Shifts In Pollination Systems Research Articles

Tracking temporal shifts in area, biomes, and pollinators in the radiation of Salvia (sages) across continents: leveraging anchored hybrid enrichment and targeted sequence data.

Premise of the StudyA key question in evolutionary biology is why some clades are more successful by being widespread geographically, biome diverse, or species‐rich. To extend understanding of how shifts in area, biomes, and pollinators impact diversification in plants, we examined the relationships of these shifts to diversification across the mega‐genus Salvia.MethodsA chronogram was developed from a supermatrix of anchored hybrid enrichment genomic data and targeted sequence data for over 500 of the nearly 1000 Salvia species. Ancestral areas and biomes were reconstructed using BioGeoBEARS. Pollinator guilds were scored, ancestral pollinators determined, shifts in pollinator guilds identified, and rates of pollinator switches compared.Key ResultsA well‐resolved phylogenetic backbone of Salvia and updated subgeneric designations are presented. Salvia originated in Southwest Asia in the Oligocene and subsequently dispersed worldwide. Biome shifts are frequent from a likely ancestral lineage utilizing broadleaf and/or coniferous forests and/or arid shrublands. None of the four species diversification shifts are correlated to shifts in biomes. Shifts in pollination system are not correlated to species diversification shifts, except for one hummingbird shift that precedes a major shift in diversification near the crown of New World subgen. Calosphace. Multiple reversals back to bee pollination occurred within this hummingbird clade.Conclusions Salvia diversified extensively in different continents, biomes, and with both bee and bird pollinators. The lack of tight correlation of area, biome, and most pollinator shifts to the four documented species diversification shifts points to other important drivers of speciation in Salvia.

Ancestral remnants or peripheral segregates? Phylogenetic relationships of two narrowly endemic Euphrasia species (Orobanchaceae) from the eastern European Alps.

Endemism in mountain ranges is considered to be the result of a number of factors, including restriction to refugia during Pleistocene climate fluctuations. However, isolation in glacial refugia cannot explain the origin of narrowly endemic taxa restricted to formerly heavily glaciated areas. Here, we investigate the phylogeny of two narrowly endemic species, Euphrasia inopinata and E. sinuata (Orobanchaceae), found exclusively in formerly heavily glaciated areas of the eastern European Alps. As both species are diploid and very similar to the widespread (allo)polyploid E. minima, we test whether the restricted distributions of E. inopinata and E. sinuata are relictual, i.e. the two species are ancestral diploid remnants of a polyploid complex, or whether they are derived, i.e. the two species are peripheral segregates of a more widespread diploid. Based on internal transcribed spacer (ITS) sequence and amplified fragment length polymorphism (AFLP) fingerprint data it is shown that E. inopinata and E. sinuata, whose diploid ploidy level is confirmed for all analysed individuals via flow cytometry, are phylogenetically closely related to diploid E. alpina s. l. (series Alpinae) instead of E. minima (series Parviflorae). In addition, there is no evidence that these two diploid species participated in the formation of allotetraploid E. minima. Thus, E. inopinata and E. sinuata are interpreted as peripheral segregates of the widespread E. alpina s. l. Shifts in pollination system from allogamy in E. alpina s. l. to autogamy in E. inopinata and E. sinuata, genetic drift in small populations and geographic isolation at the periphery of the range of E. alpina s. str. probably contributed to the morphological and ecological differentiation of E. inopinata and E. sinuata.

The diversity and evolution of pollination systems in large plant clades: Apocynaceae as a case study.

Background and AimsLarge clades of angiosperms are often characterized by diverse interactions with pollinators, but how these pollination systems are structured phylogenetically and biogeographically is still uncertain for most families. Apocynaceae is a clade of >5300 species with a worldwide distribution. A database representing >10 % of species in the family was used to explore the diversity of pollinators and evolutionary shifts in pollination systems across major clades and regions.MethodsThe database was compiled from published and unpublished reports. Plants were categorized into broad pollination systems and then subdivided to include bimodal systems. These were mapped against the five major divisions of the family, and against the smaller clades. Finally, pollination systems were mapped onto a phylogenetic reconstruction that included those species for which sequence data are available, and transition rates between pollination systems were calculated.Key ResultsMost Apocynaceae are insect pollinated with few records of bird pollination. Almost three-quarters of species are pollinated by a single higher taxon (e.g. flies or moths); 7 % have bimodal pollination systems, whilst the remaining approx. 20 % are insect generalists. The less phenotypically specialized flowers of the Rauvolfioids are pollinated by a more restricted set of pollinators than are more complex flowers within the Apocynoids + Periplocoideae + Secamonoideae + Asclepiadoideae (APSA) clade. Certain combinations of bimodal pollination systems are more common than others. Some pollination systems are missing from particular regions, whilst others are over-represented.ConclusionsWithin Apocynaceae, interactions with pollinators are highly structured both phylogenetically and biogeographically. Variation in transition rates between pollination systems suggest constraints on their evolution, whereas regional differences point to environmental effects such as filtering of certain pollinators from habitats. This is the most extensive analysis of its type so far attempted and gives important insights into the diversity and evolution of pollination systems in large clades.

Convergent evolution of floral shape tied to pollinator shifts in Iochrominae (Solanaceae).

Flower form is one of many floral features thought to be shaped by pollinator-mediated selection. Although the drivers of variation in flower shape have often been examined in microevolutionary studies, relatively few have tested the relationship between shape evolution and shifts in pollination system across clades. In the present study, we use morphometric approaches to quantify shape variation across the Andean clade Iochrominae and estimate the relationship between changes in shape and shifts in pollination system using phylogenetic comparative methods. We infer multiple shifts from an ancestral state of narrow, tubular flowers toward open, bowl-shaped, or campanulate flowers as well as one reversal to the tubular form. These transitions in flower shape are significantly correlated with changes in pollination system. Specifically, tubular forms tend to be hummingbird-pollinated and the open forms tend to be insect-pollinated, a pattern consistent with experimental work as well as classical floral syndromes. Nonetheless, our study provides one of the few empirical demonstrations of the relationship between flower shape and pollination system at a macroevolutionary scale.

Reproductive biology and nectar secretion dynamics of Penstemon gentianoides (Plantaginaceae): a perennial herb with a mixed pollination system?

BackgroundIn many plant species, pollination syndromes predict the most effective pollinator. However, other floral visitors may also offer effective pollination services and promote mixed pollination systems. Several species of the species-rich Penstemon (Plantaginaceae) exhibit a suite of floral traits that suggest adaptation for pollination by both hymenopterans and hummingbirds. Transitions from the ancestral hymenopteran pollination syndrome to more derived hummingbird pollination syndrome may be promoted if the quantity or quality of visits by hummingbirds is increased and if the ancestral pollinator group performs less efficiently. The quantification of such shifts in pollination systems in the group is still limited. We aimed to investigate floral traits linked to this pollination syndrome in Penstemon gentianoides with flowers visited by bumblebees and hummingbirds.MethodsWe investigated the floral biology, pollinator assemblages, breeding system and nectar production patterns ofP. gentianoides inhabiting a temperate montane forest in central Mexico. Pollination experiments were also conducted to assess the pollinator effectiveness of bumblebees and hummingbirds.ResultsP. gentianoides flowers are protandrous, with 8-d male phase (staminate) flowers, followed by the ∼1–7 d female phase (pistillate phase). Flowers display traits associated with hymenopteran pollination, including purple flowers abruptly ampliate-ventricose to a broad throat with anthers and stigmas included, and long lifespans. However, the nectar available in the morning hours was abundant and dilute, traits linked to flowers with a hummingbird pollination syndrome. Two hummingbird species made most of the visits to flowers, Selasphorus platycercus (30.3% of all visits), followed by Archilochus colubris (11.3%). Bumblebees (Bombus ephippiatus, B. huntii and B. weisi) accounted for 51.8% of all recorded visits, but their foraging activity was restricted to the warmer hours. Hummingbirds made more foraging bouts and visited more flowers than hymenopteran species. Flowers experimentally pollinated by B. ephippiatus produced significantly more fruits than those pollinated by S. platycercus. However, there was no statistical difference in the number of seeds produced per fruit when a bumblebee or a hummingbird was the pollinator.ConclusionsWe have shown that bumblebees and hummingbirds visit and pollinate P. gentianoides flowers. Despite floral traits resembling the hymenoptera pollination syndrome, flowers of P. gentianoides offer characteristic nectar rewards to flowers with a hummingbird pollination syndrome. Although pollination efficiency is higher among flowers visited by hymenoptera, the noteworthy percentage of fruit production and number of seeds per fruit derived from hummingbird pollination highlights the importance of hummingbirds as a functional group of pollinators that might have potential evolutionary consequences to the plants.

Pollinator-driven ecological speciation in plants: new evidence and future perspectives.

The hypothesis that pollinators have been important drivers of angiosperm diversity dates back to Darwin, and remains an important research topic today. Mounting evidence indicates that pollinators have the potential to drive diversification at several different stages of the evolutionary process. Microevolutionary studies have provided evidence for pollinator-mediated floral adaptation, while macroevolutionary evidence supports a general pattern of pollinator-driven diversification of angiosperms. However, the overarching issue of whether, and how, shifts in pollination system drive plant speciation represents a critical gap in knowledge. Bridging this gap is crucial to fully understand whether pollinator-driven microevolution accounts for the observed macroevolutionary patterns. Testable predictions about pollinator-driven speciation can be derived from the theory of ecological speciation, according to which adaptation (microevolution) and speciation (macroevolution) are directly linked. This theory is a particularly suitable framework for evaluating evidence for the processes underlying shifts in pollination systems and their potential consequences for the evolution of reproductive isolation and speciation. This Viewpoint paper focuses on evidence for the four components of ecological speciation in the context of plant-pollinator interactions, namely (1) the role of pollinators as selective agents, (2) floral trait divergence, including the evolution of 'pollination ecotypes', (3) the geographical context of selection on floral traits, and (4) the role of pollinators in the evolution of reproductive isolation. This Viewpoint also serves as the introduction to a Special Issue on Pollinator-Driven Speciation in Plants. The 13 papers in this Special Issue range from microevolutionary studies of ecotypes to macroevolutionary studies of historical ecological shifts, and span a wide range of geographical areas and plant families. These studies further illustrate innovative experimental approaches, and they employ modern tools in genetics and floral trait quantification. Future advances to the field require better quantification of selection through male fitness and pollinator isolation, for instance by exploiting next-generation sequencing technologies. By combining these new tools with strategically chosen study systems, and smart experimental design, we predict that examples of pollinator-driven speciation will be among the most widespread and compelling of all cases of ecological speciation.

Is floral scent key to shifts in pollination systems in Protea?

Is floral scent key to shifts in pollination systems in Protea?

Effects of Volatile Compounds Emitted by Protea Species (Proteaceae) on Antennal Electrophysiological Responses and Attraction of Cetoniine Beetles

Evolutionary shifts in pollination systems within a plant genus are commonly associated with changes in floral scent, reflecting selection mediated through the sensory systems of various pollinators. The most common cetoniine beetle pollinator of grassland Protea species in South Africa, Atrichelaphinis tigrina, previously has been shown to have a strong preference for the fruity floral scent of these plants over the weak scent of their bird-pollinated congeners. However, it is not known which of the many compounds found in the scent of beetle pollinated Protea species play a role for pollinator attraction. Electroantennograms (EAG) from A. tigrina beetles were recorded in response to 15 compounds emitted by Protea flower heads. EAG responses to all 15 compounds were significantly greater than those to the paraffin solvent in which they were diluted. The greatest responses were observed for aromatics (anisole, methyl benzoate, methyl salicylate, benzaldehyde) followed by the monoterpene β-linalool, which can comprise up to 66 % of fruity Protea scents. Five compounds that elicited EAG responses (benzaldehyde, β-linalool, (E/Z)-linalool oxide (furanoid), methyl benzoate, and methyl salicylate) were tested in commercially available yellow bucket traps in the field to test their attractiveness to beetles. Traps baited with methyl benzoate, β-linalool, (E/Z)-linalool oxide (furanoid), and methyl salicylate caught significantly more insects than did those containing paraffin only. Methyl benzoate also was more specifically attractive to A. tigrina than was (E/Z)-linalool oxide (furanoid) and paraffin baited controls. A second field experiment using a combination of linalool vs. paraffin baited yellow or green traps showed that trap color had a significant effect on the number of trapped beetles. Yellow traps yielded a ten-fold higher number of insect catches than did green traps. However, the combination of yellow color and the scent compound linalool yielded the highest number of catches. This study has shown that the cetoniine beetle A. tigrina can detect a variety of floral compounds and is attracted to compounds comprising a large proportion of the blend that makes up fruity Protea scents, adding support for the hypothesis that change in scent chemistry during the shift from bird to cetoniine beetle pollination in this genus were mediated by beetle sensory preferences.

Did Pollination Shifts Drive Diversification in Southern African Gladiolus? Evaluating the Model of Pollinator-Driven Speciation

The pollinator-driven ecological speciation model has frequently been invoked to explain plant richness in biodiversity hotspots. Here, by focusing on Gladiolus (260 species), a flagship example of a clade with diverse pollination biology, we test the hypothesis that high species diversity in southern Africa, one of the world's most floristically rich regions, has primarily been driven by ecological shifts in pollination systems. We use phylogenetic methods to estimate rates of transition between the seven highly specialized pollination strategies in Gladiolus. We find that pollination systems have evolved multiple times and that some pollination strategies arose by a variety of evolutionary pathways. Pollination shifts account for up to one-third of all lineage splitting events in the genus, providing partial support for the pollinator-driven speciation model. Transitions from the ancestral pollination mode to derived systems have also resulted in increased rates of diversification, suggesting that certain pollination systems may speed up speciation processes, independently of pollination shifts per se. This study suggests that frequent pollination shifts have played a role in driving high phenotypic and species diversity but indicates that additional factors need to be invoked to account for the spectacular diversification in southern African Gladiolus.

Gone with the wind: understanding evolutionary transitions between wind and animal pollination in the angiosperms

Gone with the wind: understanding evolutionary transitions between wind and animal pollination in the angiosperms

FLORAL BIOLOGY OF BABIANA (IRIDACEAE: CROCOIDEAE): ADAPTIVE FLORAL RADIATION AND POLLINATION1

Field observations, floral dissections, floral nectar, and pollen load analyses of captured insects of 53 species of Babiana Ker Gawl. show that flowers of this geophytic genus of some 90 species of Iridaceae subfamily Crocoideae, predominantly of the southern African winter-rainfall zone, are cross pollinated by a wide range of animals. These include passerine birds and insects of four different orders, Hymenoptera (mainly Apidae), Diptera (mainly Nemestrinidae), Coleoptera (Scarabaeidae), and Lepidoptera (mainly Noctuidae). Apid pollination involves two discrete systems—passive pollination by anthophorines and native Apis mellifera foraging for nectar and active pollen gathering by A. mellifera and other Apoidea foraging for pollen. From what is known about relationships within Babiana and Crocoideae, it seems likely that passive pollination by anthophorines and honeybees, with nectar secreted in zygomorphic, bilabiate flowers as a reward, is the ancestral condition; it is also the most common, demonstrated for 18 and inferred for 35 more species from all three taxonomic sections of the genus. Active pollination by honeybees and female Apoidea foraging for pollen was demonstrated in one species and is inferred for four more, all of which have radially symmetric flowers and prominent anthers. Pollination by long-proboscid nemestrinids, mostly species of Prosoeca, is recorded for 13 species and inferred for five more, while moth pollination is recorded for one species and inferred for another two. Pollination exclusively by hopliine scarab beetles, known for six species, is associated with development of radial symmetry of the flower. Passerine bird pollination, associated with the classic syndrome of a wide floral tube, red floral pigmentation, and rigid, well-exserted stamens, occurs in two species, and is inferred for one more. Species with a bimodal system in which bees and beetles both visit and accomplish pollen transfer is known for three species. Comparing pollination systems with what is known about species relationships in Babiana, we infer that long-proboscid fly pollination evolved at least four times and moth pollination three times. Active pollination by pollen-collecting bees and hopliine beetle pollination also probably evolved three times each and bird pollination twice. Pollination systems are labile, and we postulate that there has been a minimum of 14 shifts in pollination system, approximately one shift for every six species. Lastly, Babiana species show the same correlation of morphology and floral presentation with particular sets of pollinators, described for several other genera of Iridaceae, e.g., Gladiolus L., Hesperantha Ker Gawl., and Lapeirousia Pourr., as well as Geraniaceae and Orchidaceae. This increases our confidence in predicting pollinators on the basis of floral presentation in other species and genera in which pollinators have not been established.

MACROEVOLUTIONARY DATA SUGGEST A ROLE FOR REINFORCEMENT IN POLLINATION SYSTEM SHIFTS

Abstract . Reproductive isolation can evolve either as a by-product of divergent selection or through reinforcement. We used the Cape flora of South Africa, known for its high level of pollination specialization, as a model system to test the potential role of shifts in pollination system in the speciation process. Comparative analysis of 41 sisterspecies pairs (representing Geraniaceae, Iridaceae, and Orchidaceae) for which complete pollinator, edaphic, and distribution data are available showed that for sister species with overlapping distribution ranges, pollination system shifts are significantly associated with edaphic shifts. In contrast, there is no significant association between pollination system shifts and edaphic shifts for allopatric sister species. These results are interpreted as evidence for reinforcement.

MACROEVOLUTIONARY DATA SUGGEST A ROLE FOR REINFORCEMENT IN POLLINATION SYSTEM SHIFTS

Reproductive isolation can evolve either as a by-product of divergent selection or through reinforcement. We used the Cape flora of South Africa, known for its high level of pollination specialization, as a model system to test the potential role of shifts in pollination system in the speciation process. Comparative analysis of 41 sister-species pairs (representing Geraniaceae, Iridaceae, and Orchidaceae) for which complete pollinator, edaphic, and distribution data are available showed that for sister species with overlapping distribution ranges, pollination system shifts are significantly associated with edaphic shifts. In contrast, there is no significant association between pollination system shifts and edaphic shifts for allopatric sister species. These results are interpreted as evidence for reinforcement.

Radiation of Pollination Systems in the Iridaceae of sub-Saharan Africa

Seventeen distinct pollination systems are known for genera of sub-Saharan African Iridaceae and recurrent shifts in pollination system have evolved in those with ten or more species. Pollination by long-tongued anthophorine bees foraging for nectar and coincidentally acquiring pollen on some part of their bodies is the inferred ancestral pollination strategy for most genera of the large subfamilies Iridoideae and Crocoideae and may be ancestral for the latter. Derived strategies include pollination by long-proboscid flies, large butterflies, night-flying hovering and settling moths, hopliine beetles and sunbirds. Bee pollination is diverse, with active pollen collection by female bees occurring in several genera, vibratile systems in a few and non-volatile oil as a reward in one species. Long-proboscid fly pollination, which is apparently restricted to southern Africa, includes four separate syndromes using different sets of flies and plant species in different parts of the subcontinent. Small numbers of species use bibionid flies, short-proboscid flies or wasps for their pollination; only about 2 % of species use multiple pollinators and can be described as generalists. Using pollination observations for 375 species and based on repeated patterns of floral attractants and rewards, we infer pollination mechanisms for an additional 610 species. Matching pollination system to phylogeny or what is known about species relationships based on shared derived features, we infer repeated shifts in pollination system in some genera, as frequently as one shift for every five or six species of southern African Babiana or Gladiolus. Specialized systems using pollinators of one pollination group, or even a single pollinator species are the rule in the family. Shifts in pollination system are more frequent in genera of Crocoideae that have bilaterally symmetric flowers and a perianth tube, features that promote adaptive radiation by facilitating precise shifts in pollen placement, in conjunction with changes in flower colour, scent and tube length. Diversity of pollination systems explains in part the huge species diversity of Iridaceae in sub-Saharan Africa, and permits species packing locally. Pollination shifts are, however, seen as playing a secondary role in speciation by promoting reproductive isolation in peripheral, ecologically distinct populations in areas of diverse topography, climate and soils. Pollination of Iridaceae in Eurasia and the New World, where the family is also well represented, is poorly studied but appears less diverse, although pollination by both pollen- and oil-collecting bees is frequent and bird pollination rare.

Radiation in the Cape flora and the phylogeny of peacock irises Moraea (Iridaceae) based on four plastid DNA regions

Phylogenetic analyses of four plastid DNA regions, the rbcL exon, trnL intron, trnL–trnF intergenic spacer, and rps16 intron from each of 73 species in the African genus Moraea (Iridaceae: Irideae) including accessions of all major species clusters in the genus, show Moraea to be paraphyletic when Barnardiella, Galaxia, Hexaglottis, Homeria (all southern African), and Gynandriris (Eurasian as well) were recognized as separate genera. There are several small, isolated species clusters at the basal nodes of the tree that are all restricted to the winter-rainfall zone of southern Africa (the Greater Cape floral kingdom) and a few, highly derived, large species groups that have radiated extensively within the winter-rainfall zone. Mapping of floral traits shows that an Iris-type flower is ancestral in Moraea. Floral changes are associated with shifts in pollination systems, either from passive pollen deposition on long-tongued bees foraging for nectar to active pollen collection by female bees foraging for pollen, fly, or hopliine scarab beetle pollination. Dating the nodes of the phylogenetic tree using non-parametric rate smoothing with a calibration point derived from broad dating of the angiosperms indicates that the divergence between Moraea and its sister genus Ferraria occurred about 25 mya in the early Miocene. The early radiation of Moraea took place against a background of aridification and the spread of open habitats, such as desert, shrubland, and fynbos.

Radiation of Pollination Systems in Gladiolus (Iridaceae: Crocoideae) in Southern Africa

Pollination strategies adopted by the largely sub-Saharan African Gladiolus (approximately 260 species), one of the largest genera of the monocot family Iridaceae, are unusually diverse. The primary or sole pollinators include long-tongued apid and anthophorine bees (Apidae), short-tongued halictid and andrenid bees (Halictidae, Andrenidae), sometimes in combination with hopliine beetles (Scarabaeidae), long-proboscid flies (Nemestrinidae, Tabanidae), large butterflies (Satyridae), moths (mostly Noctuidae and Sphingidae), and sunbirds (Passerinae). Floral form correlates closely with pollination strategy, allowing us to infer the pollination ecology of almost all 165 species in southern Africa, although we have observations of animal visitors capable of accomplishing pollen transfer in only half this number. Pollination by apid bees foraging for nectar and passively transferring pollen brushed onto their bodies during feeding occurs in all seven sections of the genus in southern Africa and is also the most common strategy in five of these sections. Other pollinators include female bees actively foraging for pollen, or long-proboscid flies, sunbirds, moths, the satyrid butterfly, Aeropetes, all foraging for nectar, and in one species hopliine beetles that use the flowers as sites for assembly and copulation. Shifts in floral form associated with changes in pollination appear complex in the large flowers of Gladiolus species, but may in fact involve relatively simple developmental modifications, involving changes in perianth pigmentation, and often the type of marking on the tepals, presence or absence of scent, length of the perianth tube, and occasionally a shift from zygomorphy to actinomorphy. Associated with these changes is a correlated adjustment in nectar characteristics, including volume, sugar concentration, and sometimes sugar chemistry. With an inferred minimum of 32 shifts in pollination system in the 165 species in southern Africa, Gladiolus appears to have an unusually labile floral morphology, which may account for its extensive adaptive radiation.

A survey of reproductive biology in Onagraceae

Abstract Onagraceae constitute a clearly marked family of the order Myrtales, comprising 7 tribes, 17 genera, and about 674 species. Of these species, about 42% are outcrossed, 52% self-pollinated, and another 6% contain both sorts of breeding systems within a single species. In outcrossed species, the stigma is always elevated above the anthers at anthesis. The three principal modes of enforcing outcrossing are protandry, in Epilobium, Clarkia, and Lopezia (with protogyny in most species of Circaea); male sterility, independently derived in four small sections of Fuchsia; and genetic self-incompatibility, found in at least 76 species, representing 4 of the 7 tribes and 10 of the 17 genera of the family. Nearly all of the trees and shrubs in the family, but only about one third of the annuals and perennial herbs, are outcrossing. Clarkia is an example of an entirely annual genus that consists predominantly of outcrossing species, whereas Ludwigia and Epilobium are predominantly perennial genera that consist of a majority of self-pollinating species (and, in contrast to Clarkia, are largely polyploid). Less than one fifth of the trees, shrubs, and annuals in Onagraceae, but about 60% of the perennials, are polyploid. Aneuploid changes in chromosome number and the evolution of complex heterozygotes, the latter represented by 52 species of 4 different genera of the tribe Onagreae, take place largely among annual species in this family. Data summarised for the pollination systems of the approximately 283 modally outcrossing species of Onagraceae indicate that 37% of the species, representing 12 genera, are bee-pollinated; 31% bird-pollinated; 17% hawkmoth-pollinated; 7% pollinated by syrphid and tachinid flies; 6% noctuid-pollinated; and 0.4% (1 species: Clarkia concinna) by a combination of cyrtid flies and butterflies. No species is known to be modally pollinated by bats, by beetles, or by wind, and none has apomixis involving seeds, nor heterostyly. Some 22 individual shifts in pollination system would be sufficient to account for the evolution of the roughly 283 outcrossing species of the family, but an additional number of shifts probably involving at least 300 events would be necessary to account for the evolution of the 353 modally autogamous species. The repeated evolution of autogamy is clearly the most important evolutionary process involved in the multiplication of species of Onagraceae.