Was it an explosion? Using population genetics to explore the dynamics of a recent radiation within Protea (Proteaceae L.)

Adaptive radiations likely underlie much of the world’s diversity, especially that of hyper‐diverse regions. They are usually characterized by a burst of speciation early in their evolutionary history, a pattern which can be detected using population genetic tools. The Cape Floristic Region (CFR) of southwestern South Africa is home to many spectacular plant radiations. Here, we investigate the white proteas (Protea section Exsertae), a typical CFR radiation, to determine if it demonstrates the burst of speciation associated with adaptive radiations in recent models. Inferences from individual assignment, tree‐based population relationships, and pairwise F‐statistics based on 10 microsatellite loci reveal that while the white proteas radiated recently they did not radiate explosively. In addition, we found evidence that there is little gene flow between sampled populations of most species. Taken together, these results demonstrate that within a small clade, the processes underlying the radiation are different from those envisioned by current models of adaptive radiation and suggest that geographical isolation could have played a role in the diversification of the group. Our study implicates both adaptive and non‐adaptive processes in the evolution of botanical diversity of the CFR.     

Synthetic DNA probes for the identification of sibling species in the Anopheles gambiae complex

The cloned DNA sequences pAna1, pAnq1 and pAnm14, which may be used to distinguish between at least five of the six species in the Anopheles gambiae Giles complex of Afrotropical malaria vector mosquitoes, have been sequenced. Each clone was found to possess a series of repeated sequences of 41, 30 and 163 bases respectively. In pAnq1 and pAnm14 the repeats were in direct tandem array, whilst in pAna1 the repetitive sequence was found to be interspersed by 15-17 variable bases. A comparison of a number of copies of each of the repetitive sequences within the three clones enabled the definition of the consensus sequence for each repetitive element. Based on these consensus sequences, three oligonucleotides of 21, 23 and 26 bases were derived from pAna1, pAnq1 and pAnm14 respectively. When tested as probes against DNA dot-blots and squash-blots of mosquito specimens, each oligonucleotide retained the same species-specificity as the original clones from which they were derived. The radioactively labelled oligonucleotides were able to detect as little as 5 ng of target genomic DNA in an overnight autoradiographic exposure. The synthetic DNA probes will form the basis of a simplified system for the field identification of Anopheles gambiae sibling species specimens.     

The Development of Tomato Root System in Relation to the Carbohydrate Status of the Whole Plant

The decrease in growth rate of the root system or complete cessationof its growth in developed, fruit-bearing tomato plants areknown phenomena. It has been suggested that a limited supplyof carbohydrates to this organ, due to its relative weaknessin competition with the flowers and developing fruitlets isthe main cause for these disorders. This theory was tested inthe present study with plants grown in an aerohydroponic systemup to the appearance of 12–13 trusses per plant, 172 dafter transplanting. The changes in the contents of carbohydratesin the various organs during this period were monitored. Theconcentrations of soluble sugars and starch in the leaves increasedwith the increase in truss number. The upper stem was foundto contain more carbohydrates than the lower stem, while nosignificant changes in the concentration of these compoundscould be detected in the roots throughout the experiment. Nevertheless,120–130 d after transplanting, the roots of the plants,bearing five to six trusses and two to three inflorescences,ceased growing and remained at the same or a slightly reducedsize for another 40–50 d. Calculations show that at thestage of five to six trusses, 38 g total soluble sugars and35 g starch were stored in the vegetative organs. Therefore,it seems unlikely that carbon deficiency caused by the competitionwith the reproductive organs (mainly developing fruits), affectedthe root growth. Instead, it is suggested that some other factoris responsible. Lycopersicon esculentumMill; carbohydrates; root growth rate; sink-source relationship; soluble sugars; starch     

Coincidence between consumer and host occurrence: macrolepidoptera in Britain

1. The interspecific relationship between the distributions of consumers and resources is examined, using data for macrolepidoptera (moths) in Britain.
2. Monophagous moth species feeding on host plants with small geographical ranges also have small ranges, whilst those feeding on host plants with large ranges may have small or large ranges themselves. Likewise, there is an approximately triangular relationship between the proportion of the range of its host that a monophagous moth occupies and the size of the host range.
3. Most monophagous moths occupy a small proportion of the range of their host, and only feed on hosts that have relatively large geographical ranges.
4. Factors determining both the range size of a monophage and the proportion of the host plant's range that it occupies are independent of taxonomy.
5. Monophages tend to have smaller geographical ranges than congeneric polyphages, but do not occupy a smaller proportion of the ranges of the plants that they consume.     

Development, phylogeny, and taxonomy of Bostrycapulus (Caenogastropoda: Calyptraeidae), an ancient cryptic radiation

Calyptraeid gastropods are well know for the taxonomic difficulties caused by their simple, phenotypically variable shells. In this paper I demonstrate that what was previously considered to be a single species, Crepidula aculeata , is an ancient (3–15 Myr) cryptic species complex made up of at least eight species, and that this group should be placed in the genus Bostrycapulus . Despite the difficulty in finding diagnostic adult shell and anatomical features upon which species can be unambiguously identified, DNA sequences, protoconch morphology, embryonic morphology and developmental characters clearly differentiate these eight species. A single species with direct development and nurse eggs is present in the South Atlantic, and a species with planktotrophic development occurs in the equatorial Pacific. The species from Japan, Australia, Florida, the Pacific coasts of Mexico and Central America, and the Cape Verde Islands all have direct development. Most of these species are separated by > 15% divergence in COI sequence data. The fossil record of Bostrycapulus goes back to the Miocene, which agrees with genetic estimates of divergences within the genus ranging from 3 to 15 Mya. Surprisingly, these ancient species differ only slightly in morphology from each other and genetic differentiation does not correlate with geographical distance. I revise the genus Bostrycapulus on the basis of differences in adult morphology, embryonic morphology, mode of development, protoconch morphology, and DNA sequence data. I also describe four new species ( B. pritzkeri sp. nov., B. odites sp. nov., B. latebrus sp. nov. and B. urraca sp. nov. ) and remove three others ( B. gravispinosus , B. calyptraeformis , and B.  cf. tegulicius ) from synonymy with B. aculeatus .  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 75−101.     

A route to recovery: The early Silurian shallow-water shelly fauna in the northern Oslo basin

The shelly fauna of the lowest part of the Sælabonn Formation in the Hadeland district of the Oslo Region provides a rare insight into the shallow-water biota of the earliest Silurian and hence the start of biotic recovery after the end Ordovician extinction event. It is dominated by the brachiopods Dalmanella cf. pectinoides Bergström, Coolinia cf. columbana (Reed), Leptaena cf. haverfordensis Bancroft and Zygospiraella scotica (Salter) together with the trilobite Acernaspis elliptifrons (Esmark). The first three species in this unique association belong to eurytopic Ordovician survivor genera which were also present in the underlying unit in Hadeland and continued to thrive during the Silurian. Significantly, Zygospiraella and Acernaspis have no unequivocal Ordovician record but diversified rapidly and became common during the early Silurian (Rhuddanian) in many parts of the world. Moreover, Acernaspis and Zygospiraella were highly eurytopic, pioneer taxa that were among the first elements of the Rhuddanian shelly fauna to appear in many parts of the world especially around the margins of the remnant Iapetus Ocean, following the drowning of areas previously emergent during the late Ordovician sea-level lowstand. The Hadeland fauna provides evidence of a previously undocumented route (among several) by which life ultimately returned to the global diversity plateau established in the mid-Ordovician.     

Variation in Ribulose 1,5 Bisphosphate Carboxylase Content in a Range of Winter Wheat Genotypes

Pyke, K A. and Leech, R. M. 1985. Variation in nbulose 1, 5bisphosphate carboxylase content in a range of winter wheatgenotypes. J. exp. Bot. 36: 1523–1529. Amounts of ribulose 1, 5 bisphosphate carboxylase (RuBPCase;E.C 4.1.1.39 [EC] ) were measured in the first leaves of 14 hexaploidwheat genotypes. The genotypes were representative of winterwheat grown in Britain during the past 150 years. The highest levels of RuBPCase per unit leaf area were foundin semi-dwarf genotypes which had more mesophyll cells per unitleaf area and smaller cells than tall genotypes. There was nosignificant correlation relating the year of introduction ofgenotypes to either the amount of RuBPCase per leaf or the amountper mesophyll cell Semi-dwarf genotypes tended to have smallerleaves and were less variable. Genotypic variation in the cellular content of RuBPCase is discussedin terms of genotypic differences in leaf development and thepotential for maximal RuBPCase accumulation. Key words: —Ribulose bisphosphate carboxylase, semi-dwarf wheat, cell size     

BIOCHEMICAL AUTONOMY OF HIGHER PLANT CHLOROPLASTS AND THEIR SYNTHESIS OF SMALL MOLECULES

1. Mature chloroplasts are able to synthesize a wide variety of compounds of low molecular weight in addition to carbohydrates. 2. Mature chloroplasts from higher plants can synthesize fatty acids from acetate, and galactolipids from UDP-galactose; but, thus far, there is no direct evidence that chloroplasts can produce their principal fatty acid, α-linolenate, independently of the rest of the cell. 3. Chloroplasts possess the enzymic machinery necessary to generate most of the common amino acids from inorganic nitrogen plus appropriate a-keto analogs of amino acids. However, the plastids do not appear able to synthesize many α-keto carbon compounds from the initial products of photosynthetic carbon dioxide fixation. 4. Whether chloroplasts can generate their own supply of acetate remains in doubt. 5. There is little evidence for or against the existence of chloroplastic enzymes catalysing synthesis of purines and pyrimidines. 6. Recent evidence confirms that immature plastids possess the complement of enzymes required for synthesis of protochlorophyllide from 8-aminolaevulinic acid but leaves open the possibility that extrachloroplastic cofactors may be involved in protochlorophyllide biosynthesis. 7. The weight of the available evidence suggests that, despite its great metabolic versatility and possible reproductive autonomy, the chloroplast of the higher plant is not metabolically autonomous or nutritionally independent of the remainder of the plant cell. Therefore, if there is any validity to the oft-repeated speculation that chloroplasts have evolved from ancient free-living procaryotes, it appears that the evolution of the chloroplast has led to a considerable loss of nutritional autonomy concomitant with the development or preservation of photosynthetic competence.     

Biological Activities of Melanotropic Peptide Fatty Acid Conjugates

Four fatty acids (FA, palmitic, myristic, decanoic, hexanoic) were individually conjugated to the N-terminus of the α-MSH fragment analog, H-Asp⁵-His⁶-D-Phe⁷-Arg⁸-Trp⁹-Lys¹⁰-NH₂. This resulted in enhanced potency of the conjugates (compared to the unconjugated melanotropin analog) as determined in the lizard skin bioassay and in the mouse melanoma cell tyrosinase bioassay. The shorter conjugates of hexanoic and decanoic acid were at least equipotent to α-MSH in the lizard skin bioassay, whereas the longer myristoyl and palmitoyl analogs were 100 times less active. The myristoyl and palmitoyl conjugates exhibited a “creeping” potency in the lizard skin bioassay—that is, potency of the peptides increased with time in contact with the skins. These observations may be related to the more lipid nature of these FA-conjugates. In the tyrosinase assay, the conjugates were 10–100 times more active than α-MSH or the unconjugated analog. Each of the FA-melanotropic peptide conjugates exhibited prolonged (residual) melanotropic activity in both the lizard skin and melanoma cell bioassays. In other words, after removal of the melanotropin conjugates from contact with the skins or cells, responses were still manifested for hours or days thereafter. As little as 1 hr of contact with melanoma cells resulted in enhanced enzyme activity as measured 48 hr later. Since the conjugates, but not H-[Ast⁵,D-Phe⁷,Lys¹⁰]α-MSH₅-₁₀-NH₂, exhibited prolonged activity, the conversion of reversible agonists to irreversible agonists was demonstrated.