A survey of nuclear ribosomal internal transcribed spacer substitution rates across angiosperms: an approximate molecular clock with life history effects

Background  

A full understanding of the patterns and processes of biological diversification requires the dating of evolutionary events, yet the fossil record is inadequate for most lineages under study. Alternatively, a molecular clock approach, in which DNA or amino acid substitution rates are calibrated with fossils or geological/climatic events, can provide indirect estimates of clade ages and diversification rates. The utility of this approach depends on the rate constancy of molecular evolution at a genetic locus across time and across lineages. Although the nuclear ribosomal internal transcribed spacer region (nrITS) is increasingly being used to infer clade ages in plants, little is known about the sources or magnitude of variation in its substitution rate. Here, we systematically review the literature to assess substitution rate variation in nrITS among angiosperms, and we evaluate possible correlates of the variation.     

Genetics of floral traits influencing reproductive isolation between Aquilegia formosa and Aquilegia pubescens

Abstract: Reproductive isolation between Aquilegia formosa and Aquilegia pubescens is influenced by differences in their flowers through their effects on pollinator visitation and pollen transfer. Here, we investigate the genetic basis of floral characters differentiating these species. We found that in addition to the effects of flower orientation and the length of nectar spurs previously described, other characters such as flower color or odor affect hawkmoth visitation. Repeatability of measurements in an F2 population ranged from 0.53 to 0.83 among five floral traits, indicating that using the means of multiple measures per plant will substantially increase the power of a quantitative trait locus (QTL) analysis. Integration of floral traits was indicated by significant correlations among traits in an F2 population. In a separate F2 population we found that QTL for different floral traits were often closely associated, indicating that linkage or pleiotropy cause at least some of this integration. In addition, we found QTL for all floral traits examined. Because Aquilegia species are largely interfertile and vary extensively in both floral morphology and ecology, they offer the opportunity for QTL studies of a wide range of characters affecting reproductive isolation.     

Programed cell death shapes the expression of horns within and between species of horned beetles

Holometabolous insects provide an excellent opportunity to study both the properties of development as well as their evolution and diversification across taxa. Here we investigate the developmental basis and evolutionary diversification of secondary trait loss during development in the expression of beetle horns, a novel and highly diverse class of secondary sexual traits. In many species, horn growth during late larval development is followed by a period of dramatic remodeling during the pupal stage, including the complete resorption of horns in many cases. Here we show that programed cell death plays an important and dynamic role in the secondary resorption of pupal horn primordia during pupal development. Surprisingly, the degree of cell death mediated horn resorption depended on species, sex, and body region, suggesting the existence of regulatory mechanisms that can diversify quickly over short phylogenetic distances. More generally, our results illustrate that secondary, differential loss of structures during development can be a powerful mechanism for generating considerable morphological diversity both within and between species.     

Assessment of the biological health of the Brantas River, East Java, Indonesia using the Australian River Assessment System (AUSRIVAS) methodology

This study aimed to evaluate the applicability of the Australian River Assessment System (AUSRIVAS) bioassessment methodology to assess the biological health of streams in the upper-middle Brantas River catchment, East Java, Indonesia. A total of 84 `minimally disturbed' reference sites were selected and sampled for macroinvertebrates in riffle habitats. Sampling of macroinvertebrates and identification to family level was conducted by local biologists following intensive training, and under supervision. A quality control protocol was introduced to ensure the data were reliable and reproducible. A suite of `potential predictor' and `monitoring' environmental variables were also measured at each site. The macroinvertebrate data were used to develop a predictive AUSRIVAS model for the upper-middle Brantas river, and the model was then used to assess the `health' of 15 test sites in the catchment. Bioassessment outputs – Observed (O)/Expected (E) ratios – were found to be broadly related to measures of physical disturbance from land use and riparian degradation. Through the process of local reference site selection and sampling, model development, validation and subsequent use, the Australian AUSRIVAS rapid bioassessment method was assessed as being highly applicable to the upper-middle catchment sections of Indonesian river systems.