Synthesis of alternating metallocopolymers by chiral recognition

We report the synthesis of chiral enantiopure polytopic bridging ligands, which may lead to the formation of metallosupramolecular polymers with zinc (II) as metal linker. We show that chiral C₂‐symmetric bisoxazoline ligands are useful moieties to efficiently generate heterochiral complexes and thus polymeric entities. The corresponding metallopolymers were further characterized by powder X‐ray diffraction (PXRD) to obtain information on the level of crystallinity of our different metallopolymers.     

A periodic system of chiral structures in molecular biology

A systemic regularity of molecular biology is considered: the tendency towards alternating of the sense of chirality of intramolecular structural levels of DNA and proteins, namely, D–L–D–L for DNA and L–D–L–D for proteins, is observable starting from the level of asymmetric carbon in deoxyribose and amino acids. Helicity is a special case of chirality. In intermolecular interactions, the sense of chirality of the highest intramolecular structural level directly involved in the interaction prevails in each of the participants. The interaction of molecules of the same nature (protein–protein, DNA–RNA, tRNA–mRNA, and ribozymes) mainly occurs in the case of the same sense of chirality, either L–L or D–D, and for molecules of different types (DNA–protein, tRNA–amino acids, and enzyme–substrate), in the case of different senses of chirality, either D–L or L–D. An alternating sense of the chiral hierarchy of conjugated levels of macromolecular structures in proteins and nucleic acids is of general biological importance: it determines the discreteness of levels, serves as a tool of folding, and provides a structural basis for “preferred collective” (or “macroscopic mechanical”) degrees of freedom in the design of macromolecular machines, as well as being one of the mechanisms of blockwise/saltatory development of the evolutionary process. A new fundamental concept is proposed: the homochirality of primary structures of DNA and proteins determines the amount of the entropic component of the free energy, which is used in the processes of folding and molecular rearrangements.     

Chiral recognition by the copper(II) complex of 6-deoxy-6-N-(2-methylaminopyridine)-β-cyclodextrin

A modified β-cyclodextrin bearing a 2-aminomethylpyridine binding site for copper(II) (6-deoxy-6-[N-(2-methylamino)pyridine)]-β-cyclodextrin, CDampy was synthesized by C₆-monofunctionalization. The acid-base properties of the new ligand in aqueous solution were investigated by potentiometry and calorimetry, and its conformations as a function of pH were studied by NMR and circular dichroism (c.d.). The formation of binary copper(II) complexes was studied by potentiometry, EPR, and c.d. The copper(II) complex was used as chiral selector for the HPLC enantiomeric separation of underivatized aromatic amino acids. Enantioselectivity in the overall stability constants of the ternary complexes with D- or L-Trp was detected by potentiometry, whereas the complexes of the Ala enantiomers did not show any difference in stability. These results were consistent with a preferred cis coordination of the amino group of the ligand and of the amino acid in the ternary complexes (“cis effect”), which leads to the inclusion of the aromatic side chain of D-Trp, but not of that of L-Trp. In Trp-containing ternary complexes, the two enantiomers showed differences in the fluorescence lifetime distribution, consistent with only one conformer of D-Trp and two conformers of L-Trp, and the latter were found to be more accessible to fluorescence quenching by acrylamide and KI. Chirality 9:341–349, 1997. © 1997 Wiley-Liss, Inc.     

Density functional computations of Rh(I)-catalysed hydroacylation of acetic aldehyde and ethene

Density functional theory has been used to study Rh(I)-catalysed hydroacylation of acetic aldehyde and ethene. All the intermediates and the transition states were optimised completely at the B3LYP/6-311+ + G(d,p) level (LANL2DZ(d) for Rh, P). Calculation results confirm that Rh(I)-catalysed hydroacylation of acetic aldehyde and ethene is endothermic, and the total absorbed energy is about 47 kJ/mol. The hydroacylation involves four possible reaction channels, going mainly through Rh–ethene–aldehyde complexes, Rh–ethene–carbonyl complexes, Rh-ethanyl-carbonyl complexes, and Rh-ketone complexes. The formation of Rh–ethene–carbonyl complexes (i.e. Rh(I)-catalysed oxidative addition of aldehyde) is the rate-determinating step for the Rh(I)-catalysed hydroacylation. And the energy barriers of the H-transfer reaction are lower than those of the C–C bond-forming reaction, and thus the H-transfer reaction is prior to the C–C bond-forming reaction. Therefore, the dominant reaction channels predicted theoretically are the reaction channels “a” and “b”, which is well in agreement with the experiments.     

Shadoo/PrP (Sprn0/0/Prnp0/0) double knockout mice

Shadoo (Sho) is a brain glycoprotein with similarities to the unstructured region of PrP^C. Frameshift alleles of the Sho gene, Sprn, are reported in variant Creutzfeldt-Jakob disease (vCJD) patients while Sprn mRNA knockdown in PrP-null (Prnp^0/0) embryos produces lethality, advancing Sho as the hypothetical PrP-like “pi” protein. Also, Sho levels are reduced as misfolded PrP accumulates during prion infections. To penetrate these issues we created Sprn null alleles (Daude et al., Proc. Natl. Acad. Sci USA 2012; 109(23): 9035–40). Results from the challenge of Sprn null and TgSprn transgenic mice with rodent-adapted prions coalesce to define downregulation of Sho as a “tracer” for the formation of misfolded PrP. However, classical BSE and rodent-adapted BSE isolates may behave differently, as they do for other facets of the pathogenic process, and this intriguing variation warrants closer scrutiny. With regards to physiological function, double knockout mice (Sprn^0/0/Prnp^0/0) mice survived to over 600 d of age. This suggests that Sho is not pi, or, given the accumulating data for many activities for PrP^C, that the pi hypothesis invoking a discrete signaling pathway to maintain neuronal viability is no longer tenable.     

Role of social and individual experience in interaction of the meadow ant Formica pratensis (Hymenoptera: Formicidae) with ladybird imagines and hoverfly larvae

The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature (“field,” control) and laboratory reared “naive” ants of Formica pratensis Retzius, which had never met either “mature” workers or aphids and aphidophages, was observed during their pairwise interactions with ladybird imagines and hoverfly larvae. The majority of the “naive” ants perceived ladybirds as an enemy at their first encounter attacking them immediately without any prior antennation. Ants seem to have a certain innate “enemy image” that lets them react very quickly to protect aphids. Hoverfly larvae were rarely attacked by both “field” and “naive” ants (>15%). During tests with ladybirds ants from nature attacked them and also demonstrated the most aggressive reactions (series of bites and “death grip”) less frequently than the “naive” ants. The percentage of ants avoiding aphidophages after a contact with their chemical defense (reflex bleeding and glue‐like saliva) was significantly higher in the control group. Whereas the “naive” ants did not learn to avoid danger, foragers from nature usually tried to avoid negative experience and used tactics of “short bites.” Overall, experience has been proved to be unimportant for displaying key behavioral reactions underlying ant–ladybird interaction. However, accumulation of experience has been assumed to play an important role in the formation of behavioral strategy that allows honeydew collectors to drive aphidophages away with lower energy costs and avoid or minimize negative consequences of aphidophages’ chemical defense.     

Redox cycling of iron complexes of N-(dithiocarboxy)sarcosine and N-methyl-d-glucamine dithiocarbamate

Iron(II)–dithiocarbamate complexes are used to trap nitrogen monoxide in biological samples, and the resulting nitrosyliron(II)–dithiocarbamate is detected and quantified by ESR. As the chemical properties of these compounds have been little studied, we investigated whether iron dithiocarbamate complexes can redox cycle. The electrode potentials of iron complexes of N-(dithiocarboxy)sarcosine (dtcs) and N-methyl-d-glucamine dithiocarbamate (mgd) are 56 and −25 mV at pH 7.4, respectively, as measured by cyclic voltammetry. The autoxidation and Fenton reaction of iron(II)–dtcs and iron(II)–mgd were studied by stopped-flow spectrophotometry with both iron(II) complexes and dioxygen or hydrogen peroxide in excess. In the case of excess iron(II)–dtcs and –mgd complexes, the rate constants of the autoxidation and the Fenton reaction are (1.6–3.2) × 10⁴ and (0.7–1.1) × 10⁵ M⁻¹ s⁻¹, respectively. In the presence of nitrogen monoxide, the oxidation of iron(II)–dtcs and iron(II)–mgd by hydrogen peroxide is significantly slower (ca. 10–15 M⁻¹ s⁻¹). The physiological reductants ascorbate, cysteine, and glutathione efficiently reduce iron(III)–dtcs and iron(III)–mgd. Therefore, iron bound to dtcs and mgd can redox cycle between iron(II) and iron(III). The ligands dtcs and mgd are slowly oxidized by hydrogen peroxide with rate constants of 5.0 and 3.8 M⁻¹ s⁻¹, respectively.     

A Cultural History of Animals (6 Volumes)

ABSTRACT

Handling and training methods of horses, which specially emphasize the importance of understanding horse body language and the use of reinforcements, are often used in practice, yet their effects are not completely known. This study investigated whether the use of a sympathetic approach during the preparation for public auctions influenced the reactivity of young horses towards humans. Sixteen thoroughbred yearlings were prepared for the public auctions during one month: eight horses (“Control”) were handled according to conventional practices, while the others (“Treated”) were handled with two sessions of basic training based on body language. The reactivity of horses was assessed in the presence of an “unfamiliar person” and a “familiar person” inside the horse's box. The experimenter recorded the presence/absence of selected behaviors during seven observational moments: “approaching the box,” “opening the box door,” “entering the box,” and four consecutive observations every thirty seconds. Reactivity of horses was ranked during the first experience of “bit,” “grooming,” “shower,” and application of the “surcingle.” Heart rate was telemetrically recorded during this final test. At the end of the auction preparation, “Treated” horses exhibited more “contact” (p = 0.08) and “lick” (p < 0.05) behaviors in the presence of a person. “Control” horses showed higher (non-significant) percentages of negative (more nervous) rankings during “bit,” “grooming,” and “surcingle” tests. Two “Control” horses showed aggressive behavior during the application of the surcingle and the test was interrupted to guarantee person and animal safety. In this pilot study, horses handled with a sympathetic approach showed less reactive behaviors compared with “Control” horses. It would be interesting to enlarge the sample size and assess if the use of non-coercive handling during the whole training period influences their welfare positively and for a long time.     

Study of stereoselective interactions of carbamoylated quinine and quinidine with 3,5-dinitrobenzoyl α-amino acids using VCD spectroscopy in the region of C−H stretching vibrations

The stereoselective complexation of tert‐butylcarbamoyl quinine and tert‐butylcarbamoyl quinidine selectors (SOs) with 3,5‐dinitrobenzoyl (DNB) derivatives of D ‐ and L ‐alpha amino acids (DNB‐Ala, DNB‐Val, DNB‐Leu, and DNB‐Ile) as well as achiral DNB‐Gly has been studied by vibrational circular dichroism (VCD) spectroscopy in the spectral region of C H stretching vibrations. All the complexes of SOs and sterically compatible enantiomers of derivatized amino acid selectands (SAs) showed induced circular dichroism (ICD) bands in the region of aromatic C H stretching vibrations, indicating the occurrence of a π–π interaction between the aromatic moieties of SA and SO. To our knowledge, this is the first report in which a π–π interaction was observed by VCD spectroscopy in this spectral region. No ICD bands were disclosed in the spectra of the sterically incompatible SA and SO complexes. The spectral pattern in the region of aliphatic C H stretching vibrations showed interaction‐induced conformational adaptations in sterically favorable SA and SO complexes. No such spectral changes were observed for any of the sterically incompatible complexes. The DNB‐Gly complexes exhibited spectral patterns similar to those observed for sterically favorable pairs of SOs and chiral SAs. Chirality, 2011. © 2010 Wiley‐Liss, Inc.     

The model structure of the hammerhead ribozyme formed by RNAs of reciprocal chirality

RNA-based tools are frequently used to modulate gene expression in living cells. However, the stability and effectiveness of such RNA-based tools is limited by cellular nuclease activity. One way to increase RNA’s resistance to nucleases is to replace its D-ribose backbone with L-ribose isomers. This modification changes chirality of an entire RNA molecule to L-form giving it more chance of survival when introduced into cells. Recently, we have described the activity of left-handed hammerhead ribozyme (L-Rz, L-HH) that can specifically hydrolyse RNA with the opposite chirality at a predetermined location. To understand the structural background of the RNA specific cleavage in a heterochiral complex, we used circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy as well as performed molecular modelling and dynamics simulations of homo- and heterochiral RNA complexes. The active ribozyme-target heterochiral complex showed a mixed chirality as well as low field imino proton NMR signals. We modelled the 3D structures of the oligoribonucleotides with their ribozyme counterparts of reciprocal chirality. L- or D-ribozyme formed a stable, homochiral helix 2, and two short double heterochiral helixes 1 and 3 of D- or L-RNA strand thorough irregular Watson–Crick base pairs. The formation of the heterochiral complexes is supported by the result of simulation molecular dynamics. These new observations suggest that L-catalytic nucleic acids can be used as tools in translational biology and diagnostics.     

Multizooidal Budding in Parasmittina trispinosa (Johnston) (Bryozoa,Cheilostomata)

Two principally different wall types occur in the bryozoan colony: Exterior walls delimiting the super-individual, the colony, against its surroundings and interior walls dividing the body cavity of the colony thus defined into units which develop into sub-individuals, the zooids. In the gymnolaemate bryozoans generally, whether uniserial or multiserial, the longitudinal zooid walls are exterior, the transverse (proximal and distal) zooid walls interior ones. The radiating zooid rows grow apically to form “tubes” each surrounded by exterior walls but subdivided by interior (transverse) walls. The stenolaemate bryozoans show a contrasting mode of growth in which the colony swells in the distal direction to form one confluent cavity surrounded by an exterior wall but internally subdivided into zooids by interior walls. In the otherwise typical gymnolaemate Parasmittina trispinosa the growing edge is composed of a series of “giant buds” each surrounded by exterior walls on its lateral, frontal, basal and distal sides and forming an undifferentiated chamber usually 2–3 times as broad and 3 or more times as long as the final zooid. Its lumen is subdivided by interior walls into zooids 2–3, occasionally 4, in breadth. This type of zooid formation is therefore similar to the “common bud” or, better-named, “multizooidal budding” characteristic of the stenoleamates but has certainly evolved independently as a special modification of the usual gymnolaemate budding.     

Effects of regional origin and genotype on intraspecific root communication in the desert shrub Ambrosia dumosa (Asteraceae)

Previous work has shown that the contact inhibition that occurs among roots of Ambrosia dumosa shrubs has a self/nonself recognition capability. In the current study, we investigated some of the geographic and genotypic dimensions of this recognition capability by using root observation chambers to observe the effects of encounters of individual roots on root elongation rates. We measured such effects in encounters between roots of plants from the same region and compared these to effects in encounters between roots of plants from two different regions. We also measured effects of encounters between roots of plants from the same clones and compared these to effects of encounters of roots of plants from different clones. Roots of plants from the same region (population) showed the usual “nonself” precipitous decline in elongation rates following contact, but when roots of plants from different regions contacted each other, elongation rates continued unchanged. When roots of separate plants from the same clone contacted each other, the same “nonself” precipitous decline in elongation rates as seen in encounters between roots of plants of different clones from the same region occurred. Meanwhile, in these same experiments “self” contacts between sister roots connected to the same plants resulted in no changes in elongation rates. Thus, differences between individuals from two geographically separate populations of Ambrosia dumosa may be sufficient to thwart the “nonself,” population-level recognition of similarity apparently necessary for contact inhibition. Furthermore, the “self” recognition mechanism, which precludes contact inhibition between two roots on the same plant, appears to be physiological rather than genetic in nature.     

Kinetics of batch-wise enzymatic cycling system for mass production of chiral compound

Kinetics of batch-wise enzymatic cycling system (oxidoreductase-catalyzed reaction system involving enzyme-coupled cofactor regeneration) has been studied covering a broad range of the conserved total cofactor concentration, [C]₀ (=NAD(P)⁺?+?NAD(P)H), based on reasonable several assumptions. It is composed of two elementary reactions, i.e. product synthesis reaction and cofactor regeneration reaction, both of which have been expressed by Michaelis–Menten type rate equations. A novel dimensionless variable, r, has been introduced, which is defined as the concentration of one of the two cofactor components, [X] (NADH⁺ or NADPH⁺), divided by [C]₀, i.e. r .e[X]/[C]₀. The following results have been obtained. (1) The fundamental equation of the batch-wise enzymatic cycling system has been transformed to a differential equation whose formula is: dr/dT?=?N(r)/D(r) (N(r) and D(r) are quadratic equations of r having different coefficients). (2) It has been elucidated that the batch-wise enzymatic cycling system has two phases, an early short transient phase followed by a long phase in quasi-steady state (QSS). (3) In the enzymatic cycling system, r converges to a definite level regardless of any initial value of r. (4) In QSS, the definite level of r nearly equals the singular solution, r_singular, of the differential equation. (5) The actual rate of the targeted product (chiral compound) formation can be calculated by Michaelis–Menten equation in which the cofactor concentration is [C]₀×r_singular instead of [C]₀. r_singular has been proposed to name “redistribution factor”. (6) It is recommended that the “unit” of the cofactor regeneration enzyme be 2–3 times more used than the “unit” of the synthesis enzyme and that [C]₀ be 15–25 times more than the K_m value. Four special cases relating to the batch-wise enzymatic cycling system have been discussed.     

Adult population parameters and life tables of an epilachnine beetle (Coleoptera: Coccinellidae) feeding on bitter cucumber in Sumatra

The population dynamics of an epilachnine beetle, which is closely related to Epilachna sparsaDieke (henceforth called “sp. C”) and feeds on bitter cucumber Momordica charantia, was studied by mark-recapture of adults and the construction of life tables. The study was repeated three times, i.e., March–May, July–September and October–December in 1982, in Padang, Sumatra, Indonesia. After the establishment of the host plants, adults of “sp. C” soon colonized, and each study period ended in the death of the plants due to defoliation by the larvae and adults. The estimated mean length of residence of adults ranged from 6–11 days, but this was probably much shorter than the actual longevity, because the adults were so active that they flew away, or dropped off the plants, when they were approached or slightly disturbed. Life tables indicated that egg mortality ranged from 17.8–53.9%, and a parasitic wasp Tetrastichus sp. B made up 41.1–64.2% of egg mortality. Two wasps, Tetrastichus sp. C and Pediobius foveolatus killed 1.2–19.4% (7.6–100%)^* of 4th instars and only the latter species attacked the pupae, killing 24.6–59.1% (45.1–72.4%). Parasitism and starvation by overcrowding contributed most to the total mortality from egg to adult emergence, which ranged from 89.4–99.5%. “Sp. C” had a higher diversity and level of parasitism than the Japanese species, E. vigintioctopunctata. The high dispersal power of “sp. C”, coupled with the prolonged l_x−m_x schedules shown under laboratory conditions, was advantageous for exploiting the food plant which was available throughout the year, but was rather patchily distributed in space.     

Cellular and functional analysis of four mutations located in the mitochondrial ATPase6 gene

The smallest rotary motor of living cells, F0F1‐ATP synthase, couples proton flow—generated by the OXPHOS system—from the intermembrane space back to the matrix with the conversion of ADP to ATP. While all mutations affecting the multisubunit complexes of the OXPHOS system probably impact on the cell's output of ATP, only mutations in complex V can be considered to affect this output directly. So far, most of the F0F1‐ATP synthase variations have been detected in the mitochondrial ATPase6 gene. In this study, the four most frequent mutations in the ATPase6 gene, namely L156R, L217R, L156P, and L217P, are studied for the first time together, both in primary cells and in cybrid clones. Arginine (“R”) mutations were associated with a much more severe phenotype than Proline (“P”) mutations, in terms of both biochemical activity and growth capacity. Also, a threshold effect in both “R” mutations appeared at 50% mutation load. Different mechanisms seemed to emerge for the two “R” mutations: the F1 seemed loosely bound to the membrane in the L156R mutant, whereas the L217R mutant induced low activity of complex V, possibly the result of a reduced rate of proton flow through the A6 channel. J. Cell. Biochem. 106: 878–886, 2009. © 2009 Wiley‐Liss, Inc.     

Synthesis and conformational study of poly(N delta-carbobenzoxy, N delta-benzyl-L-ornithine) and poly(N delta-benzyl-L-ornithine)

Poly(N^δ-carbobenzoxy, N^δ-benzyl-L -ornithine) (PCBLO) was prepared by the standard NCA method. PCBLO was converted into poly(N^δ-benzyl-L -ornithine) (PBLO) through decarbobenzoxylation with hydrogen bromide. The monomer N^δ-benzyl-L -ornithine was synthesized by reacting L -ornithine with benzaldehyde, followed by hydrogenation. The conformation of the two polypeptides was studied by optical rotatory dispersion and circular dichroism. PCBLO forms a right-handed helix in helix-promoting solvents. In mixed solvents of chloroform and dichloroacetic acid (DCA) it undergoes a sharp helix–coil transition at 12% (v/v) DCA at 25°C, as compared with 36% for poly(N^δ-carbobenzoxy-L -ornithine) (PCLO). Like PCLO, the helix–coil transition is “inverse,” that is, high temperature favors the helical form. PBLO is soluble in water at pH below 7 and has a “coiled” conformation. In 88% (v/v) 1-propanol above pH (apparent) 9.6 it is completely helical. In 50% 1-propanol the transition pH (apparent) is about 7.4; this compares with a pH_tr of about 10 for poly-L -ornithine in the same solvent.     

Effect of non-complementary nucleotides on the rate of helix formation: kinetics of formation of poly (I)-poly (C,I) and poly (I)-poly (C,U) complexes

Apparent second-order rate constants for complex formation between poly (I) and poly (C) and copolymers of C containing non-complementary I or U residues have been determined spectrophotometrically. The rate constants decrease as the concentration of either I or U in the C strands increases–the effect seems insensitive to the species of residue involved, when differences in the thermal stabilities of the poly (I) poly (C,I) and poly (I). poly (C,U) complexes are taken into account. These results suggest that low concentrations of relatively stable defects can alter the apparent kinetic “complexity” of polynucleotides as determined by hybridization methods (C₀t analysis).     

Colony Structure in Flustra foliacea (Linnaeus) (Bryozoa,Chéilostomata)

Encrusting forms presumably represent the original mode of growth in the bryozoans. They usually exhibit a relatively low degree of colony integration. The numerous different erect colony types, certainly independently derived from this stage, show a higher degree of integration. Eventually forms arise with a strict pattern only little influenced by the environment. The Flustra foliacea colony holds an intermediate position in this respect. It forms an initial crust on a foreign substratum such as rock. The crust forms marginal lobes. The lobes collide two and two. The two components of each collision then rise back to back, owing to lack of space, into bilaminar fronds. The two zooid layers composing these erect branches and mutually encrusting the “auto-substratum” of their respective basal walls, grow much more rapidly than the initial crust on the “heterosubstratum” of the rock to finally comprise more than 95 % of the colony volume. The different rate of growth on “auto-” and “heterosubstratum” respectively is interpreted as indicating a preference for the “autosubstratum” and as the main force in the formation of erect branches. The Fl. foliacea case indicates one of the pathways from encrusting to erect colonies in the bryozoans. It is probably valid for at least some of the erect bilaminar colonies appearing in different parts of the bryozoan system.     

Spectroscopic studies of enantiomeric discrimination in jet-cooled chiral complexes.

Van der Waals complexes formed between chiral molecules in the isolated gas phase were studied by combining supersonic expansion techniques with laser spectroscopy. The weakly bound diastereoisomers formed between a chiral secondary alcohol, butan-2-ol, and a chiral aromatic derivative such as 2-naphthyl-1-ethanol or 1-phenylethanol used as a resolving agent were discriminated on the basis of the spectral shifts of the UV S(0)-S(1) transition of the chromophore. Ground-state depletion spectroscopy (hole burning) has shown that, while only one structure was detected for the 1-phenylethanol/butan-2-ol homochiral complex, the heterochiral complex is trapped in the jet under two different conformations. Two isomers have also been shown for each diastereoisomeric pair of the 2-naphthyl-1-ethanol/butan-2-ol complexes. Using a semiempirical potential model, these isomeric forms were related to calculated structures which exhibit a folded or extended geometry depending on the solvent conformation (anti or gauche). The relative binding energy of the complexes involving R-1-phenylethanol and R- or S-butan-2-ol were obtained from fragmentation threshold measurements following two-color photoionization. Comparison of the diastereoisomers exhibiting a similar spectral signature shows that the homochiral pair is more stable than the heterochiral one by about 0.7 kcal/mol. The fragmentation threshold has been shown to depend on the jet-cooled isomer and this result addresses the role of conformational control in enantioselective interactions.     

Phylogenetic relationships in the Sceloporus variabilis (Squamata: Phrynosomatidae) complex based on three molecular markers,continuous characters and geometric morphometric data

The monophyly of the Sceloporus variabilis group is well established with five species and two species complexes, but phylogenetic relationships within species complexes are still uncertain. We studied 278 specimens in 20 terminals to sample all taxa in the “variabilis group,” including three subspecies in the “variabilis complex,” and two outgroups (Sceloporus grammicus and Sceloporus megalepidurus). We assembled an extensive morphological data set with discrete and continuous characters (distances and scale counts), including geometric morphometric data (landmark coordinates of three shapes), and a three‐marker molecular data set as well (ND4, 12S and RAG1). We conducted parsimony and Bayesian phylogenetic inferences on these data, including several partitioning and weighting schemes. We suggest elevating three subspecies to full species status. Therefore, we recommend recognition of nine species in the “variabilis group.” First, S. variabilis is sister to Sceloporus teapensis. In turn, Sceloporus cozumelae is sister to Sceloporus olloporus. These four species are a monophyletic group, which is sister to Sceloporus smithi. Finally, Sceloporus marmoratus is sister of the clade of five species. The other species in the “variabilis group” (Sceloporus chrysostictus, Sceloporus couchii and Sceloporus parvus) are a paraphyletic grade at the base of the tree. Our analyses reject the existence of the “variabilis complex.” We conducted a parsimony‐based ancestral reconstruction on body size (snout–vent length), femoral pores and dorsal scales and related morphological changes to geographic distribution of the species. Our phylogenetic hypothesis will allow best designs of comparative studies with species in the “variabilis group,” one of the earliest divergent lineages in the genus.