Dispersal traits may reflect dispersal distances,but dispersers may not connect populations demographically

Ecological traits that reflect movement potential are often used as proxies for measured dispersal distances. Whether such traits reflect actual dispersal is often untested. Such tests are important because maximum dispersal distances may not be achieved and many dispersal events may be unsuccessful (without reproduction). For insects, many habitat patches harbour ‘resident’ species that are present as larvae (sedentary) and adults (winged and dispersing), and ‘itinerant’ species present only as adults that have dispersed from elsewhere and fail to reproduce. We tested whether itinerancy patterns were temporally consistent, and whether itinerant and resident species differed in wing morphology, a strong correlate of flight capability. Over 3 years and at multiple locations in a 22 km stream length, we sampled larvae and adults of caddisflies in the genus Ecnomus to categorize species as residents or itinerants. Flight capacity was measured using wing size (length and area) and shape parameters (aspect ratio and the second moment of wing area). Three species of Ecnomus were residents and three species were itinerants, and patterns were consistent over 3 years. On average, itinerant species had larger wings, suggesting a greater capacity to fly long distances. Wing shape differed between species, but did not differ systematically between residents and itinerants. Wing morphology was associated with actual but not effective dispersal of some species of Ecnomus. Morphological traits may have weak explanatory power for hypotheses regarding the demographic connectedness of populations, unless accompanied by data demonstrating which dispersers contribute new individuals to populations.     

Reproduction-longevity trade-offs reflect diet, not adaptation

A tenet of life history evolution is that allocation of limited resources results in trade‐offs, such as that between reproduction and lifespan. Reproduction and lifespan are also influenced proximately by differences in the availability of specific nutrients. What is unknown is how the evolution of the ability to use a nutritionally novel diet is reflected in this fundamental trade‐off. Does the evolution of the ability to use a nutritionally novel food maintain the trade‐off in reproduction and longevity, or do the proximate effects of nutrition alter the adapted trade‐off? We tested this by measuring trade‐offs in male milkweed bugs, Oncopeltus fasciatus, fed either an adapted diet of sunflower or the ancestral diet of milkweed. Sunflower‐fed males lived longer but invested less in reproduction, both in mating and fertility. Milkweed‐fed males invested in both mating and fertility at the expense of survival. The evolution of an expanded diet was not constrained by the existing trade‐off, but instead was accompanied by a different trade‐off between reproduction and longevity. We suggest that this occurs because diets differ in promoting germ line development or longevity.     

Signaling to a B-cell clone by Ek,but not Ak,does not reflect alteration of A k genes

The mouse B-cell clone, CH12.LX (Ia^k, Ly-1⁺, ⁺, ⁺), can be induced to differentiate and secrete antibody in an antigen-specific, H-2-restricted manner. Induction requires two signals. One must be provided by the binding of specific antigen to the membrane IgM; the other is delivered by the binding of E^k-specific T-cell hybridomas to the E^k molecules of CH12.LX (Bishop and Haughton 1986). Previous studies demonstrated that E^k-specific monoclonal antibodies (mAbs) could substitute for T cells in delivering the second differentiative signal (Bishop and Haughton 1986). Although CH12.LX cells present A^k to A^k-restricted or alloreactive T-helper cells, neither T cells nor mAbs specific for A^k induce differentiation (Bishop and Haughton 1986). However, since the A^kspecifc mAbs tested previously were -chain-specific and the Ia epitope specificity of the T cells used was unknown, it is possible that the differentiative signal delivered to the CH12.LX class 11 molecule is chain-specific. Here we report the effects of ten additional Ia^k-specific mAbs upon the differentiation of CH12.LX. In addition, a cl)NA library was prepared from CHI 2.LX cells, clones corresponding to the and chains of the A^k molecule were isolated, and their nucleotide sequences were determined. Finally, the A^k and E^k molecules of CH12.LX and H-2^k spleen cells were compared by two-dimensional gel electrophoresis to examine possible post-translational differences in the Ia^k molecules of CH12.LX.     

The nonrandom microheterogeneity of 16S rRNA genes in Vibrio splendidus may reflect adaptation to versatile lifestyles

16S rRNA molecules in a microbial strain can differ due to nucleotide variation between their genes. This is a typical trait of fast-growing bacteria to cope with different niches. We investigated characteristics of 16S rRNA genes in Vibrio splendidus strain PB1-10, from the normal flora of Atlantic halibut. Sequencing of 16S rRNA gene clones detected 35 variable positions in a total of 13 different gene copies. More than two-thirds of the substitutions occurred in regions corresponding to helix H6 and helix H17 of the 16S rRNA molecule. Possible recombination between these helixes in related bacteria ( Vibrio, Photobacterium, Colwellia ) from similar environments impacts 16S rRNA-based phylogeny of V. splendidus . We argue that these nonrandom modifications are maintained to provide a fine-tuning of the ribosome function to optimize translation machinery performance and ultimately bacterial niche fitness.     

Vibrotactile adaptation impairs discrimination of fine,but not coarse,textures

The effect of vibrotactile adaptation on the ability to discriminate textured surfaces was examined in three experiments. The surfaces were rectilinear arrays of pyramids produced by etching of silicon wafers. Adaptation to 100-Hz vibration severely hampered discrimination of surfaces with spatial periods below 100 &#119 m (Experiment 1), but had little effect on the discrimination of coarser textures (Experiment 2). To determine which vibrotactile channel—Rapidly Adapting or Pacinian—plays the larger role in mediating the discrimination of fine textures, widely separated adapting frequencies (10 and 250 Hz) were used in Experiment 3. The fact that high- but not low-frequency adaptation interfered with discrimination suggests that the Pacinian system contributes importantly to this ability. Taken as a whole, the results of this study strongly support the duplex theory of tactile texture perception, according to which different mechanisms—spatial and vibrotactile—mediate the perception of coarse and fine textures, respectively.     

Symbiovars in rhizobia reflect bacterial adaptation to legumes

Legume specificity is encoded in rhizobial genetic elements that may be transferred among species and genera. Dissemination (by lateral transfer) of gene assemblies dictating host range accounts for the existence of the same biological variant (biovar) in distinct microbiological species. Different alternative biovars may exist in a single species expanding their adaptation to different niches (legume nodules). A review of all reported biovars is presented. Instead of the term biovar, symbiotic variant (symbiovar) is proposed as a parallel term to pathovar in pathogenic bacteria. Symbiovars should be determined based on the symbiotic capabilities in plant hosts, distinguished by the differences in host range and supported by symbiotic gene sequence information.     

Females competing to reproduce: dominance matters but testosterone may not

The associations among aggression, testosterone (T), and reproductive success have been well studied, particularly in male birds. In many species, males challenged with simulated or real territorial intrusions increase T and levels of aggression, outcomes linked to higher dominance status and greater reproductive success. For females, the patterns are less clear. Females behave aggressively towards one another, and in some species, females respond to a social challenge with increases in T, but in other species they do not. Prior work on female dark-eyed juncos (Junco hyemalis) had shown that experimental elevation of T increases social status and intrasexual aggression. Here, we conducted two experiments designed to answer three questions: Are endogenous concentrations of T associated with dominance status in captive female juncos? Does dominance status influence readiness to breed in female juncos? And do captive females increase T in response to a challenge? In the first experiment, we introduced two females to a breeding aviary, allowed them to form a dominance relationship and then introduced a male. We found that dominant females were more likely to breed than subordinates, but that dominance status was not predicted by circulating T. In the second experiment, we allowed a resident male and female to establish ownership of a breeding aviary (territory) then introduced a second, intruder female. We found that resident females were aggressive towards and dominant over intruders, but T did not increase during aggressive interactions. We suggest that during the breeding season, intrasexual aggression between females may influence reproductive success, but not be dependent upon fluctuations in T. Selection may have favored independence of aggression from T because high concentrations of T could interfere with normal ovulation or produce detrimental maternal effects.     

Extensive variation,but not local adaptation in an Australian alpine daisy

Alpine plants often occupy diverse habitats within a similar elevation range, but most research on local adaptation in these plants has focused on elevation gradients. In testing for habitat‐related local adaptation, local effects on seed quality and initial plant growth should be considered in designs that encompass multiple populations and habitats. We tested for local adaptation across alpine habitats in a morphologically variable daisy species, Brachyscome decipiens, in the Bogong High Plains in Victoria, Australia. We collected seed from different habitats, controlled for maternal effects through initial seed size estimates, and characterized seedling survival and growth in a field transplant experiment. We found little evidence for local adaptation for survival or plant size, based on three adaptation measures: Home versus Away, Local versus Foreign, and Sympatric versus Allopatric (SA). The SA measure controlled for planting site and population (site‐of‐origin) effects. There were significant differences due to site‐of‐origin and planting site effects. An important confounding factor was the size of plants directly after transplantation of seedlings, which had a large impact on subsequent seedling survival and growth. Initial differences in plant width and height influenced subsequent survival across the growing season but in opposing directions: wide plants had higher survival, but tall plants had lower survival. In an additional controlled garden experiment at Cranbourne Royal Botanic Gardens, site‐of‐origin effects detected in the field experiments disappeared under more benign homogeneous conditions. Although B. decipiens from different source areas varied significantly when grown across a range of alpine habitats, these differences did not translate into a local or habitat‐related fitness advantage. This lack of local advantage may signal weak past selection, and/or weak adaptive transgeneration (plasticity) effects.     

Genomic haplotype blocks may not accurately reflect spatial variation in historic recombination intensity

Recently, genomic data have revealed a "block-like" structure of haplotype diversity on human chromosomes. This structure is anticipated to facilitate gene mapping studies, because strong associations among loci within a block may allow haplotype variation to be tagged with a limited number of markers. But its usefulness to mapping efforts depends on the consistency of the block structure within and among populations, which in turn depends on how the block structure arises. Recombination hot spots are generally thought to underlie the block structure, but haplotype blocks can also develop stochastically under random recombination, in which case the block structure will show limited consistency among populations. Using coalescent models, which we upscaled to simulate the evolution of haplotypes with many markers at fixed distances, we show that the relationship between block boundaries and historic recombination intensity may be surprisingly weak. The majority of historic recombinations do not leave a footprint in present-day linkage disequilibrium patterns, and the block structure is sensitive to factors that affect the timing of recombination relative to marker mutation events in the genealogy, such as marker frequency bias and historic population size changes. Our results give insight into the potential of stochastic events to affect haplotype block structure, which can limit the usefulness of the block structure to mapping studies.     

Beak development of early squid paralarvae (Cephalopoda: Teuthoidea) may reflect an adaptation to a specialized feeding mode

Morphological and morphometric development of the upper jaw (UJ) and lower jaw (LJ) and arm crown of Chiroteuthis cf. veranyi, Liocranchia reinhardti (oceanic species), and Doryteuthis opalescens (neritic species) paralarvae were analyzed in order to verify whether or not they are determined by developmental modes. Jaw measurements were taken, correlated with mantle length (ML) by multiple linear regression to determine relative influences on growth, and compared between species by ANOVA to identify differences. Development was expected to be similar between oceanic species, but was morphologically similar between L. reinhardti and D. opalescens, and morphometrically similar between the latter and C. cf. veranyi. UJ and LJ measurements with highest correlation with ML are larger in L. reinhardti, indicating greater beak development in this species. Rostrum robustness is higher in L. reinhardti, intermediate in D. opalescens, and lower in C. cf. veranyi, hinting at the respective prey type. Teeth (LJ) and slit, characteristics of ancestral cephalopods, are present, disappearing completely and partially on the largest specimens of L. reinhardti and D. opalescens, respectively, and remaining in all sizes of C. cf. veranyi. The results suggest that their presence in early paralarvae reflects an adaptation to sucking the pre-digested internal fluids of prey.     

Bird pollination syndrome is the plant's adaptation to ornithophily,but nectarivorous birds are not so selective

Many tropical plants are pollinated by birds and several bird phylogenetical lineages have specialised to a nectar diet. The long-assumed, intimate ecological and evolutionary relationship between ornithophilous plants and phenotypically specialised nectarivorous birds has nevertheless been questioned in recent decades, where such plant–pollinator interactions have been shown to be highly generalised. In our study, we analysed two extensive interaction datasets: bird–flower and insect–flower interactions, both collected on Mt Cameroon, west-central Africa. We tested if: 1) insects and birds interact with distinct groups of plants; 2) plants with a typical set of ornithophilous floral traits (i.e. bird pollination syndrome) interact mainly with birds; 3) birds favour plants with bird pollination syndrome and; 4) if and how the individual floral traits and plant level nectar production predict bird visitation. Bird-visited plants were typically also visited by insects, while approximately half of the plants were visited by insects only. We confirmed the validity of the bird pollination syndrome hypothesis, as plants with bird-pollination syndrome traits were visited by birds at a higher rate and mostly hosted a lower frequency of visiting insects. However, these ornithophilous plants were not more attractive than the other plants for nectar-feeding birds. Nectar production per plant individual was a better predictor of bird visitation than any other floral trait traditionally related to the bird pollination syndrome. Our study thus demonstrated the highly asymmetrical relationship between ornithophilous plants and nectarivorous birds.     

Calcium regulates some, but not all, aspects of light adaptation in rod photoreceptors

The role of calcium as a regulator of light adaptation in rod photoreceptors was examined by manipulation of the intracellular Ca2+ concentration through the use of the calcium ionophore A23187 and external Ca2+ buffers. These studies utilized suspensions of isolated and purified frog rod outer segments that retain their mitochondria-rich inner segments (OS-IS). Three criteria of the dark- and light-adapted flash response were characterized as a function of the Ca2+ concentration: (a) the time to peak, (b) the rate of recovery, and (c) the response amplitude or sensitivity. For all Ca2+ concentrations examined, the time to peak of the flash response was accelerated in the presence of background illumination, suggesting that mechanisms controlling this aspect of adaptation are independent of the Ca2+ concentration. The recovery kinetics of the flash response appeared to depend on the Ca2+ concentration. In 1 mM Ca2+-Ringer's and 300 nM Ca2+-Ringer's + A23187, background illumination enhanced the recovery rate of the response; however, in 10 and 100 nM Ca2+-Ringer's + A23187, the recovery rates were the same for dark- and light-adapted responses. This result implies that a critical level of Ca2+ may be necessary for background illumination to accelerate the recovery of the flash response. The sensitivity of the flash response in darkness (SDF) was dependent on the Ca2+ concentration. In 1 mM Ca2+-Ringer's SDF was 0.481 pA per bleached rhodopsin (Rh*); a background of four Rh*/s decreased SDF by half (Io). At 300 nM Ca2+ + A23187, SDF was reduced to 0.0307 pA/Rh* and Io increased to 60 Rh*/s. At 100 nM Ca2+ + A23187, SDF was reduced further to 0.0025 pA/Rh* and Io increased to 220 Rh*/s. In 10 nM Ca2+ + A23187, SDF was lowered to 0.00045 pA/Rh* and Io raised to 760 RhI/s. Using these values of SDF and Io for each respective Ca2+ concentration, the dependence of the flash sensitivity on background intensity could be described by the Weber-Fechner relation. Under low Ca2+ conditions + A23187, bright background illumination could desensitize the flash response. These results are consistent with the idea that the concentration of Ca2+ may set the absolute magnitude of response sensitivity in darkness, and that there exist mechanisms capable of adapting the photoresponse in the absence of significant changes in cytoplasmic Ca2+ concentration.     

Carbon source utilization patterns of Bacillus simplex ecotypes do not reflect their adaptation to ecologically divergent slopes in 'Evolution Canyon', Israel

The 'Evolution Canyons' I and II in Israel are model habitats to study adaptation and speciation of bacteria in the environment. These canyons represent similar ecological replicates, separated by 40 km, with a strongly sun-exposed and hot 'African' south-facing slope (SFS) vs. a cooler and mesic-lush 'European' north-facing slope (NFS). Previously, among 131 Bacillus simplex isolates, distinct genetic lineages (ecotypes), each specific for either SFS or NFS, were identified, suggesting a temperature-driven slope-specific adaptation. Here, we asked whether the ecological heterogeneity of SFS vs. NFS also affected carbon utilization abilities, as determined using the Biolog assay. Contrary to expectation, a correlation between substrate utilization patterns and the ecological origin of strains was not found. Rather, the patterns split according to the two major phylogenetic lineages each of which contain SFS and NFS ecotypes. We conclude that traits related to the general energy metabolism, as far as assessed here, are neither shaped by the major abiotic features of 'Evolution Canyon', namely solar radiation, temperature, and drought, nor by the soil characteristics. We further conclude that some traits diverge rather neutrally from each other, whereas other, more environmentally related traits are shaped by natural selection and show evolutionary convergence.     

Apoptosis in cumulus cells, but not in oocytes, may influence bovine embryonic developmental competence

Aim of our study was to clarify if the occurrence of apoptosis in oocytes and cumulus cells is correlated to bovine oocyte developmental competence. The cumulus-oocyte complexes (COCs) were selected according to cumulus status: G1 with more than five layers of compact cumulus cells, G2 with one to five layers of compact cumulus cells and G3 with expanded cumulus cells. The degree of apoptosis in cumulus cells and oocytes measured by caspase staining and TUNEL assay before and after maturation, and 24 h post-insemination was compared to the cleavage, blastocyst formation and hatching rates of each group. Highest cleavage, blastocyst and hatching rates were found in cumulus-oocyte complexes with more than five layers of compact cumulus cells, but no apoptosis was detected in immature or in vitro matured oocytes, regardless of the cumulus status. Many cumulus cells contained active caspases before maturation, but caspase activity declined dramatically after maturation. TUNEL positive cells were rarely observed in each cumulus-oocyte complex upon oocyte recovery, but a huge increase of them was seen after in vitro maturation. Significantly more TUNEL and caspase positive cells were found in G2 cumulus-oocyte complexes. Our results suggest that: (i) oocyte apoptosis does not account for the inferior oocyte quality of G2 and G3; (ii) apoptosis occurs in cumulus cells regardless of the number and compactness of cumulus cells; and (iii) the degree of apoptosis in the compact cumulus-oocyte complexes (G1 and G2) is negatively correlated to the developmental competence of oocyte.     

Visual pigment phosphorylation but not transducin translocation can contribute to light adaptation in zebrafish cones

The ability of cone photoreceptors to adapt to light is extraordinary. In this study we evaluated two biochemical processes, visual pigment phosphorylation and transducin translocation, for their ability to contribute to light adaptation in zebrafish cones. Since cytoplasmic Ca2+ regulates light adaptation, the sensitivities of these processes to both light and Ca2+ were examined. Cytoplasmic Ca2+ regulates the sites of light-stimulated phosphorylation. Unexpectedly, we found that Ca2+ also regulates the extent of phosphorylation of unbleached cone pigments. Immunocytochemical analyses revealed that neither light nor cytoplasmic Ca2+ influences the localization of transducin in zebrafish cones.