CAM evolution is associated with gene family expansion in an explosive bromeliad radiation.

The subgenus Tillandsia (Bromeliaceae) belongs to one of the fastest radiating clades in the plant kingdom and is characterized by the repeated evolution of Crassulacean acid metabolism (CAM). Despite its complex genetic basis, this water-conserving trait has evolved independently across many plant families and is regarded as a key innovation trait and driver of ecological diversification in Bromeliaceae. By producing high-quality genome assemblies of a Tillandsia species pair displaying divergent photosynthetic phenotypes, and combining genome-wide investigations of synteny, transposable element (TE) dynamics, sequence evolution, gene family evolution, and temporal differential expression, we were able to pinpoint the genomic drivers of CAM evolution in Tillandsia. Several large-scale rearrangements associated with karyotype changes between the 2 genomes and a highly dynamic TE landscape shaped the genomes of Tillandsia. However, our analyses show that rewiring of photosynthetic metabolism is mainly obtained through regulatory evolution rather than coding sequence evolution, as CAM-related genes are differentially expressed across a 24-h cycle between the 2 species but are not candidates of positive selection. Gene orthology analyses reveal that CAM-related gene families manifesting differential expression underwent accelerated gene family expansion in the constitutive CAM species, further supporting the view of gene family evolution as a driver of CAM evolution.

Functional traits of predators and decomposer prey determine context dependency in trophic control over ecosystems.

Research Highlight: Piccoli, G. C. d. O., Antiqueira, P. A. P., Srivastava, D. S., & Romero, G. Q. (2024). Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality. Journal of Animal Ecology, 00, 1-14. https://doi.org/10.1111/1365-2656.14063. Ecosystem functioning is controlled by the interplay between bottom-up supply of limiting nutrients and top-down animal feedback effects. However, the degree of animal versus nutrient control is context-dependent. A key challenge lies in characterizing this context dependency which is hypothesized to depend on differences in animal functional traits. Reporting on an important experiment, Piccoli et al. (2014) evaluate how interactions among functionally different predators and decomposer prey create context dependency in top-down control of a model system-tropical bromeliad tank ecosystems. Bromeliad plants hold water in their tanks supporting microcosm ecosystems containing terrestrial and aquatic insect larvae and arachnids. The ecosystems are supported by nutrients in plant litter that rains down from forest canopies into the tanks. Nutrients are released after litter is decomposed by a functionally diverse community of larval insect decomposers that differ in feeding mode and antipredator defence strategy. This decomposer community is preyed upon by an exclusively narrowly ranging aquatic insect larval predator and widely ranging spider predator that crosses between the aquatic and surrounding terrestrial ecosystems. Experimental manipulation of the animal community to test for the degree of control by predators mediated by the functionally diverse prey community included four treatments: (i) a control with the detritivores composing different function groups but without predators, (ii) the cross-ecosystem spider predator added, (iii) the purely aquatic damselfly larvae predator added and (iv) both predator types added to capture their interacting effect on ecosystem function (decomposition, nutrient release, and plant growth). Notably, the study resolved the causal pathways and strengths of direct and indirect control using structural equation modelling. These findings reveal how context dependency arises due to different capacities of the predators alone and together to overcome prey defences and control their abundances, with attendant cascading effects that diminished as well as enhanced decomposition and nutrient release to support bromeliad plant production. The study reveals that predators have a decided, albeit qualitatively and quantitatively different, hand in shaping the degree of bottom-up control through feedback effect on the release of limiting nutrients. This ground-breaking study provides a way forward in understanding the mechanisms determining context dependency in the control over ecosystem functioning.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality.

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

As espécies em um ecossistema podem afetar indiretamente múltiplos componentes da biodiversidade e funções ecossistêmicas em ecossistemas adjacentes. A magnitude destes efeitos entre ecossistemas depende dos atributos dos organismos envolvidos nas interações, incluindo características do predador, da presa e do recurso basal. No entanto, não está claro como os predadores com habitat em múltiplos ecossistemas interagem com predadores de um ecossistema único, e como isso afeta o ecossistema partilhado entre eles. Além disso, não se sabe como esses efeitos complexos do tipo top­down podem ser mediados pelas características antipredatórias da presa e pela qualidade do recurso basal. Usamos as teias alimentares de invertebrados aquáticos de bromélias­tanque como um sistema modelo para investigar essas questões. Nós manipulamos a presença de um predador estritamente aquático (larvas de zigópteros) e um predador com habitats terrestre e aquático (aranha), e examinamos os efeitos na sobrevivência de presas (grupos de detritívoros com diferentes estratégias de defesa antipredatória), decomposição de detritos foliares (de duas espécies de plantas diferindo na qualidade foliar), fluxo de nitrogênio e crescimento da planta hospedeira. Para avaliar os efeitos diretos e indiretos de cada tipo de predador em múltiplos grupos de detritívoros e, finalmente, em múltiplos processos ecossistêmicos, utilizamos modelos de equações estruturais por partes (piecewiseSEM). Para cada variável resposta, isolamos a contribuição de diferentes grupos de detritívoros bem como seus efeitos globais, comparando modelos alternativos. Larvas de zigópteros e aranhas diminuíram diretamente a sobrevivência dos detritívoros e causaram múltiplos efeitos negativos indiretos na decomposição de detritos, na ciclagem de nutrientes e no crescimento da planta hospedeira. No entanto, quando os predadores coocorreram, a aranha causou um efeito negativo não consumível na larva de zigóptero, diminuindo os efeitos líquidos, diretos e indiretos, do tipo top­down na comunidade de detritívoros aquáticos e no funcionamento do ecossistema. Tanto os atributos antipredatórios dos detritívoros quanto a qualidade dos detritos modularam a força e o mecanismo dessas cascatas tróficas. A interferência do predador foi mediada por detritívoros indefesos ou com defesa parcial. Entretanto, os detritívoros com defesas antipredatórias escaparam do consumo por larvas de zigópteros, mas não por aranhas. Predadores e detritívoros afetaram a decomposição do ecossistema e a ciclagem de nutrientes apenas na presença de detritos de alta qualidade, uma vez que os detritos de baixa qualidade foram consumidos mais por micróbios do que por invertebrados. As respostas complexas deste sistema aos predadores tanto de ecossistemas receptores quanto adjacentes destacam o papel crítico da manutenção dos componentes da biodiversidade em múltiplos ecossistemas.

Investigating the reproductive strategies of Deuterocohnia meziana (Bromeliaceae), an endangered and restricted species from South American rocky outcrops.

Studies of reproductive biology and resources availability to floral visitors by plant species are important to understand the plant-pollinator interactions that drive species adaptation. We aim to understand the relationship between reproduction mechanisms of Deuterocohnia meziana (Bromeliaceae) and pollinators. The species occurs in Bolivia and Paraguay, and it is the only species of the genus found in Brazil, where it is restricted to ironstone outcrops. These areas are currently threatened by the iron mining industry. Additionally, they face risks from fire occurrence and grazing by cattle. We analyzed the floral biology, reproductive system, phenology, and pollination ecology of a natural population of Deuterocohnia meziana, from ironstone outcrops in Brazil. The species exhibits diurnal anthesis, with stigma receptive throughout anthesis, and 77% of pollen viability. Deuterocohnia meziana produces relatively large amounts of nectar, especially early in the morning (32.8 ± 9.4 µl), with a mean sugar concentration of 23.5 (± 3.2) ºBrix. It is self-incompatible with a peak flowering occurring in August (dry season), although flowers are observed continuously throughout the year. The species exhibits two types of inflorescences, young and mature, among which an average of 13.1 and 3.6 flowers open per day, respectively. Hummingbirds and bees are the effective pollinators, although butterflies and ants also visit D. meziana flowers. The species is reliant on exogenous pollen and pollinators for fruit set. The continuous conservation of D. meziana populations and their communities is essential for preserving plant-pollinator mutualism and the floral community adapted to ironstone outcrops.

Distribution pattern in the rupiculous genus Orthophytum (Bromelioideae/Bromeliaceae) reveals high microendemicity in different types of rocky outcrops.

This study aimed to recognize the biogeographic patterns, richness, and diversity levels of the Brazilian endemic genus Orthophytum and identify their biotic components through a parsimony analysis of endemicity (PAE), to better understand the evolutionary history of this group and develop strategies for the conservation of its species. We prepared a database for the 54 currently known species of Orthophytum, including their geographical locations as obtained from digital databases of the principal herbaria of Brazil, Europe, and the USA. A parsimony analysis of endemicity (PAE) was used to delimit the areas of endemism based on two grids' sizes (1º x 1º and 2º × 2º). The majority rule consensus tree resulting from the PAE indicated three areas of endemism with high bootstrap, diversity, and richness indices: the northern portion of the Espinhaço Range, the southern portion of the Espinhaço Range, and the central portion of the Atlantic Forest. The recognition of those distribution patterns reveals a high number of microendemic species, which is discussed here.

Light intensity mediates phenotypic plasticity and leaf trait regionalization in a tank bromeliad.

BACKGROUND AND AIMS: Phenotypic plasticity allows plants to cope with environmental variability. Plastic responses to the environment have mostly been investigated at the level of individuals (plants) but can also occur within leaves. Yet the latter have been underexplored, as leaves are often treated as functional units with no spatial structure. We investigated the effect of a strong light gradient on plant and leaf traits and examined whether different portions of a leaf show similar or differential responses to light intensity. METHODS: We measured variation in 27 morpho-anatomical and physiological traits of the rosette and leaf portions (i.e. base and apex) of the tank bromeliad Aechmea aquilega (Bromeliaceae) when naturally exposed to a marked gradient of light intensity. KEY RESULTS: The light intensity received by A. aquilega had a strong effect on the structural, biochemical and physiological traits of the entire rosette. Plants exposed to high light intensity were smaller and had wider, shorter, more rigid and more vertical leaves. They also had lower photosynthetic performance and nutrient levels. We found significant differences between the apex and basal portions of the leaf under low-light conditions, and the differences declined or disappeared for most of the traits as light intensity increased (i.e. leaf thickness, adaxial trichome density, abaxial and adaxial trichome surface, and vascular bundle surface and density). CONCLUSIONS: Our results reveal a strong phenotypic plasticity in A. aquilega, particularly in the form of a steep functional gradient within the leaf under low-light conditions. Under high-light conditions, trait values were relatively uniform along the leaf. This study sheds interesting new light on the functional complexity of tank bromeliad leaves, and on the effect of environmental conditions on leaf trait regionalization.

Acid waters in tank bromeliads: Causes and potential consequences.

PREMISE: The consequences of acidity for plant performance are profound, yet the prevalence and causes of low pH in bromeliad tank water are unknown despite its functional relevance to key members of many neotropical plant communities. METHODS: We investigated tank water pH for eight bromeliad species in the field and for the widely occurring Guzmania monostachia in varying light. We compared pH changes over time between plant and artificial tanks containing a solution combined from several plants. Aquaporin transcripts were measured for field plants at two levels of pH. We investigated relationships between pH, leaf hydraulic conductance, and CO2 concentration in greenhouse plants and tested proton pump activity using a stimulator and inhibitor. RESULTS: Mean tank water pH for the eight species was 4.7 ± 0.06 and was lower for G. monostachia in higher light. The pH of the solution in artificial tanks, unlike in plants, did not decrease over time. Aquaporin transcription was higher for plants with lower pH, but leaf hydraulic conductance did not differ, suggesting that the pH did not influence water uptake. Tank pH and CO2 concentration were inversely related. Fusicoccin enhanced a decrease in tank pH, whereas orthovanadate did not. CONCLUSIONS: Guzmania monostachia acidified its tank water via leaf proton pumps, which appeared responsive to light. Low pH increased aquaporin transcripts but did not influence leaf hydraulic conductance, hence may be more relevant to nutrient uptake.

Different plant compartments, different yeasts: The example of the bromeliad phyllosphere.

The plant phyllosphere is one of the largest sources of microorganisms, including yeasts. In bromeliads, the knowledge of yeasts is dispersed and still incipient. To understand the extent of our knowledge of the subject, this review proposes to compile and synthesize existing knowledge, elucidating possible patterns, biotechnological and taxonomic potentials, bringing to light new knowledge, and identifying information gaps. For such, we systematically review scientific production on yeasts in bromeliads using various databases. The results indicated that the plant compartments flowers, fruits, leaves, and water tank (phytotelma) have been studied when focusing on the yeast community in the bromeliad phyllosphere. More than 180 species of yeasts and yeast-like fungi were recorded from the phyllosphere, 70% were exclusively found in one of these four compartments and only 2% were shared among all. In addition, most of the community had a low frequency of occurrence, and approximately half of the species had a single record. Variables such as bromeliad subfamilies and functional types, as well as plant compartments, were statistically significant, though inconclusive and with low explanatory power. At least 50 yeast species with some biotechnological potentials have been isolated from bromeliads. More than 90% of these species were able to produce extracellular enzymes. In addition, other biotechnological applications have also been recorded. Moreover, new species have been described, though yeasts were only exploited in approximately 1% of the existing bromeliads species, which highlights that there is still much to be explored. Nevertheless, it appears that we are still far from recovering the completeness of the diversity of yeasts in this host. Furthermore, bromeliads proved to be a good ecological model for prospecting new yeasts and for studies on the interaction between plants and yeasts. In addition, the yeast community diverged among plant compartments, establishing bromeliads as a microbiologically complex and heterogeneous mosaic.

Tremella ananatis sp. nov. and Tremella lamprococci sp. nov., two yeast species associated with bromeliads.

Eight yeast isolates with an affinity to the genus Tremella were obtained from bromeliads from different locations in Brazil. Although the formation of basidia and basidiocarp were not observed, on the basis of the results of sequence analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene and internal transcribed spacer (ITS) region, we suggest that these isolates represent two novel species of the genus Tremella. These yeasts are phylogenetically related to Tremella saccharicola and Tremella globispora. Therefore, we propose Tremella ananatis sp. nov. and Tremella lamprococci sp. nov. as novel yeast species of the order Tremellales (Agaricomycotina, Basidiomycota). Sequence analysis revealed that Tremella ananatis sp. nov. differs by 11 and 28 nucleotide substitutions from Tremella saccharicola in the D1/D2 sequence and ITS region, respectively. Moreover, Tremella lamprococci sp. nov. differs by 15 and 29 nucleotide substitutions from Tremella globispora in the D1/D2 sequence and ITS region, respectively. The holotypes of Tremella ananatis sp. nov. and Tremella lamprococci sp. nov. are CBS 14568T and CBS 14567T, and the MycoBank numbers are MB840480 and MB840481, respectively.

Extranuptial nectaries in bromeliads: a new record for Pitcairnia burchellii and perspectives for Bromeliaceae.

Nectar plays important roles in the relationship between plants and other organisms, both within pollination systems and as a defense mechanism. In the latter case, extranuptial nectaries (ENNs) usually attract patrolling arthropods that reduce herbivory. ENNs have been frequently reported within the "xeric clade" of Bromeliaceae, but their occurrence in other groups of bromeliads is largely unexplored, especially considering their position, secretory activity and structure. After observing the presence of ants constantly patrolling the inflorescences of Pitcairnia burchellii Mez, we searched for the presence, secretory activity, and structure of ENNs in this species. We also provide a brief review of the occurrence ENNs in Bromeliaceae. The distribution of nectaries was assessed using ant-exclusion experiments, while structural analysis was performed using standard methods for light and scanning electron microscopy. The presence of sugars in the secretion was assessed by thin-layer chromatography and glucose strip tests. Nectaries in P. burchelli are non-structured glands on the adaxial surface of floral bracts and sepals. Bracts and sepals are distinct spatial units that act over time in the same strategy of floral bud protection. Literature data reveals that ENNs might be more common within Bromeliaceae than previously considered, comprising a homoplastic feature in the family. Future perspectives and evolutionary and taxonomic implications are discussed.

"Hitchhicking with invertebrates": two reports of epibiosis by peritrich ciliates on ostracods and hydrachnid mites in tanks of epiphytic bromeliads from south Brazil.

Temporary waters are common environments found in physical and biological substrates. Among them, some bromeliads species are known to hold water in their tanks, in a habitat called phytotelmata. Phytotelmata serve as habitats for several organisms, from bacteria and protists to arthropods and anurans. Peritrich ciliates are often found as epibionts on aquatic invertebrates in these environments. Here, we report two cases of epibiosis involving Lagenophrys sp. attached to ostracods (Elpidium spp.) and Rhabdostyla sp. colonizing hydrachnid mites in the tanks of two bromeliad species. In our analysis, we measured the frequency of epibiosis considering the presence of both basibiont and epibiont in the samples. The results shown a significant difference between Elpidium sp. and Lagenophrys sp. compared to hydrachnid mites and Rhabdostyla sp. (87.5% and 19%, respectively), supported by the Kruskal-Walis test (p = 0.0003, Chi-square = 9.687). These reports are important since the knowledge of phytotelmata communities from tropical and subtropical areas is incipient, although it has been increasing over the last years. It also shows that epibiosis doesn't always represent a beneficial relationship. These two epibiosis systems found in bromeliad tanks raise questions about organism's dispersal throughout other phytotelmata and other temporary water habitats.

Draft genome of Puya raimondii (Bromeliaceae), the Queen of the Andes.

Puya raimondii, the Queen of the Andes, is an endangered high Andean species in the Bromeliaceae family. Here, we report its first genome to promote its conservation and evolutionary study. Comparative genomics showed P. raimondii diverged from Ananas comosus about 14.8 million years ago, and the long terminal repeats were likely to contribute to the genus diversification in last 3.5 million years. The gene families related to plant reproductive development and stress responses significantly expanded in the genome. At the same time, gene families involved in disease defense, photosynthesis and carbohydrate metabolism significantly contracted, which may be an evolutionary strategy to adapt to the harsh conditions in high Andes. The demographic history analysis revealed the P. raimondii population size sharply declined in the Pleistocene and then increased in the Holocene. We also designed and tested 46 pairs of universal primers for amplifying orthologous single-copy nuclear genes in Puya species.

Taxonomy of Hohenbergia lanata Pereira & Moutinho, new collections with an amendment to its description.

Hohenbergia lanata Pereira & Moutinho is an endemic bromeliad of the State of Bahia (Brazil), occurring in an altitudinal transition forest between Caatinga dry woodland and Atlantic Forest. The type material was collected by Roberto Burle-Marx, who introduced it into cultivation in his gardens, but lacking the accurate provenance, only mentioning that it was collected between Milagres and Amargosa municipalities. It was later described by Pereira & Moutinho based on a cultivated specimen. In this work, we present new specimens found in natural populations in an area that coincides with the type locality description, enabling us to expand the description of the species, as well as to provide images of the living plants in the field, adding information about its habitat. The herbarium collections revision and the new population found in the field enabled us to propose an updated conservation status and to better characterize the habit, plant architecture, and to add new morphological comparisons and geographical distribution.

Acaricidal efficacy and chemical study of hexane extracts of the leaves of Neoglaziovia variegata (Bromeliaceae) against the tick Rhipicephalus microplus.

The frequent use of acaricides against the tick Rhipicephalus microplus increases the risk of development of resistance. Recent studies have revealed that Neoglaziovia variegata, an indigenous plant species known in Brazil as 'caroá', has a deleterious effect against R. microplus. In the current study, extracts of N. variegata were studied for their possible acaricidal properties. A hexane extract of N. variegata leaves was fractionated in a chromatography column and the fractions were tested in adult tick immersion tests in triplicate using three concentrations (5, 10 and 25 mg/ml). All the fractions had harmful effects on the ticks. However, three fractions were more efficaceous. Phytochemical analysis indicated that stigmast-5-en-3-ol and stigmastanol were most abundant; they might be responsible for the acaricidal effects, making them potentially useful as alternative agents to control the tick R. microplus.

Cytotoxic Fractions from Hechtia glomerata Extracts and p-Coumaric Acid as MAPK Inhibitors.

Preliminary bioassay-guided fractionation was performed to identify cytotoxic compounds from Hechtia glomerata, a plant that is used in Mexican ethnomedicine. Organic and aqueous extracts were prepared from H. glomerata's leaves and evaluated against two cancer cell lines. The CHCl3/MeOH (1:1) active extract was fractionated, and the resulting fractions were assayed against prostate adenocarcinoma PC3 and breast adenocarcinoma MCF7 cell lines. Active fraction 4 was further analyzed by high-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry analysis to identify its active constituents. Among the compounds that were responsible for the cytotoxic effects of this fraction were flavonoids, phenolic acids, and aromatic compounds, of which p-coumaric acid (p-CA) and its derivatives were abundant. To understand the mechanisms that underlie p-CA cytotoxicity, a microarray assay was performed on PC3 cells that were treated or not with this compound. The results showed that mitogen-activated protein kinases (MAPKs) that regulate many cancer-related pathways were targeted by p-CA, which could be related to the reported effects of reactive oxygen species (ROS). A molecular docking study of p-CA showed that this phenolic acid targeted these protein active sites (MAPK8 and Serine/Threonine protein kinase 3) at the same binding site as their inhibitors. Thus, we hypothesize that p-CA produces ROS, directly affects the MAPK signaling pathway, and consequently causes apoptosis, among other effects. Additionally, p-CA could be used as a platform for the design of new MAPK inhibitors and re-sensitizing agents for resistant cancers.

Exploring molecular evolution of Rubisco in C3 and CAM Orchidaceae and Bromeliaceae.

BACKGROUND: The CO2-concentrating mechanism associated to Crassulacean acid metabolism (CAM) alters the catalytic context for Rubisco by increasing CO2 availability and provides an advantage in particular ecological conditions. We hypothesized about the existence of molecular changes linked to these particular adaptations in CAM Rubisco. We investigated molecular evolution of the Rubisco large (L-) subunit in 78 orchids and 144 bromeliads with C3 and CAM photosynthetic pathways. The sequence analyses were complemented with measurements of Rubisco kinetics in some species with contrasting photosynthetic mechanism and differing in the L-subunit sequence. RESULTS: We identified potential positively selected sites and residues with signatures of co-adaptation. The implementation of a decision tree model related Rubisco specific variable sites to the leaf carbon isotopic composition of the species. Differences in the Rubisco catalytic traits found among C3 orchids and between strong CAM and C3 bromeliads suggested Rubisco had evolved in response to differing CO2 concentration. CONCLUSIONS: The results revealed that the variability in the Rubisco L-subunit sequence in orchids and bromeliads is composed of coevolving sites under potential positive adaptive signal. The sequence variability was related to δ13C in orchids and bromeliads, however it could not be linked to the variability found in the kinetic properties of the studied species.

The low-copy nuclear gene Agt1 as a novel DNA barcoding marker for Bromeliaceae.

BACKGROUND: The angiosperm family Bromeliaceae comprises over 3.500 species characterized by exceptionally high morphological and ecological diversity, but a very low genetic variation. In many genera, plants are vegetatively very similar which makes determination of non flowering bromeliads difficult. This is particularly problematic with living collections where plants are often cultivated over decades without flowering. DNA barcoding is therefore a very promising approach to provide reliable and convenient assistance in species determination. However, the observed low genetic variation of canonical barcoding markers in bromeliads causes problems. RESULT: In this study the low-copy nuclear gene Agt1 is identified as a novel DNA barcoding marker suitable for molecular identification of closely related bromeliad species. Combining a comparatively slowly evolving exon sequence with an adjacent, genetically highly variable intron, correctly matching MegaBLAST based species identification rate was found to be approximately double the highest rate yet reported for bromeliads using other barcode markers. CONCLUSION: In the present work, we characterize Agt1 as a novel plant DNA barcoding marker to be used for barcoding of bromeliads, a plant group with low genetic variation. Moreover, we provide a comprehensive marker sequence dataset for further use in the bromeliad research community.

Genomic footprints of repeated evolution of CAM photosynthesis in a Neotropical species radiation.

The adaptive radiation of Bromeliaceae (pineapple family) is one of the most diverse among Neotropical flowering plants. Diversification in this group was facilitated by shifts in several adaptive traits or "key innovations" including the transition from C3 to CAM photosynthesis associated with xeric (heat/drought) adaptation. We used phylogenomic approaches, complemented by differential gene expression (RNA-seq) and targeted metabolite profiling, to address the mechanisms of C3 /CAM evolution in the extremely species-rich bromeliad genus, Tillandsia, and related taxa. Evolutionary analyses of whole-genome sequencing and RNA-seq data suggest that evolution of CAM is associated with coincident changes to different pathways mediating xeric adaptation in this group. At the molecular level, C3 /CAM shifts were accompanied by gene expansion of XAP5 CIRCADIAN TIMEKEEPER homologs, a regulator involved in sugar- and light-dependent regulation of growth and development. Our analyses also support the re-programming of abscisic acid-related gene expression via differential expression of ABF2/ABF3 transcription factor homologs, and adaptive sequence evolution of an ENO2/LOS2 enolase homolog, effectively tying carbohydrate flux to abscisic acid-mediated abiotic stress response. By pinpointing different regulators of overlapping molecular responses, our results suggest plausible mechanistic explanations for the repeated evolution of correlated adaptive traits seen in a textbook example of an adaptive radiation.

From micro- to macroevolution: insights from a Neotropical bromeliad with high population genetic structure adapted to rock outcrops.

Geographic isolation and reduced population sizes can lead to local extinction, low efficacy of selection and decreased speciation. However, population differentiation is an essential step of biological diversification. In allopatric speciation, geographically isolated populations differentiate and persist until the evolution of reproductive isolation and ecological divergence completes the speciation process. Pitcairnia flammea allows us to study the evolutionary consequences of habitat fragmentation on naturally disjoint rock-outcrop species from the Brazilian Atlantic Rainforest (BAF). Our main results showed low-to-moderate genetic diversity within populations, and deep population structuring caused by limited gene flow, low connectivity, genetic drift and inbreeding of long-term isolation and persistence of rock-outcrop populations throughout Quaternary climatic oscillations. Bayesian phylogenetic and model-based clustering analyses found no clear northern and southern phylogeographic structure commonly reported for many BAF organisms. Although we found two main lineages diverging by ~2 Mya during the early Pleistocene, species' delimitation analysis assigned most of the populations as independent evolving entities, suggesting an important role of disjoint rock outcrops in promoting high endemism in this rich biome. Lastly, we detected limited gene flow in sympatric populations although some hybridization and introgression were observed, suggesting a continuous speciation process in this species complex. Our data not only inform us about the extensive differentiation and limited gene flow found among Pitcairnia flammea species complex, but they also contain information about the mechanisms that shape the genetic architecture of small and fragmented populations of isolated rock outcrop of recently radiated plants.

Are thick leaves, large mesophyll cells and small intercellular air spaces requisites for CAM?

BACKGROUND AND AIMS: It is commonly accepted that the leaf of a crassulacean acid metabolism (CAM) plant is thick, with large mesophyll cells and vacuoles that can accommodate the malic acid produced during the night. The link between mesophyll characteristics and CAM mode, whether obligate or C3/CAM, was evaluated. METHODS: Published values of the carbon isotopic ratio (δ 13C) as an indicator of CAM, leaf thickness, leaf micrographs and other evidence of CAM operation were used to correlate cell density, cell area, the proportion of intercellular space in the mesophyll (IAS) and the length of cell wall facing the intercellular air spaces (Lmes/A) with CAM mode. KEY RESULTS: Based on 81 species and relatively unrelated families (15) belonging to nine orders, neither leaf thickness nor mesophyll traits helped explain the degree of CAM expression. A strong correlation was found between leaf thickness and δ 13C in some species of Crassulaceae and between leaf thickness and nocturnal acid accumulation in a few obligate CAM species of Bromeliaceae but, when all 81 species were pooled together, no significant changes with δ 13C were observed in cell density, cell area, IAS or Lmes/A. CONCLUSIONS: An influence of phylogeny on leaf anatomy was evidenced in a few cases but this precluded generalization for widely separate taxa containing CAM species. The possible relationships between leaf anatomy and CAM mode should be interpreted cautiously.