Set Of Taxa Research Articles

Amborella not a “basal angiosperm”? Not so fast

The sequence of the plastid genome of Amborella trichopoda, the putative sister to all other extant angiosperms, was recently reported (Molecular Biology and Evolution 20: 1499-1505). Goremykin et al. used sequence data for 61 plastid genes from Amborella and 12 other embryophytes in phylogenetic analyses and concluded that Amborella is not the sister to the remaining flowering plants; the monocots instead occupy this position. The authors attributed their results, which differ substantially from all recent phylogenetic analyses of angiosperms, to the increased character sampling (30 017 nucleotides in their aligned matrix) in their analysis relative to published studies that included fewer genes but more taxa. We hypothesized that the difference in topology is not due to limited character sampling in previous studies but to limited taxon sampling in the analysis by Goremykin et al. To test this, we conducted a series of phylogenetic analyses using a three-gene, 12 (or more)-taxon data set to evaluate the topological effects of (i) including three vs. 61 genes for (nearly) the same set of taxa, (ii) analyzing different codon positions, (iii) substituting representatives of other basal lineages for Amborella, (iv) replacing the grasses used to represent the monocots with other monocots, selected either for their phylogenetic position or randomly, and (v) adding other basal taxa-Nymphaea, Austrobaileya, magnoliids, and monocots-to the 12-taxon data set. Our results demonstrate that the "monocots basal" topology obtained by Goremykin et al. is not due to increased character sampling of the plastid genome; their topology was obtained using only two plastid genes or two plastid genes and one nuclear gene. This topology was also retained when either Nymphaea or Austrobaileya was substituted for Amborella, demonstrating that any of the three basal lineages will attach to Calycanthus for lack of any other close branch. Furthermore, the "monocots basal" topology is not robust to changes in sampling of monocots. Simply adding Oncidium, for example, places Amborella sister to the other angiosperms. Thus, limited taxon sampling, focusing on organisms with complete genome sequences, can lead to artifactual results.

On the generic nature of common Northern Sotho bird names: a probe into the cognitive systematization of indigenous knowledge

A major claim made here is that, in the categorization of plants and animals by peoples living in traditional societies, there exists a specifiable and partially predictable set of plant and animal taxa that represents the smallest fundamental biological discontinuities easily recognized in any particular habitat. This large but finite set of taxa is special in each system in that its members stand out as beacons on the landscape of biological reality, figuratively crying out to be named. These groupings are the generic taxa of all such systems of ethnobiological classification, and their names are precisely the names of common speech (Berlin, 1992:53). Two questions are addressed in this contribution, namely why Northern Sotho speakers tend to name birds at the generic level by grouping different species together under one and the same common name, whereas common names exist for each and every species in English and Afrikaans; and secondly, whether the Northern Sotho data support the thesis that the human mind is innately structured to organize knowledge about nature taxonomically. Regarding the first question, it is shown that there are very sound cognitive and psychological reasons why natural phenomena such as species are grouped together at the generic level under a single common name. As far as the second question is concerned, it is concluded that the Northern Sotho data do not support the widely held view that the human mind is innately endowed with the capacity to organize knowledge about nature in this way.

Skelton P, Smith A. 2002. Accompanying booklet written by Monks N. Cladistics: a practical primer on CD-ROM

Skelton P, Smith A. 2002. Accompanying booklet written by Monks N. Cladistics: a practical primer on CD-ROM

Utility of plastid psaB gene sequences for investigating intrafamilial relationships within Orchidaceae

DNA sequences of the plastid gene psaB were completed for 182 species of Orchidaceae (representing 150 different genera) and outgroup families in Asparagales. These data were analyzed using parsimony, and resulting trees were compared to a rbcL phylogeny of Orchidaceae for the same set of taxa after an additional 30 new rbcL sequences were added to a previously published matrix. The psaB tree topology is similar to the rbcL tree, although the psaB data contain less homoplasy and provide greater bootstrap support than rbcL alone. In combination, the two-gene tree recovers the five monophyletic subfamilial clades currently recognized in Orchidaceae, but fails to resolve the positions of Cypripedioideae and Vanilloideae. These new topologies help to clarify some of the anomalous results recovered when rbcL is analyzed alone. Both genes appear to be absent from the plastid genome of several achlorophyllous orchids, but are present in the form of presumably non-functional pseudogenes in Cyrtosia. This study is the first to document the utility of psaB sequences for phylogenetic studies of plants below the family level.

Novel Versus Unsupported Clades: Assessing the Qualitative Support for Clades in MRP Supertrees

Matrix representation with parsimony (MRP) supertree construction has been criticized because the supertree may specify clades that are contradicted by every source tree contributing to it. Such unsupported clades may also occur using other supertree methods; however, their incidence is largely unknown. In this study, I investigated the frequency of unsupported clades in both simulated and empirical MRP supertrees. Here, I propose a new index, QS, to quantify the qualitative support for a supertree and its clades among the set of source trees. Results show that unsupported clades are very rare in MRP supertrees, occurring most often when there are few source trees that all possess the same set of taxa. However, even under these conditions the frequency of unsupported clades was <0.2%. Unsupported clades were absent from both the Carnivora and Lagomorpha supertrees, reflecting the use of large numbers of source trees for both. The proposed QS indices are correlated broadly with another measure of quantitative clade support (bootstrap frequencies, as derived from resampling of the MRP matrix) but appear to be more sensitive. More importantly, they sample at the level of the source trees and thus, unlike the bootstrap, are suitable for summarizing the support of MRP supertree clades.

Placental mammal diversification and the Cretaceous-Tertiary boundary.

Competing hypotheses for the timing of the placental mammal radiation focus on whether extant placental orders originated and diversified before or after the Cretaceous-Tertiary (KT) boundary. Molecular studies that have addressed this issue suffer from single calibration points, unwarranted assumptions about the molecular clock, andor taxon sampling that lacks representatives of all placental orders. We investigated this problem using the largest available molecular data set for placental mammals, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant placental orders. We used the ThorneKishino method, which permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree. Analyses that used different sets of fossil constraints, different priors for the base of Placentalia, and different data partitions all support interordinal divergences in the Cretaceous followed by intraordinal diversification mostly after the KT boundary. Four placental orders show intraordinal diversification that predates the KT boundary, but only by an average of 10 million years. In contrast to some molecular studies that date the rat-mouse split as old as 46 million years, our results show improved agreement with the fossil record and place this split at 16-23 million years. To test the hypothesis that molecular estimates of Cretaceous divergence times are an artifact of increased body size subsequent to the KT boundary, we also performed analyses with a "KT body size" taxon set. In these analyses, interordinal splits remained in the Cretaceous.

GapCoder automates the use of indel characters in phylogenetic analysis

BackgroundSeveral ways of incorporating indels into phylogenetic analysis have been suggested. Simple indel coding has two strengths: (1) biological realism and (2) efficiency of analysis. In the method, each indel with different start and/or end positions is considered to be a separate character. The presence/absence of these indel characters is then added to the data set.AlgorithmWe have written a program, GapCoder to automate this procedure. The program can input PIR format aligned datasets, find the indels and add the indel-based characters. The output is a NEXUS format file, which includes a table showing what region each indel characters is based on. If regions are excluded from analysis, this table makes it easy to identify the corresponding indel characters for exclusion.DiscussionManual implementation of the simple indel coding method can be very time-consuming, especially in data sets where indels are numerous and/or overlapping. GapCoder automates this method and is therefore particularly useful during procedures where phylogenetic analyses need to be repeated many times, such as when different alignments are being explored or when various taxon or character sets are being explored. GapCoder is currently available for Windows from .

Molecular Phylogenetics of the Chiropteran Family Vespertilionidae

Limited information from existing data sets and the tremendous amount of diversity in number and kind within the chiropteran family Vespertilionidae (about one-third of all bat species) have hampered efforts to provide adequate assessments of long-standing genealogic hypotheses (e.g., monophyly of the family and of the five subfamilies). We generated approximately 2.6 kilobase pairs of mitochondrial DNA (mtDNA) sequence ecompassing three adjacent genes (12S rRNA, tRNAVal, 16S rRNA) for 120 vespertilionids representing 110 species, 37 of 44 genera, and all subfamilies. We assessed monophyly of Vespertilionidae in initial analyses of 171 taxa including representatives of all bat families (except the monotypic Craseonycteridae), and assessed lower-level relationships by analysis of several truncated taxon sets. Phylogenetic analysis of ribosomal gene sequences provides well-supported resolution for vespertilionid relationships across taxonomic levels. Furthermore, the resolution is not heavily burdened by alignment of ambiguous regions of the ribosomal gene sequences, and topologies and levels of support produced by two phylogenetic methods (Bayesian and Parsimony) agreed markedly. Our analyses suggest relationships that support many parts of the traditional classification but which also support several changes. The majority of these changes also receives support from other data sources, particularly bacular and karyotypic data. We make more than 20 taxonomic conclusions or recommendations and construct a working classification for vespertilionoid bats. Highlights include: Miniopterus (subfamily Miniopterinae) is recognized in its own family, Miniopteridae, as it represents an extremely divergent lineage relative to other vespertilionids, and in some analyses is sister to the molossids and natalids; all other vespertilionids examined form a well-supported clade; two of the traditional subfamilies within Vespertilionidae (sensu stricto) are monophyletic, Murininae and Kerivoulinae; Nyctophilinae has no validity and Vespertilioninae is paraphyletic relative to the position of Myotis; Myotis is sister to a clade containing Kerivoulinae and Murininae and is recognized in its own subfamily, Myotinae; Myotis subgenera Leuconoe, Selysius, and Myotis are polyphyletic, and a subgeneric classification reflecting geography is suggested, broadening subgenus Myotis to include the sampled Old World species, and allocating the sampled New World species to another subgenus (Aeorestes Fitzinger, 1870); Vespertilioninae (excluding Myotis) is monophyletic; Pipistrellus-like bats (i.e., the traditional tribe Vespertilionini) are divided into three tribes (Nycticeiini; Pipistrellini; Vespertilionini); and support for three tribes of Pipistrellus-like bats has several implications at the genus level. Overall, this study offers a robust working hypothesis for vespertilionid relationships and provides a good starting point for new investigations into the evolutionary history of Vespertilionidae.

Semi-strict supertrees

A method to calculate semi-strict supertrees is proposed. The semi-strict supertrees are calculated by creating the matrix that represents all the groups in the source trees (as done in already existing techniques), and then finding the trees determined by the ultra-clique. The ultra-clique is defined as the set of characters where each possible subset is compatible with each possible subset from the entire matrix. Finding the ultra-clique is computationally complex (since in most cases many of the characters have missing entries), but a heuristic method yields reliable results. When the trees have no conflict, or when there are only two trees, the method produces the exact result for any ordering of the input trees and any ordering of the groups within them; when there are more than two trees and they have conflict, a single ordering or sequence can create some spurious groups, but doing multiple sequences eliminates the spurious groups. The method uses only state set operations, and is thus easily implemented in computer programs. Unlike any existing type of supertree, semi-strict supertrees display all the groups, and only those groups, that are implied by at least some combination of the input trees and contradicted by none. The idea that supertrees should take into account the number of occurences of a given group, so as to retain some groups even in the case of conflict, is discussed; it is argued that a conceptual equivalent of the majority rule consensus is not possible when the sets of taxa differ among trees. Also, when pruning taxa from a set of trees, the supertree can display groups that contradict the consensus for the entire trees, suggesting that supertrees for matrices with very dissimilar sets of taxa should be interpreted with caution. If (for any valid reason) the data cannot be combined in a single matrix, it is advisable that the taxon sets in the matrices be as similar as possible.

Semi-strict supertrees.

A method to calculate semi-strict supertrees is proposed. The semi-strict supertrees are calculated by creating the matrix that represents all the groups in the source trees (as done in already existing techniques), and then finding the trees determined by the ultra-clique. The ultra-clique is defined as the set of characters where each possible subset is compatible with each possible subset from the entire matrix. Finding the ultra-clique is computationally complex (since in most cases many of the characters have missing entries), but a heuristic method yields reliable results. When the trees have no conflict, or when there are only two trees, the method produces the exact result for any ordering of the input trees and any ordering of the groups within them; when there are more than two trees and they have conflict, a single ordering or sequence can create some spurious groups, but doing multiple sequences eliminates the spurious groups. The method uses only state set operations, and is thus easily implemented in computer programs. Unlike any existing type of supertree, semi-strict supertrees display all the groups, and only those groups, that are implied by at least some combination of the input trees and contradicted by none. The idea that supertrees should take into account the number of occurences of a given group, so as to retain some groups even in the case of conflict, is discussed; it is argued that a conceptual equivalent of the majority rule consensus is not possible when the sets of taxa differ among trees. Also, when pruning taxa from a set of trees, the supertree can display groups that contradict the consensus for the entire trees, suggesting that supertrees for matrices with very dissimilar sets of taxa should be interpreted with caution. If (for any valid reason) the data cannot be combined in a single matrix, it is advisable that the taxon sets in the matrices be as similar as possible.

Use of the nuclear gene glyceraldehyde 3-phosphate dehydrogenase for phylogeny reconstruction of recently diverged lineages in Mitthyridium (Musci: Calymperaceae)

A portion of the nuclear gene glyceraldehyde 3-phosphate dehydrogenase ( gpd) was sequenced in 26 representatives of the paleotropical moss, Mitthyridium, and a group of 20 outgroup taxa to assess its utility for phylogenetic reconstruction compared with the better understood chloroplast markers, rps4 and trnL. Primers based on plant and fungal sequences were designed to amplify gpd in plants universally with the exclusion of fungal contaminants. The piece amplified spanned 4 introns and 3 of 9 exons, based on comparisons with complete sequence from Arabidopsis. Size variation in gpd ranged from 891 to 1007 bp, in part attributable to 6 indels of variable length found within the introns. Intron 6 contributed most of the length variation and contained a variable purine-repeat motif of possible use as a microsatellite. Phylogenetic analyses of the full gpd amplicon yielded well-resolved trees that were in nearly full accord with the trees derived from the cpDNA partitions for analyses of both the ingroup and ingroup + outgroup taxon sets. Pairwise nucleotide substitution rates of gpd were as much as 2.2 times higher than those in rps4 and 2.8 times higher than in trnL. Excision of the introns left suitable numbers of parsimony informative characters and demonstrated that the full gpd amplicon could be compartmentalized to provide resolution for both shallow and deep phylogenetic branches. Exons of gpd were found to behave in a clock-like fashion for the 26 ingroup taxa and select outgroups. In general, gpd was found to hold great promise not only for improving resolution of chloroplast-derived phylogenies, but also for phylogenetic reconstruction of recent, diversifying lineages.

Middle Cambrian (Acadian Series) conocoryphid and paradoxidid trilobites from the Upper Chamberlain's Brook Formation, Newfoundland and New Brunswick

The Fossil Brook Member of the upper Chamberlain's Brook Formation is a thin (up to 14 m) but distinctive, unconformity-bound depositional sequence recognizable from Rhode Island to eastern Newfoundland in Avalonian North America. Its diverse trilobite fauna was first described more than century ago from the limestone-rich facies of the member in southern New Brunswick. However, the systematics, stratigraphic context, and biostratigraphic significance of these trilobites have remained poorly known. A revision of the conocoryphid and paradoxidid trilobites has been completed, and the taxa set into their stratigraphic context within the middle Middle Cambrian. The faunas of the Fossil Brook are assigned to theEccaparadoxides eteminicusZone of Avalon. Although biogeographic barriers between Avalon and Gondwana remained strong in the Middle Cambrian and few shared trilobite species are present, a generalized correlation of theE. eteminicusZone into Gondwana is with theBadulesia teneraZone of the Toushamian Stage in Morocco and theBadulesiaZone of the Caesaraugustian Stage in Spain.

Multivariate analyses of invertebrate community responses to a C 12–15AE-3S anionic surfactant in stream mesocosms

The ecological effects of a C 12–15AE-3S linear alkylethoxysulfate anionic surfactant on aquatic organisms were studied in stream mesocosms. Analyses of the experimental data have yielded multiple population-level no-observed effect concentrations (NOECs) but did not provide a measure of community-level response to surfactant exposure. In the present study, the invertebrate data from the mesocosm study were further examined for community-level effects using multivariate techniques. Two multivariate statistical methods were selected as representative of recommended methods and used to analyze invertebrate abundance. One method was similarity analysis using the Bray-Curtis index, and the second method was the canonical ordination technique principal response curves recently developed for analysis of mesocosm data. Both sets of techniques detected statistically significant changes in invertebrate community structure following surfactant exposure. Ordinations constructed from Bray-Curtis similarity matrices provided clearer two-dimensional representations of these changes than ordinations from redundancy analysis. Re-displaying treatment and temporal effects on community structure on separate axes as response curves provided a clearer method for interpreting community response to surfactant exposure. Both approaches detected treatment effects in low and high abundance taxa. The highest rank abundance taxa in the pretreatment streams contributed very little to the differences observed between the control and treated streams. The same set of taxa was identified as the dominant drivers for structural differences between control and treated communities despite underlying mathematical differences in these two methods. Invertebrate community-level NOECs estimated from these different multivariate methods (2.5–5.0 mg/l) were comparable and these NOECs were similar to invertebrate population NOECs determined for this surfactant.

Using RPB1 sequences to improve phylogenetic inference among mushrooms (Inocybe, Agaricales)

An investigation of mushroom phylogeny using the largest subunit of RNA polymerase II gene sequences (RPB1) was conducted in comparison with nuclear ribosomal large subunit RNA gene sequences (nLSU) for the same set of taxa in the genus Inocybe (Agaricales, Basidiomycota). The two data sets, though not significantly incongruent, exhibit conflict among the placement of two taxa that exhibit long branches in the nLSU data set. In contrast, RPB1 terminal branch lengths are rather uniform. Bootstrap support is increased for clades in RPB1. Combined data sets increase the degree of confidence for several relationships. Overall, nLSU data do not yield a robust phylogeny when independently assessed by RPB1 sequences. This multigene study indicates that Inocybe is a monophyletic group composed of at least four distinct lineages-subgenus Mallocybe, section Cervicolores, section Rimosae, and subgenus Inocybe sensu Kühner, Kuyper, non Singer. Within subgenus Inocybe, two additional lineages, one composed of species with smooth basidiospores (clade I) and a second characterized by nodulose-spored species (clade II), are recovered by RPB1 and combined data. The nLSU data recover only clade I. The genera Astrosporina and Inocybella cannot be recognized phylogenetically. "Supersections" Cortinatae and Marginatae are not monophyletic groups.

MIDDLE CAMBRIAN (ACADIAN SERIES) CONOCORYPHID AND PARADOXIDID TRILOBITES FROM THE UPPER CHAMBERLAIN'S BROOK FORMATION, NEWFOUNDLAND AND NEW BRUNSWICK

The Fossil Brook Member of the upper Chamberlain's Brook Formation is a thin (up to 14 m) but distinctive, unconformity-bound depositional sequence recognizable from Rhode Island to eastern Newfoundland in Avalonian North America. Its diverse trilobite fauna was first described more than century ago from the limestone-rich facies of the member in southern New Brunswick. However, the systematics, stratigraphic context, and biostratigraphic significance of these trilobites have remained poorly known. A revision of the conocoryphid and paradoxidid trilobites has been completed, and the taxa set into their stratigraphic context within the middle Middle Cambrian. The faunas of the Fossil Brook are assigned to the Eccaparadoxides eteminicus Zone of Avalon. Although biogeographic barriers between Avalon and Gondwana remained strong in the Middle Cambrian and few shared trilobite species are present, a generalized correlation of the E. eteminicus Zone into Gondwana is with the Badulesia tenera Zone of the Toushamian Stage in Morocco and the Badulesia Zone of the Caesaraugustian Stage in Spain.

HOBACGEN: Database System for Comparative Genomics in Bacteria

We present here HOBACGEN, a database system devoted to comparative genomics in bacteria. HOBACGEN contains all available protein genes from bacteria, archaea, and yeast, taken from SWISS-PROT/TrEMBL and classified into families. It also includes multiple alignments and phylogenetic trees built from these families. The database is organized under a client/server architecture with a client written in Java, which may run on any platform. This client integrates a graphical interface allowing users to select families according to various criteria and notably to select homologs common to a given set of taxa. This interface also allows users to visualize multiple alignments and trees associated to families. In tree displays, protein gene names are colored according to the taxonomy of the corresponding organisms. Users may access all information associated to sequences and multiple alignments by clicking on genes. This graphic tool thus gives a rapid and simple access to all data required to interpret homology relationships between genes and distinguish orthologs from paralogs. Instructions for installation of the client or the server are available at http://pbil.univ-lyon1. fr/databases/hobacgen.html.

A taxonomic study of phlebioid fungi (Basidiomycota)

The genus Phlebia has long been regarded as a polyphyletic or paraphyletic taxon, including distinct groups of more closely related species. Consequently, the delimitation of the genus has been given different interpretations and several rearrangements have been proposed by various authors. In the present study, DNA sequences (25S, rDNA) were obtained for twenty species of the genus Phlebia and a phylogenetic analysis was performed. Because of the presumably paraphyletic nature of the genus, different outgroups were used for different sets of taxa. A core group of species, including the type Ph. radiata, is well distinguished. For the delimitation of the genus, however, the wider scope of a more weakly supported clade is proposed. This clade also includes Phlebiopsis gigantea and its combination in Phlebia is reaffirmed. Two species, Ph. griseoflavescens and Ph. tristis, are distinctly separated from this clade and should be removed from the genus. Morphological characters were used in a separate phylogenetic analysis but the result did not conform with analysis from sequence data.

Deep flowers for long tongues: reply from L.A. Nilsson

The core for disagreement about the tongue-flower elongation, coevolution versus non-coevolution, is whether a long hawkmoth tongue is used primarily for feeding or for predator avoidance. Wasserthal[1xWasserthal, L.T. Trends Ecol. Evol. 1998; 13: 459–460Abstract | Full Text | Full Text PDF | PubMedSee all References][1]considers his predation hypothesis for tongue length confirmed, but his three cited papers lack quantitative data on natural predation. Svensson et al.[2xSvensson, M.G.E., Rydell, J., and Tove, J. Trends Ecol. Evol. 1998; 13: 460Abstract | Full Text | Full Text PDF | PubMedSee all References][2]argue in support of his interpretation by anecdotal evidence. They miss the flight–elongation focus. However, I agree with them and with Samways[3xSamways, M.J. Trends Ecol. Evol. 1998; 13: 460Abstract | Full Text | Full Text PDF | PubMedSee all References][3]that major predation on large hawkmoths is expected from flying vertebrates, not arthropods in ambush a la Wasserthal.Nectar-extracting mouthparts have attained impressive extremes in euglossine bees (4 cm), nemestrinid flies (8 cm) and hummingbirds (10 cm), each set of taxa using/pollinating a unique guild of deep-flowered plants[4xSchremmer, F. Verh. D. Zool. Ges. (Suppl.). 1961; 25: 375–401See all References, 5xSee all References]. Nothing suggests that predator avoidance has influenced the elongation (co)evolution. Long-tongued hawkmoths and their deep flowers, although displaying world records (30 cm and 40 cm, respectively), are hardly exceptions in this respect. The various very deep-flowered angiosperms (e.g. Epiphyllum in neotropical Cactaceae) are probably coevolved with hawkmoth tongues.Hawkmoth flight repertoires include `on-the-spot' hovering as well as `swing-hovering' during flower-visits. Also, hummingbirds, long-tongued solitary bees (euglossines, anthophorids) and long-tongued flies (horseflies, nemestrinid and bee flies) hover on-the-spot. No doubt this behaviour favours targeting and insertion precision with the extended mouthparts into narrow nectariferous structures. Extremely long-tongued hawkmoths probably require even more precision control. Added swing-hovering may increase visual and/or olfactory information about the position of the flower. Anti-predator adaptations, on the other hand, are to be expected among other traits.Basal hawkmoth clades contain the long-tongued taxa[6xRothschild, L.W. and Jordan, K. Nov. Zool. 1903; 9: 1–972See all References][6]. But modern phylogenetic analyses (so badly needed!) are likely to show a very long tongue to be a derived, relatively late trait within several lines (e.g. Amphimoea, Coelonia). Furthermore, very long-tongued hawkmoths might not be true generalists but instead might have have guild constancy under natural, undisturbed conditions. Their opportunistic exploitation of pantropical weedy Lantana[7xWasserthal, L.T. Bot. Acta. 1997; 110: 1–17CrossRefSee all References][7], a lepidopteran-adapted species, is hardly surprising.Wasserthal's argument that `obligate synchrony and syntopy' of Xanthopan morganii praedicta and Angraecum sesquipedale would have been required for coevolution is flawed. These interactors are participants of coevolving guilds[8xNilsson, L.A. et al. Biotropica. 1987; 19: 310–318CrossRefSee all References][8]. Various pollinator shifts may well have occurred, as are commonplace in the history of orchids and other angiosperms[9xVogel, S. Bot. Stud. 1954; 1: 1–338See all References, 10xJohnson, S.D., Linder, H.P., and Steiner, K.E. Am. J. Bot. 1997; 85: 402–411CrossRefSee all References]. Coevolution and shifting occur by relatively `better' pollinators. The basis for Darwin's reciprocal-effect model is that a competitive visitor with a non-bottom-reaching tongue better contacts the flower's pollination organs[11xSee all References][11]. The depth of spur and the length of reward-extracting organ become inter-dependent and matching at the population level[12xSteiner, K.E. and Whitehead, V.B. Evolution. 1990; 44: 1701–1707CrossRefSee all References][12]. A consistently bottom-reaching, although competitive, hawkmoth tongue excludes pollinator shifts, as indicated by Xanthopan on Angraecum compactum[7xWasserthal, L.T. Bot. Acta. 1997; 110: 1–17CrossRefSee all References][7]. Some 100 Madagascan angraecoids have demonstrably retained adaptation to medium-tongued hawkmoths. Angraecum sesquipedale, guild-member angiosperms, Xanthopan and major hawkmoth competitors are evidently coevolved.The intention of Wasserthal's study has not been overlooked, nor has the difficulty of obtaining natural interaction data. Our team still recorded frequent pollination of A. sesquipedale in 1983 and 1986. Wasserthal's study of the same populations, species and systems in Madagascar has partly led to more questions than answers, and he has yet to adopt a plausible evolutionary interpretation of his observations.

Fossil datum and paleobiological event terms, paleontostratigraphy, chronostratigraphy, and the definition of Land Mammal “Age” boundaries

ABSTRACT The confusion between operational and theoretical terms has been common in stratigraphic paleontology. This science includes the descriptive subdiscipline of biostratigraphy and the more interpretational subdisciplines of biochronology and ecostratigraphy. Paleontostratigraphic terms ending in “-zone” refer to intervals of rock, while those ending in “-chron” refer to spans of time. Fossil datum terms (Lowest/Highest Stratigraphie Datum = LSD/HSD) refer to the lowest/highest stratigraphic occurrence of fossils of a taxon in a given section, and define the boundaries of biostratigraphic units (fossizones = intervals of strata). Fossizones may be divided into epizones (the known extent of the fossizone) and entozones (the actual extent of the fossizone). Fossil datum terms with intrinsic temporal connotations are Oldest/Youngest Known Record (OKR/YKR). The time between the presumed OKR and YKR of a taxon in a given area is the apparent temporal range (parachron), which must be separated from the even more theoretical concept of the true temporal range (biochron). Paleobiological event terms (First/Last Historical Appearance = FHA/LHA) refer to the evolution, immigration, dispersal, emigration, and extinction of living individuals of a taxon, and define the boundaries of biochronologic units (biochrons = spans of time). Biochrons may be divided into holochrons (temporal range of the defining taxon/taxa in either a given continent or the whole world) and teilchrons (temporal range in either an individual basin or paleobio-geographic province). Geochronologic units (geochrons) are spans of time defined by two “golden spikes” in designated boundary stratotype sections, and geochronostratigraphic units (geochronozones) are the sets of rock formed during such geochrons. In contrast, biochronostratigraphic units (biochronozones) are the sets of rock formed during biochrons, without reference to any particular stratigraphie section. Land Mammal “Ages” (LMAs) should not be redefined as formal geochronologic/geochronostratigraphic units. Single-taxon definitions of LMA boundaries may be appropriate in cases where few immigrational events seem to have occurred over an appreciable interval of time on a given continent. However, in view of the relatively low potential for continent-wide biochronologic resolution generally available in terrestrial sections, most LMAs should be regarded as Oppel disjunctive biochrons, whose beginnings are theoretically defined as the point in time corresponding to whichever of the immigrational or evolutionary appearances of a specified set of taxa is the oldest.

Biodiversity assessment and conservation strategies

The efficient representation of all species in conservation planning is problematic. Often, species distribution is assessed by dividing the land into a grid; complementary sets of grids, in which each taxon is represented at least once, are then sought. To determine if this approach provides useful surrogate information, species and higher taxon data for South African plants and animals were analyzed. Complementary species sets did not coincide and overlapped little with higher taxon sets. Survey extent and taxonomic knowledge did not affect this overlap. Thus, the assumptions of surrogacy, on which so much conservation planning is based, are not supported.