@article {Lindqvist:2007p7988,
	title = {Polyglutamine variation in a flowering time protein correlates with island age in a Hawaiian plant radiation},
	journal = {BMC Evol Biol},
	volume = {7},
	year = {2007},
	month = {Jan},
	pages = {105},
	abstract = {BACKGROUND: A controversial topic in evolutionary developmental biology is whether morphological diversification in natural populations can be driven by expansions and contractions of amino acid repeats in proteins. To promote adaptation, selection on protein length variation must overcome deleterious effects of multiple correlated traits (pleiotropy). Thus far, systems that demonstrate this capacity include only ancient or artificial morphological diversifications. The Hawaiian Islands, with their linear geological sequence, present a unique environment to study recent, natural radiations. We have focused our research on the Hawaiian endemic mints (Lamiaceae), a large and diverse lineage with paradoxically low genetic variation, in order to test whether a direct relationship between coding-sequence repeat diversity and morphological change can be observed in an actively evolving system. RESULTS: Here we show that in the Hawaiian mints, extensive polyglutamine (CAG codon repeat) polymorphism within a homolog of the pleiotropic flowering time protein and abscisic acid receptor FCA tracks the natural environmental cline of the island chain, consequent with island age, across a period of 5 million years. CAG expansions, perhaps following their natural tendency to elongate, are more frequent in colonists of recently-formed, nutrient-rich islands than in their forebears on older, nutrient-poor islands. Values for several quantitative morphological variables related to reproductive investment, known from Arabidopsis fca mutant studies, weakly though positively correlate with increasing glutamine tract length. Together with protein modeling of FCA, which indicates that longer polyglutamine tracts could induce suboptimally mobile functional domains, we suggest that CAG expansions may form slightly deleterious alleles (with respect to protein function) that become fixed in founder populations. CONCLUSION: In the Hawaiian mint FCA system, we infer that contraction of slightly deleterious CAG repeats occurred because of competition for resources along the natural environmental cline of the island chain. The observed geographical structure of FCA variation and its correlation with morphologies expected from Arabidopsis mutant studies may indicate that developmental pleiotropy played a role in the diversification of the mints. This discovery is important in that it concurs with other suggestions that repetitive amino acid motifs might provide a mechanism for driving morphological evolution, and that variation at such motifs might permit rapid tuning to environmental change.},
	keywords = {Alleles, DNA: Plant, Genes: Plant, Hawaii, Mentha, Minisatellite Repeats, Peptides, Phylogeny, Plant Proteins, Selection: Genetic, Sequence Homology: Amino Acid, Species Specificity},
	doi = {10.1186/1471-2148-7-105},
	author = {Charlotte Lindqvist and Liisa Laakkonen and Victor A Albert}
}
@article {Sykorova:2007p7980,
	title = {The cultivation bias: different communities of arbuscular mycorrhizal fungi detected in roots from the field, from bait plants transplanted to the field, and from a greenhouse trap experiment},
	journal = {Mycorrhiza},
	volume = {18},
	number = {1},
	year = {2007},
	month = {Dec},
	pages = {1{\textendash}14},
	abstract = {The community composition of arbuscular mycorrhizal fungi (AMF) was investigated in roots of four different plant species (Inula salicina, Medicago sativa, Origanum vulgare, and Bromus erectus) sampled in (1) a plant species-rich calcareous grassland, (2) a bait plant bioassay conducted directly in that grassland, and (3) a greenhouse trap experiment using soil and a transplanted whole plant from that grassland as inoculum. Roots were analyzed by AMF-specific nested polymerase chain reaction, restriction fragment length polymorphism screening, and sequence analyses of rDNA small subunit and internal transcribed spacer regions. The AMF sequences were analyzed phylogenetically and used to define monophyletic phylotypes. Overall, 16 phylotypes from several lineages of AMF were detected. The community composition was strongly influenced by the experimental approach, with additional influence of cultivation duration, substrate, and host plant species in some experiments. Some fungal phylotypes, e.g., GLOM-A3 (Glomus mosseae) and several members of Glomus group B, appeared predominantly in the greenhouse experiment or in bait plants. Thus, these phylotypes can be considered r strategists, rapidly colonizing uncolonized ruderal habitats in early successional stages of the fungal community. In the greenhouse experiment, for instance, G. mosseae was abundant after 3 months, but could not be detected anymore after 10 months. In contrast, other phylotypes as GLOM-A17 (G. badium) and GLOM-A16 were detected almost exclusively in roots sampled from plants naturally growing in the grassland or from bait plants exposed in the field, indicating that they preferentially occur in late successional stages of fungal communities and thus represent the K strategy. The only phylotype found with high frequency in all three experimental approaches was GLOM A-1 (G. intraradices), which is known to be a generalist. These results indicate that, in greenhouse trap experiments, it is difficult to establish a root-colonizing AMF community reflecting the diversity of these fungi in the field roots because fungal succession in such artificial systems may bias the results. However, the field bait plant approach might be a convenient way to study the influence of different environmental factors on AMF community composition directly under the field conditions. For a better understanding of the dynamics of AMF communities, it will be necessary to classify AMF phylotypes and species according to their life history strategies.},
	keywords = {Bromus, DNA: Fungal, Ecosystem, Inula, Medicago sativa, Molecular Sequence Data, Mycorrhizae, Origanum, Phylogeny, Polymerase Chain Reaction, Species Specificity},
	doi = {10.1007/s00572-007-0147-0},
	author = {Zuzana S{\'y}korov{\'a} and Kurt Ineichen and Andres Wiemken and Dirk Redecker}
}
