Using leaf anatomy to solve taxonomic problems within the Anemopaegma arvense species complex (Bignonieae,Bignoniaceae)

Anemopaegma is a monophyletic lineage included in the tribe Bignonieae. The genus is taxonomically problematic, especially in the Anemopaegma arvense species complex, a group whose taxa have been delimited on the basis of leaf external morphology. Here we study the leaf anatomy of all three species and nine varieties currently included in this species complex (A. acutifolium DC., A. arvense (Vell.) Stellf. ex de Souza and A. glaucum Mart. ex DC.) in search for additional characters that may help circumscribe taxa within this group. For comparison, this study also investigated the leaf anatomy of two species that are morphologically similar to representatives of the species complex but currently placed outside it (A. album Mart. ex DC. and A. scabriusculum Mart. ex DC.). All taxa were analyzed using standard anatomical procedures and light microscopy. In addition, leaves of A. acutifolium and Anemopaegma album were analyzed with scanning electron microscopy (SEM). Overall, stomata position, composition of the vascular system of the petiole, midrib, lateral veins and margin constitution represented the most important anatomical features for the recognition of the species and varieties. The study also demonstrated that A. scabriusculum presents leaf anatomical traits that differ from those encountered in species of the Anemopaegma arvense complex, corroborating earlier anatomical and molecular phylogenetic results and indicating that A. scabriusculum is indeed best placed outside the A. arvense species complex. Leaf anatomical data also support the synonymization of some varieties of A. mirandum with A. arvense, as well as varieties of A. glaucum into this species.     

Biogeography and evolution of Dolichandra (Bignonieae,Bignoniaceae)

Little information on evolutionary relationships of Neotropical organisms or on the factors that have shaped the diversity currently encountered in this region is available. However, it is clear that biotic interactions and abiotic aspects have played important roles for species diversification in the region. This study focuses on Dolichandra (Bignonieae, Bignoniaceae), a clade of Neotropical lianas that is distributed broadly across different habitats and with diverse pollination and dispersal systems. We used sequences from two plastid DNA markers (ndhF and rpl32‐trnL) and one nuclear gene (PepC) to infer phylogenetic relationships in Dolichandra using parsimony and Bayesian approaches. We then used this phylogenetic framework as basis to study the biogeographic history, reconstruct the evolution of morphological characters and test the impact of morphology and environment on the diversification of the genus. More specifically, we: (1) time‐calibrate the phylogenetic tree of Dolichandra; (2) estimate the ancestral areas of the various lineages; (3) estimate the ancestral states of discrete and continuous morphological traits; (4) test for phylogenetic signal in environmental and phenotypic data; and (5) test whether morphological characters and/or niche evolution are correlated with cladogenesis. All Dolichandra spp. are monophyletic in the combined molecular phylogeny; relationships among species are generally well resolved, although poorly supported in some instances. The genus is inferred to have originated 36.43–26.23 Mya, possibly in eastern South America. Ancestral state reconstructions of continuous and discrete floral characters inferred a mixed morphology as the ancestral condition for the group. Phylogenetic signal differed between perianth and sexual whorls and gradual evolution was recovered for all traits except style length and anther length. Environmental variables showed no phylogenetic signal and a pattern of variation that was not correlated with branch length, suggesting that environmental transitions were concomitant with speciation. Dispersal is inferred to be the main driver of the differential distribution observed among species. In addition, climatic preferences and floral characters seem to have been important reproductive barriers in Dolichandra. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 403–420.     

Palynological survey of subtribe Pithecocteniinae (Bignonieae,Bignoniaceae)

The pollen morphology of subtribe Pithecocteniinae was reviewed. Thirty species of the six genera currently recognized, namely Amphilophium, Distictis, Distictella, Glaziovia, Haplolophium and Pithecoctenium, were considered. All the species surveyed fell into one of the two pollen groups: (1) inaperturate, spheroid pollen; and (2) stephanocolpate, prolate pollen. The former group included the studied species of Distictis, Distictella and Pithecoctenium, the latter species of Amphilophium, Glaziovia and Haplolophium. The variation of exine sculpture and thickness did not show any taxonomic relationships. An argument for considering pollen features, together with other morphological characters, to elucidate monophyletic units within Pithecocteniinae is presented. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 155–162.     

Untangling the phylogeny of neotropical lianas (Bignonieae, Bignoniaceae)

The tribe Bignonieae (Bignoniaceae) is a large and morphologically diverse clade of neotropical lianas. Despite being a conspicuous component of the neotropical flora, the systematics of the tribe has remained uncertain due to confusing patterns of morphological variation within the group. Chloroplast (ndhF) and nuclear (PepC) DNA sequences were used here to reconstruct the phylogeny of Bignonieae. Individual analyses of ndhF and PepC were highly similar to one another, yet localized differences in the placement of six species suggests some conflict between data sets. Combined analyses result in trees that are consistent with those from the individual analyses and provide greater support for the suggested relationships. This phylogeny provides important new insights into the systematics of the tribe. It identifies 21 strongly supported species groups, eight of which broadly correspond to currently recognized genera. In addition, each of these 21 species groups is supported by morphological synapomorphies. The consistency between morphological and molecular data suggests that the current phylogeny provides a solid framework for a formal revision of the generic-level classification and for addressing other aspects of the biology of Bignonieae.     

Evolution of floral morphology and pollination system in Bignonieae (Bignoniaceae)

The radiation of angiosperms is associated with shifts among pollination modes that are thought to have driven the diversification of floral forms. However, the exact sequence of evolutionary events that led to such great diversity in floral traits is unknown for most plant groups. Here, we characterize the patterns of evolution of individual floral traits and overall floral morphologies in the tribe Bignonieae (Bignoniaceae). We identified 12 discrete traits that are associated with seven floral types previously described for the group and used a penalized likelihood tree of the tribe to reconstruct the ancestral states of those traits at all nodes of the phylogeny of Bignonieae. In addition, evolutionary correlations among traits were conducted using a maximum likelihood approach to test whether the evolution of individual floral traits followed the correlated patterns of evolution expected under the "pollination syndrome" concept. The ancestral Bignonieae flower presented an Anemopaegma-type morphology, which was followed by several parallel shifts in floral morphologies. Those shifts occurred through intermediate stages resulting in mixed floral morphologies as well as directly from the Anemopaegma-type morphology to other floral types. Positive and negative evolutionary correlations among traits fit patterns expected under the pollination syndrome perspective, suggesting that interactions between Bignonieae flowers and pollinators likely played important roles in the diversification of the group as a whole.     

The rise and evolution of the cambial variant in Bignonieae (Bignoniaceae)

SUMMARY Cambial variants represent a form of secondary growth that creates great stem anatomical diversity in lianas. Despite the importance of cambial variants, nothing is known about the developmental mechanisms that may have led to the current diversity seen in these stems. Here, a thorough anatomical analysis of all genera along the phylogeny of Bignonieae (Bignoniaceae) was carried out in order to detect when in their ontogeny and phylogeny there were shifts leading to different stem anatomical patterns. We found that all species depart from a common developmental basis, with a continuous, regularly growing cambium. Initial development is then followed by the modification of four equidistant portions of the cambium that reduce the production of xylem and increase the production of phloem, the former with much larger sieve tubes and an extended lifespan. In most species, the formerly continuous cambium becomes disjunct, with cambial portions within phloem wedges and cambial portions between them. Other anatomical modifications such as the formation of multiples of four phloem wedges, multiple-dissected phloem wedges, and included phloem wedges take place thereafter. The fact that each novel trait raised on the ontogenetic trajectory appeared in subsequently more recent ancestors on the phylogeny suggests a recapitulatory history. This recapitulation is, however, caused by the terminal addition of evolutionary novelties rather than a truly heterochronic process. Truly heterochronic processes were only found in shrubby species, which resemble juveniles of their ancestors, as a result of a decelerated phloem formation by the variant cambia. In addition, the modular evolution of phloem and xylem in Bignonieae seems to indicate that stem anatomical modifications in this group occurred at the level of cambial initials.     

Sporophytic apomixis in polyploid Anemopaegma species (Bignoniaceae) from central Brazil

Apomixis and polyploidy have been important in the evolution of the angiosperms, and sporophytic apomixis has been associated with polyembryony and polyploidy in tropical floras. We studied the occurrence of polyembryony in populations of tetraploid Anemopaegma acutifolium, A. arvense and A. glaucum from the Brazilian cerrados, and histological features of sexual and apomictic processes were investigated in A. acutifolium. All populations and species were polyembryonic (68.9–98.4% of seeds). Normal double fertilization occurred in most ovules, with exceptions being that 3% of ovules were penetrated but not fertilized and in 4% of ovules both synergids were penetrated. The penetration of both synergids suggests a continuous attraction of pollen tubes and polyspermy. Adventitious embryo precursor cells (AEPs) arose from nucellar and integumental cells of the ovule in pollinated and unpollinated A. acutifolium, indicating sporophytic apomixis. However, further embryo and endosperm development required pollination and fertilization. This pseudogamy also allows concurrent sexual embryo development. Similar polyembryony rates and polyploidy indicated that A. arvense and A. glaucum are also apomictic, forming an agamic complex similar to that observed for some species of confamilial, but not closely related Handroanthus. The co‐occurrence of apomixis and polyploidy in different groups of Bignoniaceae indicates homoplasious origin of these agamic complexes. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 77–91.     

Climate niche conservatism does not explain restricted distribution patterns in Tynanthus (Bignonieae,Bignoniaceae)

Studies on niche evolution allow us to establish how species niches have changed over time and to identify how long‐term evolutionary processes have led to present‐day species distributions. Here, we investigate the patterns of climatic niche evolution in Tynanthus (Bignonieae, Bignoniaceae), a genus of narrowly distributed species. We test the hypothesis that niche conservatism has played an important role in the history of this group of Neotropical lianas. We perform univariate and multivariate comparisons between climatic niches of species and associated environmental data with information on phylogenetic relationships. We encountered considerable divergence in niches among species, indicating that niche conservatism in climatic variables does not seem to have played a key role in the history of the genus. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 95–109.     

Leaf cuticular waxes of Tanaecium (Bignonieae,Bignoniaceae): Chemical composition and taxonomic implications

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Recovering the drivers of sampling bias in Bignonieae (Bignoniaceae) and identifying priority areas for new survey efforts

Biodiversity and Conservation - Identifying knowledge gaps and the potential biases and limitations of biological databases is essential for biogeographical research, to efficiently plan...     

Evaluating character partitioning and molecular models in plastid phylogenomics at low taxonomic levels: A case study using Amphilophium (Bignonieae,Bignoniaceae)

The accurate analyses of massive amounts of data obtained through next‐generation sequencing depend on the selection of appropriate evolutionary models. Many plastid phylogenomic studies typically analyze plastome data as a single partition, or divided by a region, using a concatenate “supergene” approach. The effects of molecular evolutionary models and character partition strategies on plastome‐based phylogenies have generally been evaluated at higher taxonomic levels in green plants. Using plastome data from 32 species of Amphilophium, a genus of Neotropical lianas, we explored potential sources of topological incongruence with different plastid genome datasets and approaches. Specifically, we evaluated the effects of compositional heterogeneity, codon usage bias, positive selection, and incomplete lineage sorting as sources of systematic error (i.e., the recovery of well‐supported conflicting topologies). We compared different datasets (e.g., non‐coding regions, exons, and codon‐aligned and translated amino acids) using concatenated approaches under site‐heterogeneous and site‐homogeneous models, as well as multispecies coalescent (MSC) methods. We found incongruences in recovered phylogenetic relationships, which were mainly located in short internodes. The MSC and concatenated approaches recovered similar topologies. The analysis of GC content and codon usage bias indicated higher substitution rates and AT excess at the third codon positions, and we found evidence of positive selection in 3% of amino acid sites. There were no significant differences among species in site biochemical profiles. We argue that the selection of appropriate partition strategies and evolutionary models is important to increase accuracy in phylogenetic relationships, even when using plastome datasets, which is still the primarily used genome in plant phylogenetics.     

New species of <Emphasis Type="Italic">Pleonotoma</Emphasis> (Bignonieae,Bignoniaceae) from Amazonia,Brazil

Two new species of Pleonotoma Miers (Bignonieae, Bignoniaceae) from Brazilian Amazonia are described and illustrated: Pleonotoma fissicalyx B. M. Gomes & Proen?a and P. longiflora B. M. Gomes & Proen?a. P. fissicalyx is characterised by foliaceous prophylls of the axillary bud, 3-ternate leaves, a large number of short racemes concentrated at the apex of the flowering branch with many visible pedicel scars, a laterally fissured, almost spathaceous calyx, and a small, narrow hypocrateriform corolla with subexserted anthers; the fruits are unknown. P. longiflora is characterised by the combination of weakly tetragonal branchlets with unribbed angles, non-foliaceous, flat, rounded prophylls of axillary bud with an eccentric tip, 2-ternate leaves, broad axillary racemes, an elongate tubular calyx and a hypocrateriform corolla up to 12 cm long; its inclusion within Pleonotoma is confirmed by molecular phylogeny.     

Mixed pollen load and late‐acting self‐incompatibility flexibility in Adenocalymma peregrinum (Miers) L.G. Lohmann (Bignonieae: Bignoniaceae)

• Mixed cross and self‐pollen load on the stigma (mixed pollination) of species with late‐acting self‐incompatibility system (LSI) can lead to self‐fertilized seed production. This “cryptic self‐fertility” may allow selfed seedling development in species otherwise largely self‐sterile. Our aims were to check if mixed pollinations would lead to fruit set in LSI Adenocalymma peregrinum, and test for evidence of early‐acting inbreeding depression in putative selfed seeds from mixed pollinations.
• Experimental pollinations were carried out in a natural population. Fruit and seed set from self‐, cross and mixed pollinations were analysed. Further germination tests were carried out for the seeds obtained from treatments.
• Our results confirm self‐incompatibility, and fruit set from cross‐pollinations was three‐fold that from mixed pollinations. This low fruit set in mixed pollinations is most likely due to a greater number of self‐ than cross‐fertilized ovules, which promotes LSI action and pistil abortion. Likewise, higher percentage of empty seeds in surviving fruits from mixed pollinations compared with cross‐pollinations is probably due to ovule discounting caused by self‐fertilization. Moreover, germinability of seeds with developed embryos was lower in fruits from mixed than from cross‐pollinations, and the non‐viable seeds from mixed pollinations showed one‐third of the mass of those from cross‐pollinations.
• The great number of empty seeds, lower germinability, lower mass of non‐viable seeds, and higher variation in seed mass distribution in mixed pollinations, strongly suggests early‐acing inbreeding depression in putative selfed seeds. In this sense, LSI and inbreeding depression acting together probably constrain self‐fertilized seedling establishment in A. peregrinum.

     

Polyploidy and aneuploidy inOphrys,Orchis, andAnacamptis (Orchidaceae)

Studies on chromosome numbers and karyotypes in Orchid taxa from Apulia (Italy) revealed triploid complements inOphrys tenthredinifera andOrchis italica. InO. tenthredinifera there is no significant difference between the diploid and the triploid karyotypes. The tetraploid cytotype ofAnacamptis pyramidalis forms 36 bivalents during metaphase I in embryo sac mother cells. Aneuploidy was noticed inOphrys bertolonii ×O. tarentina with chromosome numbers n = 19 and 2n = 38. There were diploid (2n = 2x = 36), tetraploid (2n = 4x = 72), hexaploid (2n = 6x = 108) and octoploid (2n = 8x = 144) cells in the ovary wall of the diploid hybridOphrys apulica ×O. bombyliflora. Evolutionary trends inOphrys andOrchis chromosomes are discussed.     

Polyploidy and new chromosome counts in Helichrysum (Asteraceae,Gnaphalieae)

Mitotic chromosome numbers are reported for 31 populations representing 28 taxa of Helichrysum. Twelve are new and eight others provide confirmation of a unique previous reference. A new chromosome number, 2n = 42, is reported for H. odoratissimum. Polyploidy is confirmed as the most significant evolutionary trend in chromosome number within the genus. Chromosome data agree with trends observed in phylogenetic studies: a South African and diploid origin of the genus, followed by a radiation and diversification in southern Africa and several migrations towards the north of the African continent, the Mediterranean basin and Asia. Expansion and diversification of the genus have been accompanied by several genome duplications which have led to the acquisition of the tetraploid, hexaploid and octoploid levels, all in several independent events. Both autopolyploidy and allopolyploidy are suggested as probable speciation agents within the genus. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 511–521.     

楸树大小孢子发生与雌雄配子体发育的研究

运用石蜡切片法和整体透明法对楸树(Catalpa bungei C.A.Meyer)大、小孢子发生及雌、雄配子体发育过程进行了研究.结果表明:楸树可育雄蕊2枚,花药4室,药壁发育属双子叶型,腺质异型绒毡层.小孢子母细胞减数分裂为同时型,四分体后小孢子不分离形成正四面体型四合花粉,偶有左右对称型和十字交叉型.成熟花粉为二细胞型,无萌发孔.子房上位,2室,中轴胎座,胚珠多数,倒生,单珠被,薄珠心,具珠被绒毡层.单孢原直接发育为大孢子母细胞,四分体线形排列,合点端大孢子发育为功能大孢子,胚囊发育为蓼型.雄蕊发育早于雌蕊,花开后雌、雄蕊趋于同熟.研究认为:虽然楸树雌、雄蕊发育过程中均存在一定比例的败育,但其花而不实"并非雄性或雌性不育所致.推测与其授粉受精和胚后发育有关.     

Foliar Nectaries and Glandular Trichomes in Catalpa (Bignoniaceae)

The Tertiary relic genus Catalpa, containing 11 Old and New World species, has multiple nectaries in the junctions of the major veins on the lower leaf surfaces. The generalized structure of the nectaries consists of a single, basal cell, and a single row of vertically oriented secretory cells. The nectaries are small, and contain no vascular tissue. Glandular and nonglandular trichomes are also present on the leaves. The glandular trichomes are structurally very similar to the nectaries, and probably are their precursors. Development of multiple nectaries in the lower leaf surface vein axils is considered to be an advanced strategy for attracting beneficial insects to control or minimize the effects of herbivorous insects. Chinese and American species of Catalpa are closely related, and have greater numbers of nectaries in more locations on the lower leaf surface than west Indian species. Herbivory pressures in the West Indies are postulated to be lower than on the continents, i.e. Asia and North America.     

Polyploidy,flowering phenology and climatic adaptation in Heteropogon contortus (Gramineae)

Chromosome numbers of 2n = 39, 40, 50, 60, 69, 70, 80 and 90 are reported for Heteropogon contortus from a world collection. The numbers 2n = 39, 69, 70 and 90 are new to the literature. The cytogeographic distribution indicates that the tropical latitudes are almost exclusively occupied by tetraploids while the sub-tropical latitudes are characterized by a wide range of ploidy levels from tetraploid to nonaphid. Observations on the time of flowering of these accessions using uniform grass garden techniques indicate that pan-tropical populations are made up almost exclusively of late flowering lines and those from subtropical areas are of mixed lines showing great diversity from early to late flowering types. The association of polyploidy and flowering time are discussed in relation to the possible origin of H. contortus, to its adaptation and migration. It seems reasonable to suggest that polyploidy and the development of an earlier flowering response are both adoptively advantageous and have been selected for the species’migration into sub-tropical latitudes.     

Polyploidy in Aconitum subgenus Lycoctonum (Ranunculaceae)

Chromosome numbers and morphology in 22 populations belonging to 11 taxa of Aconitum subgenus Lycoctonum (Ranunculaceae) from China were studied. Some taxa were diploid, with 2 n  = 16, but four species and two varieties were found to be tetraploid, with 2 n  = 32. They are concentrated in the Hengduan Mountains region in south-west China, indicating that polyploidy could have played an important role in the speciation of the subgenus in this region, one of the areas of the world with a high concentration of endemic species. The relationships of some of the species are discussed.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 343–353.