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Elena Conti - One of the best experts on this subject based on the ideXlab platform.
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Primulaceae phylogeny 265 taxa chronogram
2016Co-Authors: Jurriaan M. De Vos, Rafael O Wuest, Elena ContiAbstract:Contains maximum clade credibility tree with median node heights of 265 Primulaceae taxa, based on a 3 locus cpDNA dataset. Branchlengths in absolute time (MY), estimated using the UCLN clock model in BEAST. Tree is taken from the study of De Vos JM, Hughes C, Schneeweiss GM, Moore BR, Conti E. Heterostyly accelerates diversification via reduced extinction in Darwin’s primroses. Submitted manuscript. TreeBASE reference TB2:S1482
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Binary scoring of Heterostyly, 124 taxa dataset
2016Co-Authors: Jurriaan M. De Vos, Rafael O Wuest, Elena ContiAbstract:Contains scoring (Heterostyly, homostyly) of breeding system for the 124 taxa of the Primula clad
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The draft genome of Primula veris yields insights into the molecular basis of Heterostyly
Genome Biology, 2015Co-Authors: Michael D Nowak, Michael Lenhard, Giancarlo Russo, Ralph Schlapbach, Elena ContiAbstract:Background The flowering plant Primula veris is a common spring blooming perennial that is widely cultivated throughout Europe. This species is an established model system in the study of the genetics, evolution, and ecology of heterostylous floral polymorphisms. Despite the long history of research focused on this and related species, the continued development of this system has been restricted due the absence of genomic and transcriptomic resources. Results We present here a de novo draft genome assembly of P. veris covering 301.8 Mb, or approximately 63% of the estimated 479.22 Mb genome, with an N50 contig size of 9.5 Kb, an N50 scaffold size of 164 Kb, and containing an estimated 19,507 genes. The results of a RADseq bulk segregant analysis allow for the confident identification of four genome scaffolds that are linked to the P. veris S -locus. RNAseq data from both P. veris and the closely related species P. vulgaris allow for the characterization of 113 candidate Heterostyly genes that show significant floral morph-specific differential expression. One candidate gene of particular interest is a duplicated GLOBOSA homolog that may be unique to Primula ( PveGLO2 ), and is completely silenced in L-morph flowers. Conclusions The P. veris genome represents the first genome assembled from a heterostylous species, and thus provides an immensely important resource for future studies focused on the evolution and genetic dissection of Heterostyly. As the first genome assembled from the Primulaceae, the P. veris genome will also facilitate the expanded application of phylogenomic methods in this diverse family and the eudicots as a whole.
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Heterostyly promotes disassortative pollination and reduces sexual interference in darwin s primroses evidence from experimental studies
Functional Ecology, 2014Co-Authors: Barbara Keller, James D. Thomson, Elena ContiAbstract:Summary Different strategies to reduce selfing and promote outcrossing have evolved in hermaphroditic flowers. Heterostyly, a complex floral polymorphism that occurs in at least 27 families of angiosperms, is hypothesized to achieve both goals by optimizing cross-pollination (via disassortative pollen transfer) and restricting gamete wastage to autogamy (via the reduction in sexual interference between male and female organs). In heterostylous flowers, the reciprocal positioning of sexual organs in different morphs and the pollen incompatibility system within flower or between flowers of the same morph are thought to optimize both male and female functions, reducing the conflicts inherent to the occurrence of both sexual organs in the same reproductive unit. Specific elements of the disassortative-pollination and sexual-interference hypotheses have been tested individually before. However, despite the long-standing interest in Heterostyly – ever since Darwin's seminal work on primroses – the predictions derived from these two hypotheses have never been experimentally and systematically examined in the same system. Using distylous primroses (Primula elatior, P. vulgaris), we compare pollen transfer (i) between reciprocal and non-reciprocal flowers; (ii) from anthers onto different parts of the pollinator's body; and (iii) within flower and between flowers of the same morph. We further test whether (iv) anther–stigma distance correlates with self-pollen transfer and whether (v) seed set differs after pollinations with compatible, incompatible and both pollen types. Reciprocal herkogamy promotes differential placement of pollen onto different parts of the pollinator's body, thus effecting transfer of more pollen to reciprocal than to non-reciprocal stigmas and realizing the key predictions of the disassortative-pollination hypothesis. However, short-styled flowers transfer pollen more disassortatively than long-styled flowers in both species, whereas long-styled flowers export more pollen to non-reciprocal than to reciprocal stigmas in P. vulgaris, thus compromising male function in this species. Furthermore, larger distance between sexual organs lowers self- and intra-morph pollination and the pollen incompatibility system decreases seed production after self-pollination, thus diminishing sexual interference. Our results help us understand how the morphological and physiological components of Heterostyly contribute to optimizing pollen transfer and minimizing self- and intra-morph pollination, thus promoting more efficient outcrossing in species with this floral polymorphism.
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Heterostyly accelerates diversification via reduced extinction in primroses
Proceedings of The Royal Society B: Biological Sciences, 2014Co-Authors: Colin E Hughes, Jurriaan M. De Vos, Gerald M Schneeweiss, Brian R Moore, Elena ContiAbstract:The exceptional species diversity of flowering plants, exceeding that of their sister group more than 250-fold, is especially evident in floral innovations, interactions with pollinators and sexual systems. Multiple theories, emphasizing flower–pollinator interactions, genetic effects of mating systems or high evolvability, predict that floral evolution profoundly affects angiosperm diversification. However, consequences for speciation and extinction dynamics remain poorly understood. Here, we investigate trajectories of species diversification focusing on Heterostyly, a remarkable floral syndrome where outcrossing is enforced via cross-compatible floral morphs differing in placement of their respective sexual organs. Heterostyly evolved at least 20 times independently in angiosperms. Using Darwin's model for Heterostyly, the primrose family, we show that Heterostyly accelerates species diversification via decreasing extinction rates rather than increasing speciation rates, probably owing to avoidance of the negative genetic effects of selfing. However, impact of Heterostyly appears to differ over short and long evolutionary time-scales: the accelerating effect of Heterostyly on lineage diversification is manifest only over long evolutionary time-scales, whereas recent losses of Heterostyly may prompt ephemeral bursts of speciation. Our results suggest that temporal or clade-specific conditions may ultimately determine the net effects of specific traits on patterns of species diversification.
Victoria Ferrero - One of the best experts on this subject based on the ideXlab platform.
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delving into the loss of Heterostyly in rubiaceae is there a similar trend in tropical and non tropical climate zones
Perspectives in Plant Ecology Evolution and Systematics, 2012Co-Authors: Victoria Ferrero, Danny Rojas, Angel Vale, Luis NavarroAbstract:Abstract Heterostyly is a specialised floral polymorphism consisting in the presence within the populations of two or three morphs that differ reciprocally in sexual organ position. The function of Heterostyly has usually been related to the promotion of cross-pollination fostered by the perfect adjustment between pollinators and flower morphologies. Rubiaceae is the largest family in which this polymorphism is present. Nevertheless, just a few studies on the evolution of Heterostyly have been carried out in this family. To investigate the appearance and maintenance of Heterostyly we select the subfamily Rubioideae as study group. Rubioideae occur in both tropical and temperate regions and since the tropics are known to contain higher biodiversity and greater ecological specialisation than temperate areas, we characterise the taxa as tropical, non-tropical or mixed distributed (when they are present in tropical and non-tropical areas) and explored whether the Heterostyly, as a specialised system, is more stable in tropical regions than in other climates of the world. Ancestral nodes in Rubioideae present Heterostyly, which also is maintained along most evolutionary lineages of this group. Although we do not find a significant correlation between the presence of Heterostyly and the climate zones along the whole subfamily, our results show that two of the main clades in the Spermacoceae alliance where Heterostyly is lost are distributed in non-tropical areas or, at least, they are not restricted to tropical distributions. These results partially support the hypothesis that plant lineages when exposed to different pollination scenarios may evolve towards divergent pollination systems and different degrees of specialisation. However, a more detailed analysis at the species level is suggested for future studies.
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unusual Heterostyly style dimorphism and self incompatibility are not tightly associated in lithodora and glandora boraginaceae
Annals of Botany, 2012Co-Authors: Victoria Ferrero, Juan Arroyo, Silvia Castro, Luis NavarroAbstract:Background and Aims Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining Heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system.
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reciprocal style polymorphisms are not easily categorised the case of Heterostyly in lithodora and glandora boraginaceae
Plant Biology, 2011Co-Authors: Victoria Ferrero, Juan Arroyo, I Chapela, Luis NavarroAbstract:Interest in reciprocal floral polymorphisms, such as Heterostyly, has increased in recent decades because they can be used as suitable model systems to study mechanisms of outbreeding and disassortative mating in plants. Heterostylous plants are characterised by the presence of discrete morphs that differ in sex organ position and in some other ancillary traits. As regards sex organ deployment, different types of polymorphisms have been described, depending on number and type of discrete classes present in populations and degree of reciprocity between them. However, a clear-cut characterisation of stylar polymorphisms does not appear to be the best approach when there is great variability among populations because of continuous variation of some of traits examined. A recent study in Lithodora sensu lato (recently split into two separate genera, Lithodora and Glandora) showed a wide variation in sex organ position across species in the genus, which warrants precise population analysis of stylar polymorphism and its reciprocity. We provide a detailed morphometric analysis of flower sexual traits and include those considered to be ancillary characters. We report a wide variation in these traits in populations of Lithodora s.l. and highlight the subjectivity of the former characterisation of style polymorphism based on visual inspection. Ancillary traits appear repeatedly in Lithodora and Glandora, particularly in the latter. The appearance of these traits seems to be related to greater reciprocity between sexual whorls in Glandora, with the exception of G. prostrata. These results agree with evolutionary steps proposed in the build-up of Heterostyly according to some evolutionary models. We also examined variation in polymorphisms in light of current models for evolution of Heterostyly, and, more specifically, we sought to verify the prediction that flower traits as a whole (i.e., flower integration) respond to selective pressure to assure the exact location of pollen on the pollinator body. Most reciprocal populations and species, where between-morph pollen transfer is expected to be higher, would show greater integration. Our results confirm this hypothesis.
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part of a special issue on plant mating systems unusual Heterostyly style dimorphism and self incompatibility are not tightly associated in lithodora and glandora boraginaceae
2011Co-Authors: Victoria Ferrero, Silvia Castro, J Arroyo, Luis NavarroAbstract:†Background and Aims Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining Heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system. †Methods We examine the incompatibility systems in species with different stylar polymorphisms from the genera Lithodora and Glandora (Boraginaceae). We then test whether evolution towards reciprocal herkogamy is associated with the acquisition of incompatibility. To this end, a phylogeny of these genera and related species is reconstructed and the morphological and reproductive changes that occurred during the course of evolution are assessed. †Key Results Both self-compatibility and self-incompatibility are found within the studied genera, along with different degrees of intra-morph compatibility. We report for the first time extensive variability among members of the genus Glandora and related species in terms of the presence or absence of intraspecies polymorphism and heteromorphic incompatibility. Overall, our results do not support a tight link between floral polymorphism and incompatibility systems. †Conclusions The independent evolution of stylar polymorphism and incompatibility appears to have occurred in this group of plants. This refutes the canonical view that there is strong linkage between these reproductive traits.
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Heterostyly and pollinators in plumbago auriculata plumbaginaceae
South African Journal of Botany, 2009Co-Authors: Victoria Ferrero, C De Vega, G I Stafford, J Van Staden, Steven D JohnsonAbstract:Plants with hermaphrodite flowers risk conflict between male and female sexual function due to close proximity of sexual organs. Heterostyly, a genetic floral polymorphism characterized mainly by reciprocal herkogamy, may reduce this sexual conflict by increasing the precision of pollen transfer between morphs. This sexual organ reciprocity is often associated with various ancillary characters and a heteromorphic incompatibility system. Here we describe the morphometrics associated with Heterostyly and ancillary characters in Plumbago auriculata. Using controlled pollination experiments, we show that this species has a heteromorphic incompatibility system. We also document the fauna of long-proboscid fly and butterfly pollinators in a P. auriculata population in KwaZulu-Natal, South Africa. © 2009 SAAB. Published by Elsevier B.V. All rights reserved.
Luis Navarro - One of the best experts on this subject based on the ideXlab platform.
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delving into the loss of Heterostyly in rubiaceae is there a similar trend in tropical and non tropical climate zones
Perspectives in Plant Ecology Evolution and Systematics, 2012Co-Authors: Victoria Ferrero, Danny Rojas, Angel Vale, Luis NavarroAbstract:Abstract Heterostyly is a specialised floral polymorphism consisting in the presence within the populations of two or three morphs that differ reciprocally in sexual organ position. The function of Heterostyly has usually been related to the promotion of cross-pollination fostered by the perfect adjustment between pollinators and flower morphologies. Rubiaceae is the largest family in which this polymorphism is present. Nevertheless, just a few studies on the evolution of Heterostyly have been carried out in this family. To investigate the appearance and maintenance of Heterostyly we select the subfamily Rubioideae as study group. Rubioideae occur in both tropical and temperate regions and since the tropics are known to contain higher biodiversity and greater ecological specialisation than temperate areas, we characterise the taxa as tropical, non-tropical or mixed distributed (when they are present in tropical and non-tropical areas) and explored whether the Heterostyly, as a specialised system, is more stable in tropical regions than in other climates of the world. Ancestral nodes in Rubioideae present Heterostyly, which also is maintained along most evolutionary lineages of this group. Although we do not find a significant correlation between the presence of Heterostyly and the climate zones along the whole subfamily, our results show that two of the main clades in the Spermacoceae alliance where Heterostyly is lost are distributed in non-tropical areas or, at least, they are not restricted to tropical distributions. These results partially support the hypothesis that plant lineages when exposed to different pollination scenarios may evolve towards divergent pollination systems and different degrees of specialisation. However, a more detailed analysis at the species level is suggested for future studies.
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unusual Heterostyly style dimorphism and self incompatibility are not tightly associated in lithodora and glandora boraginaceae
Annals of Botany, 2012Co-Authors: Victoria Ferrero, Juan Arroyo, Silvia Castro, Luis NavarroAbstract:Background and Aims Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining Heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system.
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reciprocal style polymorphisms are not easily categorised the case of Heterostyly in lithodora and glandora boraginaceae
Plant Biology, 2011Co-Authors: Victoria Ferrero, Juan Arroyo, I Chapela, Luis NavarroAbstract:Interest in reciprocal floral polymorphisms, such as Heterostyly, has increased in recent decades because they can be used as suitable model systems to study mechanisms of outbreeding and disassortative mating in plants. Heterostylous plants are characterised by the presence of discrete morphs that differ in sex organ position and in some other ancillary traits. As regards sex organ deployment, different types of polymorphisms have been described, depending on number and type of discrete classes present in populations and degree of reciprocity between them. However, a clear-cut characterisation of stylar polymorphisms does not appear to be the best approach when there is great variability among populations because of continuous variation of some of traits examined. A recent study in Lithodora sensu lato (recently split into two separate genera, Lithodora and Glandora) showed a wide variation in sex organ position across species in the genus, which warrants precise population analysis of stylar polymorphism and its reciprocity. We provide a detailed morphometric analysis of flower sexual traits and include those considered to be ancillary characters. We report a wide variation in these traits in populations of Lithodora s.l. and highlight the subjectivity of the former characterisation of style polymorphism based on visual inspection. Ancillary traits appear repeatedly in Lithodora and Glandora, particularly in the latter. The appearance of these traits seems to be related to greater reciprocity between sexual whorls in Glandora, with the exception of G. prostrata. These results agree with evolutionary steps proposed in the build-up of Heterostyly according to some evolutionary models. We also examined variation in polymorphisms in light of current models for evolution of Heterostyly, and, more specifically, we sought to verify the prediction that flower traits as a whole (i.e., flower integration) respond to selective pressure to assure the exact location of pollen on the pollinator body. Most reciprocal populations and species, where between-morph pollen transfer is expected to be higher, would show greater integration. Our results confirm this hypothesis.
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part of a special issue on plant mating systems unusual Heterostyly style dimorphism and self incompatibility are not tightly associated in lithodora and glandora boraginaceae
2011Co-Authors: Victoria Ferrero, Silvia Castro, J Arroyo, Luis NavarroAbstract:†Background and Aims Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining Heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system. †Methods We examine the incompatibility systems in species with different stylar polymorphisms from the genera Lithodora and Glandora (Boraginaceae). We then test whether evolution towards reciprocal herkogamy is associated with the acquisition of incompatibility. To this end, a phylogeny of these genera and related species is reconstructed and the morphological and reproductive changes that occurred during the course of evolution are assessed. †Key Results Both self-compatibility and self-incompatibility are found within the studied genera, along with different degrees of intra-morph compatibility. We report for the first time extensive variability among members of the genus Glandora and related species in terms of the presence or absence of intraspecies polymorphism and heteromorphic incompatibility. Overall, our results do not support a tight link between floral polymorphism and incompatibility systems. †Conclusions The independent evolution of stylar polymorphism and incompatibility appears to have occurred in this group of plants. This refutes the canonical view that there is strong linkage between these reproductive traits.
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evolutionary transitions of style polymorphisms in lithodora boraginaceae
Perspectives in Plant Ecology Evolution and Systematics, 2009Co-Authors: Victoria Ferrero, Juan Arroyo, Pablo Vargas, John D Thompson, Luis NavarroAbstract:Floral polymorphisms provide suitable model systems to test hypotheses concerning the evolution of outbreeding in plants. Although Heterostyly has evolved in more than 28 angiosperm families, the evolutionary pathways involving related floral conditions have not yet been fully resolved. In this study, the reconstruction of ancestral states of style polymorphism, with both parsimony and maximum likelihood methods, was carried out for Boraginaceae species in the tribe Lithospermeae, particularly in the genus Lithodora sensu lato, where species present a wide variety of stylar conditions. Detailed floral morphometric analysis confirm different types of style polymorphism within Lithodora. They also reveal a novel style polymorphism (relaxed style dimorphism) in which anther height is variable within a flower (each anther being at a different height), which contrasts to regular distyly (constant anther height within flowers). Style monomorphism is likely to be the ancestral condition in Lithospermeae where the evolution of distyly has occurred several times. Style dimorphism is probably ancestral to distyly, as predicted by certain evolutionary models proposed for Heterostyly. However, a reversion from distyly to style dimorphism also appears to occur in this tribe. This is the first documented occurrence of such a transition. This secondary style dimorphism is of the relaxed type and demonstrates the labile nature of floral polymorphisms, which are not necessarily a transition towards Heterostyly. We discuss the selective forces involved in the evolution, maintainance and loss of style polymorphisms.
Juan Arroyo - One of the best experts on this subject based on the ideXlab platform.
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deconstructing Heterostyly the evolutionary role of incompatibility system pollinators and floral architecture
Evolution, 2013Co-Authors: Rocio Santosgally, Alejandro Gonzalezvoyer, Juan ArroyoAbstract:Darwin's early work on Heterostyly and related style polymorphisms (the presence of two or three style morphs within a population) generated much interest to understand how precise interactions between ecological and genetic mechanisms influence the evolution of floral diversity. Here we tested three key hypotheses proposed to explain the evolution of Heterostyly: (i) the presence of self-incompatibility; (ii) the role of pollinators in promoting dissasortative mating; and (iii) floral architecture, which restricts pollinators' movements and ensures more exact pollen deposition on their bodies. We combined data from experiments, field observations, and published studies to test whether evolution of style polymorphism in Narcissus is driven by the incompatibility system, pollinator guilds, or floral architecture, within a phylogenetic framework. Neither differences in pollinator environment nor the presence of genetic self-incompatibility were correlated with presence of style polymorphism. However, our results indicate that the evolution of style polymorphism was driven by the presence of a narrow and long floral tube.
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unusual Heterostyly style dimorphism and self incompatibility are not tightly associated in lithodora and glandora boraginaceae
Annals of Botany, 2012Co-Authors: Victoria Ferrero, Juan Arroyo, Silvia Castro, Luis NavarroAbstract:Background and Aims Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining Heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system.
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reciprocal style polymorphisms are not easily categorised the case of Heterostyly in lithodora and glandora boraginaceae
Plant Biology, 2011Co-Authors: Victoria Ferrero, Juan Arroyo, I Chapela, Luis NavarroAbstract:Interest in reciprocal floral polymorphisms, such as Heterostyly, has increased in recent decades because they can be used as suitable model systems to study mechanisms of outbreeding and disassortative mating in plants. Heterostylous plants are characterised by the presence of discrete morphs that differ in sex organ position and in some other ancillary traits. As regards sex organ deployment, different types of polymorphisms have been described, depending on number and type of discrete classes present in populations and degree of reciprocity between them. However, a clear-cut characterisation of stylar polymorphisms does not appear to be the best approach when there is great variability among populations because of continuous variation of some of traits examined. A recent study in Lithodora sensu lato (recently split into two separate genera, Lithodora and Glandora) showed a wide variation in sex organ position across species in the genus, which warrants precise population analysis of stylar polymorphism and its reciprocity. We provide a detailed morphometric analysis of flower sexual traits and include those considered to be ancillary characters. We report a wide variation in these traits in populations of Lithodora s.l. and highlight the subjectivity of the former characterisation of style polymorphism based on visual inspection. Ancillary traits appear repeatedly in Lithodora and Glandora, particularly in the latter. The appearance of these traits seems to be related to greater reciprocity between sexual whorls in Glandora, with the exception of G. prostrata. These results agree with evolutionary steps proposed in the build-up of Heterostyly according to some evolutionary models. We also examined variation in polymorphisms in light of current models for evolution of Heterostyly, and, more specifically, we sought to verify the prediction that flower traits as a whole (i.e., flower integration) respond to selective pressure to assure the exact location of pollen on the pollinator body. Most reciprocal populations and species, where between-morph pollen transfer is expected to be higher, would show greater integration. Our results confirm this hypothesis.
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evolutionary transitions of style polymorphisms in lithodora boraginaceae
Perspectives in Plant Ecology Evolution and Systematics, 2009Co-Authors: Victoria Ferrero, Juan Arroyo, Pablo Vargas, John D Thompson, Luis NavarroAbstract:Floral polymorphisms provide suitable model systems to test hypotheses concerning the evolution of outbreeding in plants. Although Heterostyly has evolved in more than 28 angiosperm families, the evolutionary pathways involving related floral conditions have not yet been fully resolved. In this study, the reconstruction of ancestral states of style polymorphism, with both parsimony and maximum likelihood methods, was carried out for Boraginaceae species in the tribe Lithospermeae, particularly in the genus Lithodora sensu lato, where species present a wide variety of stylar conditions. Detailed floral morphometric analysis confirm different types of style polymorphism within Lithodora. They also reveal a novel style polymorphism (relaxed style dimorphism) in which anther height is variable within a flower (each anther being at a different height), which contrasts to regular distyly (constant anther height within flowers). Style monomorphism is likely to be the ancestral condition in Lithospermeae where the evolution of distyly has occurred several times. Style dimorphism is probably ancestral to distyly, as predicted by certain evolutionary models proposed for Heterostyly. However, a reversion from distyly to style dimorphism also appears to occur in this tribe. This is the first documented occurrence of such a transition. This secondary style dimorphism is of the relaxed type and demonstrates the labile nature of floral polymorphisms, which are not necessarily a transition towards Heterostyly. We discuss the selective forces involved in the evolution, maintainance and loss of style polymorphisms.
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three dimensional reciprocity of floral morphs in wild flax linum suffruticosum a new twist on Heterostyly
New Phytologist, 2006Co-Authors: Scott W Armbruster, Rocio Perezbarrales, Juan Arroyo, Mary E Edwards, Pablo VargasAbstract:Here, we studied the floral morphology and pollination of the distylous plant Linum suffruticosum (Linaceae) in southern Spain. We observed a previously unreported form of distyly that involved twisting and bending of styles and stamens during floral development to achieve three-dimensional reciprocity of anthers and stigmas in the long-styled (pin) and short-styled (thrum) morphs. This developmental pattern causes pin pollen to be placed on the underside of pollinating Usia flies (Bombyliidae), and thrum pollen to be placed on the top of the thorax and abdomen. The pin stigmas contact the flies on the dorsum, apparently picking up predominantly thrum pollen, and the thrum stigmas contact the flies on the ventral surface, apparently picking up predominantly pin pollen. This form of Heterostyly would appear on morphological grounds to be far more efficient in dispersing pollen between compatible morphs than the typical pin-thrum system. If so, this plant fits Darwin's prediction of efficient pollen flow between heterostylous morphs more closely than anything Darwin himself reported. Molecular phylogenetic analyses indicate that this form of Heterostyly evolved in a lineage that already had typical Heterostyly. The analyses also indicate that there have been several independent origins of Heterostyly in Linum and at least one reversal to stylar monomorphism.
Spencer C. H. Barrett - One of the best experts on this subject based on the ideXlab platform.
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the genomic selfing syndrome accompanies the evolutionary breakdown of Heterostyly
Molecular Biology and Evolution, 2021Co-Authors: Xinjia Wang, Spencer C. H. Barrett, Hong Wang, Li Zhong, Wei ZhouAbstract:The evolutionary transition from outcrossing to selfing can have important genomic consequences. Decreased effective population size and the reduced efficacy of selection are predicted to play an important role in the molecular evolution of the genomes of selfing species. We investigated evidence for molecular signatures of the genomic selfing syndrome using 66 species of Primula including distylous (outcrossing) and derived homostylous (selfing) taxa. We complemented our comparative analysis with a microevolutionary study of P. chungensis, which is polymorphic for mating system and consists of both distylous and homostylous populations. We generated chloroplast and nuclear genomic data sets for distylous, homostylous, and distylous-homostylous species and identified patterns of nonsynonymous to synonymous divergence (dN/dS) and polymorphism (πN/πS) in species or lineages with contrasting mating systems. Our analysis of coding sequence divergence and polymorphism detected strongly reduced genetic diversity and heterozygosity, decreased efficacy of purifying selection, purging of large-effect deleterious mutations, and lower rates of adaptive evolution in samples from homostylous compared with distylous populations, consistent with theoretical expectations of the genomic selfing syndrome. Our results demonstrate that self-fertilization is a major driver of molecular evolutionary processes with genomic signatures of selfing evident in both old and relatively young homostylous populations.
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a most complex marriage arrangement recent advances on Heterostyly and unresolved questions
New Phytologist, 2019Co-Authors: Spencer C. H. BarrettAbstract:Heterostylous genetic polymorphisms provide paradigmatic systems for investigating adaptation and natural selection. Populations are usually comprised of two (distyly) or three (tristyly) mating types, maintained by negative frequency-dependent selection resulting from disassortative mating. Theory predicts this mating system should result in equal style-morph ratios (isoplethy) at equilibrium. Here, I review recent advances on Heterostyly, focusing on examples challenging stereotypical depictions of the polymorphism and unresolved questions. Comparative analyses indicate multiple origins of Heterostyly, often within lineages. Ecological studies demonstrate that structural components of Heterostyly are adaptations improving the proficiency of animal-mediated cross-pollination and reducing pollen wastage. Both neutral and selective processes cause deviations from isoplethy in heterostylous populations, and, under some ecological and demographic conditions, cause breakdown of the polymorphism, resulting in either the evolution of autogamy and mixed mating, or transitions to alternative outcrossing systems, including dioecy. Earlier ideas on the genetic architecture of the S-locus supergene governing distyly have recently been overturned by discovery that the dominant S-haplotype is a hemizygous region absent from the s-haplotype. Ecological, phylogenetic and molecular genetic data have validated some features of theoretical models on the selection of the polymorphism. Although Heterostyly is the best-understood floral polymorphism in angiosperms, many unanswered questions remain.
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phylogeographic insights on the evolutionary breakdown of Heterostyly
New Phytologist, 2017Co-Authors: Wei Zhou, Spencer C. H. Barrett, Xinjia Wang, Hong WangAbstract:The breakdown of Heterostyly to homostyly is a classic system for the investigation of evolutionary transitions from outcrossing to selfing. Loss of sexual polymorphism is characterized by changes to population morph structure and floral morphology. Here, we used molecular phylogeography to investigate the geographical context for the breakdown process in Primula chungensis, a species with distylous and homostylous populations. We genotyped plants from 20 populations throughout the entire range in south-west China using the chloroplast intergenic spacer (trnL-trnF), nuclear internal transcribed spacer (ITS) and 10 nuclear microsatellite loci, and determined the genetic relationships among populations and the variation in floral traits associated with homostyle evolution. The marker data identified two multi-population lineages (Tibet and Sichuan) and one single-population lineage (Yunnan), a pattern consistent with at least two independent origins of homostyly. Evidence from flower and pollen size variation is consistent with the hypothesis that transitions to selfing have arisen by the same genetic mechanism involving recombination and/or mutation at the distyly linkage group. Nevertheless, flowers of homostylous lineages have followed divergent evolutionary trajectories following their origin, resulting in populations with both approach and reverse herkogamy. Our study illustrates a rare example of the near-complete replacement of sexual polymorphism by floral monomorphism in a heterostylous species.
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Heterostyly in the lamiaceae the case of salvia brandegeei
Plant Systematics and Evolution, 2000Co-Authors: Spencer C. H. Barrett, D H Wilken, W W ColeAbstract:Heterostyly rarely occurs in families with strongly zygomorphic flowers. For this reason Darwin (1877) doubted whether Heterostyly would occur in the Lamiaceae and recent reviews have not reported the floral polymorphism in this family. Here we describe distyly in a rare species ofSalvia restricted to bluffs and seaward canyons on Santa Rosa Island (Santa Barbara Co., California) and northwestern Baja California (Mexico).Salvia brandegeei is morphologically distylous with populations composed of equal frequencies of long-and short-styled morphs differing reciprocally in stigma and anther position. Controlled hand pollinations demonstrated no significant differences in the seed set of self, intramorph or intermorph pollinations. Unlike most heterostylous species investigated,S. brandegeei does not possess diallelic incompatibility or ancillary polymorphisms of pollen and stigmas. We propose that the evolution of distyly inS. brandegeei may have been associated with an ecological shift to a new environment in which protandry failed to prevent increased levels of geitonogamy. Heterostyly was then selected because it increased the proficiency of cross-pollination. The origin of distyly in self-compatibleS. brandegeei is consistent with Lloyd and Webb's theoretical model for the evolution of distyly.
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stylar polymorphisms and the evolution of Heterostyly in narcissus amaryllidaceae
1996Co-Authors: Spencer C. H. Barrett, David G Lloyd, Juan ArroyoAbstract:In outcrossing hermaphrodite plants, the separate functions of pollen dispersal and pollen receipt may interfere with one another so that fitness as a paternal or maternal parent is compromised (van der Pijl, 1978; Bawa and Opler, 1975; Lloyd and Yates, 1982; Lloyd and Webb, 1986; Webb and Lloyd, 1986; Bertin and Newman, 1993; Harder and Barrett, 1995). This is particularly likely in flowers in which the sex organs are close together and mature at the same time. Interference can potentially take several forms, including the obstruction by pistils of efficient pollen dispatch by pollinators, stamens restricting access by pollinators to stigmas, thus reducing pollen deposition, and the deleterious effects of self-pollination on maternal function due to stigmatic, stylar, or ovular clogging. Although there is some experimental evidence for self-pollen interference (Shore and Barrett, 1984; Barrett and Glover, 1985; Bertin and Sullivan, 1988; Palmer et al., 1989; Waser and Price, 1991; Scribailo and Barrett, 1994), the other two forms of pollen-pistil interference have seldom been investigated (see, however, Barrett and Glover, 1985; Kohn and Barrett, 1992a).