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Primula veris flowers obtained from a forest population that clearly illustrate the observed deviation in stigma positioning in the L-morph individuals contrasted against an S-morph flower.
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Background and Aims Distyly is a floral polymorphism characterized by the presence of two discrete morphs with reciprocal positioning of anthers and stigmas in flowers on different plants within the same population. Although reciprocal herkogamy and associated floral traits are generally thought to be discrete and strict polymorphisms, little is kn...
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... below the threshold value (R < 0Á05) at which a species or population can be denoted as 'distylous' ( Sánchez et al., 2008), a considerable number of plants in the forest populations had flowers with strong deviations from per- fect reciprocity. A number of plants (<10 %) even showed no spatial separation at all between stigmas and anthers ( Fig. 5), and therefore can be denoted as homostyles. However, the ob- served type of homostyly does not fit to the classical homosty- lous syndrome [long-homostyly, i.e. homozygous S-morph individuals (SS)] as reported in other Primula species (Crosby, 1949;Curtis and Curtis, 1985;Piper and Charlesworth, 1986), or other distylous species ...
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... envi- ronments (e.g. Guggisberg et al., 2006Guggisberg et al., , 2009Carlson et al., 2008;De Vos et al., 2012). Although this classic type of homo- styly has previously been found in some P. veris individuals in the UK (Scott, 1865), the homostylous individuals observed here showed low-level positioning of sexual organs (i.e. short- homostyly; Fig. 5) and their self-incompatibility system was ...
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Evolutionary breakdown from rigorous outbreeding to self-fertilization frequently occurs in angiosperms. Since the pollinators are not necessary, self-compatible populations often reduce investment in floral display characteristics and pollination reward. Primula forbesii is a biennial herb with distribution restricted to southwest China; it was in...
Outcrossing plant species are more likely to exhibit autonomous selfing in marginal habitats to ensure reproduction under conditions of limited pollinator and/or mate availability. Distyly is a classical paradigm that promotes outcrossing; however, little is known about the variation in floral traits associated with distylous syndrome in marginal p...
Enantiostyly is a floral polymorphism consisting in the presence of two floral morphs that differ in the deflection of the style to the right or left in the populations. Monomorphic enantiostyly consists in plants showing both morphs within an individual and is thought to promote pollen transference between morphs, reduce levels of self-pollination...
Distyly is a widespread floral polymorphism characterized by the flowers within a population showing reciprocal placement of the anthers and stigma. Darwin hypothesizes that distyly evolves to promote precise pollen transfer between morphs. Primula chungensis exhibits two types of anther heights, and these two types of anthers show pollen of two di...
Distyly is a floral polymorphism characterized by the presence of two discrete morphs with reciprocal positioning of anthers and stigmas in flowers on different plants in the same population. For a distylous system to function effectively, the presence of suitable pollinators that transfer pollen from the two morphs (a short-styled S-morph and a lo...
Citations
... One significant trend is the increased prevalence of autonomous selfing in fragmented habitats to ensure reproduction under pollen limitation (Jacquemyn et al., 2012). This evolutionary shift is often associated with morphological changes, such as the reduction in the level of herkogamy when plant-pollinator networks are disrupted (Brys & Jacquemyn, 2015;Eckert et al., 2010). In such cases, the diallelic S-locus supergene, which controls reciprocal herkogamy and determines the length of thrum and pin morphologies, becomes critically important as it serves as a fundamental genetic mechanism for maintaining self-incompatibility (Li et al., 2007(Li et al., , 2015. ...
Understanding the combined effects of climate change and habitat fragmentation on the adaptive potential of plant populations is essential for devising effective conservation strategies. This is particularly important where mating system variation impacts the evolutionary consequences of habitat fragmentation. Here we aimed to reveal how habitat fragmentation and climate adaptation jointly influence the evolutionary trajectories in Primula elatior, a heterostylous self-incompatible and dispersal-constrained forest herb. We quantified the genomic variation and degree of herkogamy, a floral trait reducing self-pollination, across 60 geographically paired populations of Primula elatior across Europe, each pair featuring contrasting levels of habitat fragmentation. Our findings revealed a large and unique set of adaptive outliers in more fragmented landscapes, compared to high-connectivity ones, despite the geographic proximity of the sampling pairs. This suggests elevated selective pressures in fragmented habitats, mirrored by a reduced adaptive potential to cope with climate change. Finally, a minority of genetic variants associated with herkogamy were influenced by current levels of habitat fragmentation and population size, potentially signalling early indicators of evolutionary mating system changes in response to pollinator limitation. Because evolutionary trajectories and adaptive potential are expected to be increasingly affected by habitat fragmentation, our findings underscore the importance of considering both habitat fragmentation and climate adaptation in conservation research and planning.
... Given this pattern, it is clear that it is important to better understand the relationship between this floral polymorphism and the ecological mechanisms explaining pollen transfer in distylous species (Castro et al., 2004;Consolaro et al., 2011;Ferrero et al., 2017;Hodgins & Barrett, 2008;Matias et al., 2020). For instance, although reciprocal herkogamy is considered the main characteristic defining distyly, variation in the positioning of anthers and stigmas is frequently reported in distylous species, indicating that reciprocity between sexual organs is rarely perfect (e.g., Armbruster et al., 2017;Brys & Jacquemyn, 2015;Faivre & Mcdade, 2001;Ferrero et al., 2011;Keller et al., 2012;Pailler & Thompson, 1997). Deviations from perfect reciprocity could affect the match between pollinators and sexual floral organs, resulting in asymmetrical pollen segregation in pollinators' bodies (Brys et al., 2008;Massinga et al., 2005;Wolfe & Barrett, 1989), consequently modifying the expected patterns of legitimate pollen transfer . ...
... Similar results were found in several populations of Waltheria ovata, which despite presenting substantial variation in the height of sexual organs were all distylous (Bramow et al., 2013;see below). It has been shown that variability in the level of reciprocity (Brys & Jacquemyn, 2015;Jacquemyn et al., 2018) can have significant impacts on pollen transfer patterns and plant reproductive success (Brys & Jacquemyn, 2019;Matias et al., 2020). In this sense, the adaptive inaccuracy index obtained for W. rotundifolia flowers showed a similar contribution of low-and high-level organs to the deviation from perfect reciprocity, suggesting that legitimate pollen deposition should be high (Armbruster et al. 2017). ...
... Two factors may explain this. First, in species with strict self-incompatibility such as W. rotundifolia, assortative pollen transfer may have little influence on mating patterns and thus on the morph ratios (Brys & Jacquemyn, 2015;Matias et al., 2020). Interestingly, although a small proportion of self-pollen grains and selfpollen tubes germinated and entered the ovary, respectively, no seeds were produced after self-pollination. ...
The genus Waltheria is known for having a high percentage of distylous species (ca. 85%). However, distyly has only been comprehensively studied in a few Waltheria species. The study of distyly is of particular ecological relevance given the occurrence of exotic pollinators in natural ecosystems nowadays, which could potentially affect legitimate pollen transfer between floral morphs. In the present study, we characterized the sexual reciprocity between floral morphs in the tropical shrub Waltheria rotundifolia , we tested if the pollen transfer patterns were in accordance with proper distyly, and we tested its incompatibility system. Reciprocity was characterized by measuring sexual traits, while pollen traits were measured to evaluate the presence of ancillary polymorphisms. The efficiency of distyly to promote legitimate pollen transfer was determined by quantifying pollen loads deposited on stigmas and on the body of Apis mellifera , the main floral visitor of W. rotundifolia . Finally, hand pollinations were performed to determine the strength of the incompatibility system. Flowers exhibit a reciprocal arrangement of sexual organs and pollen ancillary features typical of distylous plants. We observed a differential placement of pollen on the body of A. mellifera . However, intermorph differences in the pollen loads and legitimate pollen deposited on stigmas suggest inefficient pollen transfer by A. mellifera . Hand pollinations revealed the presence of a heteromorphic incompatibility system. Overall, our results show that although factors for disassortative pollen transfer are present in the studied population, W. rotundifolia exhibits asymmetric pollen deposition probably due to A. mellifera foraging behavior.
... It has been found for P. veris, even though rarely, that long-styled morphs show moderate intra-morph compatibility, with some chance of the development of seed set through intra-morph pollination (14.7%). In contrast, the probability of successful reproduction as a result of crossing between short-styled morphs is negligible (0.6%; Wedderburn & Richards 1990;Brys & Jacquemyn 2015). Because of the variation in self-compatibility between the two morph types (Wedderburn & Richards 1990), L-morphs can have a reproductive advantage in small and fragmented populations as they have more potential mates to reproduce with than S-morphs. ...
... Primula veris is a species characteristic of semi-natural grasslands, many of which have suffered a drastic decrease in area and connectivity over the past century. P. veris has been a model species in several previous studies on heterostyly and habitat fragmentation (Van Rossum et al. 2004, 2006Brys & Jacquemyn 2015;Aavik et al. 2020), as well as on the evolution of heterostyly (Huu et al. 2016(Huu et al. , 2020Potente et al. 2022). Thanks to its published high-quality genome (Nowak et al. 2015;Potente et al. 2022), this species serves as an ideal study system to explore the patterns of genetic diversity in response to fluctuations in morph ratios in recently fragmented grasslands. ...
... Second, we hypothesised that morph ratio bias will have an overall negative impact on the genetic diversity of P. veris. Third, following the previous suggestions that there is no strict intra-morph incompatibility in L-morphs in P. veris (Wedderburn & Richards 1990;Brys & Jacquemyn 2015), we hypothesised that partial intra-morph compatibility of L-morphs would lead to higher inbreeding within L-morphs. We also hypothesised that stricter within-morph incompatibility between S-morphs would lead to higher genetic diversity within S-morphs. ...
Populations of heterostylous plant species are ideally composed of equal frequencies of two (distylous) or three (tristylous) morphologically different floral morphs. Intra‐morph incompatibility helps to avoid inbreeding and to maintain genetic diversity, supporting plant fitness and long‐term viability. Habitat fragmentation can lead to skewed morph ratios and thereby reduce the abundance of compatible mates. This, in turn, can result in a loss of genetic diversity. We tested whether the genetic diversity of heterostylous plants is affected by morph ratio bias using populations of the distylous grassland plant Primula veris in recently fragmented grasslands.
We recorded morph frequencies and population sizes in 30 study populations of P. veris on two Estonian islands characterised by different degrees of habitat fragmentation. Examining variation of thousands of single nucleotide polymorphisms (SNPs) and heterostyly‐specific genetic markers, we quantified overall and morph‐specific genetic diversity and differentiation in these populations.
Morph frequencies deviated more in smaller populations. Skewed morph ratios had a negative effect on the genetic diversity of P. veris in more fragmented grasslands. In the populations of better‐connected grassland systems, genetic differentiation among S‐morphs was higher than among L‐morphs.
Our study shows that deviations from morph balance are stronger in small populations and have a negative impact on the genetic diversity of the distylous plant P. veris . Together with the direct negative effects of habitat loss and decreased population size on the genetic diversity of plants, morph ratio bias may intensify the process of genetic erosion, thus exacerbating the local extinction of heterostylous species.
... The first PC axis was 51.12% correlated to UV red variability, while the blue band was 86.1% correlated and the green band was 76.59% correlated. Stigma height (SH) and the anther height (AH) were separately determined in the field for 60 populations along the range (see study system and sampling) with a 0.01 mm precision digital caliper to evaluate herkogamy based on the guidelines of Brys and Jacquemyn (2015). The potential breakdown of biochemical selfincompatibility systems (Bawa et al., 2011;Dickinson, 1990) was evaluated with manual selfpollination to circumvent potential barriers caused by heteromorphic self-incompatibility. ...
Climate change and the resulting increased drought frequencies pose considerable threats to forest herb populations, particularly where additional environmental challenges jeopardize responses to selection. Specifically, habitat fragmentation may impede climate adaptation through its impact on the distribution of adaptive genetic variation, and cause evolutionary shifts in mating systems. To assess how habitat fragmentation disrupts climate adaptation, we conducted a common garden experiment with Primula elatior offspring originating from 24 populations sampled along a latitudinal gradient with varying climate and landscape characteristics. We then quantified a range of vegetative, regulatory, and reproductive traits under distinct soil moisture regimes to evaluate imprints of local adaptation and phenotypic plasticity. Additionally, we conducted a more extensive field campaign in 60 populations along the same latitudinal gradient to evaluate the potential evolutionary breakdown of reciprocal herkogamy. For large, connected populations, our results demonstrated an evolutionary shift from a drought avoidance strategy in southern populations to a drought tolerance strategy in northern populations. However, habitat fragmentation disrupted climate clines and the adaptive responses to drought stress in key traits related to growth, biomass allocation and water regulation. Additionally, our findings indicate the onset of evolutionary breakdown in reciprocal herkogamy and divergence in other key flower traits. The disruption of climate clines, drought responses, and adaptations in mating systems contributed to a substantially diminished flowering investment across the distribution range, with the most pronounced effects observed in southern fragmented populations. We present novel empirical evidence of how habitat fragmentation disrupts climate adaptation and drought tolerance in a wide range of traits along the range of the forest herb Primula elatior. These findings emphasize the need to account for habitat fragmentation while designing effective conservation strategies in order to preserve and restore resilient meta-populations of forest herbs amidst ongoing global changes.
... Primula officinalis is a small plant, which is usually found in limestone pastures, poor in nutrients, grassland or coastal dunes. It can be also found along forest edges and open forests of mixed oak and beech [1]. Primula officinalis is a perennial plant, with bush appearance and a height of 15-30 cm. ...
The oldest form of treatment, over time, was phytotherapy, which was probably born with human being. Popular medicine has developed on an empirical basis in the context of a magical world where analogy and coincidence have played an important role in choosing remedy plants. Regarding the multiple biological effects of Primula officinalis Hill., the scientific literature highlighted anti-asthmatic, anti-inflammatory and strong antiviral properties. Glycosides contained in this plant have a role in the treatment of kidney and biliary disorders, bronchitis and some gastrointestinal diseases. Primrose is an endangered plant in many Western European countries. In Romania, the plant is found in hills, pastures and alpine meadows up to about 2300-2400 m altitude. Research regarding introduction to culture are ongoing at National Institute of Research and Development for Potato and Sugar Beet Braşov. This paper presents the results obtained regarding the cultivation technology and the establishment of the possibility for introduction into culture. To establish these experiences, the plants were harvested from the spontaneous flora in 2016 and then acclimated to the greenhouses in the Technology Department, Laboratory of medicinal and aromatic plants. In the second experimental year, during the vegetation, observations and measurements were made in dynamics on each experimental variant to highlight the phenological stages regarding the formation of vegetative and generative organs in Primula officinalis (the emergence, the development of the foliar apparatus, the initiation of the floral buttons, the appearance of flowering stems, flowering, capsule and seed formation).
... Heterostyly is considered a classic model for promoting pollen dispersal efficiency and avoiding the harmful influences of inbreeding depression (Barrett, 1992(Barrett, , 2019Brys & Jacquemyn, 2015;Ganders, 1979). However, the breakdown of sexual polymorphism frequently occurs in numerous heterostylous families, giving rise to self-compatible homostyly (H-morph) with stigma and anther at the same level (Brys & Jacquemyn, 2015;Darwin, 1877;Li & Johnston, 2001;Zhong et al., 2019;Zhou et al., 2017). ...
... Heterostyly is considered a classic model for promoting pollen dispersal efficiency and avoiding the harmful influences of inbreeding depression (Barrett, 1992(Barrett, , 2019Brys & Jacquemyn, 2015;Ganders, 1979). However, the breakdown of sexual polymorphism frequently occurs in numerous heterostylous families, giving rise to self-compatible homostyly (H-morph) with stigma and anther at the same level (Brys & Jacquemyn, 2015;Darwin, 1877;Li & Johnston, 2001;Zhong et al., 2019;Zhou et al., 2017). Homostyly is also related to two floral morphs, namely the "long homostyles," with high-level stigma and anthers; or "short homostyles," with low-level stigma and anthers. ...
... The hypothesis of reproductive assurance explains the occurrence of homostyly in heterostylous populations (Darwin, 1876), in which due to the unreliable service of pollinators and the limited number of pollen donors in extreme environments or colonizing episodes, the transition to self-pollination is conducive (Brys & Jacquemyn, 2015;Busch & Delph, 2012;Moeller, 2006;Shao et al., 2019;Yuan et al., 2017;Zhang et al., 2021). Homostyly formation may also follow long-distance dispersal and establishment of polyploid (Barrett et al., 2009;Barrett & Shore, 1987;Naiki, 2012). ...
Evolutionary breakdown from rigorous outbreeding to self-fertilization frequently occurs in angiosperms. Since the pollinators are not necessary, self-compatible populations often reduce investment in floral display characteristics and pollination reward. Primula forbesii is a biennial herb with distribution restricted to southwest China; it was initially a self-incompatible distylous species, but after 20 years of artificial domestication, homostyly appeared. This change in style provides an ideal material to explore the time required for plant mating systems to adapt to new environmental changes and test whether flower attraction has reduced following transitions to selfing. We did a survey in wild populations of P. forbesii where its seeds were originally collected 20 years ago and recorded the floral morph frequencies and morphologies. The floral morphologies, self-incompatibility, floral scent, and pollinator visitation between distyly and homostyly were compared in greenhouse. Floral morph frequencies of wild populations did not change, while the cultivated population was inclined to L-morph and produced homostyly. Evidence from stigma papillae and pollen size supports the hypothesis that the homostyly possibly originated from mutations of large effect genes in distylous linkage region. Transitions to self-compatible homostyly are accompanied by smaller corolla size, lower amounts of terpenoids, especially linalool and higher amounts of fatty acid derivatives. The main pollinators in the greenhouse were short-tongued Apis cerana. However, homostyly had reduced visiting frequency. The mating system of P. forbesii changed rapidly in just about 20 years of domestication, and our findings confirm the hypothesis that the transition to selfing is accompanied by decreased flower attraction.
... However, the reciprocity between floral morphs is never perfect, and deviations from this expected placement are often reported, sometimes affecting disassortative pollen transfer and pollen deposition (Ornelas et al., 2004;Hernández & Ornelas, 2007;Brys & Jacquemyn, 2010;Keller et al., 2014;Deschepper et al., 2018;Jacquemyn et al., 2018;Furtado et al., 2021). Reciprocal herkogamy also reduces the chances of self-interference, because the herkogamy within flowers decreases interference between pollen deposition and removal (Keller et al., 2014;Brys & Jacquemyn, 2015;Li et al., 2018). In addition, distylous species are frequently characterized by a heteromorphic self-incompatibility system that prevents selfing and intra-morph mating (Lloyd & Webb, 1992;Barrett & Shore, 2008). ...
Morphological niche partitioning between related syntopic plants that are distylous (with short- and long-styled morphs) is complex. Owing to differences in the heights of stigmas and anthers, each floral morph must place pollen onto two distinct parts of the body of the pollinator. This led us to hypothesize that such partitioning should be more accurate among distylous syntopic species in comparison to combinations with other related plants that do not co-occur. We tested these assumptions using a set of Palicourea (Rubiaceae) species as a model system. We compared the distribution, flowering phenology, floral measurements and reciprocity of sexual organ heights of two syntopic species (Palicourea rigida and Palicourea coriacea) and one non-syntopic congener (Palicourea marcgravii). The three species overlapped in their distributions and flowering periods. The position of sexual organs was, in most cases, partitioned between syntopic populations, with low overlap in anther and stigma heights. However, we found a higher overlap involving the non-syntopic species, especially between Palicourea rigida and Palicourea marcgravii. Additionally, reciprocity of sexual organs was more accurate in intraspecific inter-morph combinations (i.e. legitimate organ correspondence) in comparison to intraspecific intra-morph, interspecific syntopic and interspecific non-syntopic combinations. The partitioning of morphological traits between syntopic species might facilitate the differential placement of pollen on the body of the pollinator and reduce the chances of interspecific interference.
... Some of its natural sites are endangered as a result of massive deforestation, by cultivating land or by intensive grazing. It can also be found along forest edges and in mixed forests of oak and beech (Brys and Jacquemyn, 2009). ...
This paper aims to study aspects of biology and cultivation technology for introduction into the culture of the species Primula officinalis Hill., medicinal valuable plant both from a phytotherapeutic and economic point of view. The species Primula officinalis Hill. is popularly known as cuckoo's beak, aglic, aglicel or cuckoo's boot The research was performed on plants harvested from spontaneous flora (Rucăr-Bran area). Then the plants were acclimatized in the greenhouses of NIRDSPB Braşov, Technology laboratory. After acclimatizing the material, a rigorous selection was made, choosing the most uniform plants in terms of number of leaves, height and health. The experimental factors were factor A - distance between rows with graduations: 25 cm, 50 cm, 75 cm and factor B - distance between plants in a row with graduations: 10 cm, 25 cm, 50 cm. Our results shown that the variant with a large nutrition space (75/25 cm), with an average number of seven plants grown in a row, has an average of eight stems with flowers on each plant, being clearly superior to the other variants. The production of fresh herba (kg/ha) for the species Primula officinalis L. was influenced by both factors (A and B). By variance analysis regarding the two factors studied on the average number of flowering stems it is found that the number of flowering stems depends, largely, on the nutrition space.
... Therefore, it is generally assumed that the positions of stigmas and anthers are subject to strong selective pressures that maintain the floral polymorphism fixed and stable (Dulberger, 1992;Lloyd and Webb, 1992b). Empirical evidence suggests that substantial intraspecific floral variation occurred in some distylous species because of selection pressure under specific habitats, resulting in profound ecological and evolutionary significance (Richards and Koptur, 1993;Ferrero et al., 2009Ferrero et al., , 2011Sampson and Krebs, 2012;Brys and Jacquemyn, 2015). However, to the best of our knowledge, the patterns of variation of morphological traits unique to the distylous floral syndrome have not yet been explicitly compared between peripheral and central populations, even though such comparisons have potential importance for explaining the ecological and evolutionary role of the heterostyly. ...
... High species diversity in the Primula provides ample opportunities for investigating the variation and maintenance mechanism of a distylous floral syndrome (Ganders, 1979;Richards, 2003). Many studies on the Primula have shown that a small number of floral traits, especially the relative position of reproductive organs, can remarkably affect the pollen transfer and mating patterns, thus having far-reaching ecological and evolutionary implications (e.g., Nishihiro et al., 2000;Keller et al., 2012Keller et al., , 2014Brys and Jacquemyn, 2015;Liu et al., 2015;Deschepper et al., 2018;Jiang et al., 2018). Even in homostylous species, Primula halleri, small amounts of herkogamy variation during anthesis can have large effects on the reproductive strategy (de Vos et al., , 2014. ...
... Highly significant correlations were detected between CTL and the positions of sexual organs in both morphs (Supplementary Table 5), as documented in other distylous Primula species, suggesting that corolla tube elongation plays an important role in the spatial arrangement of sexual organs in the Primula genus (Kálmán et al., 2007;Zhu et al., 2009;Keller et al., 2012;Brys and Jacquemyn, 2015). Interestingly, compared with central populations, marginal populations exhibited longer corolla tubes and higher positioning of stigmas and anthers in both morphs (Figure 3). ...
Outcrossing plant species are more likely to exhibit autonomous selfing in marginal habitats to ensure reproduction under conditions of limited pollinator and/or mate availability. Distyly is a classical paradigm that promotes outcrossing; however, little is known about the variation in floral traits associated with distylous syndrome in marginal populations. In this study, we compared the variation in floral traits including stigma and anther height, corolla tube length, herkogamy, and corolla diameter between the central and peripheral populations of the distylous Primula wannanensis, and assessed the variation of floral traits at early and late florescence stages for each population. To evaluate the potential consequences of the variation in floral traits on the mating system, we investigated seed set in each population under both open-pollinated and pollinator-excluded conditions. The flower size of both short- and long-styled morphs was significantly reduced in late-opening flowers compared with early opening flowers in both central and peripheral populations. Sex-organ reciprocity was perfect in early opening flowers; however, it was largely weakened in the late-opening flowers of peripheral populations compared with central populations. Of these flowers, disproportionate change in stigma height (elongated in S-morph and shortened in L-morph) was the main cause of reduced herkogamy, and seed set was fairly high under pollinator-excluded condition. Our results provide empirical support for the hypothesis on the evolution of delayed autonomous selfing in marginal populations of distylous species. Unsatisfactory pollinator service is likely to have promoted reproductive assurance of distylous plants with largely reduced herkogamy mimicking “homostyles.”
... Variations in floral characteristics in distylous populations are common (e.g. Brys and Jacquemyn, 2015;Coelho and Barbosa, 2003;Consolaro et al., 2009;Faivre and McDade, 2001;Pereira et al., 2006;Rodrigues and Consolaro, 2013;Sá et al., 2016;Sobrevila et al., 1983;Sugawara et al., 2013). Such variations range from differences in the precision of the heights of anthers and stigma in flowers at individual or population levels to the breakdown of distyly with homostylous flowers (stigmas and anthers at the same level) or monomorphy (with all flowers long-or short style). ...
... Variations in the reciprocity of anthers and stigmas affect legitimate pollen transfer between morphs, pollination efficiency, and consequently the reproductive success of populations (Armbruster et al., 2017;Brys and Jacquemyn, 2019;Furtado et al., 2021;Jacquemyn et al., 2018). These variations may be used to identify trends and to foresee selective pressures on distylous groups much earlier than the breakdown or disruption of floral polymorphism, which commonly involve loss of self-incompatibility and transitions to alternative breeding systems (Baker et al., 2000b;Brys et al., 2008bBrys et al., , 2008aBrys and Jacquemyn, 2015;Pérez-Barrales and Arroyo, 2010;Simón-Porcar et al., 2014). However, instead of revealing selective pressures initiating distyly breakdown, or even divergence among distylous populations (Haller et al., 2014), such variation may be intrinsic to distyly systems and benefit reciprocal herkogamy and pollen transfer (Ganguly and Barua, 2021). ...
... We suggest that the correlation among indices is important to maintain the adjustment of distyly in the studied populations. In distylous plants, the reciprocal position of anthers and stigmas is the main characteristic that promotes the disassortative pollination among morphs and limits selfing and sexual interference (Barrett, 2010;Barrett and Shore, 2008;Brys and Jacquemyn, 2015;Keller et al., 2014). The adjustment among floral morphological traits such as anther and stigma organs is a way to optimize pollination and reproduction, and may also be viewed as a phenotypic integration (Armbruster et al., 1999;Murren, 2002;Ordano et al., 2008). ...
Heterostyly is a polymorphism in which populations comprise two (distyly) or three (tristyly) floral morphs with reciprocal positioning of the height of the anthers and stigmas (reciprocal herkogamy). Such reciprocal herkogamy permits precise pollen placement on pollinators’ bodies and pollination success by promoting disassortative pollen transfer between floral morphs. Here, we aimed to understand how the different components of reciprocity relate to and differ from each other in distylous flowers, and whether factors, such as genus, morph-ratio variation, and corolla tube length influence the imprecisions in the sexual organs within populations. We gathered literature and original morphometrics data comprising 98 Palicourea and Psychotria populations from 44 species, the two largest distylous Rubiaceae genera, which differ in some floral features and pollination systems (hummingbirds vs. insects, respectively). We estimated reciprocity using new inaccuracy indices and standardization techniques, which allowed comparisons among a wide array of populations. Our results showed that maladaptive bias (i.e. departure from optimum reciprocity) of low organs was higher than the other decomposed inaccuracies indices tested. In addition, inaccuracy of low organs was higher than those of high organs. We did not find any relation of either genus, morph-ratio variation, or corolla tube length on general inaccuracy measurements. Apparently, pollinator-mediated selection on floral traits, imposed by different pollinators groups, did not differ markedly among the studied distylous Rubiaceae. This is the first study on inaccuracy components for such an ample array of populations and provides insights on the relative importance of morphological traits that optimize the functionality of distyly. We highlight the applicability of using standardized reciprocity indices for cross populational investigations, which may both support previous insights and reveal unknown patterns in distylous plants.
