Identifying gaps in the photographic record of the vascular plant flora of the Americas

Field photographs of plant species are crucial for research and conservation, but the lack of a centralized database makes them difficult to locate. We surveyed 25 online databases of field photographs and found that they harboured only about 53% of the approximately 125,000 vascular plant species of the Americas. These results reflect the urgent need for a centralized database that can both integrate and complete the photographic record of the world's flora.

Paleoaltingia gen. nov., a new genus of Altingiaceae from the Late Cretaceous of New Jersey

PREMISE

Altingiaceae is a small family with a bimodal Northern Hemisphere distribution in eastern North America and eastern Asia, and a rich Cenozoic fossil record. The charcoalified fossil infructescence Paleoaltingia gen. nov. from Turonian (Late Cretaceous) deposits of New Jersey, provides new evidence of early Altingiaceae reproductive structures and has biogeographical implications in understanding modern distribution.

METHODS

Fossils were prepared using standard methods for obtaining and processing mesofossils. The fossils were examined with light microscopy, and scanning electron microscopy for observing structural and anatomical details. Phylogenetic analyses were performed using a combined matrix of molecular and morphological data.

RESULTS

Based on morphological features of the fossil and the phylogenetic analyses, the new genus, Paleoaltingia, with two species (Paleoaltingia ovum-dinosauri and P. polyodonta) is erected. The phylogenetic position of Paleoaltingia confirms affinities with living Altingiaceae.

CONCLUSIONS

The combination of characters-simple capitate infructescence, syncarpous bicarpellate, and bilocular ovary, unique sterile phyllome structures-indicates that the fossil taxa have close affinities to modern Altingiaceae. The unique characters of the phyllomes provide new information on the floral diversity of Altingiaceae. The emergence of Paleoaltingia in Late Cretaceous sediments of Northeastern North America represents the earliest fossil record of Altingiaceae and provides new insights into its biogeography.

52 million years old Eucalyptus flower sheds more than pollen grains

PREMISE

Fossils provide fundamental evidence of the evolutionary processes that crafted today's biodiversity and consequently for understanding life on Earth. We report the finding of Myrtaceidites eucalyptoides pollen grains preserved within the anthers of a 52-million-year-old Eucalyptus flower collected at Laguna del Hunco locality of Argentinean Patagonia and discuss its implications in understanding the evolutionary history of the iconic Australian genus Eucalyptus.

METHODS

Pollen grains were extracted from the flower's anthers and were then observed under light microscopy and scanning electron microscopy. The phylogenetic position of the fossil was investigated by adding pollen data to a previously published total-evidence matrix and analyzing it using parsimony.

RESULTS

We erect the species Eucalyptus xoshemium for the fossil flower. Pollen extracted from E. xoshemium belongs to the species Myrtaceidites eucalyptoides, which, until now, was only known as dispersed pollen. The numerous pollen grains recovered from the single flower allowed estimation of M. eucalyptoides' variability. Results of the phylogenetic analysis reinforce the position of this fossil within crown group Eucalyptus.

CONCLUSIONS

The discovery of these pollen grains within a Patagonian Eucalyptus fossil flower confirms the hypothesis that Myrtaceidites eucalyptoides represents fossil pollen in the Eucalyptus lineage, extends the geographic and stratigraphic fossil pollen record, and supports an earlier age for crown-group eucalypts.

Eocene Fagaceae from Patagonia and Gondwanan legacy in Asian rainforests

The beech-oak family Fagaceae dominates forests from the northern temperate zone to tropical Asia and Malesia, where it reaches its southern limit. We report early Eocene infructescences of Castanopsis, a diverse and abundant fagaceous genus of Southeast Asia, and co-occurring leaves from the 52-million-year-old Laguna del Hunco flora of southern Argentina. The fossil assemblage notably includes many plant taxa that associate with Castanopsis today. The discovery reveals novel Gondwanan history in Fagaceae and the characteristic tree communities of Southeast Asian lower-montane rainforests. The living diaspora associations persisted through Cenozoic climate change and plate movements as the constituent lineages tracked post-Gondwanan mesic biomes over thousands of kilometers, underscoring their current vulnerability to rapid climate change and habitat loss.

Response to Comment on "Eocene Fagaceae from Patagonia and Gondwanan legacy in Asian rainforests"

Denk et al agree that we reported the first fossil Fagaceae from the Southern Hemisphere. We appreciate their general enthusiasm for our findings, but we reject their critiques, which we find misleading and biased. The new fossils unequivocally belong to Castanopsis, and substantial evidence supports our Southern Route to Asia hypothesis.

Evolution of phytochemical diversity in Pilocarpus (Rutaceae)

The evolution of phytochemical diversity and biosynthetic pathways in plants can be evaluated from a phylogenetic and environmental perspective. Pilocarpus Vahl (Rutaceae), an economically important medicinal plant in the family Rutaceae, has a great diversity of imidazole alkaloids and coumarins. In this study, we used phylogenetic comparative methods to determine whether there is a phylogenetic signal for chemical traits across the genus Pilocarpus; this included ancestral reconstructions of continuous and discrete chemical traits. Bioclimatic variables found to be associated with the distribution of this genus were used to perform OLS regressions between chemical traits and bioclimatic variables. Next, these regression models were evaluated to test whether bioclimatic traits could significantly predict compound concentrations. Our study found that in terms of compound concentration, variation is most significantly associated with adaptive environmental convergence rather than phylogenetic relationships. The best predictive model of chemical traits was the OLS regression that modeled the relationship between coumarin and precipitation in the coldest quarter. However, we also found one chemical trait was dependent on phylogenetic history and bioclimatic factors. These findings emphasize that consideration of both environmental and phylogenetic factors is essential to tease out the intricate processes in the evolution of chemical diversity in plants. These methods can benefit fields such as conservation management, ecology, and evolutionary biology.

Ecometabolomic Analysis of Wild Populations of Pilocarpus pennatifolius (Rutaceae) Using Unimodal Analyses

Studies examining the diversity of plant specialized metabolites suggest that biotic and abiotic pressures greatly influence the qualitative and quantitative diversity found in a species. Large geographic distributions expose a species to a great variety of environmental pressures, thus providing an enormous opportunity for expression of environmental plasticity. Pilocarpus, a neotropical genus of Rutaceae, is rich in alkaloids, terpenoids, and coumarins, and is the only commercial source of the alkaloid pilocarpine for the treatment of glaucoma. Overharvesting of species in this genus for pilocarpine, has threatened natural populations of the species. The aim of this research was to understand how adaptation to environmental variation shapes the metabolome in multiple populations of the widespread species Pilocarpus pennatifolius. LCMS data from alkaloid and phenolic extracts of leaf tissue were analyzed with environmental predictors using unimodal unconstrained and constrained ordination methods for an untargeted metabolomics analysis. PLS-DA was used to further confirm the chemoecotypes of each site. The most important variables contributing to the alkaloid variation between the sites: mean temperature of wettest quarter, as well as the soil content of phosphorus, magnesium, and base saturation (V%). The most important contributing to the phenolic variation between the sites: mean temperature of the wettest quarter, temperature seasonality, calcium and soil electrical conductivity. This research will have broad implications in a variety of areas including biocontrol for pests, environmental and ecological plant physiology, and strategies for species conservation maximizing phytochemical diversity.

Mid-Cretaceous angiosperm radiation and an asterid origin of bilaterality: diverse and extinct "Ericales" from New Jersey

PREMISE OF THE STUDY

Numerous fossils from the Upper Cretaceous have been confidently placed within modern crown groups. Many 95-75 Myr-old taxa, however, including the taxon described herein, do not fit well with known extant crown or stem groups. Understanding such fossils and their possible affinities would certainly enhance our understanding of the circumstances involved in a major eudicot radiation.

METHODS

Bulk samples from the Old Crossman Clay Pit were prepared using standard methodology, which includes several washing and sieving steps, and a treatment with hydrofluoric acid. The fossil taxon was coded into a matrix built from the combination of two previously published morphological matrices and was analyzed using the parsimony criterion with the computer program TNT.

KEY RESULTS

The fossils have a unique combination of characters relative to living and fossil Ericales taxa, and therefore, a new genus, Teuschestanthes, is erected. Mosaic evolution and rapid parallel changes in such groups blur taxonomic distinctions, and these issues are exacerbated by limited numbers of characters available in fossils. Teuschestanthes flowers are slightly bilaterally symmetrical and somewhat variable with regard to petal disposition, suggesting an early stage in transition to bilaterality from radial symmetry early in eudicot history under pollinator selective pressure.

CONCLUSIONS

While Teuschestanthes shares characters with modern Ericales and Sapindales, there are significant non-overlapping differences between Teuschestanthes and modern Sapindales (notably, among others, ovule number). Based on available evidence, however, the position of Teuschestanthes is likely as an early offshoot of the stem clade of core Ericales (Ericales sensu stricto). Its relatively unstable floral plan may presage subsequent bilaterality associated with growing selective pressure by advanced pollinators.

A late Cretaceous fagalean inflorescence preserved in amber from New Jersey

PREMISE OF THE STUDY

An inflorescence with three pistillate flowers in amber from the early Upper Cretaceous (Turonian, ~90-94 million years ago) of central New Jersey represents the oldest known flowers with features present in an early stem complex of the Fagales. The inflorescence has characteristics of Nothofagaceae, but also has strikingly distinct characters that suggest it is intermediate between Nothofagus and other Fagales. This intermediacy is consistent with its northern hemisphere distribution.

METHODS

We investigated this new fossil by comparing it with extant and fossil members of the Fagales using light microscopy and nano-computed tomography. In addition, for exploring its relationships, we mapped the morphological characters onto a widely accepted molecular-based tree of modern basal Fagales using standard methods of character optimization.

KEY RESULTS

The phylogenetic position of the fossil inflorescence can be unequivocally determined by the presence of unique features, singly and in combination, that are found only in "basal" members of Fagales. The fossil adds critical information on the features of the early stem Fagales, evolution of the cupule in Nothofagaceae and Fagaceae, and a reasonable biogeographic hypothesis for the differentiation of southern (e.g., Nothofagaceae) and northern hemisphere Fagales.

CONCLUSIONS

This new fossil provides insight into the early evolution of Fagales and suggests that early stem Fagales that had not yet differentiated into modern families were present in the Late Cretaceous of North America. Based on available evidence, the fossil is best interpreted as an early stem member of the Fagales, with features that suggest a transition from a more generalized Nothofagus-like fagalean ancestor with some unique presumably plesiomorphic features. The presence of an enlarged perianth and flexuous styles also suggests the possibility of insect pollination, which has been lost in all Fagales with the exception of some members of subfamily Castaneoideae in Fagaceae sensu stricto (which otherwise are very different from this fossil). The poorly developed, bract-like cupule valves of the fossil can be interpreted as primitive (i.e., incipient) or as reduced from more developed cupules that are found in most modern Fagaceae and Nothofagaceae.

A mosaic Lauralean flower from the Early Cretaceous of Myanmar

PREMISE OF THE STUDY

The floral history of early angiosperms is far from complete. The fossil discussed here has the potential to expand our knowledge of timing, reproductive biology, and paleobiogeography in early angiosperms.

METHODS

Cutting-edge methodologies in CT scanning in conjunction with tomography software have opened new possibilities for discovering details in amber-preserved fossils that were inaccessible for meaningful study in the past.

KEY RESULTS

The fossil is small and complex, cupulate, with numerous stamens and a suite of characters distributed in the modern families of Laurales. The most parsimonious placement of the fossil based on morphology is as a sister taxon of Atherospermataceae + Gomortega (Gomortegaceae).

CONCLUSIONS

This fossil taxon, a Laurasian Lauralean from the mid-Cretaceous, is an important example of fossil Laurales with implications for biogeography and timing in the radiation and extinction in this group.

Climate reconstruction analysis using coexistence likelihood estimation (CRACLE): a method for the estimation of climate using vegetation

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PREMISE OF THE STUDY

Plant distributions have long been understood to be correlated with the environmental conditions to which species are adapted. Climate is one of the major components driving species distributions. Therefore, it is expected that the plants coexisting in a community are reflective of the local environment, particularly climate.•

METHODS

Presented here is a method for the estimation of climate from local plant species coexistence data. The method, Climate Reconstruction Analysis using Coexistence Likelihood Estimation (CRACLE), is a likelihood-based method that employs specimen collection data at a global scale for the inference of species climate tolerance. CRACLE calculates the maximum joint likelihood of coexistence given individual species climate tolerance characterization to estimate the expected climate.•

KEY RESULTS

Plant distribution data for more than 4000 species were used to show that this method accurately infers expected climate profiles for 165 sites with diverse climatic conditions. Estimates differ from the WorldClim global climate model by less than 1.5°C on average for mean annual temperature and less than ∼250 mm for mean annual precipitation. This is a significant improvement upon other plant-based climate-proxy methods.•

CONCLUSIONS

CRACLE validates long hypothesized interactions between climate and local associations of plant species. Furthermore, CRACLE successfully estimates climate that is consistent with the widely used WorldClim model and therefore may be applied to the quantitative estimation of paleoclimate in future studies.

Oldest known Eucalyptus macrofossils are from South America

The evolutionary history of Eucalyptus and the eucalypts, the larger clade of seven genera including Eucalyptus that today have a natural distribution almost exclusively in Australasia, is poorly documented from the fossil record. Little physical evidence exists bearing on the ancient geographical distributions or morphologies of plants within the clade. Herein, we introduce fossil material of Eucalyptus from the early Eocene (ca. 51.9 Ma) Laguna del Hunco paleoflora of Chubut Province, Argentina; specimens include multiple leaves, infructescences, and dispersed capsules, several flower buds, and a single flower. Morphological similarities that relate the fossils to extant eucalypts include leaf shape, venation, and epidermal oil glands; infructescence structure; valvate capsulate fruits; and operculate flower buds. The presence of a staminophore scar on the fruits links them to Eucalyptus, and the presence of a transverse scar on the flower buds indicates a relationship to Eucalyptus subgenus Symphyomyrtus. Phylogenetic analyses of morphological data alone and combined with aligned sequence data from a prior study including 16 extant eucalypts, one outgroup, and a terminal representing the fossils indicate that the fossils are nested within Eucalyptus. These are the only illustrated Eucalyptus fossils that are definitively Eocene in age, and the only conclusively identified extant or fossil eucalypts naturally occurring outside of Australasia and adjacent Mindanao. Thus, these fossils indicate that the evolution of the eucalypt group is not constrained to a single region. Moreover, they strengthen the taxonomic connections between the Laguna del Hunco paleoflora and extant subtropical and tropical Australasia, one of the three major ecologic-geographic elements of the Laguna del Hunco paleoflora. The age and affinities of the fossils also indicate that Eucalyptus subgenus Symphyomyrtus is older than previously supposed. Paleoecological data indicate that the Patagonian Eucalyptus dominated volcanically disturbed areas adjacent to standing rainforest surrounding an Eocene caldera lake.

Pentapetalum trifasciculandricus gen. et sp. nov., a thealean fossil flower from the Raritan Formation, New Jersey, USA (Turonian, Late Cretaceous)

The study of fossil flowers in the last 25 years has greatly increased our understanding of angiosperm diversification. Following that tradition, we here describe a new fossil taxon from the Late Cretaceous of New Jersey, Pentapetalum trifasciculandricus Martínez-Millán, Crepet et Nixon gen. et sp. nov. It includes actinomorphic pentamerous flowers with quincuncial calyx, imbricate corolla, numerous stamens of markedly different heights, and a superior tricarpellate ovary, which are morphologically consistent with the flowers of the Theaceae s.l. and of members of the order Theales sensu Cronquist. Cladistic analyses including 45 extant taxa plus the fossil, 61 morphological characters, and different combinations of the molecular markers rbcL, matK, trnL-trnF, matR, and ITS support its inclusion in the order Ericales sensu APG. Comparison with extant taxa using traditional methods of identification suggests a relation with the Theaceae s.s. (Stewartia), but the phylogenetic analyses do not support this view. Instead, the phylogenetic analysis suggests some relation to the Ternstroemiaceae/Pentaphylacaceae (Theaceae s.l.), exemplifying the importance of evaluating identifications in a phylogenetic context. The description of Pentapetalum further adds to the ample diversity of Ericales in the Late Cretaceous.

An extinct calycanthoid taxon, Jerseyanthus calycanthoides , from the Late Cretaceous of New Jersey

A new fossil genus and species, Jerseyanthus calycanthoides, is described from the Late Cretaceous (Turonian, ∼90 MYBP) Raritan Formation of New Jersey. Flowers have cupulate receptacles bearing imbricately arranged tepals that subtend a series of recurved tepals near the cup margin. Recurved tepal subtends a "stamen-staminode" pair, that includes a laminar stamen with ramified connective extensions, and an outer staminode. Outer staminodes are geniculate and incurved, and in aggregate their inner extremities define a circular area above the carpels and carpellodes. Each "stamen-staminode" pair apparently subtends (is opposite to) an inner tepal. Pollen is rounded and disulculate, with tectate columellate wall structure. Carpels are located at the center of the receptacle and have elongate styles that extend to and beyond the opening defined by the staminodal organs. Carpels are surrounded by tomentose carpellodes. Carpels include one marginally ridged seed. While these fossils do not match exactly any living species in morphology, they share numerous characters with extant members of Calycanthaceae and can be unequivocally placed within that family. Affinities of Jerseyanthus and Virginianthus were evaluated by including them in a combined analysis for the Laurales. Jerseyanthus is placed within Calycanthaceae as a sister taxon to the modern genus Calycanthus.

Fossil evidence and phylogeny: the age of major angiosperm clades based on mesofossil and macrofossil evidence from Cretaceous deposits

The fossil record has played an important role in the history of evolutionary thought, has aided the determination of key relationships through mosaics, and has allowed an assessment of a number of ecological hypotheses. Nonetheless, expectations that it might accurately and precisely mirror the progression of taxa through time seem optimistic in light of the many factors potentially interfering with uniform preservation. In view of these limitations, attempts to use the fossil record to corroborate phylogenetic hypotheses based on extensive comparisons among extant taxa may be misplaced. Instead we suggest a method-minimum age node mapping-for combining reliable fossil evidence with hypotheses of phylogeny. We use this methodology in conjunction with a phylogeny for angiosperms to assess timing in the history of major angiosperm clades. This method places many clades both with and without fossil records in temporal perspective, reveals discrepancies among clades in propensities for preservation, and raises some interesting questions about angiosperm evolution. By providing a context for understanding the gaps in the angiosperm fossil record this technique lends credibility and support to the remainder of the angiosperm record and to its applications in understanding a variety of aspects of angiosperm history. In effect, this methodology empowers the fossil record.

Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early angiosperms

Based on recent molecular systematics studies, the water lily lineage (Nymphaeales) provides an important key to understanding ancestral angiosperm morphology and is of considerable interest in the context of angiosperm origins. Therefore, the fossil record of Nymphaeales potentially provides evidence on both the timing and nature of diversification of one of the earliest clades of flowering plants. Recent fossil evidence of Turonian age (approximately 90 million years B.P.) includes fossil flowers with characters that, upon rigorous analysis, firmly place them within Nymphaeaceae. Unequivocally the oldest floral record of the Nymphaeales, these fossils are closely related to the modern Nymphaealean genera Victoria (the giant Amazon water lily) and Euryale. Although the fossils are much smaller than their modern relatives, the precise and dramatic correspondence between the fossil floral morphology and that of modern Victoria flowers suggests that beetle entrapment pollination was present in the earliest part of the Late Cretaceous.

A comparative flower and fruit anatomical study of Quercus acutissima, a biennial-fruiting oak from the Cerris group (Fagaceae)

A developmental series of flowers and fruits of Quercus acutissima (subgenus Quercus section Cerris) was collected over a growing season and examined for an intersectional, comparative anatomical study. Pistillate flowers of the current growing season, each consisting of a pistil with three long, slightly recurved styles, six tepals, and an inconspicuous ovary subtended by a few cycles of cupule scales, emerged in early May, were pollinated by mid-May, and then were quiescent for the remainder of the growing season. Flowers from the previous growing season resumed growth in mid-May, each forming three locules delimited by septa in the ovary, with two bitegmic, epitropous ovules developing in each locule. Mature embryo sacs were present by mid-July of the second growing season, although embryos were not observed until early August. Fruit maturation was complete by late September. Features that have not been described previously for the section Cerris include early-lignifying endocarp trichomes, persistent septa, and leaf primordia buttresses on the embryo. A comparison of flower and fruit developmental features with sections Quercus sensu stricto and Lobatae revealed a mosaic of shared features among the three sections.

Divisestylus gen. nov. (aff. Iteaceae), a fossil saxifrage from the Late Cretaceous of New Jersey, USA

Fossilized flowers and fruits from the Upper Cretaceous (Turonian, ca. 90 million years [my] before present) Raritan Formation of New Jersey are described as the new genus Divisestylus with two species, D. brevistamineus and D. longistamineus. The fossils are fusainized and three-dimensionally preserved. Morphological characteristics suggest affinities with extant Saxifragaceae and Iteaceae, two closely related families in Saxifragales. Similarities include a pentamerous perianth, calyx fused below into a hypanthium with free sepal lobes above, haplostemonous androecium with stamens situated opposite the calyx lobes, inferior ovary, bicarpellate gynoecium, numerous ovules on axile placentas, conspicuous intrastaminal nectary ring, and capsulate fruit opening apically. The unique fusion of the gynoecium, with carpels and stigmas fused but styles free, indicates closer affinities with extant Iteaceae, whereas other characters, such as basifixed anthers in D. brevistamineus, tricolpate and striate pollen grains, and anomocytic stomata, indicate closer affinities to Saxifragaceae. Cladistic analyses utilizing molecular data from a previously published analysis and morphological data as well as morphological data alone demonstrate the fossils share a more recent common ancestor with Iteaceae than Saxifragaceae, thereby making Divisestylus the oldest fossils known with clear affinities to Iteaceae.

Triuridaceae fossil flowers from the Upper Cretaceous of New Jersey

We report here on a series of fossil flowers exhibiting a mosaic of characters present in the extant monocot family Triuridaceae. Phylogenetic analyses of morphological data from a broad sample of extant monocots confirm the affinities of the fossils with modern Triuridaceae. The fossil flowers were collected from outcrops of the Raritan Formation (Upper Cretaceous, ∼90 million years before present), New Jersey, USA. These are the oldest known unequivocal monocot flowers. Because other reports of "earliest" monocots are all based on equivocal character suites and/or ambiguously preserved fossil material, the Triuridaceae fossils reported here should also be considered as the oldest unequivocal fossil monocots. Flowers are minute and unisexual (only male flowers are known); the perianth is composed of six tepals, lacking stomata. The unicyclic androecium is of three stamens with dithecal, monosporangiate, extrorse anthers that open by longitudinal slits. The endothecium has U-shaped type thickenings. Pollen grains are monosulcate. The triurid fossil flowers can be separated into three distinctive species. On the basis of phylogenetic analyses of morphological characters, the fossil taxa nest within the completely saprophytic achlorophyllous Triuridaceae supporting the interpretation that the extinct plants were also achlorophyllous and saprophytic. If so, this represents the earliest known fossil occurrence of the saprophytic/mycotrophic habit in angiosperms.

Archaefructaceae, a new basal angiosperm family

Archaefructaceae is proposed as a new basal angiosperm family of herbaceous aquatic plants. This family consists of the fossils Archaefructus liaoningensis and A. sinensis sp. nov. Complete plants from roots to fertile shoots are known. Their age is a minimum of 124.6 million years from the Yixian Formation, Liaoning, China. They are a sister clade to all angiosperms when their characters are included in a combined three-gene molecular and morphological analysis. Their reproductive axes lack petals and sepals and bear stamens in pairs below conduplicate carpels.

Archaefructaceae, a new basal angiosperm family

Archaefructaceae is proposed as a new basal angiosperm family of herbaceous aquatic plants. This family consists of the fossils Archaefructus liaoningensis and A. sinensis sp. nov. Complete plants from roots to fertile shoots are known. Their age is a minimum of 124.6 million years from the Yixian Formation, Liaoning, China. They are a sister clade to all angiosperms when their characters are included in a combined three-gene molecular and morphological analysis. Their reproductive axes lack petals and sepals and bear stamens in pairs below conduplicate carpels.

The evolution of minor vein phloem and phloem loading

Phylogenetic analysis provides a rational basis for comparative studies of phloem structure and phloem loading. Although several types of minor vein companion cell have been identified, and progress has been made in correlating structural features of these cells with loading mechanisms, little is known about the phylogenetic relationships of the different types. To add to the available data on companion cells, we analyzed the ultrastructure of minor veins in Euonymus fortunei and Celastrus orbiculatis (Celastraceae) leaves and determined that in these species they are specialized as intermediary cells. This cell type has been implicated in symplastic phloem loading. The data were added to published data sets on minor vein phloem characteristics, which were then mapped to a well-supported molecular tree. The analysis indicates that extensive plasmodesmatal continuity between minor vein phloem and surrounding cells is ancestral in the angiosperms. Reduction in plasmodesmatal frequency at this interface is a general evolutionary trend, punctuated by instances of the reverse. This is especially true in the case of intermediary cells that have many plasmodesmata, but other distinguishing characteristics as well, and have arisen independently at least four, and probably six, times in derived lineages. The character of highly reduced plasmodesmatal frequency in minor vein phloem, common in crop plants, has several points of origin in the tree. Thus, caution should be exercised in generalizing results on apoplastic phloem loading obtained from model species. Transfer cells have many independent points of origin, not always from lineages with reduced plasmodesmatal frequency.

The earliest fossil evidence of the Hamamelidaceae: Late Cretaceous (Turonian) inflorescences and fruits of Altingioideae

Fossilized pistillate inflorescences, fruits, and pollen grains from the Turonian (∼90 million years before present) of New Jersey are described as a new genus, Microaltingia, in the family Hamamelidaceae. The fossils are remarkably preserved in exceptional detail. Several morphological and anatomical characters suggest affinities with Hamamelidaceae. These include capitate inflorescences, florets with a hypanthium, two-carpellate gynoecia, perigynous flowers, tricolpate reticulate pollen, a three-layered carpel wall, scalariform perforation plates with oblique end walls, and scalariform and opposite/alternate intervascular pitting. The gross morphology of pistillate inflorescences, unisexual flowers, phyllome structure, numerous ovules per carpel, and mode of carpel dehiscence indicate affinities with subfamily Altingioideae, which includes the modern genera Liquidambar and Altingia. Cladistic analysis using a previously published morphological matrix and scoring the fossil for available characters supports the position of the fossil as a sister taxon of modern Altingioideae. Although the fossil exhibits a mosaic of characters found within modern Hamamelidaceae, it is not identical to any modern taxon. Based on cladistic analysis, the fossil appears to be a basal "altingioid" that lacks the derived pollen found in extant Altingioideae and retains the more plesiomorphic tricolpate pollen found in the rest of Hamamelidaceae. The floral characters of the fossils, including phyllomes with stomata, short and straight styles, and small perprolate pollen grains, also indicate the possibility of insect pollination.

Phylogeny reconstruction using duplicate genes

In this paper, we propose a new method (uninode coding) for coding duplicate (paralogous) genes to infer species trees. Uninode coding incorporates data from duplicated and unduplicated gene copies in phylogenetic analyses of taxa. Uninode coding utilizes global parsimony through the inclusion of both duplicated and unduplicated gene copies, allows one to code all data sources from a taxon into a single terminal, and overcomes problems of character dependence among duplicated and unduplicated gene copies. We present an example of uninode coding using the phytochrome A and phytochrome C data from a study by Donoghue and Mathews.

Phylogeny, biogeography, and processes of molecular differentiation in Quercus subgenus Quercus (Fagaceae)

Quercus is one of the most abundant and economically important genera of woody plants in the Northern Hemisphere. To infer phylogenetic relationships within Quercus subgenus Quercus, chloroplast DNA (cpDNA) restriction sites and nucleotide sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of the nuclear ribosomal DNA repeat were obtained for 44 individuals, including 25 species, intraspecific samples, and three outgroups. Separate parsimony analyses of each data set showed that individual gene trees were congruent and often complementary in supporting clades that generally corresponded to previously recognized taxonomic groups. Only one instance of strongly supported gene tree incongruence was detected and this anomalous pattern was explained best by ancient introgression of cpDNA across sectional boundaries. Simultaneous parsimony analysis of the pruned data sets supported the recognition of the strictly Eurasian section Cerris and resolved a novel hypothesis for the major infrageneric groups (Cerris- (Lobatae- (Protobalanus + Quercus sensu stricto))). The biogeographic hypothesis that all major oak lineages evolved locally at middle latitudes within the general distribution of their fossil ancestors was fully supported. This set of relationships also suggested a New World origin for the widespread white oaks of the Northern Hemisphere (section Quercus s. s.). For both data sets, inter- and intraspecific sampling within section Protobalanus showed little correspondence to morphological species. Greater cladistic structure among the samples was obtained by cpDNA restriction sites and two well-delimited plastomes types comprising a total of 15 distinct haplotypes were resolved. Haplotypes of 2 of the peripheral species in this species complex occupy terminal portions of one of the plastome clades, suggesting a more recent origin relative to those of more widespread species. The phylogeography of the two divergent plastome types suggested a north-south pattern, consistent with a Late Tertiary disjunction in the ancestral distribution of section Protobalanus.

Temporal and spatial genetic variation within and among populations of the mosquito Culex tarsalis (Diptera: Culicidae) from California

The genetic structure of 11 populations of Culex tarsalis Coquillett from California and 1 population from Nevada was examined at 18 loci using polyacrylamide gel electrophoresis. Six populations from northern and southern California were sampled repeatedly to determine if the genetic structure of Cx. tarsalis changes seasonally. Significant differences in allele frequencies at 13 different loci were seen in 3 populations over time as determined by contingency chi-square tests. Nei's genetic distance coefficients among different sampling dates was consistently < 0.025. The number of alleles per locus in these populations ranged from 1.6 to 2.7, whereas the average heterozygosity ranged from 0.086 to 0.228. No single locus was found to vary in a consistent pattern within all populations that were sampled repeatedly. These results indicate that Cx. tarsalis populations are genetically stable over time and that temporal variation is due to fluctuations in population size or immigration of genetically distinct individuals. In contrast, Cx. tarsalis did exhibit some differences in genetic structure that were related to geographical features including the Sierra Nevada and the Tehachapi Mountains of southern California. Genetically differentiated populations occurred in Nevada, southern and northeastern California, and the Central Valley of California. Little differentiation was observed among populations located in the Central Valley of California and those located at high elevations in the Sierra Nevada. Thus, in the populations examined, mountain ranges or arid conditions that limit the number of larval development sites appeared to be important barriers to the dispersal of Cx. tarsalis.

Two new fossil flowers of magnoliid affinity from the Late Cretaceous of New Jersey

Two taxa of cupulate magnoliid fossil flowers, Cronquistiflora and Detrusandra, are described from the Late Cretaceous (Turonian, ∼90 million years before present [MYBP]) Raritan (or lower Magothy) Formation of New Jersey. The fossil taxa are represented by flowers at various stages of development, associated fragments of cup-shaped floral receptacles with attached anthers, and isolated anthers. Both taxa have laminar stamens with adaxial thecae and valvate dehiscence. Pollen is boat-shaped and foveolate in anthers associated with Cronquistiflora and spherical with reticulate ornamentation in Detrusandra. Cup-shaped receptacles are externally bracteose in both taxa. The receptacle of Cronquistiflora is broader than the campanulate one of Detrusandra. Cronquistiflora also has more carpels (∼50 in a spiral vs. ∼5 in a whorl or tight spiral). In Detrusandra the carpels are surrounded by dorsiventrally flattened structures (pistillodes?) that are remote from the attachment of the stamens near the distal rim of the receptacular cupule. Detrusandra stigmas are rounded and bilobed, while those of Cronquistiflora, although bilateral in symmetry, are somewhat peltate. The fossil taxa share prominent characters with extant cupulate magnoliids (e.g., Eupomatia, Calycanthus), but also share characters with other magnoliids including Winteraceae. These fossils represent taxa that are character mosaics relative to currently recognized families. Inclusion of these fossils in existing data matrices and ensuing phylogenetic analyses effect changes in tree topologies consistent with their mosaicism relative to modern taxa. But such analyses do not definitively demonstrate the affinities of the fossils other than illustrating that these fossils are generalized magnoliids. Additional analysis of modern and fossil magnoliids is necessary to fully appreciate the phylogenetic significance and positions of these fossil taxa. However, the results of the phylogenetic analyses do introduce the possibility that extinct taxa of Magnoliales with cupulate floral receptacles were transitional between basal angiosperms and those with tricolpate pollen. The fossils provide insights into the timing of evolution of character complexes now associated with coleopteran pollination.

The distribution of species of the Aedes increpitus complex in the western United States

Maps of the California and Oregon distribution of members of the Aedes increpitus complex (Aedes clivis Lanzaro and Eldridge, Aedes increpitus Dyar, and Aedes washinoi Lanzaro and Eldridge) are presented that are based on collections reported by Lanzaro and Eldridge (1992) and new collections from various sites, many in the Central Valley of California. Analysis of individually reared specimens by polyacrylamide gel electrophoresis and conventional morphological methods confirmed the diagnostic value of isozymes for these species and of larval head hairs for distinguishing Ae. clivis from other members of the complex. Other larval characters and pupal hairs did not appear to have diagnostic value. An additional site was discovered where apparent hybrids between Ae. washinoi and Ae. increpitus occur, and a single possible hybrid between Ae. washinoi and Ae. clivis was found at a site where these species had previously been reported to occur sympatrically.

Oldest fossil flowers of hamamelidaceous affinity, from the Late Cretaceous of New Jersey

Exceptionally well-preserved staminate inflorescences, pistillate inflorescences, and detached stamens with important phylogenetic and paleoecological implications have been discovered from the Turonian (ca. 88.5-90.4 million years B.P.) Raritan Formation of New Jersey. The fossils have a combination of floral and pollen characters found in various genera of modern entomophilous and anemophilous Hamamelidaceae and anemophilous Platanus (Platanaceae). The floral characters of the fossils, including a sepal cup, staminal tube, and apparently nectariferous staminodes, indicate that this taxon was probably insect pollinated. The juxtaposition of character complexes in an extinct taxon from disparate modern taxa provides an interesting phylogenetic perspective on the origins of Hamamelidaceae and is a striking example of a fossil that is a mosaic of familial level characters relative to modern taxa. Of even broader interest, however, is the occurrence of staminodal nectaries that have structural characters intermediate between the fossil's functional stamens and modern hamamelidaceous petals. This transitional staminode morphology in the context of the other fossil characters suggests a staminodal origin of petals in the hamamelid-rosid lineage. This hypothesis is supported by the apparent staminode position within the fossil flowers where petals are found in modern genera. The character complex of morphologically transitional staminodes, a staminal tube, and sepal cup can be viewed as prehypanthial, lacking only fusion of the staminal tube to the sepal cup. The appearance of the character complex embodied in these flowers during the late mid-Cretaceous may signal the early stages of the relationship between specialized pollinators, such as bees, and the hamamelid-rosid-asterid lineage of angiosperms, arguably one of the most important events in angiosperm radiation.

Compliance with supportive periodontal therapy

All new patients commencing supportive periodontal therapy (periodontal maintenance) after treatment in a specialist periodontal practice from 1983 to 1986 were identified from practice records. Based on their compliance with the recommended schedule of visits, the patients were classified as either compliant or non-compliant. The results indicated that there were no significant differences between compliant and non-compliant patients with regards to age, sex, number of missing teeth, plaque score, or periodontal disease severity. More non-compliant patients than compliant patients were smokers (P less than 0.05). By contrast, more compliant patients were covered by private dental insurance (P less than 0.01) and more had periodontal surgery during treatment (P less than 0.001). Only 36% of the initial patient sample was found to be compliant at the end of 1989, with the greatest patient loss in the first year of supportive periodontal therapy of about 42%. The annual attrition rate decreased in subsequent years to average about 10% of those remaining in each year, indicating that a patient is more likely to remain compliant if he or she attends for at least 1 year of supportive periodontal treatment. Non-compliant patients were sent a questionnaire seeking reasons for their non-compliance. Forty percent of the questionnaires were returned. The most common reason given for non-compliance was that a general dental practitioner was attending to the patient's periodontal treatment needs. Many considered supportive periodontal therapy to be too expensive, while a significant proportion considered that they no longer required treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbiological assays as predictors of the response to periodontal therapy

Thirty-four patients with periodontal disease each had subgingival plaque samples collected from four sites (one from each quadrant) in their mouths. The relative proportions of spirochaetes, motile rods and cocci were determined using dark field microscopy and the proportion of anaerobic to aerobic microorganisms was calculated after culture. In addition, clinical recordings were made at these sampled sites. The patients then underwent a course of periodontal treatment and were placed on a maintenance programme. The clinical recordings were repeated and the results examined to ascertain if the original microbiological or clinical measurements could have been used to predict the response to therapy. Of the baseline recordings, the initial probing depth, the initial attachment level and the presence of suppuration all showed a positive correlation with the degree of pocket reduction or attachment gain produced by treatment. The percentage of cocci in the subgingival plaque correlated negatively with the treatment response. Suppuration seemed to be associated primarily with the original pocket depth while the percentage of cocci in subgingival plaque showed a true relationship with the amount of attachment gained after periodontal therapy. The significance of this finding is discussed.

The relationship between microbiological assays and the clinical signs of periodontal disease

Ninety-five patients with periodontal disease each had subgingival plaque samples collected from four sites (one from each quadrant) in their mouths. The relative proportions of spirochaetes, motile rods and cocci were determined using dark field microscopy and the proportion of anaerobic to aerobic micro-organisms calculated after culture. In addition, clinical recordings were made. The only significant correlations observed were between probing depth or attachment loss and the proportion of cocci in the plaque (negative association), probing depth or attachment loss and sites which were suppurating or displayed a radiolucent interdental crest (positive association), and the percentage of cocci and sites with a radiolucent interdental crest (negative association). Partial correlation analysis controlling for probing depth or attachment loss showed that a significant inverse association between the percentages of cocci and the presence of a radiolucent interdental crest remained. No significant associations were observed between clinical signs such as bleeding on probing or suppuration and the microbiological assays. Overall there was a poor correlation between many of the signs thought by some to indicate periodontal disease activity.