Astralagus ertterae (Fabaceae), a New Species from the Southern Sierra Nevada

Astragalus ertterae, a new species from pinyon pine woodlands, southern Sierra Nevada, Kern County, California, is described and illustrated. This remarkable new species is morphologically closest to A. bicristatus in sect. Bicristati but differs in its dwarf stature, pilose indumentum, short peduncles, somewhat smaller flowers, and especially in a pod only half as long and proportionately twice as plump

Lunatics.

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An evolutionary disc model of the edge-on galaxy NGC 5907

We present a physical model that explains the two disparate observational facts: 1) the exponential vertical disc structure in the optical and NIR of the non-obscured part of the stellar disc and 2) the enhanced FIR/submm luminosity by about a factor of four near the obscured mid-plane, which requires additional dust and also stellar light to heat the dust component. We use multi-band photometry in U, B, V, R, and I- band combined with radiative transfer through a dust component to fit simultaneously the vertical surface-brightness and colour index profiles in all bands adopting a reasonable star formation history and dynamical heating function. The final disc model reproduces the surface-brightness profiles in all bands with a moderately declining star formation rate and a slowly starting heating function for young stars. The total dust mass is 57 million solar masses as required from the FIR/submm measurements. Without a recent star burst we find in the midplane an excess of 5.2-, 4.0-, and 3.0-times more stellar light in the U-, B-, and V-band, respectively. The corresponding stellar mass-to-light ratios are 0.91 in V- and 1.0 in R-band. The central face-on optical depth in V-band is 0.81 and the radial scale length of the dust is 40% larger than that of the stellar disc. Evolutionary disc models are a powerful method to understand the vertical structure of edge-on galaxies. Insights to the star formation history and the dynamical evolution of stellar discs can be gained. FIR/submm observations are necessary to restrict the parameter space for the models.Comment: 17 pages, 12 figures (24 files), A&A in pres

Floral uniformity through evolutionary time in a species-rich tree lineage

Changes in floral morphology are expected across evolutionary time and are often promoted as important drivers in angiosperm diversification. Such a statement, however, is in contrast to empirical observations of species-rich lineages that show apparent conservative floral morphologies even under strong selective pressure to change from their environments. Here, we provide quantitative evidence for prolific speciation despite uniform floral morphology in a tropical species-rich tree lineage. We analyse floral disparity in the environmental and phylogenetic context of Myrcia (Myrtaceae), one of the most diverse and abundant tree genera in Neotropical biomes. Variation in floral morphology among Myrcia clades is exceptionally low, even among distantly related species. Discrete floral specialisations do occur, but these are few, present low phylogenetic signal, have no strong correlation with abiotic factors, and do not affect overall macroevolutionary dynamics in the lineage. Results show that floral form and function may be conserved over large evolutionary time scales even in environments full of opportunities for ecological interactions and niche specialisation. Species accumulation in diverse lineages with uniform flowers apparently does not result from shifts in pollination strategies, but from speciation mechanisms that involve other, nonfloral plant traits