Several members of Selaginella are renowned for their ability to survive extreme drought and "resurrect" when conditions improve. Many of these belong to subgenus Tetragonostachys, a group of ∼45 species primarily found in North and Central America, with substantial diversity in the Sonoran and Chihuahuan Deserts. We evaluated the monophyly and the age of subgenus Tetragonostachys and assess how drought tolerance contributed to the evolution of this clade.
Abstract:
Insect-fern interactions are not as well characterized as insect-angiosperm interactions. For example, the imitation of unique fern structures by insects has not been observed. On a recent trip to Puerto Rico, we collected ferns that bore small Lepidoptera imitating fern sori. Herbarium specimen searches indicate that these Lepidoptera are restricted to the Caribbean on ferns with highly visible sporangia. A possible selective pressure for the evolution of lepidopteran soral crypsis is wasp parasitism, as evidence of parasitoid wasps was found. However, it is more likely that soral crypsis evolved to avoid visually oriented predators such as birds or lizards.
PMID: 21693439;Abstract:
The Asteraceae (Compositae) is a large family of over 20,000 wild, weedy, and domesticated species that comprise approximately 10% of all angiosperms, including annual and perennial herbs, shrubs and trees, and species on every continent except Antarctica. As a result, the Asteraceae provide a unique opportunity to understand the evolutionary genomics of lineage radiation and diversification at numerous phylogenetic scales. Using publicly available expressed sequence tags from 22 species representing four of the major Asteraceae lineages, we assessed neutral and nonneutral evolutionary processes across this diverse plant family. We used bioinformatic tools to identify candidate genes under selection in each species. Evolution at silent and coding sites were assessed for different Gene Ontology functional categories to compare rates of evolution over both short and long evolutionary timescales. Our results indicate that patterns of molecular change across the family are surprisingly consistent on a macroevolutionary timescale and much more so more than would be predicted from the analysis of one (or many) examples of microevolution. These analyses also point to particular classes of genes that may be crucial in shaping the radiation of this diverse plant family. Similar analyses of nuclear and chloroplast genes in six other plant families confirm that many of these patterns are common features of the plant kingdom. © 2011 The Author.
PMID: 20576738;PMCID: PMC2924827;Abstract:
Background and AimsTo assess the number and phylogenetic distribution of large-scale genome duplications in the ancestry of Actinidia, publicly available expressed sequenced tags (ESTs) for members of the Actinidiaceae and related Ericales, including tea (Camellia sinensis), were analysed.MethodsSynonymous divergences (Ks) were calculated for all duplications within gene families and examined for evidence of large-scale duplication events. Phylogenetic comparisons for a selection of orthologues among several related species in Ericales and two outgroups permitted placement of duplication events in relation to lineage divergences. Gene ontology (GO) categories were analysed for each whole-genome duplication (WGD) and the whole transcriptome.Key ResultsEvidence for three ancient WGDs in Actinidia was found. Analyses of paleologue GO categories indicated a different pattern of retained genes for each genome duplication, but a pattern consistent with the dosage-balance hypothesis among all retained paleologues.ConclusionsThis study provides evidence for one independent WGD in the ancestry of Actinidia (Ad-), a WGD shared by Actinidia and Camellia (Ad-), and the well-established At- WGD that occurred prior to the divergence of all taxa examined. More ESTs in other taxa are needed to elucidate which groups in Ericales share the Ad- or Ad- duplications and their impact on diversification. © The Author 2010.
