быстром достижении договоренностей. Неуспешные переговорщики обладают более узким смыслообразующим психологическим контекстом, в котором психологическая информация ориентирована на самого переговорщика, а не на его собеседника; хуже понимают эмоции своего оппонента, ориентированы на ценность «свобода», обладают меньшим количеством корреляций между ценностями и эмоциональным интеллектом, что проявляется в ситуации переговоров в поведении, ориентированном только на себя и свои интересы. Результаты анализа гендерных особенностей участников краткосрочных деловых переговоров показали, что успешные переговорщики мужского и женского полов обладают более схожим смыслообразующим психологическим контекстом, в отличие от неуспешных. По мнению авторов, результаты данного исследования могут стать основой для формирования программ повышения квалификации опытных переговорщиков, которые ведут переговоры в условиях ограниченного временного ресурса. The article is the first attempt to research psychological peculiarities of negotiation holding through the prism of contextual approach and the notion of context. The article presents a theoretical and empirical model of the investigation of the notion of psychological context and its effects on participants of short-term business negotiations. The model encompasses a system of individual and psychological characteristics which shape various aspects of the negotiation process and negotiation situation and enable one to hold effective negotiations. The aforementioned characteristics encompass emotional intellect, level of reflexivity, and negotiation orientation. The analysis of a survey investigating the results of 52 negotiations with the participation of 104 experienced negotiators shows that successful negotiators are highly familiar with wide psychological context and can analyze the semantic environment and collect psychological information associated with their opponents; they are good at understanding other people’s emotions, they fully appreciate the concept of love, their reflexivity, emotional intellect and values are highly interrelated. In the process of negotiations, they seek to satisfy both their needs and the needs of their opponent, which enables them to successfully achieve negotiation goals. Unsuccessful negotiators work with a narrower psychological context and fail to collect psychological information associated with their opponents, they fail to fully understand the emotions of their opponents, they appreciate the value of freedom, their reflexivity, emotional intellect and values are not interrelated; their behaviour during negotiations is selfish, they focus solely on their interests. The investigation of gender characteristics of the participants of short-term business negotiations shows that unlike unsuccessful negotiators, successful negotiators (both male and female) function within similar psychological contexts. According to the authors of the article, the results of the investigation can be used as a basis for the implementation of professional development programs for experienced negotiators participating in short-term negotiations.

The Diversity and Dynamics of Sex Determination in Dioecious Plants

The diversity of inflorescences among flowering plants is captivating. Such charm is not only due to the variety of sizes, shapes, colors, and flowers displayed, but also to the range of reproductive systems. For instance, hermaphrodites occur abundantly throughout the plant kingdom with both stamens and carpels within the same flower. Nevertheless, 10% of flowering plants have separate unisexual flowers, either in different locations of the same individual (monoecy) or on different individuals (dioecy). Despite their rarity, dioecious plants provide an excellent opportunity to investigate the mechanisms involved in sex expression and the evolution of sex-determining regions (SDRs) and sex chromosomes. The SDRs and the evolution of dioecy have been studied in many species ranging from Ginkgo to important fruit crops. Some of these studies, for example in asparagus or kiwifruit, identified two sex-determining genes within the non-recombining SDR and may thus be consistent with the classical model for the evolution of dioecy from hermaphroditism via gynodioecy, that predicts two successive mutations, the first one affecting male and the second one female function, becoming linked in a region of suppressed recombination. On the other hand, aided by genome sequencing and gene editing, single factor sex determination has emerged in other species, such as persimmon or poplar. Despite the diversity of sex-determining mechanisms, a tentative comparative analysis of the known sex-determining genes and candidates in different species suggests that similar genes and pathways may be employed repeatedly for the evolution of dioecy. The cytokinin signaling pathway appears important for sex determination in several species regardless of the underlying genetic system. Additionally, tapetum-related genes often seem to act as male-promoting factors when sex is determined via two genes. We present a unified model that synthesizes the genetic networks of sex determination in monoecious and dioecious plants and will support the generation of hypothesis regarding candidate sex determinants in future studies.

Edge effects and mating patterns in a bumblebee-pollinated plant

Researchers have long assumed that plant spatial location influences plant reproductive success and pollinator foraging behaviour. For example, many flowering plant populations have small, linear or irregular shapes that increase the proportion of plants on the edge, which may reduce mating opportunities through both male and female function. Additionally, plants that rely on pollinators may be particularly vulnerable to edge effects if those pollinators exhibit restricted foraging and pollen carryover is limited. To explore the effects of spatial location (edge vs. interior) on siring success, seed production, pollinator foraging patterns and pollen-mediated gene dispersal, we established a square experimental array of 49 Mimulus ringens (monkeyflower) plants. We observed foraging patterns of pollinating bumblebees and used paternity analysis to quantify male and female reproductive success and mate diversity for plants on the edge versus interior. We found no significant differences between edge and interior plants in the number of seeds sired, mothered or the number of sires per fruit. However, we found strong differences in pollinator behaviour based on plant location, including 15 % lower per flower visitation rates and substantially longer interplant moves for edge plants. This translated into 40 % greater pollen-mediated gene dispersal for edge than for interior plants. Overall, our results suggest that edge effects are not as strong as is commonly assumed, and that different plant reproduction parameters respond to spatial location independently.

Structural and temporal modes of heterodichogamy and similar patterns across angiosperms

Different kinds of synchronization of flowering, and of male and female function, have evolved in many angiosperms. The most complex patterns are heterodichogamy, pseudoheterodichogamy and duodichogamy. In this review, their occurrence across angiosperms is shown and the diversity in heterodichogamy and duodichogamy is outlined. Heterodichogamy is characterized by the occurrence of two temporally complementary genetic morphs, whereas in peudoheterodichogamy and duodichogamy only one morph occurs. In duodichogamy, the two phases result from alternating periods of several days of the same phase three or more times during a flowering season; however, they are of irregular length. In pseudoheterodichogamy, the two phases result from repeated flushes of flowering within individuals always with one or two flowerless days in between. In contrast to duodichogamy, the male and female phases alternate in a daily rhythm coordinated with the day-night rhythm. Heterodichogamy and similar patterns of synchronization are scattered across angiosperms; however, they are especially common in the Magnoliales, Laurales, Canellales, Zingiberales, Ranunculales, Trochodendrales, Fagales, Rosales, Malpighiales, Malvales, Sapindales, Caryophyllales and Apiales.

Hermaphrodites and parasitism: size-specific female reproduction drives infection by an ephemeral parasitic castrator

Sex can influence patterns of parasitism because males and females can differ in encounter with, and susceptibility to, parasites. We investigate an isopod parasite (Hemioniscus balani) that consumes ovarian fluid, blocking female function of its barnacle host, a simultaneous hermaphrodite. As a hermaphrodite, sex is fluid, and individuals may allocate energy differentially to male versus female reproduction. We predicted the relationship between barnacle size and female reproductive function influences the distribution of parasites within barnacle populations. We surveyed 12 populations spanning ~400 km of coastline of southern California and found intermediate-sized barnacles where most likely to be actively functioning as females. While it is unclear why larger individuals are less likely to be actively reproducing as females, we suggest this reduced likelihood is driven by increased investment in male reproductive effort at larger sizes. The female function-size relationship was mirrored by the relationship between size and parasitism. We suggest parasitism by Hemioniscus balani imposes a cost to female function, reinforcing the lack of investment in female function by the largest individuals. Within the subset of suitable (=female) hosts, infection probability increased with size. Hence, the distribution of female function, combined with selection for larger hosts, primarily dictated patterns of infection.

Sex chromosome evolution via two genes

The origin of sex chromosomes has been hypothesized to involve the linkage of factors with antagonistic effects on male and female function. Garden asparagus (Asparagus officinalis L.) is an ideal species to test this hypothesis, as the X and Y chromosomes are cytologically homomorphic and recently evolved from an ancestral autosome pair in association with a shift from hermaphroditism to dioecy. Mutagenesis screens paired with single-molecule fluorescence in situ hybridization (smFISH) directly implicate Y-specific genes that respectively suppress female organ development and are necessary for male gametophyte development. Comparison of contiguous X and Y chromosome shows that loss of recombination between the genes suppressing female function (SUPPRESSOR OF FEMALE FUNCTION, SOFF) and promoting male function (TAPETAL DEVELOPMENT AND FUNCTION 1, aspTDF1) is due to hemizygosity. We also experimentally demonstrate the function of aspTDF1. These finding provide direct evidence that sex chromosomes can evolve from autosomes via two sex determination genes: a dominant suppressor of femaleness and a promoter of maleness.

Sexual selection and inbreeding: two efficient ways to limit the accumulation of deleterious mutations

Theory and empirical data showed that two processes can boost selection against deleterious mutations, thus facilitating the purging of the mutation load: inbreeding, by exposing recessive deleterious alleles to selection in homozygous form, and sexual selection, by enhancing the relative reproductive success of males with small mutation loads. These processes tend to be mutually exclusive because sexual selection is reduced under mating systems that promote inbreeding, such as self-fertilization in hermaphrodites. We estimated the relative efficiency of inbreeding and sexual selection at purging the genetic load, using 50 generations of experimental evolution, in a hermaphroditic snail (Physa acuta). To this end, we generated lines that were exposed to various intensities of inbreeding, sexual selection (on the male function) and nonsexual selection (on the female function). We measured how these regimes affected the mutation load, quantified through the survival of outcrossed and selfed juveniles. We found that juvenile survival strongly decreased in outbred lines with reduced male selection, but not when female selection was relaxed, showing that male-specific sexual selection does purge deleterious mutations. However, in lines exposed to inbreeding, where sexual selection was also relaxed, survival did not decrease, and even increased for self-fertilized juveniles, showing that purging through inbreeding can compensate for the absence of sexual selection. Our results point to the further question of whether a mixed strategy combining the advantages of both mechanisms of genetic purging could be evolutionary stable.

Equality between the sexes in plants for costs of reproduction; evidence from the dioecious Cape genus Leucadendron (Proteaceae)

It has been argued that sexual allocation is greater for female function than male function in plants in general and specifically for the large dioecious Cape genus Leucadendron. Here, we use new interpretations of published information to support the hypothesis of equality between sexes in this genus. The explanations are based on the fire ecology of the Cape that results in reproductive synchrony, reproductive doubling and competitive symmetry. Firstly, strict post-fire seedling establishment of the reseeder life-history in the Cape results in single-aged populations. Consequently, the reproductive and vegetative schedules of males must synchronously track that of females. This implies equal allocation to sex. Secondly, after fires, dioecious females have double the seedling to adult ratio of co-occurring hermaphrodites. This indicates that being liberated from male function allows females access to resources that double their fitness compared to hermaphrodites. Therefore, male and female costs of reproduction are equal in hermaphrodites. Thirdly, competitive symmetry must occur because males and female plants will frequently encounter each other as close near neighbours. Competitive asymmetry would both reduce mating opportunities and skew local sex ratios. The evidence to date is for 1:1 sex ratios in small plots and this indicates competitive symmetry and a lack of dimorphic niches. Finally, vegetatively dimorphic species must also allocate equally to sex, or else sexual asynchrony, lack of reproductive doubling or competitive asymmetry will occur.