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.     

Phylogenetic relationships and ecological speciation in the mistletoe Tristerix (Loranthaceae): the influence of pollinators, dispersers, and hosts

Phylogenies can provide valuable information on biotic and abiotic factors associated with speciation. We examined species relationships in Tristerix (Loranthaceae), a genus of 11 species with an Andean distribution from Colombia to Chile. A previous classification divided Tristerix into subgenera Tristerix (two species) and Metastachys (nine species). We tested this classification by generating a molecular phylogeny of the genus using nuclear ribosomal DNA ITS and chloroplast atpB-rbcL intergenic spacer and trnL-F regions. All partitions generally gave congruent trees, thus a combined analysis was conducted. Tristerix was composed of a northern clade (six species) and a southern clade (four species). Tristerix verticillatus and T. penduliflorus (Metastachys) were strongly supported as members of the (southern) subgenus Tristerix clade. Speciation appears to be correlated with the emergence of matorral and cloud forest biomes and is driven by interactions with pollinators and seed dispersers. Tristerix aphyllus is sister to T. corymbosus of the matorral, not to neighboring temperate forest populations, thus rendering the latter species paraphyletic. This ecological speciation event may have occurred in sympatry. Tristerix provides excellent examples of how, during the orography of the Andes, many dynamic and interacting ecological factors have influenced their speciation.     

Resource‐directed foraging of the Neotropical mistletoe Struthanthus flexicaulis (Loranthaceae)

• Some parasitic plants are capable of vegetative propagation, which allows them access to new hosts and improves nutrient availability. We aimed to determine what factors positively influence this propagation in the xylem‐tapping Struthanthus flexicaulis, focusing on the use of directed foraging as a means of optimising access to resources.
• The study site was a rupicolous plant community in southeast Brazil. We evaluated how the success of branch propagation (by contagion) of the mistletoe is influenced by the crown height and density of its main host, the legume Mimosa calodendron. Oriented foraging was tested through comparing the response of mistletoe branches toward a potential host (resources) or a plastic net (no resources).
• Successful contagion was related to high density and the departure height of a branch from a host crown. In a high‐density area, 89% of branches reached a new host versus 21% in a low‐density area. Formation of an appressorium on either the plastic nets or hosts elicited branch growth reorientation towards it, as well as development of new branches. These responses were significantly stronger towards hosts than nets, and attributed to effective xylem tapping.
• The foraging strategy of S. flexicaulis benefits from branch response (growth and reorientation) to the development of appressoria and their resulting haustoria. The growth of appressoria on non‐resource substrates and the ensuing response optimises the mistletoe spread by allowing these substrates to act as physical support for spreading branches and to infect a host that was previously out of reach.

     

New species of Acizzia Heslop-Harrison (Hemiptera: Psyllidae) from Australian mistletoe (Loranthaceae)

Three new species of Acizzia are described from Australian mistletoe (Loranthaceae: Amyema spp.). These are: A. loranthacae sp. n., A. amyemae sp. n. and A. pendulae sp. n. They are characterised by: male proctiger with prominent posterior lobe; antenna 1.9–2.9 times width of head; forewing with costal break and pterostigma, with pattern in A. amyemae and A. pendulae but not in A. loranthacae ; and female proctiger simple in A. amyemae and A. pendulae but with prominent dorso-apical process in A. loranthacae . The Loranthaceae is a new host family record for Acizzia . Given the probable radiation of Acizzia on mimosaceous hosts, its occurrence on eucalypt-inhabiting mistletoe, yet its apparent absence from mistletoes on Acacia, is discussed.     

Is the pollen‐limited mistletoe Peraxilla tetrapetala (Loranthaceae) also seed limited?

Abstract Seed production in the endemic New Zealand mistletoe Peraxilla tetrapetala (Loranthaceae) has been shown to be consistently pollen limited, but to date there has been no test of whether the species is also seed limited. If it is not seed limited, then pollen limitation may have no effect on population size. We tested for seed limitation by sowing seeds onto host trees at high and low densities at two sites, and following survival for up to 69 months. Our rationale was that unless there is strong density‐dependent seedling mortality sufficient to negate increases in seed supply, the species would be seed limited. We simultaneously measured pollen limitation at both sites using pollen augmentation. Peraxilla tetrapetala was strongly pollen limited at both sites over 7 years at Ohau (mean Pollen Limitation Index 0.62), and 12 years at Craigieburn (mean PLI 0.44), before and during the seed‐limitation study. There was no significant overall negative effect of density on survival in sown P. tetrapetala seeds over 42–69 months. There was a significant positive effect: seeds were more likely to adhere to branches when sown at high densities. This initial advantage to high‐density seeds was gradually eroded by slightly (but non‐significantly) lower survival rates of adhered seeds at high density. By the end of the study there was no significant difference in overall survival in high and low density plantings. This means that P. tetrapetala was apparently both pollen limited and seed limited at both our sites. Hence, reduced densities of native bird pollinators caused by introduced mammalian carnivores are likely to reduce the density of adult mistletoes in the next generation. However, the generality of this result may be affected by the fact that mistletoes do not have a dense ‘seedling shadow’ under the parent mistletoe.     

Host compatibility of the cloud forest mistletoe Psittacanthus schiedeanus (Loranthaceae) in Central Veracruz, Mexico

The consequences of the seed deposition of the parasitic mistletoe Psittacanthus schiedeanus were evaluated in a 32-mo study. We conducted a field seed inoculation experiment to determine variation in seed adhesion, seed germination, seedling establishment, and plant survival to reproduction among five host species and to evaluate whether these post-dispersal processes explain mistletoe prevalence and specificity at the regional scale. Seeds without an exocarp were inoculated onto branches of individuals of the five most common host species identified in nature in central Veracruz, México. Seed fate was monitored for 2 yr, at weekly intervals for the first 2 mo and at 2-mo intervals thereafter. The height and diameter of experimental host branches and canopy cover above them were measured to see if these factors affected mistletoe establishment. Significant differences in seed attachment and seed germination were found among host species. Fewer seeds remained attached on experimental branches of Quercus germana than those of Liquidambar styraciflua, Acacia pennatula, and Platanus mexicana. Although significant differences in seed germination were observed among species (significantly greater on A. pennatula), >70% of mistletoe seeds germinated within the first 5 wk on all host species. Towards the end of the inoculation experiment, more mistletoe seedlings survived, grew, and then flowered on Liquidambar styraciflua than on A. pennatula, P. mexicana, Q. germana, or Q. leiophylla. Host branch initial height and diameter did not affect seedling survival, but seedlings survived better on trees where the canopy was more open. Our results suggest that Liquidambar styraciflua is the most compatible host species with P. schiedeanus in central Veracruz. Not surprisingly, Liquidambar is by far the most common host tree for P. schiedeanus in this area as well. We suggest that the observed local specialization is a result of seed dispersal as consequence of bird foraging and territorial behavior, host abundance, and host species compatibility.     

Parasite-host network analysis provides insights into the evolution of two mistletoe lineages(Loranthaceae and Santalaceae)

Mistletoes are ecologically important parasitic plants,with> 1600 species from five lineages worldwide.Mistletoe lineages exhibit distinct patterns of species diversification and host specificity,however,the mechanisms underlying these differences are poorly understood.In this study,we analysed a comprehensive parasite-host network,including 280 host species from 60 families and 22 mistletoe species from two lineages(Santalaceae and Loranthaceae) in Xishuangbanna,located in a biodiversity hot...     

Morphology,biology, and systematic relationships ofDesmaria (Loranthaceae)

Desmaria mutabilis is unique inLoranthaceae in having dimorphic shoots, the short shoots producing a terminal inflorescence. Other unusual features in the family are well differentiated bud scales and deciduousness. The normal position of mature plants on the trunks of large trees is shown to be a consequence of profuse vegetative reproduction from the epicortical roots, the predominant growth direction of the latter towards the trunk from the original site of establishment on a lateral branch, and the ability of epicortical roots to generate haustorial contacts through heavy host bark. The seedling is heterocotylar, one cotyledon being phanerocotylar, the other cryptocotylar and functioning as a haustorial organ in the endosperm. It is suggested thatDesmaria is a member of the primitive complex of loranthaceous genera which includesGaiadendron.     

Evolutionary relationships of the prolyl oligopeptidase family enzymes.

The prolyl oligopeptidase (POP) family of serine proteases includes prolyl oligopeptidase, dipeptidyl peptidase IV, acylaminoacyl peptidase and oligopeptidase B. The enzymes of this family specifically hydrolyze oligopeptides with less than 30 amino acids. Many of the POP family enzymes have evoked pharmaceutical interest as they have roles in the regulation of peptide hormones and are involved in a variety of diseases such as dementia, trypanosomiasis and type 2 diabetes. In this study we have clarified the evolutionary relationships of these four POP family enzymes and analyzed POP sequences from different sources. The phylogenetic trees indicate that the four enzymes were present in the last common ancestor of all life forms and that the beta-propeller domain has been part of the family for billions of years. There are striking differences in the mutation rates between the enzymes and POP was found to be the most conserved enzyme of this family. However, the localization of this enzyme has changed throughout evolution, as three archaeal POPs seem to be membrane bound and one third of the bacterial as well as two eukaryotic POPs were found to be secreted out of the cell. There are also considerable distinctions between the mutation rates of the different substrate binding subsites of POP. This information may help in the development of species-specific POP inhibitors.     

A rejoinder onOryctina (Loranthaceae)

Both of the two main generic features ofOryctina (Loranthaceae), i.e., its dioeciousness and its absence of floral bracteoles, are based on misinterpretations. Instead, both species appear to be monoecious, and both are bracteolate. Nevertheless,Oryctina should be maintained as a distinct genus, probably most closely related toMaracanthus.     

Evolutionary relationships among squids of the family Gonatidae (Mollusca: Cephalopoda) inferred from three mitochondrial loci

The oceanic squid family Gonatidae (Mollusca: Cephalopoda) is widely distributed in subpolar and temperate waters, exhibiting behavioral and physiological specializations associated with reproduction. Females of several species undergo muscular degeneration upon maturation; origins of this complex morphogenic change are unknown, hindering our understanding of ecological and morpho-physiological adaptations within the family. To provide further information regarding the evolutionary relationships within Gonatidae, three mitochondrial loci (12S rRNA, 16S rRNA, and cytochrome c oxidase subunit I) were analyzed for 39 individuals representing fourteen gonatid and six outgroup cephalopod species. In addition to elucidating relationships among gonatids, molecular data provided more information than morphological data for problematic specimens. Although some data sets are incongruent or have low nodal support values, combined molecular analysis confirms the presence of gonatid groups previously established by morphological characteristics (i.e., possessing radular teeth in seven longitudinal rows and muscular mantle tissue). These characteristics are basal to taxa possessing radular teeth in five longitudinal rows and less muscular mantle tissue, indicating that the derived forms are those species exhibiting physiological adaptation such as tissue degeneration upon maturation and egg brooding.     

Evolutionary selection pressure and family relationships among connexin genes

We suggest an extension of connexin orthology relationships across the major vertebrate lineages. We first show that the conserved domains of mammalian connexins (encoding the N-terminus, four transmembrane domains and two extracellular loops) are subjected to a considerably more strict selection pressure than the full-length sequences or the variable domains (the intracellular loop and C-terminal tail). Therefore, the conserved domains are more useful for the study of family relationships over larger evolutionary distances. The conserved domains of connexins were collected from chicken, Xenopus tropicalis, zebrafish, pufferfish, green spotted pufferfish, Ciona intestinalis and Halocynthia pyriformis (two tunicates). A total of 305 connexin sequences were included in this analysis. Phylogenetic trees were constructed, from which the orthologies and the presumed evolutionary relationships between the sequences were deduced. The tunicate connexins studied had the closest, but still distant, relationships to vertebrate connexin 36, 39.2, 43.4, 45 and 47. The main structure in the connexin family known from mammals pre-dates the divergence of bony fishes, but some additional losses and gains of connexin sequences have occurred in the evolutionary lineages of subsequent vertebrates. Thus, the connexin gene family probably originated in the early evolution of chordates, and underwent major restructuring with regard to gene and subfamily structures (including the number of genes in each subfamily) during early vertebrate evolution.     

Chromosomal relationships of the tortoises (family Testudinidae)

Banded chromosomes of five species of testudinid turtles (Geochelone pardalis, G. elongata, G. elephantopus, Gopherus berlandieri, and G. polyphemus) reveal little variation within either genus, although there are differences in amount and distribution of heterochromatin between Geochelone pardalis and G. elongata. The chromosomal position and size of the nucleolar-organizer region differs between species of the two genera.Comparisons of standard karyotypes of these species and Malacochersus tornieri with data in the literature on other tortoises show a diploid number of 52 characterizes the family. These data are consistent with those for other families which show turtles are karyotypically conservative. G-banded chromosomes of Geochelone are identical to those of Chinemys reevesi, a karyotypically primitive batagurine emydid, supporting a derivation of the tortoises from a batagurine ancestor.     

Outcrossing increases infection success in the holoparasitic mistletoe <Emphasis Type="Italic">Tristerix aphyllus</Emphasis> (Loranthaceae)

Most studies on the fitness advantage of outbreeding in host–parasite systems have been assessed from the host rather than the parasite perspective. Here, we performed experimental pollination treatments to evaluate the consequences of outbreeding on fitness-related traits in the holoparasitic mistletoe Tristerix aphyllus in a 2-year field study. Results indicate that self-pollinated plants had a lower fruit production than outcrossed plants (20.4% and 29.5% reduction in 2002 and 2003, respectively), and resulting inbred fruits were smaller than outcrossed fruits in both years. No effect was detected for seed mass. The percentage of germination of inbred seeds was 15.1% and 6.0% lower than outcrossed seeds in 2002 and 2003, respectively. Inbred seedlings had shorter radicles, which translated to a 71.6% and 60.0% reduction in infection success compared with outcrossed plants in 2002 and 2003, respectively. Overall, our results revealed significant inbreeding depression on almost every trait that was examined. Although the mean value of traits varied from a year to another, the magnitude of inbreeding depression did not change significantly between years. Our findings constitute the first evidence that outcrossing increases infection success and probably virulence in parasitic plant populations.     

Validation and redescription ofOryctina (Loranthaceae)

The formerly obscure genusOryctina v.Tiegh. is redescribed and validated. It is shown to include two species, an old one, previously known asOryctanthus scabridus Eichl., nowOryctina scabrida (Eichl.) v.Tiegh., and a new one,Oryctina subaphylla Rizz., both from Brazil.     

A second species of Ligaria (Loranthaceae)

The combinationLigaria teretiflora (Rizzini) Kuijt is proposed, based onPsittacanthus teretiflorus Rizzini, adding a second species to the genus.Ligaria teretiflora differs fromL. cuneifolia (Ruiz & Pavón) Van Tieghem in having articulated pedicels and obovate leaves which lack a necrotic apex.     

Flavonols from Scurrula ferruginea Danser (Loranthaceae)

Three natural flavonols compounds have been isolated from the ethyl acetate fraction of Scurrula ferruginea Danser (Loranthaceae). Besides quercetin and quercitrin, an unusual flavonol glycoside 4"-O-acetylquercitrin was isolated. Structures were determined using spectroscopic methods including UV, NMR and HRMS-EI. The incidence of 4"-O-acetylquercitrin, not previously reported in the Loranthaceae, is discussed. Cytotoxic evaluation on four human cancer cell lines showed quercetin to be the most active with IC50 of 35 microM on U251 (human glioblastoma cells).     

Endothecial thickenings in the another wall ofPhthirusa adunca (Loranthaceae)

The thickenings in the anther wall ofPhthirusa adunca are confined to the endothecium. This observation resembles the previous report onP. pyrifolia.     

Evolutionary history of the poly(ADP-ribose) polymerase gene family in eukaryotes

Background  

The Poly(ADP-ribose)polymerase (PARP) superfamily was originally identified as enzymes that catalyze the attachment of ADP-ribose subunits to target proteins using NAD⁺ as a substrate. The family is characterized by the catalytic site, termed the PARP signature. While these proteins can be found in a range of eukaryotes, they have been best studied in mammals. In these organisms, PARPs have key functions in DNA repair, genome integrity and epigenetic regulation. More recently it has been found that proteins within the PARP superfamily have altered catalytic sites, and have mono(ADP-ribose) transferase (mART) activity or are enzymatically inactive. These findings suggest that the PARP signature has a broader range of functions that initially predicted. In this study, we investigate the evolutionary history of PARP genes across the eukaryotes.