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Multi locus plastid phylogeny of Bromelioideae (Bromeliaceae) and the taxonomic utility of petal appendages and pollen characters

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  • Goethe-Universität Frankfurt am Main and Senckenberg Research Institute Frankfurt

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For the first time a molecular phylogeny based on five plastid markers is presented for subfamily Bromelioideae (Bromeliaceae). The species set includes 40 genera / 81 species of Bromeliaceae representing all subfamilies: Bromehoideae (29 genera / 58 species), Tillandsioideae (6 genera / 8 species) and Pitcairnioideae s.l. (5 genera / 14 species). Basal clades among the Bromehoideae are identified, nevertheless the "Core Bromelioids" comprising the majority of the species display low resolution. The phylogeny obtained makes evident, that the generic concept for Aechmea Ruiz & Pav. and its allied taxa does not describe monophyletic groups. The same holds true for several subgenera of Aechmea. The phylogeny allows the assessment ofthe systematic value of two characters that have been regarded as systematic valuable for generic delimitation in the (sub)family, 1) the petal appendages and 2) the pollen morphology. Basal Bromehoideae are characterized by sulcate pollen, while the more derived Bromehoideae display three different pollen types and several transitions between the character states.
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... In addition, some clades often consist of species with similar ranges, at least at the scale of co-occurrence within a single country or state. The phylogenetic reconstruction of Schulte & Zizka (2008) also indicated that groups of genera with similar geographic distribution (and possibly origin) might be closely related. Similar results were obtained by Aguirre-Santoro et al. (2015 when analyzing lineages in the Ronnbergia alliance. ...
... This point of view is supported by the late ontogenetic development of petal appendages, which can be lost and/or gained repeatedly without affecting the development and function of other floral organs (Brown & Terry 1992). Based on a multilocus plastid phylogeny, Schulte & Zizka (2008) concluded that petal appendages are too homoplasious to be used in the higher-level classification of Bromeliaceae, showing several independent origins within the family as well as within Bromelioideae. The lack of petal appendages was recovered as an ancestral character in Bromelioideae by Schulte & Zizka (2008) and specifically for the "Ronnbergia alliance" by Aguirre-Santoro et al. (2016). ...
... Based on a multilocus plastid phylogeny, Schulte & Zizka (2008) concluded that petal appendages are too homoplasious to be used in the higher-level classification of Bromeliaceae, showing several independent origins within the family as well as within Bromelioideae. The lack of petal appendages was recovered as an ancestral character in Bromelioideae by Schulte & Zizka (2008) and specifically for the "Ronnbergia alliance" by Aguirre-Santoro et al. (2016). Brown & Terry (1992) recognized Bromelioideae as the subfamily with the most complex and variable petal appendages. ...
Article
Generic status for the Amazonian Hylaeaicum is proposed within the Aechmea alliance, excluding it from the “Nidularioid complex” in general and from Neoregelia in particular. The monophyly of this new genus is supported by molecular phylogenetic analyses. The taxonomic circumscription of Hylaeaicum is based on the combination of geographical range and morphological characters, such as clonal growth, inflorescence structure, petal and corolla conformation, petal appendages, ovary, ovule, stigma, pollen, fruit, and seed, as well as seed anatomy, thoroughly documented and illustrated from field-collected specimens that flowered in cultivation in the Rio de Janeiro Botanical Garden, the Marie Selby Botanical Gardens, and in Refúgio dos Gravatás. The presence of seeds with long bicaudate appendages on both chalazal and micropylar ends is reported for the first time in Bromelioideae and considered an important character to distinguish Hylaeaicum from the related genera in the Aechmea alliance. In order to support the morphological distinctness of Hylaeaicum, the most varied and complete documentation of stigmata, fruits, and seeds of Bromelioideae is also presented for the first time, covering 24 genera and 17 subgenera. Fourteen new combinations, including 12 species and two varieties, are proposed.
... Bromelioideae established by Schulte and Zizka (2008). The early diverging lineages comprise six genera (Bromelia, Deinacanthon, Fascicularia, Fernseea, Greigia, Ochagavia) and share morphological similarities in terms of the terrestrial life form, lack of water impounding leave rosettes, mostly C3 metabolism (excluding Bromelia with CAM), sulcate pollen, absence of petal appendages, and an occurrence in mostly dry habitats. ...
... Greigia and Fernseea (e.g. Smith and Downs, 1979;Benzing, 2000;Schulte and Zizka, 2008;Schulte et al., 2009). Facultative epiphytic plants were reported only for the genus Fascicularia (Zizka et al., 1999). ...
... Facultative epiphytic plants were reported only for the genus Fascicularia (Zizka et al., 1999). be the key innovations of this group resulting in an increased speciation (due to CAM) and decreased extinction (due to tank habit) (Schulte et al., 2008;Schulte and Zizka, 2009;. Figure Previous studies hypothesised that the lineages of Puyoideae and Bromelioideae diverged about 10 mya around the southern Andes and more precisely maybe in central Chile (Givnish et al., 2007(Givnish et al., , 2011(Givnish et al., , 2014Jabaily and Sytsma, 2010). ...
Thesis
Full-text available
Phylogenetic trouble unleashed The first part of my thesis deals with a comprehensive phylogeny of the Bromelioideae subfamily. The family Bromeliaceae is subdivided into eight subfamilies, one of them is the Bromelioideae. Phylogenetic relationships among the Bromelioideae are still poorly understood and many of the extant genera are suspected to be not monophyletic. Especially Aechmea, the largest and most polymorphic genus constitutes many questions and the genus was used as a depot for taxonomically problematic species. The phylogenetic study presented here is the most comprehensive one so far, covering about half of the known species (434 of 965, Table 1) of Bromelioideae. The phylogeny was generated using plastid (atpB-rbcL, matK, rps16, ycf1_1, ycf1_6) and nuclear (AGT1_exon, ETS, G3PDH, PHYC, RPB2) genetic markers. The markers were analysed individually as well as combined using maximum likelihood and Bayesian analysis. The comparison of plastid vs. nuclear data revealed significant differences which were discussed in detail and hypothesised to indicate hybridisation in certain lineages. Nevertheless, the combination of both datasets increased the overall resolution of the phylogeny and was used to discuss the results in the light of previous studies. The entire phylogeny was divided into 32 groups for discussion. These groups represent potential genera or starting points for further studies in order to reorganise the polyphyletic genera of Bromelioideae into monophyletic lineages. Many extant genera of the eu-Bromelioideae were found to be not monophyletic. Monophyly was observed for the genera Acanthostachys, Billbergia, Cryptanthus, Disteganthus, Hoplocrypanthus, Lapanthus, Orthocryptanthus, Orthophytum, Rokautskyia, Ronnbergia, Sincoraea, Wittmackia and the monotypic ones (Deinacanthon, Eduandrea, Fascicularia, Hohenbergiopsis, Pseudananas). The genus concept proposed by Smith and Downs (1979) is therefore rejected, as well as the taxonomic utility of petal appendages, which were mainly used to delimit genera. In summary, this study and recent studies highlighted other morphological characters (e.g. pollen morphology, stigma type) as much more informative. However, no single character should be used to delimit genera and combinations of relevant characters are required. Even the petal appendages can pose a taxonomical important character at certain taxonomic level. The combination of biogeography and phylogeny revealed that species of some groups which co- occur in a biome or region are also phylogenetically closely related. These groups were not recognised before because the misinterpretation of homoplastic characters led to wrong taxonomical conclusion. For example, the recent re-organisation of the Cryptanthoid group and the re-establishment of Wittmackia with the former Hohenbergia subgen. Wittmackiopsis species highlighted, among other characters, the importance of biogeography. Another case is the subgenus Neoregelia subgen. Hylaeaicum which is geographically and phylogenetically separated from the Nidularioid group and therefore has to be excluded. 5 The large phylogeny presented here gives evidence for multiple invasions of the Brazilian biomes (Amazon Forest, Atlantic Forest, Cerrado, Caatinga) as well as of Central America and the Greater Antilles. It is important to note that the phylogeny is lacking resolution in the deeper nodes. Confident assumptions are therefore hindered and the historical biogeography of Bromelioideae remains cryptic. Anyway, the Atlantic Forest is nowadays the diversity hotspot of the core Bromelioideae and critically endangered. Extensive conservation efforts are required to protect the diverse flora, including the bromeliads. The genetic markers used so far in bromeliad phylogenies provided only limited variation resulting in often unresolved complexes. The search for additional suitable genetic markers in bromelioid phylogenies yielded the nuclear marker AGT1. The amplified fragment consists of one well conserved exon region as well as a highly variable intron. The intron was too variable for aligning it across the entire bromelioid set. On the other hand, the intron provides relevant information for inferring phylogenies of closely related species groups (e.g. in Ananas, Cryptanthoid group). Furthermore, AGT1 is proposed as a genetic barcode in Bromelioideae because it poses much more information then the commonly used ones (e.g. matK). Does size matter? The second part of this thesis deals with the genome size evolution within the family Bromeliaceae. Samples from seven subfamilies were screened with the emphasis on the subfamily Bromelioideae. The data were combined with data from literature and the observed patterns were discussed in relation to known phenomena (e.g. correlations to environment and life form). In the second sub-chapter I have chosen the species Tillandsia usneoides to study the intraspecific genome size variation in combination with morphology and biogeography. Genome size and base composition were measured using the flow cytometry technique. Bromeliaceae comprises mostly diploid species with predominantly 50 small chromosomes (2n), small genome sizes (0.59-4.11 pg) and normal GC content (36.46-42.21 %) compared to other families. Polyploidy was observed so far in the subfamilies Bromelioideae, Tillandsioideae and Pitcairnioideae. Triploids, tetraploids and potential hexaploids were identified. The genera show significant differences in holoploid genome size and base composition throughout the entire family. GC content is weakly positively correlated with genome size. Significant intraspecific genome size variation has been observed, including polyploidization, but no endopolyploidy and no variation in dioecious species. Within the subfamily Bromelioideae, the observed genome size between the early diverging lineages and the core Bromelioideae supports this division. The differences are due to a higher proportion of polyploids in the early diverging lineages and a significant higher 6 GC content in the core Bromelioideae. Both groups differ in their life strategies and occupy principally different habitats with corresponding morphological adaptations. Hence, the early diverging lineages are predominantly terrestrial and xeromorphic. In contrast, the prevailing epiphytic core Bromelioideae are characterised by a tank habit and mostly adapted to more humid environments. Across the family and the subfamily Bromelioideae in particular, significant genome size differences between the different life forms have been observed, but no correlation to biomes within Brazil. Tillandsia usneoides is the most widely distributed species of the family Bromeliaceae. It ranges from the southeastern United States to Argentina and Chile. Tillandsia usneoides grows epiphytic and is dispersed by seeds as well as by fragments of the plant. Within the species striking morphological differences can be observed as far as size characters are concerned. Morphotypes have shown to be stable in cultivation while growing under the same conditions. In order to investigate possible reasons for the variation the relative genome size of 75 specimens covering the whole distribution range was measured and combined with morphological, distribution and climatic data. Significant variation in the relative genome size corresponded to the morphological differences and reflected the north-south distribution gradient. Genome size and morphotypes showed a positive correlation, as well as with the mean temperature of the driest and coldest quarter and the minimal temperature of the coldest month.
... Traditionally, the presence of petal appendages is of great importance and is one of the most frequently used intracalyx diagnostic characteristic in Bromeliaceae (Smith & Downs, 1974, 1977. However, it appears that the evolutionary history of Bromeliaceae has included multiple origins and losses of petal appendages, calling into question its value as a character used to separate genera (Schulte & Zizka, 2008;Aguirre-Santoro, Michelangeli & Stevenson, 2016). ...
... The combination of a great structural and morphological diversity with limited knowledge about the consistent delimitation of species and, consequently, of the genus and its subgenera, makes systematics and taxonomy of Aechmea challenging. Many authors consider Aechmea to be the most challenging taxon for current research and potentially a polyphyletic group (Smith & Downs, 1979;Smith & Till, 1998;Faria, Wendt & Brown, 2004;Schulte, Horres & Zizka, 2005;Wanderley & Martins, 2007;Schulte & Zizka, 2008;Sass & Specht, 2010;Faria, Wendt & Brown, 2010;Heller et al., 2015). ...
... Previous studies have revealed little variation in genetic markers that have traditionally been used to construct phylogenetic histories of Bromeliaceae (Terry, Brown & Olmstead, 1997, Givnish et al., 2011, Versieux et al., 2012. Phylogenetic hypotheses indicate that petal appendages appeared several times as an evolutionary adaptation, influenced by pollinators (Schulte & Zizka, 2008;Aguirre-Santoro et al., 2016). Some functions attributed to petal appendages include prevention of nectar evaporation with consequent stabilization of sugar concentration and viscosity (Brown & Terry, 1992;Benzing, 2000), and reduction of the space between the filaments and style along the floral tube, directing the mouthparts of the visitor to the nectary, thus ensuring successful transfer of pollen among individuals (Brown & Gilmartin, 1984, 1989Evans & Brown, 1989). ...
Article
Aechmea (Bromeliaceae) is a large genus with controversial systematics and distinct flower shapes and pollinators. We explored floral anatomy and development in two Aechmea spp. belonging to different subgenera to contribute useful information on reproductive biology and taxonomy. We examined floral buds using scanning electron and light microscopy to characterize the development of septal nectaries, petal appendages, ovules, stamens and carpels. In A. gamosepala, we confirmed that the petal appendages develop late, whereas in A. correia-araujoi they develop earlier during floral development. Petal appendage formation included positional changes, possibly affecting floral attributes and visitation by insects, rather than vertebrates. Nectar is released through three basal orifices distally on the ovary, and here we document the link between the nectary region, through discrete canals, upward to the conduplicate lobes of the wet stigma. Improved understanding of the floral development and morphology of Aechmea may help to explain the existence of polymorphic flowers in this genus and may have implications for studies on interactions with pollinators and systematics.
... The morphological data analysed in Aechmea corroborate its difficult delimitation in relation to other related genera of Bromelioideae. Thus, there is much overlap of generic characters, few of which are unique to each taxon (Wanderley & Martins 2007;Schulte & Ziska 2008;Sass & Specht 2010;Evans et al. 2015;Heller et al. 2015;Goetze et al. 2016). ...
... The subgenus Ortgiesia covers species that are characterised by a combination of mucronate and conate sepals, and cucullate petals, which separate them from the species in the remaining subgenera (Smith & Downs 1979). Ortgiesia has emerged as monophyletic in some studies (Horres et al. 2007;Schulte & Ziska 2008;Silvestro et al. 2014) and paraphyletic in others (Sass & Specht 2010;Evans et al. 2015) and is confirmed as a natural group by Goetze et al. (2016) Wanderley and Moreira (2000) have highlighted the importance of adding more morphological characters to the generic delimitation in Bromeliaceae, emphasising the use of pollen morphology for a more consistent diagnostic analysis. Molecular phylogenetic analyses which have used pollen characters have been increasingly taken into consideration in several important studies on angiosperms, especially in Monocotyledons (Furness & Rudall 2001;Thornhill & Crisp 2012;da Fourny et al. 2013;Tuler et al. 2017), where the pollen data is relevant for defining clades in Bromeliaceae (Harley & Zavada 2000;Furness & Rudall 2001;Aguirre-Santoro et al. 2016). ...
... The relationship between these species in the authors' research was recognised in part by the palynotaxonomic distinction found in this work. It was noted that the phylogenetic relationships presented by the authors were very close to those observed by other authors (Horres et al. 2007;Schulte & Ziska 2008;Silvestro et al. 2014;Evans et al. 2015). ...
Article
The pollen morphology of 16 species of Aechmea subgenus Ortgiesia is characterised, represented by 59 specimens including original data provided for A. kleinii, A. pimenti-velosoi, A. winkleri, Aechmea sp1 and Aechmea sp2. The pollen grains are monads, subisopolar, amb ellipsoidal, slightly flattened/convex in equatorial view, presenting some spheroidal pollen grains at a small percentage, 2(3)-porate, with small to large pores, pore shape circular or elliptic. The exine on the central area of the pollen grain varied from ‘reticulate’ to ‘predominantly microreticulate’ and less frequently from ‘foveolate’ to ‘microreticulate’. Ortgiesia may be considered stenopalynous by the porate aperture pattern and reticulate sculpturing in most cases. However, some secondary details of the exine ornamentation, such as the size variations of the lumina near the pores, as well as the size and shape of the lumina and muri in the central area of the pollen grain, helped to recognise some groups. Multivariate analyses, based on the pollen grain metric variables, similarly grouped species that are morphologically and taxonomically related by their vegetative and reproductive characteristics, such as A. calyculata and A. kleinii, and A. gamosepala and A. cylindrata, while in the remaining species the palynological similarity was less or null, such as in A. blumenavii and A. kertezsiae; A. blumenavii and A. calyculata; A. caudata and A. coelestis; A organensis and A. coelestis, A. gracilis and A. coelestis. Our results allowed an improved morphological characterisation of Ortgiesia and brought to light important data to complement the palynotaxonomy of the subgenus.
... Bromeliaceae is a plant family found almost exclusively in the Neotropics that has a striking evolutionary history (Givnish et al., 2011(Givnish et al., , 2014. Common cases of homoplasy in Bromeliaceae reinforce the importance of morphological convergence along the evolutionary history of the family (Barfuss, Samuel, Till, & Stuessy, 2005;Crayn, Winter, & Smith, 2004;Givnish et al., 2014;Sass & Specht, 2010;Schulte & Zizka, 2008). ...
... Morphological convergence is associated with inaccurate systematics and evolutionary relationships in Bromelioideae -one of eight subfamilies of Bromeliaceae Heller, Leme, Schulte, Benko-Iseppon, & Zizka, 2015;Louzada et al., 2014;Sass & Specht, 2010;Schulte, Barfuss, & Zizka, 2009;Schulte & Zizka, 2008). However, cases of convergence in Bromelioideae have never been studied to understand their importance in this subfamily's evolutionary history. ...
Article
Aim We investigate the evolutionary mechanisms that allow morphologically convergent lineages to share the same geographical space. We compared the evolutionary events that occurred along the diversification of Karawata and Aechmea subgen. Chevaliera in the Atlantic Forest by (a) verifying whether the climatic niches and habitats of Karawata and Chevaliera are similar; (b) testing whether the two groups had the same pattern of colonization in the Atlantic Forest; and (c) evaluating whether they had the same evolutionary dynamics of environmental space occupation. Location Brazilian Atlantic Forest Taxon Karawata and Aechmea subgen. Chevaliera (Bromeliaceae: Bromelioideae) Methods We explored differences in evolutionary dynamics between Karawata and Chevaliera by (a) analyzing their divergence times using Bayesian inference with a relaxed molecular clock; (b) estimating ancestral ranges and habitats with Dispersion Extinction Cladogenesis Lagrange and Statistical Dispersal Vicariance analyses; (c) testing climatic niche similarity, equivalency and overlap using principal component analysis; and, (d) evaluating shifts in speciation dynamics using Bayesian Analysis of Macroevolutionary Mixtures. Results Karawata and Chevaliera most likely originated in the Pliocene and diversified during the Pleistocene. The two clades originated in ombrophilous forests and shared a similar environmental space. However, Karawata and Chevaliera show different dynamics in the occupation of geographical and environmental spaces. Main Conclusions Our results suggest that the São Francisco and Jequitinhonha Rivers acted as geographical barriers for Karawata and Chevaliera. Differences in spatial and environmental evolutionary dynamics have allowed the two groups to occupy similar habitats as well as environmental and geographical spaces in the Brazilian Atlantic Forest.
... Encholirium, and Deuterocohnia (Gomes-da-Silva et al. 2019). Discussions of this kind are largely obscured in Aechmea due to the poor resolution of its phylogenetic history and evidence against its monophyly (Schulte and Zizka 2008;Sass and Specht 2010;Heller et al. 2015). ...
Article
Full-text available
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.
... However, ontogenetic sequences revealed that petal appendages are the last external multicellular structures formed during the development (Brown & Terry, 1992). Several studies have demonstrated the fragility of this character to differentiate genera due to high levels of homoplasy (Schulte & Zizka, 2008;Barfuss et al., 2016; Gomes-da-Silva & Souza-Chies, 2017). Nevertheless, the transfer of Vriesea spp. with petal appendages to Tillandsia proposed by Grant (1993Grant ( , 1995Grant ( , 2004 was corroborated by the phylogenetic analyses of Barfuss et al. (2016) Barfuss et al. (2016). ...
Article
Vriesea is the second largest genus in Tillandsioideae, the most diverse subfamily of Bromeliaceae. Although recent studies focusing on Tillandsioideae have improved the systematics of Vriesea, no consensus has been reached regarding the circumscription of the genus. Here, we present a phylogenetic analysis of core Tillandsioideae using the nuclear gene phyC and plastid data obtained from genome skimming. We investigate evolutionary relationships at the intergeneric level in Vrieseeae and at the intrageneric level in Vriesea s.s. We sampled a comprehensive dataset, including 11 genera of Tillandsioideae and nearly 50% of all known Vriesea spp. Using a genome skimming approach, we obtained a 78 483-bp plastome alignment containing 35 complete and 55 partial protein-coding genes. Phylogenetic trees were reconstructed using maximum-likelihood based on three datasets: (1) the 78 483 bp plastome alignment; (2) the nuclear gene phyC and (3) a concatenated alignment of 18 subselected plastid genes + phyC. Additionally, a Bayesian inference was performed on the second and third datasets. These analyses revealed that Vriesea s.s. forms a well-supported clade encompassing most of the species of the genus. However, our results also identified several remaining issues in the systematics of Vriesea, including a few species nested in Tillandsia and Stigmatodon. Finally, we recognize some putative groups within Vriesea s.s., which we discuss in the light of their morphological and ecological characteristics.
... Smith & Kress (1990) elevated the 7 heterotypic subgenera of the 1979-treatment to the rank of genus, but this did not eliminate the confusion and was mostly not followed by later authors. All recent molecular studies agree that Aechmea in the traditional circumscription is highly polyphyletic (Schulte & al. 2005, Horres & al. 2007, Schulte & Zizka 2008, Schulte & al. 2009, Evans & al. 2015, Heller & al. 2015, Aguirre-Santoro & al. 2016. Sass & Specht (2010) not only confirm the genus to be polyphyletic, but moreover found its species to be dispersed throughout the higher core bromelioids, making several other genera paraphyletic. ...
Article
The continuous refinement of the morphological, anatomical, and molecular studies on the genera of the “Cryptanthoid complex”, mainly considering the recently discovered outlier species, gave rise to new interpretations of species relationships. It reinforced the monophyly of the groups, and allowed the recognition of the new monotypic genus Siqueiranthus based on a morphologically unique endemic species from northeastern Brazil on the brink of extinction, as well as generic status for Krenakanthus and Orthocryptanthus previously conceived as subgenera of Orthophytum, with readjustments in the positioning of some species. An integrative approach with the combination of multiple traits and the critical assessment of the diagnostic characters proved to be useful for the establishment of the new monophyletic genera. A new unusual species of Orthophytum is also described and illustrated, and its phylogenetic relationships are discussed.
Article
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Universal primers for amplifying and sequencing a noncoding spacer between the atpB and rbcL genes ofthe chloroplast DNA were constructed from the published sequences of Marchantia (a liverwort), tobacco, and rice. Our results indicate an evolutionary trend of increasing spacer size from liverworts, through mosses, to vascular plants. This atpB-rbcL spacer is AT-rich, consistent with other chloroplast noncoding spacers. Due to weak functional constraints, the spacer is evolving rapidly. A sequence identity of 92.2% was observed between spacers of two closely related moss species, Rhytidiadelphus loreus and R. triquestrus. Insertion/deletion events are common in the evolution of this spacer. A 23 bp deletion occurrs in R. loreus. Variation is found between two populations of Amorphophallus henryi (Araceae) and between individuals in a populations of Pasania formosana (Fagaceae). We suggest that this spacer will be useful for molecular systematics at the subspecific, specific, and generic levels and, in some species, for population genetics studies.
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The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
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Dark CO2 fixation was surveyed among species representing all three bromeliad subfamilies. Net CO2 exchange (qualitative) and absolute malate accumulation were measured. The species tested formed two groups according to their capacity for net dark CO2 uptake (Type I, negative and Type II, positive). Net positive dark CO2 fixation was associated with high PEP-carboxylase activity, with a leaf anatomy characterized by a succulent photosynthetic parenchyma with sizable vacuoles, and with xeric environments. In the field net malate accumulation was high even at night temperatures above 20C. Observations on the distribution of the different CO2 fixation patterns and associated morphological traits suggests that evolution of Bromeliaceae proceeded from a high light demanding ancestor adapted to open terrestrial, wet habitats. A subsequent invasion of arid habitats (terrestrial or epiphytic) was accompanied by the development of xerophytic adaptations including 'Crassulacean Acid Metabolism' in more than one evolutionary line.
Article
Species of Tillandsioideae are usually epiphytic and portray a range of habits from strongly xeric with thick, narrow leaves that are densely covered with conspicuous, shield-shaped, moisture-absorbing trichomes to mesic with broad, thin leaves having few and inconspicuous trichomes. Phenetic groupings and evolutionary tree construction of the nine subgenera of Tillandsia and Vriesea and of the 36 species of T. subg. Phytarrhiza by means of cluster analysis, Wagner network, and character compatability, show subgenera with the xeric and mesic habit on the same major branches and with T. subg. Allardtia in an ancestral position on the subgeneric tree. Of the 36 species of T. subg. Phytarrhiza, the 17 of xeric habit are largely on separate branches and the five species of mesic habit, mostly Ecuadorian, are centrally located on the evolutionary tree between the xeric and the 14 semi-mesic species. A phenogram based on 43 characters and portraying overall similarity supports the separation of most of the xeric from the mesic species on the Phytarrhiza tree. The xeric and semi-mesic habits seem to have evolved several times; initially during evolutionary differentiation that we recognize at the generic and subgeneric levels. Xeric and semi-mesic species follow mesic ones on each of several different branches of the Phytarrhiza tree. Pleistocene climatic history in South America helps to explain the repeated evolution of species with the xeric habit. During the past decade, we have come to recognize from paleoclimatological studies in South America that the Quaternary climate, especially in upland areas, has undergone a series of humid and xeric phases. Such would have alternately favored evolution of xeric and mesic bromeliads and this seems to have occurred.
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— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.