Mobile larynx in Mongolian gazelle: Retraction of the larynx during rutting barks in male Mongolian gazelle (Procapra gutturosa Pallas, 1777)

This study provides the first evidence of pronounced temporary laryngeal descent in a bovid species. An elaborate acoustic display is prominent in male courtship behavior of polygynous Mongolian gazelle. During rut, rounding up of females is accompanied by continuous head‐up barking by dominant males. Throughout the rut their evolutionarily enlarged larynx descends to a low mid‐neck resting position. In the course of each bark the larynx is additionally retracted toward the sternum by 30% of the resting vocal tract length. A geometric model of active larynx movements was constructed by combining results of video documentation, dissection, skeletonization, and behavioral observation. The considerable distance between resting position and maximal laryngeal descent suggests a backward tilting of the hyoid apparatus and an extension of the thyrohyoid connection during the retraction phase. Return to the resting position is effected by strap muscles and by the elastic recoil of the pharynx and the thyrohyoid connection. An intrapharyngeal inflation of the peculiar palatinal pharyngeal pouch of adult males is inferred from a short‐time expansion of the ventral neck region rostral to the laryngeal prominence. The neck of adult dominant males is accentuated by long gray guard hairs during the rut. The passive swinging of the heavy larynx of adult males during locomotion gives the impression of a handicap imposed on rutting males. Apparently, this disadvantage becomes outweighed by the profits for reproductive success. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

How selection affects phenotypic fluctuation

The large degree of phenotypic fluctuation among isogenic cells highlighted by recent studies on stochastic gene expression confers fitness on some individuals through a ‘bet‐hedging’ strategy, when faced with different selective environments. Under a single selective environment, the fluctuation may be suppressed through evolution, as it prevents maintenance of individuals around the fittest state and/or function. However, as fluctuation can increase phenotypic diversity, similar to mutation, it may contribute to the survival of individuals even under a single selective environment. To discuss whether the fluctuation increases over the course of evolution, cycles of mutation and selection for higher GFP fluorescence were carried out in Escherichia coli. Mutant genotypes possessing broad GFP fluorescence distributions with low average values emerged under strong selection pressure. These ‘broad mutants’ appeared independently on the phylogenetic tree and increased fluctuations in GFP fluorescence were attributable to the variance in mRNA abundance. In addition to the average phenotypic change by genetic mutation, the observed increase in phenotypic fluctuation acts as an evolutionary strategy to produce an extreme phenotype under severe selective environments.     

Morphology and development of the subterranean organs of the achlorophyllous Sciaphila polygyna (Triuridaceae)

The subterranean organs of the achlorophyllous Sciaphila polygyna (Triuridaceae) are described, depicted, and structurally explained for the first time. Unlike other Triuridaceae, the subterranean system of S. polygyna appears as a complex star-like structure of short, but thickened, roots as well as scale leaves and shoots. A complete series of sections revealed the following construction. In the axil of a scale leaf at a shoot of first order, a side shoot of second order as well as a pair of endogenous shoot-borne roots arise. This side shoot of second order also develops a scale leaf very early in ontogeny, which again gives rise to a side shoot of third order and a pair of shoot-borne roots. Other scale leaves at shoots of any order may also bear shoots and root pairs. This growth pattern occurs in a very close manner without internode elongation, resulting in the clumped, star-like appearance. The structures described superficially resemble the root systems of many mycoheterotrophic plants from other families. Comparisons with respect to how they develop, however, show that these similar root systems can result from distinct developmental patterns, suggesting independent evolutionary pathways and a considerable evolutionary pressure towards abbreviated and thickened roots in mycoheterotrophic plants. Possible advantages as well as evolutionary implications of the structures described are discussed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 295–301.     

A Novel Phase of Li15Si4 Synthesized under Pressure

Li₁₅Si₄, the only crystalline phase that forms during lithiation of the Si anode in lithium‐ion batteries, is found to undergo a structural transition to a new phase at 7 GPa. Despite the large unit cell of Li₁₅Si₄ (152 atoms in the unit cell), ab initio evolutionary metadynamics (using the USPEX code) successfully predicts the atomic structure of this new phase (β‐Li₁₅Si₄), which has an orthorhombic structure with an Fdd2 space group. In the new β‐Li₁₅Si₄ phase Si atoms are isolated by Li atoms analogous to the original cubic phase (α‐Li₁₅Si₄), whereas the atomic packing is more efficient owing to the higher Si? Li coordination number and shorter Si? Li, Li? Li bonds. β‐Li₁₅Si₄ has substantially larger elastic moduli compared with α‐Li₁₅Si₄, and has a good electrical conductivity. As a result, β‐Li₁₅Si₄ has superior resistance to deformation and fracture under stress. The theoretical volume expansion of Si would decrease 25% if it transforms to β‐Li₁₅Si₄, instead of α‐Li₁₅Si₄, during lithiation. Moreover, β‐Li₁₅Si₄ can be recovered back to ambient pressure, providing opportunities to further investigate its properties and potential applications.     

Ecological genetics of range size variation in Boechera spp. (Brassicaceae)

Many taxonomic groups contain both rare and widespread species, which indicates that range size can evolve quickly. Many studies have compared molecular genetic diversity, plasticity, or phenotypic traits between rare and widespread species; however, a suite of genetic attributes that unites rare species remains elusive. Here, using two rare and two widespread Boechera (Brassicaceae) species, we conduct a simultaneous comparison of quantitative trait diversity, genetic diversity, and population structure among species with highly divergent range sizes. Consistent with previous studies, we do not find strong associations between range size and within‐population genetic diversity. In contrast, we find that both the degree of phenotypic plasticity and quantitative trait structure (Q_ST) were positively correlated with range size. We also found higher F_ST: Q_ST ratios in rare species, indicative of either a greater response to stabilizing selection or a lack of additive genetic variation. While widespread species occupy more ecological and climactic space and have diverged at both traits and markers, rare species display constrained levels of population differentiation and phenotypic plasticity. Combined, our results provide evidence for a specialization–generalization trade‐off across three orders of magnitude of range size variation in the ecological model genus, Boechera.     

Modular Skeletal Evolution in Sticklebacks Is Controlled by Additive and Clustered Quantitative Trait Loci

Understanding the genetic architecture of evolutionary change remains a long-standing goal in biology. In vertebrates, skeletal evolution has contributed greatly to adaptation in body form and function in response to changing ecological variables like diet and predation. Here we use genome-wide linkage mapping in threespine stickleback fish to investigate the genetic architecture of evolved changes in many armor and trophic traits. We identify >100 quantitative trait loci (QTL) controlling the pattern of serially repeating skeletal elements, including gill rakers, teeth, branchial bones, jaws, median fin spines, and vertebrae. We use this large collection of QTL to address long-standing questions about the anatomical specificity, genetic dominance, and genomic clustering of loci controlling skeletal differences in evolving populations. We find that most QTL (76%) that influence serially repeating skeletal elements have anatomically regional effects. In addition, most QTL (71%) have at least partially additive effects, regardless of whether the QTL controls evolved loss or gain of skeletal elements. Finally, many QTL with high LOD scores cluster on chromosomes 4, 20, and 21. These results identify a modular system that can control highly specific aspects of skeletal form. Because of the general additivity and genomic clustering of major QTL, concerted changes in both protective armor and trophic traits may occur when sticklebacks inherit either marine or freshwater alleles at linked or possible “supergene” regions of the stickleback genome. Further study of these regions will help identify the molecular basis of both modular and coordinated changes in the vertebrate skeleton.