Character divergences and convergences in canopy-dwelling Loranthaceae

The Loranthaceae is the largest plant family with aerial branch parasites termed mistletoes. Three genera of Loranthaceae are terrestrial root parasites and the remaining 72 genera are aerial parasites. Several characters, including habit, haustorial type, germination pattern, pollen morphology, chromosome number, inflorescence morphology and flower merosity, fusion, symmetry and size, are considered to reflect evolutionary relationships within the family. Convergence is a common evolutionary pattern and can confound interpretations of evolution. We investigated character evolution by mapping character states onto a phylogenetic tree based on the nuclear ITS and chloroplast trnL–trnF regions. Convergences in form were found in several characters, including habit, haustorial type, flower symmetry and merosity. These convergences typically correspond to ecological parameters such as pollination syndrome or stresses associated with the canopy habit. Other characters such as chromosome number and germination pattern illustrate divergent evolution among clades.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 101–113.     

An origin of aerial branch parasitism in the mistletoe family, Loranthaceae

The large mistletoe family, Loranthaceae, contains 75 genera and approximately 1000 species. The family originated in the Southern Hemisphere and dispersed, apparently early, between fragments of Gondwana. It is now widely distributed on land surfaces of the former supercontinent. The Loranthaceae has three terrestrial, root-parasitic genera-a habit considered ancestral-and 72 genera of aerial, branch parasites. For almost two centuries, the origin of the mistletoe habit has been of interest to biologists. Two main evolutionary pathways have been proposed to explain the transition from terrestrial to aerial parasitism in the family. One theorizes the presence of an intermediate climbing ancestor in the path to the aerial habit. The other proposes a direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. Here we present molecular and morphological evidence that (1) the terrestrial species Nuytsia floribunda is ancestral within the Loranthaceae, (2) aerial parasitism has had multiple origins in the family, (3) the first aerial branch parasites had epicortical roots, and (4) the origin of aerial parasitism in one Old World clade involved the direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. Our results suggest that it is not necessary to evoke a climbing intermediate in the origins of aerial parasitism in the Santalales.     

Comparative haustorium morphology and vegetative reproduction in the Old World genus Scurrula L. (Loranthaceae) from the Central Nepal Himalayas

In a comparative morphological study of haustoria in the four Scurrula species occurring in the Annapurna Conservation Area (ACA) of Nepal, only one basic type of haustorium was found, regardless of host and elevation, namely a primary haustorium (leading to a wood rose) with epicortical root. The endophytic system of the primary haustorium, however, showed differences, which allowed classification into (1) flanging endophyte, (2) flanging endophyte with radial shaft, and (3) sinker endophyte. Scurrula elata and Scurrula gracilifolia showed marked differences in haustorium morphology on different hosts. Scurrula elata is most successful in establishing over a wide range of hosts due to its specific haustorium morphology and endophyte system. Epicortical roots of the genus Scurrula resemble those of other Old World Loranthaceae morphologically and functionally, but differ significantly from New World species. Vegetative reproduction by means of epicortical roots, which develop secondary haustoria and shoots, is very common in all four Scurrula species. The number of root-borne shoots produced by secondary haustoria varied among Scurrula species, depending on the age of the mistletoes as well as the length and vigour of the roots.     

Chromosome numbers in African and Madagascan Loranthaceae and Viscaceae

Eighty-five chromosome numbers representing about 63 species and 23 genera are reported for African and Madagascan Loranthaceae. The base chromosome number of all genera studied is χ= 9. This chromosome number also typifies all other Old World genera of the tribe Lorantheae, and thus supports the previously suggested thesis that the Asian and African Loranthaceae are relatively closely related. Seventy-six chromosome numbers, representing three genera ( Arceuthobium, Korthalsella, Viscum ) and 40 species are reported for African and Madagascan Viscaceae. Most of the data are for Viscum. The number χ= 14 is suggested as the base chromosome number for both Viscum and the family as a whole. The Madagascan Visca , however, have a modal chromosome number of χ= 13. Aneuploid chromosome numbers of χ= 12, 11 and 10 occur in Viscum at the north-south distributional extremes in southern Africa and Europe and, with the addition χ= 13, in all the species with eastward distributions in Madagascar, Asia and Australia. Polyploidy is rare in African and Madagascan members of both families, as is generally also true for other parts of the world where they have been studied. Translocation heterozygosity is reported for a number of species in Viscum.     

Stem anatomy of neotropical <Emphasis Type="Italic">Dioscorea</Emphasis> L. (Dioscoreaceae) and its importance to the systematics of the genus

We anatomically characterized the aerial stems of the genus Dioscorea and evaluated the use of these anatomical characteristics to better understand the taxonomy, systematics, and diversity of the component species in the neotropics. Fragments of the aerial stems of 23 species were collected for anatomical analyses utilizing conventional cytohistological techniques. Stem anatomy did not support the subgenera and neotropical sections of Dioscorea, although D. sect. Monadelpha demonstrated similar anatomical characteristics with the representatives analyzed in the present work, supporting the possible monophyletism of that section. Some New World species demonstrated characteristics described earlier for Old World species, such as two phloem units internal to the large-diameter vessels. New characters to the vascularization of new world species are described, as a single ring of vascular bundles, intercalating common and cauline bundles. Tylosoids and actinocytic stomata were the first time reported in Dioscorea, and the vascular patterns are revisited with a systematic approach.     

A phylogeny of the "evil tribe" (Vernonieae: Compositae) reveals Old/New World long distance dispersal: support from separate and combined congruent datasets (trnL-F, ndhF, ITS)

The Vernonieae is one of the major tribes of the largest family of flowering plants, the sunflower family (Compositae or Asteraceae), with ca. 25,000 species. While the family's basal members (the Barnadesioideae) are found in South America, the tribe Vernonieae originated in the area of southern Africa/Madagascar. Its sister tribe, the Liabeae, is New World, however. This is the only such New/Old World sister tribe pairing anywhere in the family. The Vernonieae is now found on islands and continents worldwide and includes more than 1500 taxa. The Vernonieae has been called the "evil tribe" because overlapping character states make taxonomic delimitations difficult at all levels from the species to the subtribe for the majority of taxa. Juxtaposed with these difficult-to-separate entities are monotypic genera with highly distinctive morphologies and no obvious affinities to any other members of the tribe. The taxonomic frustration generated by these contrary circumstances has resulted in a lack of any phylogeny for the tribe until now. A combined approach using DNA sequence data from two chloroplast regions, the ndhF gene and the noncoding spacer trnL-F, and from the nuclear rDNA ITS region for 90 taxa from throughout the world was used to reconstruct the evolutionary history of the tribe. The data were analyzed separately and in combination using maximum parsimony (MP), minimum evolution neighbor-joining (NJ), and Bayesian analysis, the latter producing the best resolved and most strongly supported tree. In general, the phylogeny shows Old World taxa to be basal and New World taxa to be derived, but this is not always the case. Old and New World species are found together in two separate and only distantly related clades. This is best explained by long-distance dispersal with a minimum of two trans-oceanic exchanges. Meso/Central America has had an important role in ancient dispersals between the Old and New World and more recent movements from South to North America in the New World.     

A complete generic phylogeny of Malpighiaceae inferred from nucleotide sequence data and morphology

? Premise of the study: The Malpighiaceae include ～1300 tropical flowering plant species in which generic definitions and intergeneric relationships have long been problematic. The goals of our study were to resolve relationships among the 11 generic segregates from the New World genus Mascagnia, test the monophyly of the largest remaining Malpighiaceae genera, and clarify the placement of Old World Malpighiaceae. ? Methods: We combined DNA sequence data for four genes (plastid ndhF, matK, and rbcL and nuclear PHYC) from 338 ingroup accessions that represented all 77 currently recognized genera with morphological data from 144 ingroup species to produce a complete generic phylogeny of the family. ? Key results and conclusions: The genera are distributed among 14 mostly well-supported clades. The interrelationships of these major subclades have strong support, except for the clade comprising the wing-fruited genera (i.e., the malpighioid+Amorimia, Ectopopterys, hiraeoid, stigmaphylloid, and tetrapteroid clades). These results resolve numerous systematic problems, while others have emerged and constitute opportunities for future study. Malpighiaceae migrated from the New to Old World nine times, with two of those migrants being very recent arrivals from the New World. The seven other Old World clades dispersed much earlier, likely during the Tertiary. Comparison of floral morphology in Old World Malpighiaceae with their closest New World relatives suggests that morphological stasis in the New World likely results from selection by neotropical oil-bee pollinators and that the morphological diversity found in Old World flowers has evolved following their release from selection by those bees.     

Bayesian mixed models and the phylogeny of pitvipers (Viperidae: Serpentes)

The subfamily Crotalinae (pitvipers) contains over 190 species of venomous snakes distributed in both the Old and New World. We incorporated an extensive sampling of taxa (including 28 of 29 genera), and sequences of four mitochondrial gene fragments (2.3kb) per individual, to estimate the phylogeny of pitvipers based on maximum parsimony and Bayesian phylogenetic methods. Our Bayesian analyses incorporated complex mixed models of nucleotide evolution that allocated independent models to various partitions of the dataset within combined analyses. We compared results of unpartitioned versus partitioned Bayesian analyses to investigate how much unpartitioned (versus partitioned) models were forced to compromise estimates of model parameters, and whether complex models substantially alter phylogenetic conclusions to the extent that they appear to extract more phylogenetic signal than simple models. Our results indicate that complex models do extract more phylogenetic signal from the data. We also address how differences in phylogenetic results (e.g., bipartition posterior probabilities) obtained from simple versus complex models may be interpreted in terms of relative credibility. Our estimates of pitviper phylogeny suggest that nearly all recently proposed generic reallocations appear valid, although certain Old and New World genera (Ovophis, Trimeresurus, and Bothrops) remain poly- or paraphyletic and require further taxonomic revision. While a majority of nodes were resolved, we could not confidently estimate the basal relationships among New World genera and which lineage of Old World species is most closely related to this New World group.     

Ultrastructure of Angiosperm Haustoria--A Review

It has been clear for many years that the evolution of parasitismin the angiosperms has taken place independently in a numberof unrelated groups (Kuijt, 1969). In other words, the parasiticorgans (haustoria) which both structurally and physiologicallyjoin host and parasite are remarkable instances of convergentevolution in these different groups. The main thread which canbe followed throughout the many anatomical studies which inthe past have been carried out on haustoria is the search forcommon denominators between various groups; that is, as to howmuch the haustoria of unrelated taxa have come to resemble eachother. When Solms-Laubach (1867–1868) more than a century agoreviewed the structure of angiosperm haustoria it required wellover one hundred pages to do so. Needless to say the bulk ofour present knowledge has been obtained since that time, andlight microscopy continues to unearth significant new information.In a recent review of haustorial anatomy (Kuijt, 1969), severalstructural parallelisms are noted. The advent of electron microscopyhas, since the latter review, resulted in a great deal of additionalinformation which has enabled certain comparisons between groupsto be made. Ultrastructural studies have quite naturally concentratedon the most readily available which, of course, are also thosewhich have been most i ntensively studied with the light microscopein the past. The haustoria of several families, such as Rafflesiaceae,Balanophoraceae, Hydnoraceae, and Lennoaceae, have scarcelybeen studied even with the light microscope. The purpose of the present paper is to give a general reviewof present knowledge of the ultrastructure of haustoria. Todo so we must of necessity ignore most recent purely anatomicalwork, except where relevant to the topics under discussion.Ultrastructural observations have been made on mistletoes (Arceuthobiumand Phthirusa, Loranthaceae), Santalaceae (several genera),Scrophulariaceae(Castilleja), Orobanchaceae (Orobanche) andConvolvulaccae (Cuscuta), in which order the discussion willproceed.     

Haustorial Structure and Functioning of the Root Hemiparastic Tree Nuytsia floribunda(Labill.) R.Br. and Water Relationships with its Hosts

Observations on the origin and mature structure of the haustoriumof the Western Australian Christmas tree (Nuytsia floribunda)corroborate and extend the findings of earlier workers. We showthat the previously described sclerenchymatous ‘horn’or ‘prong’ formed within the haustorium acts asa sickle-like cutting device which transversely severs the hostroot and then becomes lodged in haustorial collar tissue directlyopposite to that where it originated. The cutting process isdeduced to be rapid and the gland-like fluid filled structurein the haustorium is suggested to generate a hydrostatic forcedriving the device through the host root. The haustorial parenchymacells at the tight junction between the endophytic part of thehaustorium and the cut face of the host root develop balloon-likeoutgrowths which intrude into the lumina of severed xylem vesselsof the host. Experiments feeding 0.05% (w/v) basic fuchsin tofreshly cut ends of host root segments distal to terminally-attachedmature haustoria demonstrate an apoplastic pathway from hostxylem elements fractured at the interface into haustorial parenchyma,and thence through vascular tissue to the haustorium into thetranspiring plant of Nuytsia. Application of labelled water(D₂O) to uncut basal roots of potted plants ofAcacia acuminataparasitized by Nuytsia results in labelling of leafy shootsof parasite and host, indicative of haustorial uptake of waterby Nuytsia from host root xylem in the intact association. Measurementsof xylem water potentials of pot-cultured seedling Nuytsia associatedwith a range of hosts, or of mature trees of Nuytsia and partnerwoody hosts in the native habitat, demonstrate consistentlymore negative potentials in the parasite than host, suggestingthat the parasite may regularly obtain xylem water through itshaustorial apparatus. Copyright 2000 Annals of Botany Company Root hemiparasite, Nuytsia floribunda, Loranthaceae, haustorial structure, host–parasite water relations     

On the loss of uricolytic activity during primate evolution--I. Silencing of urate oxidase in a hominoid ancestor

Urate oxidase activity is not detectable in liver homogenates from the gibbon, orangutan, chimpanzee, gorilla and human. Liver homogenates from five genera of Old World and two genera of New World monkeys have easily detectable levels of urate oxidase activity. There is no evidence for extant detectable intermediate steps in the loss of urate oxidase activity in the hominoids. Urate oxidase activity from Old World and New World monkeys is stable, a simple observation which debunks a long-standing myth. Urate oxidase activity was silenced in an ancestor to the five living genera of hominoids after divergence from the Old World monkeys.     

Inter-generic variation in the male genitalia of the Braconinae (Insecta, Hymenoptera, Braconidae)

Male genitalia belonging to representatives of a total of 72 genera of Old and New World Braconinae have been examined by light and scanning electron microscopy. On the basis of features of the volsellae (setosity), the parameres (setosity), the digitus (number of teeth, shape) and basal ring (posterior extension) it was possible to identify certain generic groupings which support the general suprageneric divisions of the subfamily based on other taxonomic characters. The male genitalia are thus shown to provide a potentially useful new set of characters for the higher level classification of the braconine genera.     

A Late Miocene Accipitrid (Aves: Accipitriformes) from Nebraska and Its Implications for the Divergence of Old World Vultures

Background

Old World vultures are likely polyphyletic, representing two subfamilies, the Aegypiinae and Gypaetinae, and some genera of the latter may be of independent origin. Evidence concerning the origin, as well as the timing of the divergence of each subfamily and even genera of the Gypaetinae has been elusive.

Methodology/Principal Findings

Compared with the Old World, the New World has an unexpectedly diverse and rich fossil component of Old World vultures. Here we describe a new accipitriform bird, Anchigyps voorhiesi gen. et sp. nov., from the Ash Hollow Formation (Upper Clarendonian, Late Miocene) of Nebraska. It represents a form close in morphology to the Old World vultures. Characteristics of its wing bones suggest it was less specialized for soaring than modern vultures. It was likely an opportunistic predator or scavenger having a grasping foot and a mandible morphologically similar to modern carrion-feeding birds.

Conclusions/Significance

The new fossil reported here is intermediate in morphology between the bulk of accipitrids and the Old World gypaetine vultures, representing a basal lineage of Accipitridae trending towards the vulturine habit, and of its Late Miocene age suggests the divergence of true gypaetine vultures, may have occurred during or slightly before the Miocene.     

Mitogenomic perspectives into sciaenid fishes' phylogeny and evolution origin in the New World

Sciaenid fishes are widely distributed throughout the coastal waters and estuaries of the world. A total of 23 genera of this family are endemic to the Old World. However, evolutionary relationships among Old World sciaenid fishes and their origin have remained unresolved despite their diversity and importance. Besides, hypotheses that explain the origin and biogeographical distribution of sciaenid fishes are controversial. In this study, the complete mitochondrial genome sequences of seven representative sciaenid species were determined and a well-resolved tree was recovered. This new timescale demonstrated that the sciaenid originated during the late Jurassic to early Cretaceous Period. The estimated origin time of sciaenid fish is 208 Mya, and the origin of Old World sciaenid is estimated at 126 Mya. Reconstruction of ancestral distributions indicated a plesiomorphic distribution and center of origin in the New World, with at least one lineage subsequently dispersed to the Old World. Moreover, we conclude that the common ancestors of Old World sciaenid fishes were derived from species of New World.     

Studies on new types of haustoria in some Central EuropeanRhinanthoideae (Scrophulariaceae)

Two new types of haustoria have been found in many representatives ofRhinanthoideae. Metahaustoria are stimulated by host roots but lack contact with them. They develop a massive haustorial core with a large- and a smalled-celled portion, but little vascular core. In very old metahaustoria the vascular core is much enlarged and numerous tracheal elements develop in the reduced haustorial core and cortex. Warthaustoria are very small, occur only in the upper portions of the root system, and have host contacts. Vascular and haustorial core, and the endophyte are lacking, the intrusive cells are usually not endogenous, but rather roothair-like. Wart-haustoria may represent reduced and partly inhibited normal haustoria.     

EXPERIMENTAL INITIATION OF HAUSTORIA IN AGALINIS PURPUREA (SCROPHULARIACEAE)

The initiation and early developmental stages of the haustorium were studied in Agalinis purpurea (Scrophulariaceae). Plants were grown in a 0.9% agar inorganic medium with a 0.5% sucrose supplement. Root exudate collected from Lespedeza sericea induced the initiation of haustoria, with earliest stages evident in 6-12 hr. A 30-min exposure to exudate produced an increased frequency of haustoria and a 24-hr exposure yielded haustorial frequencies equal to the number that were initiated on control plants continuously exposed to root exudate for the 5-day growth period. The early cytological features of haustorial development are described and the possible significance of haustorial initiation in host recognition is discussed.     

Monophyly and phylogeny of cuckoos (Aves, Cuculidae) inferred from osteological characters

A reanalysis of 32 characters from the literature previously deemed diagnostic of the Cuculidae revealed only five to be synapomorphic. I subsequently examined skeletons from 54 avian families and identified nine additional synapomorphies that supported cuckoo monophyly. My cladistic analysis of 33 cuculid genera using 135 skeletal characters differs markedly from currently accepted taxonomies. The most striking deviation is the placement of both New and Old World parasitic cuckoos in the Cuculinae, supporting the evolution of brood parasitism in a single event rather than three times as previously proposed. Unlike earlier classifications, the Cuculinae also includes the facultative parasites Coccyzus. This, suggests that the ancestral Coccyzus was an obligate parasite, and is consistent with the many behavioral adaptations to parasitism exhibited by this genus. Other changes include the placement of three subfamilies, comprising non-parasitic, terrestrial cuckoos of Old World (Centropodinae and Carpococcystinae) and New World (Neomorphinae) distribution, in basal positions on the tree. Nineteen characters support a sister relationship between the Hoatzin ( Opisthocamus hoatzin Müller) and turacos (Musophagidae), and not cuckoos. Three synapomorphies of the os carpi ulnare were found to unite the Cuculidae, turacos, and the Hoatzin, suggesting that these three diverse taxa may constitute a monophyletic group.     

A Phylogeny‐Based Comparison of Tarantula Spider Anti‐Predator Behavior Reveals Correlation of Morphology and Behavior

We studied anti‐predator strategies in nine species of tarantulas from Asia, Africa, and the Americas. Tarantulas in the New World possess urticating hairs which induce inflammation when in contact with vertebrate mucus membranes and skin. In contrast, tarantulas from the Old World lack this defense but are observed to exhibit a much greater willingness to escalate to an active defense when provoked. We had three goals: (1) describe the behaviors exhibited by each taxon in response to two levels of provocation, (2) look for the presence of alternative classes of anti‐predator strategy as predicted by the Old World–New World dichotomy in aggressive defense, and (3) examine the evolution of these behaviors in the context of the phylogeny of the group. We compared the response of nine different mygalomorph spider genera to two levels of aversive stimuli: puffs of air and prodding. We found that the overall structure of the defensive behavior was similar between the different taxa, consisting of fleeing, rearing, striking, and biting. Some genera did exhibit unique behaviors such as stridulating (Hysterocrates) or rocking (Haplopelma and Selenocosmia). We found that the genera from the New World exhibited low levels of escalation in their defense behaviors, while those from the Old World readily escalated to striking and biting. Our findings are consistent with the hypothesis that the possession of urticating hairs is associated with very low levels of active defense behaviors such as striking and biting. The phylogenetic analysis indicates that both the notable levels of aggression displayed by the African taxa tested and the relative passivity of the New World tarantulas each represents a synapomorphy.     

Parasites reveal movement of bats between the New and Old Worlds

The global distribution of bat taxa indicates that the Atlantic and Pacific Oceans are effective barriers to movement between the Old and New Worlds. For instance, one of the major suborders, Yinpterochiroptera, has an exclusively Old World distribution, and within the other, Yangochiroptera, no species and only five genera are common to both. However, as bats are sometimes blown out to sea, and have colonised isolated islands, occasional natural movement between the New and Old Worlds does appear to be possible. Here we identify new genotypes of a blood parasite, Trypanosoma dionisii, in Old World bats that are closely related to South American strains. Using highly conservative calibration points, divergence of Old and New World strains is estimated to have occurred 3.2-5.0 million years ago (MYA), depending on the method used (upper 95% CL for maximum time 11.4MYA). The true date of divergence is likely to be considerably more recent. These results demonstrate that taxon-specific parasites can indicate historical movements of their hosts, even where their hosts may have left no lasting phylogenetic footprint.     

Bioinformatic Analysis Reveals Genome Size Reduction and the Emergence of Tyrosine Phosphorylation Site in the Movement Protein of New World Bipartite Begomoviruses

Begomovirus (genus Begomovirus, family Geminiviridae) infection is devastating to a wide variety of agricultural crops including tomato, squash, and cassava. Thus, understanding the replication and adaptation of begomoviruses has important translational value in alleviating substantial economic loss, particularly in developing countries. The bipartite genome of begomoviruses prevalent in the New World and their counterparts in the Old World share a high degree of genome homology except for a partially overlapping reading frame encoding the pre-coat protein (PCP, or AV2). PCP contributes to the essential functions of intercellular movement and suppression of host RNA silencing, but it is only present in the Old World viruses. In this study, we analyzed a set of non-redundant bipartite begomovirus genomes originating from the Old World (N = 28) and the New World (N = 65). Our bioinformatic analysis suggests ∼120 nucleotides were deleted from PCP’s proximal promoter region that may have contributed to its loss in the New World viruses. Consequently, genomes of the New World viruses are smaller than the Old World counterparts, possibly compensating for the loss of the intercellular movement functions of PCP. Additionally, we detected substantial purifying selection on a portion of the New World DNA-B movement protein (MP, or BC1). Further analysis of the New World MP gene revealed the emergence of a putative tyrosine phosphorylation site, which likely explains the increased purifying selection in that region. These findings provide important information about the strategies adopted by bipartite begomoviruses in adapting to new environment and suggest future in planta experiments.