Reproductive cycle of Pistacia lentiscus (Anacardiaceae) in Southern Italy

ABSTRACT

The reproductive cycle of Pistacia lentiscus L. from southern Italy is described with special emphasis on phenology and reproductive success. The species flowers in spring, its fruits ripen in autumn and has a latent ovary period during the summer. Vegetative growth starts immediately after anthesis (end of March) and finishes by the second week of June. Bud sections showed that flower induction occurred a few weeks after shoot development. However, no change in the overall appearance of the buds was noticeable before the following spring. Flowering is very synchronous within a plant, and a clear overlap in the flowering times of the two sexes occurred in the population studied. Although P. lentiscus seems to be highly reproductive because of the numerous fruits generally found on the plants in autumn, its reproductive success (as percent of flowers which develop fruits with seed) is low. Very large numbers of flowers never develop fruit and drop at different stages during fruit development. Moreover, numerous fruits have no seed because of parthenocarpy, embryo abortion or insect damage. In P. lentiscus, low reproductive success is not uniform within the population because the number of empty fruits per plant is highly variable between the plants. Our observations suggest that rain at flowering can make pollination a limiting factor for fruit set because of the reduction in the quantity of available pollen. Since these results are in agreement with those reported for populations in Israel and Spain, such phenomena could be genetically determined, and therefore common to this species throughout the Mediterranean region.     

Female biased sex ratios in Pistacia lentiscus L. (Anacardiaceae)

Sex ratios of populations of the dioecious shrub Pistacia lentiscus L. (Anacardiaceae) were studied. Several hypotheses concerning biased sex ratios were tested. The expected pattern of male preponderance in stressful habitats was not found. The populations located in a microclimatic gradient, such as a slope, did not display a male-biased sex ratio on the stressful middle slope. The populations located in a climatic gradient did not display a male-biased sex ratio in the more xeric habitats. Testing the hypothesis of female preponderance when pollen grain competition exists, we found a significant correlation in the direction opposite to that predicted by this hypothesis. Low density of individuals (an estimate of pollen density) correlates with a high preponderance of females but the sex ratio approaches 1:1 when density increases. This correlation should have an upper threshold in 1:1 because male-biased sex ratios have never been found.     

Pistacia lentiscus cv. Chia (Anacardiaceae) on Chios island

The author discusses the history of an unusual form ofPistacia lentiscus L. (referred to as var.chia (Desf. exPoiret) DC. on the basis of literature data and personal field observations on Chios island. As a result of incisions made on the trunk and stems the tree exudes a specific resinous gum called mastic. The production of mastic currently amounts to 160–170 tons per annum and plays an important role in the economy of the island constituting the main source of income for approx. 20 villages in the south of Chios. The history of mastic dates back 2500 years to the time ofHerodotus. The author points out that on the plantation only male individuals are cultivated; these have been selected over a long period based on mastic yield. As they represent a group of cultivated clones it would be preferable to consider them as a collective cultivar Chia.     

Unraveling reticulate evolution in North American dryopteris (dryopteridaceae)

ABSTRACT: BACKGROUND: The thirteen species of Dryopteris in North America have long been suspected of having undergone a complicated history of reticulate evolution via allopolyploid hybridization. Various explanations for the origins of the allopolyploid taxa have been suggested, and though most lines of evidence have supported the so-called "semicristata" hypothesis, contention over the group's history has continued in several recent, conflicting studies. RESULTS: Sequence data from nine plastid and two nuclear markers were collected from 73 accessions representing 35 species of Dryopteris. Sequences from each of the allopolyploids are most closely related to their progenitor species as predicted by the "semicristata" hypothesis. Allotetraploid D. campyloptera appears to be derived from a hybrid between diploid D. expansa and D. intermedia; D. celsa, from diploid D. ludoviciana x D. goldiana; and D. carthusiana and D. cristata, from diploid "D. semicristata" x D. intermedia and D. ludoviciana, respectively. Allohexaploid D. clintoniana appears to be derived from D. cristata x D.goldiana. The earliest estimated dates of formation of the allopolyploids, based on divergence time analyses, were within the last 6 Ma. We found no evidence for recurrent formation of any of the allopolyploids. The sexual allopolyploid taxa are derived from crosses between parents that show intermediate levels of genetic divergence relative to all pairs of potential progenitors. In addition, the four allotetraploids are transgressive with respect to geographic range relative to one or both of their parents (their ranges extend beyond those of the parents), suggesting that ecological advantages in novel habitats or regions may promote long-term regional coexistence of the hybrid taxa with their progenitors. CONCLUSIONS: This study provides the first thorough evaluation of the North American complex of woodferns using extensive sampling of taxa and genetic markers. Phylogenies produced from each of three datasets (one plastid and two nuclear) support the "semicristata" hypothesis, including the existence of a missing diploid progenitor, and allowed us to reject all competing hypotheses. This study demonstrates the value of using multiple, biparentally inherited markers to evaluate reticulate complexes, assess the frequency of recurrent polyploidization, and determine the relative importance of introgression vs. hybridization in shaping the histories of such groups.     

Development and characterization of eight polymorphic microsatellite loci from Pistacia lentiscus L. (Anacardiaceae)

We have developed a set of eight polymorphic nuclear microsatellite markers for the Mediterranean shrub Pistacia lentiscus by means of an enriched library method. Characterization for the eight loci was carried out on 42 individuals from two populations sampled in southern Spain. The overall number of alleles detected was 59, ranging from three to 13 per locus. Expected heterozygosity per locus and population ranged from 0.139 to 0.895. Two loci albeit only in one population (Seville) departed significantly from Hardy-Weinberg equilibrium expectations and no linkage disequilibrium between pairs of loci was detected. These markers will be used in studies of gene flow across a fragmented landscape.     

Chloroplast DNA evidence for reticulate evolution in Eucalyptus (Myrtaceae)

Four highly differentiated chloroplast DNA (cpDNA) lineages were identified in the forest tree species Eucalyptus globulus Labill. (Myrtaceae) in Australia using restriction site polymorphisms from Southern analysis. The cpDNA variation did not conform with ssp. boundaries, yet there was a strong geographical pattern to the distribution of the lineages. One lineage (C) was geographically central and widespread, whereas the other three lineages were found in peripheral populations: Western (W), Northern (N) and Southern (S). Thirteen haplotypes were detected in E. globulus , seven of which belonged to clade C. At least three of the cpDNA lineages (C, N and S) were shared extensively with other species. On the east coast of the island of Tasmania, there was a major north–south difference in cpDNA in the virtually continuous distribution of E. globulus . Northern populations harboured haplotypes from clade C while southeastern populations harboured a single haplotype from clade S. This difference was also reflected in several co-occurring endemic species. It is argued that the extensive cpDNA differentiation within E. globulus is likely to originate from interspecific hybridization and 'chloroplast capture' from different species in different parts of its range. Superficially, this hybridization is not evident in taxonomic traits; however, large-scale common garden experiments have revealed a steep cline in quantitative genetic variation that coincides with the haplotype transition in Tasmania. Our cpDNA results provide the strongest evidence to date that hybridization has had a widespread impact on a eucalypt species and indicate that reticulate evolution may be occurring on an unappreciated scale in Eucalyptus .     

Molecular evidence of reticulate evolution in the subgenus Plantago (Plantaginaceae)

Polyploidization is a frequent evolutionary event in plants that has a large influence on speciation and evolution of the genome. Molecular phylogenetic analyses of the taxonomically complex subgenus Plantago were conducted to elucidate intrasubgeneric phylogenetic relationships. A nuclear-encoding single-copy gene, SUC1 (1.0-1.8 kb), was sequenced in 24 taxa representing all five sections of the subgenus Plantago and two taxa from subgenus Coronopus as the outgroup. Fifteen known polyploids and one putative polyploid were sampled to examine polyploid origins and occurrence of reticulate evolution by cloning and sequence analysis of SUC1. Phylogenetic relationships were estimated using maximum parsimony, neighbor-joining, and Bayesian analyses. For the first time, our analysis provides a highly resolved phylogenetic tree. Subgenus Plantago formed a well-supported monophyletic clade. In contrast, alleles from polyploid species were scattered across the whole SUC1 phylogenetic tree, and some independent allopolyploids originated from hybridization between distant lineages. One reason for this taxonomic complexity can be attributed to reticulate evolution within the subgenus Plantago. Our results also suggest the possibility of two independent long-distance dispersals between the northern and southern hemispheres.     

Floral structure and evolution in the Anacardiaceae

WANNAN, B. S. & QUINN, C. J, 1991. Floral structure and evolution in the Anacardiaceae. Carpel morphology and anatomy is investigated in 17 genera and carpellode morphology in 12 genera. There is an evolutionary sequence in the family from poorly differentiated, nearly apocarpous gynoecia towards syncarpous gynoecia with clearly defined stigmata, styles and ovaries. There has also been marked reduction culminating in pseudomonomery. The carpellodes of the male flowers appear more conservative, and provide evidence of affinities between genera with quite different fertile gynoecia. The characters have been polarized using Burseraceae as a sister group. Data from these sources, as well as from pericarp anatomy, wood anatomy and biflavonoid content indicate that the long standing intrafamilial classification into five tribes is artificial, and that the two small satellite families, Blepharocaryaceae and Julianiaceae should be included in the family. A large monophyletic group is recognized comprised of essentially four of the existing tribes (Anacardiëae, Dobineëae, Semecarpeae, Rhoëae), as well as the two satellite families. This group incorporates two subgroups of more closely allied genera. The remaining genera (mostly Spondiadeae) are very diverse, and for the present are placed in an artificial group characterised by a set of plesiomorphs. Relationships within this group must be resolved before a satisfactory taxonomy of the family can be achieved.     

Weak interactions between avian and insect frugivores: the case of Pistacia terebinthus L. (Anacardiaceae)

Vertebrate frugivores often feed on fruits upon or within which insects also feed, yet little information exists on the potential magnitude of interactions between these consumers. The Mediterranean shrub Pistacia terebinthus, the birds that consume its fruits, and the wasps that feed upon its seeds are examined in this study. P. terebinthus produces a highly variable fraction of final-sized red fruits that never become mature (green-colored). Red fruits can be immature, parthenocarpic, aborted, or attacked by wasps, and their pulp is much less nutritious than that of mature fruits. A total of 20 bird species consumed the fruits in the study area. Legitimate dispersers accounted for 39% of the total fruit removal, while pulp eaters and seed predators accounted for the remainder. Birds strongly preferred the mature fruits (only 4% of the fruits consumed were red). The incidence of wasps in the seeds ranged from 0 to 42% of the crop in 1989 and from 0 to 24% in 1990. The influence of avian and insect frugivore guilds on each other appears to be quite low because of the narrow overlap in resource utilization by birds and wasps, and an overall low intensity of wasp seed predation. From an evolutionary perspective, the possible ability of wasps to preclude fruit maturation appears not to be attributable to the present interaction with avian frugivores.     

Phylogenetics, biogeography, and staminal evolution in the tribe Mentheae (Lamiaceae)

? Premise of the study: The mint family (Lamiaceae) is the sixth largest family of flowering plants, with the tribe Mentheae containing about a third of the species. We present a detailed perspective on the evolution of the tribe Mentheae based on a phylogenetic analysis of cpDNA and nrDNA that is the most comprehensive to date, a biogeographic set of analyses using a fossil-calibrated chronogram, and an examination of staminal evolution. ? Methods: Data from four cpDNA and two nrDNA markers representing all extant genera within the tribe Mentheae were analyzed using the programs BEAST, Lagrange, S-DIVA, and BayesTraits. BEAST was used to simultaneously estimate phylogeny and divergence times, Lagrange and S-DIVA were used for biogeographical reconstruction, and BayesTraits was used to infer staminal evolution within the tribe. ? Key results: Currently accepted subtribal delimitations are shown to be invalid and are updated. The Mentheae and all five of its subtribes have a Mediterranean origin and have dispersed to the New World multiple times. The vast majority of New World species of subtribe Menthinae are the product of a single dispersal event in the mid-late Miocene. At least four transitions from four stamens to two stamens have occurred within Mentheae, once in the subtribe Salviinae, once in the subtribe Lycopinae, and at least twice in the subtribe Menthinae. ? Conclusions: Worldwide cooling trends probably played a large role in the diversification and present day distribution of the tribe Mentheae. Additional work is needed to ascertain relationships within some Mentheae genera, especially in the subtribe Menthinae.     

Molecular evidence for the compilospecies model of reticulate evolution in Armeria (Plumbaginaceae)

Cladistic analyses of the nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) sequences from 55 samples corresponding to 34 taxa in the genus Armeria reveal that ITS sequence diversity among and within species utterly conflicts with patterns of morphological similarity. Three facts are apparent from the results here reported: (1) different samples of a single subspecies, A. villosa subsp. longiaristata, appear in three of the five major clades; (2) samples of at least one of the six subspecies of A. villosa appear in four of the five major clades; and (3) the composition of major clades shows greater congruence with the geographic origin of plants than with the traditional systematic arrangement based primarily on morphology. Specifically, the clades here termed Ia, II, III, and IV each encompass terminals restricted to geographically delimited areas. There are alternative explanations for the ITS pattern, but the most likely one is that nucleotide positions supporting the major clades are due, in some of the samples, to concerted evolution following horizontal transfer (gene flow) rather than to recency of common ancestry. This interpretation is consistent with previous systematic and experimental evidence and implies that reticulation in Armeria may be extensive. Harlan and de Wet (1963, Evolution 17:497-501) proposed the compilospecies concept to account for situations in which a genetically "aggressive" species captures portions of the genome of other sympatric species by means of extensive introgression. Evidence of extensive reticulation, ecological diversification, and geographic pattern indicates that A. villosa may fit the compilospecies concept, which is here supported on molecular grounds for the first time.     

Reconstructing reticulate evolution in species-theory and practice.

We present new methods for reconstructing reticulate evolution of species due to events such as horizontal transfer or hybrid speciation; both methods are based upon extensions of Wayne Maddison's approach in his seminal 1997 paper. Our first method is a polynomial time algorithm for constructing phylogenetic networks from two gene trees contained inside the network.We allow the network to have an arbitrary number of reticulations, but we limit the reticulation in the network so that the cycles in the network are node-disjoint ("galled"). Our second method is a polynomial time algorithm for constructing networks with one reticulation, where we allow for errors in the estimated gene trees. Using simulations, we demonstrate improved performance of this method over both NeighborNet and Maddison's method.     

Preliminary investigations of hybridization/reticulate evolution in Guaranidrilus (Enchytraeidae: Oligochaeta)

The identification of gut diverticula at 7/8 as a synapomorphy and recognition of all taxa of Guaranidrilus has been obscured by losses of gut diverticula within the lineage. The homoplastic occurrence of basally unpaired peptonephridia in some enchytraeid species has similarly obscured the limits of Hemienchytraeus. Taxa with unpredictable relationships, morphogenic irregularities in some reproductive structures, and, apparently, modified modes of reproduction, suggest the possibilities of hybridization between taxa with both close and distant relationships.     

Phylogenetic analysis under reticulate evolution

The usual assumption that species have evolved from a common ancestor by a simple branching process--where each branch is genetically isolated--has been challenged by the observation of frequent hybridization between species in natural populations. In fact, most plant species are thought to have hybrid origins. This reticulate pattern of species evolution has posed problems in the definition of speciation and in phylogenetic reconstruction, especially when molecular data are used. As a result, hybridization has been largely treated as an evolutionary accident or statistical error in phylogenetic analysis. In this paper, I explicitly incorporate hybridization as an evolutionary occurrence and then conduct phylogenetic reconstruction. I first examine the reticulate evolution under a pure drift model, and then extend the theory to fit a mutation model. A least-squares method is developed for reconstructing a reticulate phylogeny using gene frequency data. The efficacy of the method under the pure drift model is verified via Monte Carlo simulations.     

Phylogenetics and evolution of host-plant use in leaf-mining sawflies (Hymenoptera: Tenthredinidae: Heterarthrinae)

The habit of mining within leaves has evolved convergently in numerous plant-feeding insect taxa. Many leaf-mining groups contain a large number of species with distinct feeding preferences, which makes them highly suitable for studies on the evolutionary history of host-plant use and on the role of niche shifts in speciation. We aimed to clarify the origin, classification, and ecological evolution of the tenthredinid sawfly subfamily Heterarthrinae, which contains c. 150 leaf-mining species that collectively feed on over 20 plant genera around the world. For this, we reconstructed the phylogeny of representative heterarthrine species and diverse outgroups from the superfamily Tenthredinoidea on the basis of DNA sequence data collected from two mitochondrial (CoI and Cytb) and two nuclear (EF-1α and NaK) genes. Thereafter, we inferred the history of niche diversification within Heterarthrinae by plotting larval host-plant associations on the trees, and by contrasting a time-calibrated leaf-miner phylogeny with the phylogeny of their host plants. The results show that: (1) heterarthrine leaf-miners constitute a monophyletic group that arose from external-feeding blennocampine lineages within the Tenthredinidae c. 110-80 million years ago; (2) heterarthrines generally radiated well after their host taxa, and extant host-plant associations therefore result from a combination of host conservatism and occasional shifts among available plant taxa; and (3) diversification in Heterarthrinae apparently occurs by multiple mechanisms, including sympatric or allopatric ecological speciation, non-ecological allopatric speciation, and possibly allochronic speciation. Overall, both present and historical host-use patterns within the Heterarthrinae exhibit striking similarities to patterns found in co-occurring herbivore taxa.     

Phylogenetics and evolution of phyllotaxy in the Solomon's seal genus Polygonatum (Asparagaceae: Polygonateae)

Polygonatum is the largest and most complex genus in tribe Polygonateae, comprising approximately 57 species widely distributed in the warm temperate, subtropical and boreal zones of the Northern Hemisphere. However, phylogenetic relationships in the genus remain poorly understood. The objectives of this study were to reconstruct the phylogenetic relationships of the genus using four plastid markers, and to examine the evolution of leaf arrangement in Polygonatum in the phylogenetic context of its closely related taxa. Thirty Polygonatum species were sampled to infer phylogenetic relationships using maximum‐likelihood and Bayesian analyses. The evolution of leaf arrangements was reconstructed using Bayesian, parsimony and likelihood methods. The phylogenetic analyses supported the current generic delimitation of Polygonatum, with Heteropolygonatum recognized as a distinct genus. Three major lineages in Polygonatum were well supported, largely correlated with geographical distribution and the most recent classification at the sectional level. However, our results did not support the currently recognized series, especially the two large series Verticillata and Alternifolia. Bayesian analyses support the alternate‐leaf arrangement as the ancestral state for Polygonatum, but parsimony and maximum‐likelihood analyses suggest an equivocal state for crown Polygonatum. Leaf arrangement was found to be evolutionarily labile. A new nomenclatural combination was made: P olygonatum section S ibirica (L.I.Abramova) Y.Meng, comb. nov. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 435–451.     

Primate numts and reticulate evolution of capped and golden leaf monkeys (Primates: Colobinae)

A recent phylogenetic study of langurs and leaf monkeys of South Asia suggested a reticulate evolution of capped and golden leaf monkeys through ancient hybridization between Semnopithecus and Trachypithecus. To test this hybridization scenario, I analysed nuclear copies of the mitochondrial cytochrome b gene (numts) from capped, golden and Phayre’s leaf monkeys. These numts were aligned with mitochondrial cytochrome b sequences of various species belonging to the genera Semnopithecus and Trachypithecus. In the phylogenetic tree derived from this alignment, the numts fell into three distinct clades (A, B and C) suggesting three independent integration events. Clade A was basal to Semnopithecus, and clades B and C were basal to Trachypithecus. Among the numts in clades A and C were sequences derived from species not represented in their respective sister mitochondrial groups. This unusual placement of certain numts is taken as additional support for the hybridization scenario. Based on the molecular dating of these integration events, hybridization is estimated to have occurred around 7.1 to 3.4 million years ago. Capped and golden leaf monkeys might have to be assigned to a new genus to reconcile their unique evolutionary history. Additionally, northeast India appears to be a ‘hot spot’ for lineages that might have evolved through reticulate evolution.     

Reconstructing patterns of reticulate evolution in plants

Until recently, rigorously reconstructing the many hybrid speciation events in plants has not been practical because of the limited number of molecular markers available for plant phylogenetic reconstruction and the lack of good, biologically based methods for inferring reticulation (network) events. This situation should change rapidly with the development of multiple nuclear markers for phylogenetic reconstruction and new methods for reconstructing reticulate evolution. These developments will necessitate a much greater incorporation of population genetics into phylogenetic reconstruction than has been common. Population genetic events such as gene duplication coupled with lineage sorting and meiotic and sexual recombination have always had the potential to affect phylogenetic inference. For tree reconstruction, these problems are usually minimized by using uniparental markers and nuclear markers that undergo rapid concerted evolution. Because reconstruction of reticulate speciation events will require nuclear markers that lack these characteristics, effects of population genetics on phylogenetic inference will need to be addressed directly. Current models and methods that allow hybrid speciation to be detected and reconstructed are discussed, with a focus on how lineage sorting and meiotic and sexual recombination affect network reconstruction. Approaches that would allow inference of phylogenetic networks in their presence are suggested.     

Phylogenetics of paniceae (poaceae)

Paniceae demonstrate unique variability of photosynthetic physiology and anatomy, including both non-Kranz and Kranz species and all subtypes of the latter. This variability suggests hypotheses of independent origin or reversals (e.g., from C(4) to C(3)). These hypotheses can be tested by phylogenetic analysis of independent molecular characters. The molecular phylogeny of 57 species of Paniceae was explored using sequences from the grass-specific insert found in the plastid locus rpoC2. Phylogenetic analyses confirmed some long-recognized alliances in Paniceae, some recent molecular phylogenetic results, and suggested new relationships. Broadly, Paniceae were found to be paraphyletic with Andropogoneae, Panicum was found to be polyphyletic, and Oplismenus hirtellus was resolved as the sister group to the remaining ingroup species. A particularly well-supported clade in the rpoC2 tree included four genera with non-Kranz species and three with distinctively keeled paleas. As previously suggested, the PCK (phosphoenol pyruvate carboxykinase) C(4) subtype arose once within Paniceae. All clades with non-Kranz species had Kranz ancestors or sister taxa suggesting repeated loss of the Kranz syndrome.