Cryptic Evolution: Does Environmental Deterioration Have a Genetic Basis?

Cryptic evolution has been defined as adaptive evolutionary change being masked by concurrent environmental change. Empirical studies of cryptic evolution have usually invoked a changing climate and/or increasing population density as the form of detrimental environmental change experienced by a population undergoing cryptic evolution. However, Fisher (1958) emphasized that evolutionary change in itself is likely to be an important component of "environmental deterioration," a point restated by Cooke et al. (1990) in the context of intraspecific competition. In this form, environmental deterioration arises because a winning lineage has to compete against more winners in successive generations as the population evolves. This "evolutionary environmental deterioration" has different implications for the selection and evolution of traits influenced by resource competition than general environmental change. We reformulate Cooke's model as a quantitative genetic model to show that it is identical in form to more recent developments proposed by quantitative geneticists. This provides a statistical framework for discriminating between the alternative hypotheses of environmental change and environmental deterioration caused by evolutionary change. We also demonstrate that in systems where no phenotypic change has occurred, there are many reasonable biological processes that will generate patterns in predicted breeding values that are consistent with what has been interpreted as cryptic evolution, and care needs to be taken when interpreting these patterns. These processes include mutation, sib competition, and invisible fractions.     

Cytotoxic Michael-type amine adducts of alpha-methylene lactones alantolactone and isoalantolactone

Two series of cytotoxic (IC50, K562 cell line, 1-24 microM) alpha-aminomethyl substituted lactones 3 and 4 were prepared by stereoselective Michael-type addition of amines to alantolactone (1) and isoalantolactone (2). The lactones 1 and 2 and their amine adducts induce apoptosis and act as alkylating agents.     

Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system

The Southern Plateau subantarctic region, southeast of New Zealand, is an important feeding area for birds, seals and fish, and a fishing ground for commercially significant species. The Southern Plateau is a major morphometric feature, covering approximately 433,620 km² with average depth of 615 m. The region is noted for its relatively low levels of phytoplankton biomass and primary production that is iron-limited. In order to evaluate the implications of these attributes for the functioning of this ecosystem a steady-state, 19-compartment model was constructed using Ecopath with Ecosim software of Christensen et al. [www.ecopath.org]. The system is driven by primary production that is primarily governed by the supply of iron and light. The total system biomass of 6.28 g C m⁻² is very low compared with systems so far modelled with a total system throughput of 1136 g C m⁻² year⁻¹. In the model, the Southern Plateau retains 69% of the biomass in the pelagic system and 99% of total production. Although fish are caught demersally, most of their food is part of production in the pelagic system. Top predators represent about 0.3% of total biomass and account for about 0.24 g C m⁻² year⁻¹ of food consumed made up of birds 0.058 g C m⁻² year⁻¹, seals 0.041 g C m⁻² year⁻¹, and toothed 0.094 g C m⁻² year⁻¹ and baleen whales 0.051 g C m⁻² year⁻¹. This amounts to 105,803 tonnes carbon over the whole of the Southern Plateau and is about 17% of the total amount of food eaten by non-mesopelagic fish. Mean transfer efficiencies between trophic levels II and IV of 23% are at the high end of the range reported in the literature. In the model, adult fish production is almost completely accounted for by the fisheries take (32%), consumption by seals (7%), toothed whales (21%), other adult fish (13%), and squid (20%). Fish and squid catches are at the trophic levels of 4.8 and 5.0, respectively. The gross efficiency of the fishery is 0.018% (catch/primary production). Although not all data come from direct knowledge of this system, the model reflects its general characteristics, namely a low primary production system dominated by the microbial loop, low sedimentation to the seafloor, high transfer efficiencies, a long food web and supporting high-level predators.     

Mitochondrial phylogeny of extant Hawaiian tree snails (Achatinellinae)

Hawaiian tree snails in the endemic subfamily Achatinellinae display a staggering variety of shell colors and banding patterns. Despite numerous attempts to classify this morphological variation, a conclusive phylogeny has not been proposed. To improve conservation efforts, we sought to better understand the species identities and phylogenetic relationships among the extant species of Achatinella and Partulina using partial mitochondrial 16S ribosomal DNA sequences. The reconstructed phylogeny showed a high degree of support for more recent branches, but gave little support to deeper nodes. The most confident branches challenge previous systematic arrangements of these snails, grouping species that previously had been placed into different subgenera. High levels of sequence divergence within some species may reflect the long-term isolation of subpopulations. Rapid rates of sequence divergence may have saturated base substitutions and contributed to the lack of resolution of higher-order relationships. We did not find support for the monophyly of the Achatinella species, nor thus for a single colonization of Oahu from Maui Nui.     

GENETIC POPULATION STRUCTURE AND MATING SYSTEM IN CHONDRUS CRISPUS (RHODOPHYTA)1

Chondrus crispus Stackh. has been intensely studied, yet no study to date has elucidated its population structure or mating system despite many populations in which there was a haploid bias and lack of male gametophytes. Therefore, 12 nuclear microsatellite loci were identified in this red alga. Microsatellite markers were developed and tested against a panel of specimens collected from two shore levels at two sites in Brittany, France: Pointe de Primel and Pointe de la Jument, Concarneau. Single locus genetic determinism was verified at eight polymorphic loci, as only one band was observed for haploid genotypes, whereas one or two bands were observed for diploids. These markers enabled the detection of unique genotypes within sampled populations, indicating that very few fronds shared the same multilocus genotype. This finding suggests that asexual reproduction was not the prevailing mode of reproduction. In addition, we explored the hierarchical population structure showing that gene flow is restricted at small spatial scales (<50 m) between upper and lower Chondrus‐range populations within a shore. Sexual reproduction predominated in the populations of C. crispus studied, but probably due to fine‐scale spatial substructuring, inbreeding was also significant. In conclusion, this study reveals that fine‐scale genetic variation is of major importance in C. crispus, suggesting that differences between microhabitats should be essential in understanding evolutionary processes in this species.     

Stoichiometry, ATP/2e values, and energy requirements for reactions catalyzed by nitrogenase from Azotobacter vinelandii.

The stoichiometry of the nitrogenase ATP-dependent H2 evolution and ecetylene reduction reactions using S2O4(2-) as an electron source was studied by various techniques. For each mole of S2O4(2-) oxidized to 2SO3(2-) by the enzyme-catalyzed reactions at 25 degrees and pH 8, 1 mol of H2 (1 mol of ethylene for acetylene reduction) and two protons are produced. Under these conditions, 4.5 mol of ATP was hydrolyzed to ADP and inorganic phosphate for each S2O4(2-) oxidized. ATP/S2O4(2-) (ATP/2e) values determined at 5 degree intervals from 10 to 35 degrees were found to go through a minimum at 20 degrees. This effect is explained in terms of possible enzyme structure modifications. Calorimetric measurements for the enzyme-catalyzed H2 evolution and acetylene reduction reactions gave deltaH values of -32.4 and -75.1 kcal/mol of S2O4(2-), respectively.