1 99311 nterestingy, the effect of betaine may have been just the opposte, that is, to enhance the difference between the forces requ~red to Induce the trans~t~on in AT-arid CG-r~ch regions 24 The f~tted Kuhn segment length of 15 A rnpes a persstence length of 7.5 A for ssDNA Ths vdue s about half that estrnated by E K Achter end G. Fesenfed iB~ooolyt-ies 10. 1625 (1 971)] for apurineted ssDNA by us~ng g h t scattering ancl sedilnentat~on I: was assumed n that study that 1 M NaCl s a theta solvent for ssDNA. In the present study, the contrectie force on e ssDNA molecule n 1 M NaCl. extrepoated to zero extenson, was about 5 pN (see Fig. 6, nset blue). Ths force offset probably Indicates secondat? st1 ucture forlnation or condensailon with~n the --~olecule If such structure forlned n the sednentation studes, then an erroneously large value for the r~gidty of ssDNA end for RNA could hzve been obtzned 25 In the presence of adenosne trphosphate (ATP) or ATPiylS. RecA ~lndergoes an aloster~c change n t o a high-affnty form that bnds dsDNA cooperatvey n a stocholnetrc rato of 1 RecN3 bp of dsDNA to form a r~ght-handed h e c a falnent [S C \!Vest, An!iii Rev B I O C~J~~ 61. 603 (1 992)] There are six RecA molec~~les and 18 6 bp;turn of the DNA molecule that s overstretched by a factor of 1 5 t~mes its B-form contour length 26. A Klug and F H C Cr~ck [h'atatlii -e 255. 530 (1975)l have suqgtisted that formaton of a few highly bent regons or "knks" n DNA mght be energetcaly fawarable relative to srnooth bendng o. er a longer DNA length. The argument requres that after the ensung of a o c a z e d knk n the DNA molec~lle, the energy re3,u red to bend ;he DNA further by an angle 8 at that locat~on, be smaller than the energy needed to bend the DNA by the same angle before the ensuing of the knk Ths s ndeed obsetved n macroscopic eastc medawhen the deformaton goes beyond the eastc nto the "plastc" regme (a plastc straw s a good example) 27 Carboxyate-polystyrene beads (3 56 ILm n dameter. CV = 2.7'0, Spherotech) were covelently coated vlith streptav~d~n uslng l-ethyl-3-(3-d1methylam1nopropy) carbodmde (EDAC) Each molecule was puled both r~ght and left from the p~pette to determ n e the pont of attachment of the molecule on the ppette bead. Because the o p t c a y trapped bead can rotate freely, but the ppette-trapped bead cannot. Ex can be deterlnned n abso ute un~ts jmlcrometers), In each F-Ex cuwe, data representng the folowng four processes s ~~~p e r i m p o s e d : extendng the molecule to right of the ppette, then relaxing t froln the right, extendng t leftward, then relaxng t from the left. Each data point was taken after a -0.5 ILm change n extension and a 2-s waitn g perod. The force sgna was then averaged for an add~t~ona 2 s and recorded A complete r~ghr-left stretch cycle took about 10 m n . 28 A video showing actual bead-DNA-bead assembly IFlg. 1 B) can be viewed on the Word W!de Web at 29. D W! . Ussey. R \VJ Hoepfner, R R Sinden Met!i-0dS E~z J /~o / 21 2. 262 (1 992) 30.The nat...

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The Labridae is one of the most structurally and functionally diversified fish families on coral and rocky reefs around the world, providing a compelling system for examination of evolutionary patterns of functional change. Labrid fishes have evolved a diverse array of skull forms for feeding on prey ranging from molluscs, crustaceans, plankton, detritus, algae, coral and other fishes. The species richness and diversity of feeding ecology in the Labridae make this group a marine analogue to the cichlid fishes. Despite the importance of labrids to coastal reef ecology, we lack evolutionary analysis of feeding biomechanics among labrids. Here, we combine a molecular phylogeny of the Labridae with the biomechanics of skull function to reveal a broad pattern of repeated convergence in labrid feeding systems. Mechanically fast jaw systems have evolved independently at least 14 times from ancestors with forceful jaws. A repeated phylogenetic pattern of functional divergence in local regions of the labrid tree produces an emergent family-wide pattern of global convergence in jaw function. Divergence of close relatives, convergence among higher clades and several unusual 'breakthroughs' in skull function characterize the evolution of functional complexity in one of the most diverse groups of reef fishes.

Recent advances in high-throughput sequencing library preparation and subgenomic enrichment methods have opened new avenues for population genetics and phylogenetics of nonmodel organisms. To multiplex large numbers of indexed samples while sequencing predominantly orthologous, targeted regions of the genome, we propose modifications to an existing, in-solution capture that utilizes PCR products as target probes to enrich library pools for the genomic subset of interest. The sequence capture using PCR-generated probes (SCPP) protocol requires no specialized equipment, is highly flexible and significantly reduces experimental costs for projects where a modest scale of genetic data is optimal (25-100 genomic loci). Our alterations enable application of this method across a wider phylogenetic range of taxa and result in higher capture efficiencies and coverage at each locus. Efficient and consistent capture over multiple SCPP experiments and at various phylogenetic distances is demonstrated, extending the utility of this method to both phylogeographic and phylogenomic studies.