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Connaraceae is a pantropical family of about 200 species containing lianas and small trees with remarkably diverse floral polymorphisms, including distyly, tristyly, homostyly, and dioecy. To date, relationships within the family have not been investigated using a targeted molecular phylogenetic treatment, severely limiting systematic understanding and reconstruction of trait evolution. Accordingly, their last infrafamilial classification was based only on morphological data. Here, we used phylogenomic data obtained using the Angiosperms353 nuclear target sequence capture probes, sampling all tribes and almost all genera, entirely from herbarium specimens, to revise infrafamilial classification and investigate the evolution of heterostyly. The backbone of the resulting molecular phylogenetic tree is almost entirely resolved. Connaraceae consists of two clades, one containing only the African genus Manotes (4 or 5 species), which we newly recognize at the subfamily level. Vegetative and reproductive synapomorphies are proposed for Manotoideae. Within Connaroideae, Connareae is expanded to include the former Jollydoreae. The backbone of Cnestideae, which contains more than half of the Connaraceae species, remains incompletely resolved. Reconstructions of reproductive system evolution are presented that tentatively support tristyly as the ancestral state for the family, with multiple parallel losses, in agreement with previous hypotheses, plus possible re-gains. However, the great diversity of stylar polymorphisms and their phylogenetic lability preclude a definitive answer. Overall, this study reinforces the usefulness of herbarium phylogenomics, and unlocks the reproductive diversity of Connaraceae as a model system for the evolution of complex biological phenomena. [ABSTRACT FROM AUTHOR]

Aim: Many biogeographic analyses require some form of automated state assignment to tips of phylogenetic trees, reflecting a species presence or absence in a particular area, e.g., a biome. As datasets get exponentially larger, such procedures may increasingly induce errors (here called tip‐state‐error), but the specific algorithmic cause and consequence on downstream estimation of dispersal and extinction rates remains poorly known. We aim to improve automated tip‐scoring methods in the context of the alpine biome by leveraging elevation information. We document the profound effect of tip‐state‐errors on Dispersal‐Extirpation‐Cladogenesis (DEC) models. Location: The European Alpine Arc. Taxon: Three thousand three hundred seventeen vascular plant species, emphasizing six focal genera: Campanula, Carex, Festuca, Ranunculus, Saxifraga, and Viola. Methods: We use GBIF data to classify whether species occur above the upper climatic treeline using a newly developed algorithm ElevDistr or a gridded landscape model of thermal belts, under various filtering thresholds. We compared classification performance using the Flora Alpina as validation data. To determine if tip‐state‐error biases the dispersal and extirpation rate estimation, we fit DEC models for selected clades using tip‐states from different classification models. Results: ElevDistr is less error prone than other approaches. Filtering thresholds lower the false positive rate but increase the false negative rate. Inflated false positive rates bias the dispersal rate estimation upward, while inflated false negative rates lead to upward bias in extirpation rate estimation. Main Conclusions: Even moderate tip‐state‐error may lead to profound systematic bias in dispersal and extinction rate estimation if an unbalanced ratio between false positive and false negative rates occurs. Therefore, careful validation is imperative, though ElevDistr alleviates this problem in the context of the alpine environment. Overall, our results suggest contrasting rates of alpine biome shifts across the studied genera and have major implications for studies addressing the likelihood of niche evolution versus geographic dispersal. [ABSTRACT FROM AUTHOR]

Changes in chromosome numbers may strongly affect reproductive barriers, because individuals heterozygous for distinct karyotypes are typically expected to be at least partially sterile or to show reduced recombination. Therefore, several classic speciation models are based on chromosomal changes. One import mechanism generating variation in chromosome numbers is fusion and fission of existing chromosomes, which is particularly likely in species with holocentric chromosomes, i.e. chromosomes that lack a single centromere. Holocentric chromosomes evolved repeatedly across the tree of life, including in Lepidoptera. Although changes in chromosome numbers are hypothesized to be an important driver of the spectacular diversification of Lepidoptera, comparative studies across the order are lacking. We performed the first comprehensive literature survey of karyotypes for Lepidoptera species since the 1970s and tested if, and how, chromosomal variation might affect speciation. Even though a meta-analysis of karyological differences between closely related taxa did not reveal an effect on the degree of reproductive isolation, phylogenetic diversification rate analyses across the 16 best-covered genera indicated a strong, positive association of rates of chromosome number evolution and speciation. These findings suggest a macroevolutionary impact of varying chromosome numbers in Lepidoptera and likely apply to other taxonomic groups, especially to those with holocentric chromosomes. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'. [ABSTRACT FROM AUTHOR]

Hybrid enrichment is an increasingly popular approach for obtaining hundreds of loci for phylogenetic analysis acrossmany taxa quickly and cheaply. The genes targeted for sequencing are typically single-copy loci, which facilitate a more straightforward sequence assembly and homology assignment process. However, this approach limits the inclusion of most genes of functional interest, which often belong to multi-gene families. Here, we demonstrate the feasibility of including large gene families in hybrid enrichment protocols for phylogeny reconstruction and subsequent analyses of molecular evolution, using a new set of bait sequences designed for the "portullugo" (Caryophyllales), a moderately sized lineage of flowering plants (~2200 species) that includes the cacti and harbors many evolutionary transitions to C4 and CAM photosynthesis. Including multi-gene families allowed us to simultaneously infer a robust phylogeny and construct a dense sampling of sequences for a major enzyme of C4 and CAM photosynthesis, which revealed the accumulation of adaptive amino acid substitutions associated with C4 and CAMorigins in particular paralogs. Our final set ofmatrices for phylogenetic analyses included 75-218 loci across 74 taxa, with ~50% matrix completeness across data sets. Phylogenetic resolution was greatly improved across the tree, at both shallow and deep levels. Concatenation and coalescent-based approaches both resolve the sister lineage of the cacti with strong support: Anacampserotaceae + Portulacaceae, two lineages of mostly diminutive succulent herbs of warm, arid regions. In spite of this congruence, BUCKy concordance analyses demonstrated strong and conflicting signals across gene trees. Our results add to the growing number of examples illustrating the complexity of phylogenetic signals in genomic-scale data. [ABSTRACT FROM AUTHOR]

Premise of research. Self-compatibility is a requirement for reproductive assurance via selfing and may therefore be beneficial in environments with infrequent or unpredictable pollinator service. However, selfcompatible plants may spatially separate anthers from stigmatic surface within flowers (herkogamy), potentially preventing autonomous self-pollination while promoting outcrossing. We investigated the effects of herkogamy on patterns of mating in a self-compatible, homostylous alpine herb, Primula halleri, which evolved from obligately outcrossing, heterostylous ancestors. Primula halleri displays diminishing herkogamy during anthesis, affecting its capacity for self-pollination. Specifically, we tested whether higher herkogamy at the end of anthesis (terminal herkogamy) promotes higher outcrossing rates at the cost of lower seed set, while lower terminal herkogamy ensures seed set via self-pollination at the cost of inbreeding. Methodology. We estimated family- and population-level genetic outcrossing rates in four populations using microsatellites and derived an estimate for inbreeding depression. We tested effects of different levels of terminal herkogamy on means and variances of outcrossing rates. We also assessed whether seed set was resource or pollen limited. We interpreted results in light of previously published data on seed set with and without pollinator-exclusion treatment. Pivotal results. Population-level outcrossing rates ranged between 0.5 and 0.8. Outcrossing rates of plants with higher terminal herkogamy had similar means but lower variances than those of plants with lower terminal herkogamy. This result demonstrates that separation between sexual organs larger than 1 mm in mature flowers favors outbreeding, while below this threshold, delayed selfing ensures reproduction. Conclusions. Contrary to long-held notions about the association of homostyly and selfing, we provide new genetic evidence that the homostylous P. halleri adopts a mixed mating system due to variable herkogamy. Moreover, our results support a trade-off between seed number and seed quality effected through variation in herkogamy, illustrating that herkogamy affects multiple aspects of reproductive fitness simultaneously. [ABSTRACT FROM AUTHOR]

A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100-1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification-the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05-0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimación de la Tasa Normal de Extinción de Especies [ABSTRACT FROM AUTHOR]

The evolution of the flower is commonly thought to have spurred angiosperm diversification. Similarly, particular floral traits might have promoted diversification within specific angiosperm clades. We hypothesize that traits promoting the precise positional transfer of pollen between flowers might promote diversification. In particular, precise pollen transfer might produce partial reproductive isolation that facilitates adaptive divergence between parapatric populations differing in their reproductive-organ positions. We investigate this hypothesis with an individual-based model of pollen transfer dynamics associated with heterostyly, a floral syndrome that depends on precise pollen transfer. Our model shows that precise pollen transfer can cause sexual selection leading to divergence in reproductive-organ positions between populations served by different pollinators, pleiotropically causing an increase in reproductive isolation through a “magic trait” mechanism. Furthermore, this increased reproductive isolation facilitates adaptive divergence between the populations in an unlinked, ecologically selected trait. In a different pollination scenario, however, precise pollen transfer causes a decrease in adaptive divergence by promoting asymmetric gene flow. Our results highlight the idea that magic traits are not “magic” in isolation; in particular, the effect size of magic traits in speciation depends on the external environment, and also on other traits that modify the strength of the magic trait's influence on non-random mating. Overall, we show that the evolutionary consequences of pollen transfer dynamics can depend strongly on the available pollinator fauna and on the morphological fit between flowers and pollinators. Furthermore, our results illustrate the potential importance of even weak reproductive isolating barriers in facilitating adaptive divergence. [ABSTRACT FROM AUTHOR]

Amazonian rainforests are among the most species-rich terrestrial habitats on Earth. The aim of this study was to analyze phylogenetic diversity (PD) patterns of orchid bee assemblages along a latitudinal gradient of 15° from northern Peru to central Bolivia and to relate them to climatic factors and geological history. We expanded an existing phylogeny of orchid bees and analyzed the PD of 15 orchid bee assemblages along a latitudinal gradient using mean pair-wise phylogenetic distance. The resulting pattern was correlated to climatic factors and elevation. We found a hump-shaped pattern of PD that peaked in central Peru and decreased towards the equatorial and especially towards the southern, subtropical sites. The decrease in PD towards higher latitudes is a common pattern found in many taxa, which in our case correlates with increasing climatic seasonality. However, the decrease towards the equatorial sites is unusual and may be related to a particular historic event: the northern sites with low PD are situated in the area of the former Lake Pebas, which covered western Amazonia until 3 mya. After the lake disappeared orchid bees mainly belonging to two distantly related species groups apparently colonized the region and diversified, which led to the comparatively low observed PD. In contrast, in central Peru, no in situ radiations were detected, hence the assemblages were composed of species from diverse phylogenetic lineages. Additionally, we identified multiple phylogenetically independent radiations of regionally restricted Euglossa species along the latitudinal gradient that, according to a published, dated phylogeny, diversified roughly 3-1 mya. The hump-shaped latitudinal pattern of PD of the orchid bees of western Amazonia thus appears to have resulted from a preponderance of early divergent lineages in central Peru and of young radiations from distantly related clades colonizing higher latitudes, possibly triggered by historic climate fluctuations and major geological events. [ABSTRACT FROM AUTHOR]

Cyanobacteria are among the most diverse prokaryotic phyla, with morphotypes ranging from unicellular to multicellular filamentous forms, including those able to terminally (i.e., irreversibly) differentiate in form and function. It has been suggested that cyanobacteria raised oxygen levels in the atmosphere around 2.45-2.32 billion y ago during the Great Oxidation Event (GOE), hence dramatically changing life on the planet. However, little is known about the temporal evolution of cyanobacterial lineages, and possible interplay between the origin of multicellularity, diversification of cyanobacteria, and the rise of atmospheric oxygen. We estimated divergence times of extant cyanobacterial lineages under Bayesian relaxed clocks for a dataset of 165 rRNA sequences representing the entire known diversity of this phylum. We tested whether the evolution of multicellularity overlaps with the GOE, and whether multicellularity is associated with significant shifts in diversification rates in cyanobacteria. Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE. [ABSTRACT FROM AUTHOR]

Background and Aims Heterostyly is a floral polymorphism that has fascinated evolutionary biologists since Darwin's seminal studies on primroses. The main morphological characteristic of heterostyly is the reciprocal placement of anthers and stigmas in two distinct (distyly) floral morphs. Variation in the degree of intermorph sexual reciprocity is relatively common and known to affect patterns of pollen transfer within species. However, the partitioning of sexual organ reciprocity within and between closely related species remains unknown. This study aimed at testing whether intermorph sexual reciprocity differs within vs. between primrose species that hybridize in nature and whether the positions of sexual organs are correlated with other floral traits. Methods Six floral traits were measured in both floral morphs of 15 allopatric populations of Primula elatior, P. veris and P. vulgaris, and anther–stigma reciprocity was estimated within and between species. A combination of univariate and multivariate approaches was used to test whether positions of reproductive organs were less reciprocal between than within species, to assess correlations between sexual organ positions and other corolla traits, and to quantify differences between morphs and species. Key Results The three species were morphologically well differentiated in most floral traits, except that P. veris and P. vulgaris did not differ significantly in sexual organ positions. Overall, lower interspecific than intraspecific sexual organ reciprocity was detected. This decrease was marked between P. elatior and P. vulgaris, intermediate and variable between P. elatior and P. veris, but negligible between P. veris and P. vulgaris. Conclusions Differences in anther and stigma heights between the analysed primrose species were of the same magnitude or larger than intraspecific differences that altered pollen flow within other heterostylous systems. Therefore, it is possible to suggest that considerable reductions of sexual organ reciprocity between species may lower interspecific pollen flow, with potential effects on reproductive isolation. [ABSTRACT FROM AUTHOR]

Abstract: The type section of Primula (Primulaceae), here considered to include seven species, is phylogenetically quite isolated in its genus. Although its species are popular ornamentals, traditional medicinal plants and model organisms for the study of heterostyly, the section has not yet been studied from a phylogenetic or evolutionary perspective. Using phylogenetic analysis of nuclear ITS and plastid data from all species and subspecies, we find that widespread Primula elatior is genetically heterogeneous and non-monophyletic to most if not all of the other ingroup taxa. The Genealogical Sorting Index (GSI) indicates that the assumption of all currently accepted species being independent lineages is consistent with the data. It is possible that P. elatior in its current circumscription may represents the disjointed remnant of an ancestral species from which the other recognized species diverged. However, based on available data, the alternative possibility of introgression explaining the non-monophyly of this species cannot be excluded. Species trees show P. elatior and P. veris as sister species. Primula vulgaris and P. juliae are closely related, while, in contrast to previous assumptions, P. renifolia does not appear to be a close relative of P. megaseifolia. With the section’s isolation from the rest of the genus and very short internal branches, our dataset also presents a case study of the confounding effects of different branch length priors on the Bayesian estimation of resulting branch length estimates. Experimental runs using different priors confirm the problem of resulting estimates varying by orders of magnitude, while topology and relative branch lengths seem unaffected. [Copyright &y& Elsevier]

The authors offer observation on a study, conducted by A. E. Zanne et al, wherein they examined cold tolerance in plants. Topics covered include the climate character underlying their analyses, concerns over their evolutionary trajectories, and the authors' claim that the preferred trajectories of Zanne and colleagues could have nothing to do with what actually happened during angiosperm evolution.

The impact of large-scale chromosomal rearrangements, such as fusions and fissions, on speciation is a long-standing conundrum. We assessed whether bursts of change in chromosome numbers resulting from chromosomal fusion or fission are related to increased speciation rates in Erebia, one of the most species-rich and karyotypically variable butterfly groups. We established a genome-based phylogeny and used state-dependent birth-death models to infer trajectories of karyotype evolution. We demonstrated that rates of anagenetic chromosomal changes (i.e., along phylogenetic branches) exceed cladogenetic changes (i.e., at speciation events), but, when cladogenetic changes occur, they are mostly associated with chromosomal fissions rather than fusions. We found that the relative importance of fusion and fission differs among Erebia clades of different ages and that especially in younger, more karyotypically diverse clades, speciation is more frequently associated with cladogenetic chromosomal changes. Overall, our results imply that chromosomal fusions and fissions have contrasting macroevolutionary roles and that large-scale chromosomal rearrangements are associated with bursts of species diversification. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The repeated transition from outcrossing to selfing is a key topic in evolutionary biology. However, the molecular basis of such shifts has been rarely examined due to lack of knowledge of the genes controlling these transitions. A classic example of mating system transition is the repeated shift from heterostyly to homostyly. Occurring in 28 angiosperm families, heterostyly is characterized by the reciprocal position of male and female sexual organs in two (or three) distinct, usually self‐incompatible floral morphs. Conversely, homostyly is characterized by a single, self‐compatible floral morph with reduced separation of male and female organs, facilitating selfing. Here, we investigate the origins of homostyly in Primula vulgaris and its microevolutionary consequences by integrating surveys of the frequency of homostyles in natural populations, DNA sequence analyses of the gene controlling the position of female sexual organs (CYPᵀ), and microsatellite genotyping of both progeny arrays and natural populations characterized by varying frequencies of homostyles. As expected, we found that homostyles displace short‐styled individuals, but long‐style morphs are maintained at low frequencies within populations. We also demonstrated that homostyles repeatedly evolved from short‐styled individuals in association with different types of loss‐of‐function mutations in CYPᵀ. Additionally, homostyly triggers a shift to selfing, promoting increased inbreeding within and genetic differentiation among populations. Our results elucidate the causes and consequences of repeated transitions to homostyly within species, and the putative mechanisms precluding its fixation in P. vulgaris. This study represents a benchmark for future analyses of losses of heterostyly in other angiosperms. see also the Perspective by Deborah Charlesworth [ABSTRACT FROM AUTHOR]

Premise of the Study: Calandrinia are small, succulent herbs that vary broadly in habitat, morphology, life history, and photosynthetic metabolism. The lineage is placed within the Montiaceae, which in turn is sister to the rest of the Portulacineae (Caryophyllales). Calandrinia occupy two distinct biogeographic regions, one in the Americas (~14 species), and one in Australia (~74 species). Past analyses of the Montiaceae present conflicting hypotheses for the phylogenetic placement and monophyly of Calandrinia, and to date, there has been no molecular phylogenetic analysis of the Australian species. Methods: Using a targeted gene enrichment approach, we sequenced 297 loci from multiple gene families across the Montiaceae, including all named and 16 putative new species of Australian Calandrinia, and the enigmatic monotypic genus Rumicastrum. Key Results: All data sets and analyses reject the monophyly of Calandrinia, with Australian and New World Calandrinia each comprising distinct and well‐supported clades, and Rumicastrum nested within Australian Calandrinia. We provide the first well‐supported phylogeny for Australian Calandrinia, which includes all named species and several phrase‐named taxa. Conclusions: This study brings much needed clarity to relationships within Montiaceae and confirms that New World and Australian Calandrinia do not form a clade. Australian Calandrinia is a longtime resident of the continent, having diverged from its sister lineage ~30 Ma, concurrent with separation of Australia from Antarctica. Most diversification occurred during the middle Miocene, with lowered speciation and/or higher extinction rates coincident with the establishment of severe aridity by the late Miocene. [ABSTRACT FROM AUTHOR]

Premise of the Study: Next‐generation sequencing facilitates rapid production of well‐sampled phylogenies built from very large genetic data sets, which can then be subsequently exploited to examine the molecular evolution of the genes themselves. We present an evolutionary analysis of 83 gene families (19 containing carbon‐concentrating mechanism (CCM) genes, 64 containing non‐CCM genes) in the portullugo clade (Caryophyllales), a diverse lineage of mostly arid‐adapted plants that contains multiple evolutionary origins of all known photosynthesis types in land plants (C3, C4, CAM, C4‐CAM, and various intermediates). Methods: We inferred a phylogeny of 197 individuals from 167 taxa using coalescent‐based approaches and individual gene family trees using maximum likelihood. Positive selection analyses were conducted on individual gene family trees with a mixed effects model of evolution (MEME). We devised new indices to compare levels of convergence and prevalence of particular residues between CCM and non‐CCM genes and between species with different photosynthetic pathways. Key Results: Contrary to expectations, there were no significant differences in the levels of positive selection detected in CCM versus non‐CCM genes. However, we documented a significantly higher level of convergent amino acid substitutions in CCM genes, especially in C4 taxa. Conclusions: Our analyses reveal a new suite of amino acid residues putatively important for C4 and CAM function. We discuss both the advantages and challenges of using targeted enrichment sequence data for exploratory studies of molecular evolution. [ABSTRACT FROM AUTHOR]

• Mixture modelling analysis of 7204 δ13C values infers three clusters, opposing the expectation of two clusters from a bimodal distribution. • Well-sampled lineage specific δ13C surveys reveal continuous or discontinuous, unimodal or bimodal distribution patterns of δ13C values. • Any coding of CAM vs. C 3 based on a δ13C threshold undervalues the diversity of CAM and is a likely source of error in studies of CAM evolution. The stable carbon isotope composition of plant tissues, commonly expressed as δ13C, holds a wealth of information about photosynthetic pathway, water relations and stress physiology. Crassulacean acid metabolism (CAM) is a derived form of photosynthesis that allows plants to fix carbon at a higher water-use efficiency compared to the ancestral C 3 photosynthesis. While the central carbon-fixing enzyme of C 3 plants, Rubisco, strongly discriminates against the heavy 13C isotope, CAM is characterized by a dual use of Rubisco and the much less discriminating PEP carboxylase as carbon-fixing enzymes, causing the δ13C values of CAM plant tissues to be generally less negative than those found in C 3 plants. Past studies of δ13C variation in CAM plant lineages have repeatedly found a bimodal distribution with very few samples representative of the range around -20‰ that is intermediate between C 3 - and CAM-like values. Although δ13C values of facultative CAM plants have long been known to extend well into the range below -20‰, this value is often tentatively used as threshold for character coding to distinguish C 3 from CAM species in studies of CAM evolution. Compiling 6623 δ13C values reported in the literature for CAM/C 3 vascular plant lineages and presenting new data for 581 accessions mainly of the succulent Mesembryanthemoideae (Aizoaceae) and Aeonieae (Crassulaceae), we here investigate the diverse patterns of δ13C distribution in different plant families and sub-familial taxa and demonstrate that a bimodal distribution is not universally present in all lineages. Moreover, we show by means of mixture modelling that the bimodal distribution of δ13C values in the full dataset as well as in the very well-sampled Bromeliaceae is best described by a combination of three rather than two Gaussian distributions with one intermediary cluster between the more evident clusters of C 3 - and CAM-like values. In view of these results and the furthermore emerging unimodal distribution of δ13C values in Mesembryanthemoideae with mean close to -20‰, we conclude that the evident continuum between CAM and C 3 photosynthesis cautions against the usage of a δ13C threshold in macroevolutionary studies. Finally, the observed diversity of δ13C distribution patterns between monophyletic lineages urges for lineage-specific reconstructions rather than a unifying model of CAM evolution. [ABSTRACT FROM AUTHOR]