Evolutionary consequences of extensive morph loss in tristylous decodon verticillatus (Lythraceae): a shift from tristyly to distyly?

The evolution of distyly from tristyly has occurred repeatedly, especially in the Lythraceae. However, the evolutionary forces involved remain unclear since species exhibiting transitional stages between tristyly and distyly have rarely been studied. The self-compatible, wetland perennial Decodon verticillatus (Lythraceae) may provide this transitional variation since populations commonly lack style morphs, particularly the mid-styled (M) morph. In dimorphic populations lacking the M morph, anthers positioned at the mid level in both the long- (L) and short-styled (S) morphs have lost their target stigma, setting the stage for either evolutionary repositioning of mid-level anthers to increase pollen export to L and S stigmas, or increased variability in mid-level anther position resulting from relaxed selection. We examined these two hypotheses by comparing floral morphology in eight dimorphic and ten trimorphic populations from throughout the species’ range. We found no evidence that loss of the M morph has led to evolutionary modification of mid-level stamens. While mid-level stamens of the S morph were 11.0 ± 4.0% (mean ± 1 SE) longer than those of the L morph in dimorphic populations, divergence in stamen length between morphs occurred to the same extent (10.4 ± 2.0%) in trimorphic populations and cannot be attributed to the absence of the M morph. Analyses of variability using median ratio tests revealed no difference in the variability of mid-level stamen length between dimorphic and trimorphic populations. Mid-level stamens were not more variable than long- and short-level stamens within dimorphic populations. The consistent divergence in mid-level stamens between the L and S morphs may reflect morph-specific differences in the optimal position of mid-level anthers for maximizing cross-pollination and avoiding self-fertilization.     

Does frequency-dependence determine male morph survival in the bulb mite Rhizoglyphus robini?

Alternative reproductive phenotypes (ARPs) represent discrete morphological variation within a single sex; as such ARPs are an excellent study system to investigate the maintenance of phenotypic variation. ARPs are traditionally modelled as a mixture of pure strategies or as a conditional strategy. Most male dimorphisms are controlled by a conditional strategy, where males develop into a particular phenotype as a result of their condition which allows them to reach a certain threshold. Individuals that are unable to reach the threshold of a conditional strategy are considered to ‘make the best of a bad job’; however, these individuals can have their own fitness merits. Given these fitness merits, condition-dependent selection alone is not sufficient to maintain a conditionally determined male dimorphism and other mechanisms, most likely frequency-dependent selection, are required. We studied in an experiment, the male dimorphic bulb mite Rhizoglyphus robini—where males are fighters that can kill other males or benign scramblers—to assess the strength of frequency-dependent survival in a high and low-quality environment. We found that male survival was frequency-dependent in the high-quality environment but not the low-quality environment. In the high-quality environment the survival curves of the two morphs crossed but the direction of frequency-dependence was opposite to what theory predicts.     

Do group dynamics affect colour morph clines during a range shift?

Species exhibiting colour polymorphism are thought to have an ecological advantage at the landscape scale, because spatial segregation of alternatively adapted ecotypes into diverse habitats can increase the species' niche breadth and thus confer greater geographic range size. However, morph frequencies are also influenced by intrapopulational processes such as frequency‐ or density‐dependent social interactions. To identify how social feedback may affect clinal variation in morph frequencies, we investigated reciprocal interactions between morph‐specific thermal tolerance, local climatic conditions and social environments, in the context of a colour‐morph frequency cline associated with a recent range expansion in blue‐tailed damselflies (Ischnura elegans) in Sweden. Cold tolerances of gynochromes (female‐like female morph) were positively correlated with local gynochrome frequencies, suggesting a positive frequency‐dependent fitness benefit. In contrast, androchrome (male‐mimic female morph) cold tolerances were improved following recent exposure to cold weather, suggesting a beneficial environmental acclimation effect. Thus, according to an environment‐matching hypothesis for clinal variation, androchrome frequencies should therefore increase towards the (cooler) range limit. In contrast to this prediction, gynochrome frequencies increased at the expanding range limit, consistent with a positive frequency‐dependent social feedback that is beneficial when invading novel climates. Our results suggest that when phenotypes or fitnesses are affected by interactions with conspecifics, beneficial social effects on environmental tolerances may (i) facilitate range shifts, and (ii) reverse or counteract typical patterns of intraspecific interactions and environment‐matching clines observed in stable populations observed over broader geographic scales.     

Extracellular nucleotides are active in evoking the “winged” morph of Euplotes octocarinatus

Extracellular nucleosidephosphates and -deoxyphosphates at micromolar concentrations induce Euplotes octocarinatus to change its ovoid cellshape into a “winged” morph. ATP/dATP and adenosine-tetraphosphate are most active, foUowed by CTP/dCTP, UTP/dTTP, and GTP/dGTP; ADP has less, while AMP, adenosine, cAMP, pyrophosphate and tripolyphosphate have no morphogenetic activity. Euplotes changes morphogenetically a few hours after being exposed to these compounds; changes are completed within 24–36 hr. Cell division is regularly stopped during this time. Transformed Euplotes are protected from certain predators which is reminiscent of the response triggered by predator-released proteins.     

Substrate preference in a colonial spider: is substrate choice affected by color morph?

Animals can show preference for a particular background as a way of decreasing visibility. Species with color polymorphism may have morph‐dependent background preference. I test this hypothesis on the orb‐weaving spider Parawixia bistriata. Adult females of P. bistriata present two distinct morphs characterized by brown and yellow opisthosomata. This nocturnal spider can be found in its retreat on the vegetation during the day. In order to examine whether females exhibit substrate preference dependent on their color morph, I first recorded the distribution of color morphs on different substrates (leaf and branch) and then performed a mark and release experiment. Field censuses indicated that the yellow morph was associated with leaves while the brown morph was found on either substrate type. The results of a mark and reciprocal release experiment agreed with the censuses and suggest that the two morphs differ in their association to substrate type: yellow females were associated with the leaf substrate, while brown females showed no association to a particular substrate type. Possible forces behind these differences in substrate choice are discussed.     

Do genetic structure and landscape heterogeneity impact color morph frequency in a polymorphic salamander?

Landscape heterogeneity plays an important role in population structure and divergence, particularly for species with limited vagility. Here, we used a landscape genetic approach to identify how landscape and environmental variables affect genetic structure and color morph frequency in a polymorphic salamander. The eastern red‐backed salamander, Plethodon cinereus, is widely distributed in northeastern North America and contains two common color morphs, striped and unstriped, that are divergent in ecology, behavior, and physiology. To quantify population structure, rates of gene flow, and genetic drift, we amplified 10 microsatellite loci from 648 individuals across 28 sampling localities. This study was conducted in northern Ohio, where populations of P. cinereus exhibit an unusually wide range of morph frequency variation. To test whether genetic distance was more correlated with morph frequency, elevation, canopy cover, waterways, ecological niche or geographic distance, we used resistance distance and least cost path analyses. We then examined whether landscape and environmental variables, genetic distance or geographic distance were correlated with variation in morph frequency. Tests for population structure revealed three genetic clusters across our sampling range, with one cluster monomorphic for the striped morph. Rates of gene flow and genetic drift were low to moderate across sites. Genetic distance was most correlated with ecological niche, elevation and a combination of landscape and environmental variables. In contrast, morph frequency variation was correlated with waterways and geographic distance. Thus, our results suggest that selection is also an important evolutionary force across our sites, and a balance between gene flow, genetic drift and selection interact to maintain the two color morphs.     

Seasonal variation in energy intake and condition of harp seals: Is there a harp seal morph? Problems for bioenergetic modelling

Seasonal changes in mass, fat depth, condition index and energy intake were measured in eight captive harp seals (Phoca groenlandica) over a 15-month period. Two of the five adult females were pregnant but lost their pups before term. There were large shifts in all variables measured. The range of these changes in the individual adult animals were for mass, 15–89%, blubber depth 56–240%, and condition index 13–23% (girth x 100)/length. Daily energy consumption varied from as little as 1.16 MJ to as much as 70.97 MJ. The two young males showed larger seasonal changes than the adults. Consistent with our earlier studies of harbour seals (Phoca vitulina) , there was either a significantly negative or no correlation between energy intake and changes in mass or fat. Mass and blubber thickness were positively related in the male seals, however, this was true of the females only during spring and summer. Water and air temperature varied indirectly with changes in blubber thickness in all but two seals. It is proposed that metabolic rate varies seasonally in seals. The implications of these findings are discussed in the light of their impact on bioenergetic modelling.     

Within-population genetic variation in the distylous Primula veris: Does floral morph anisoplethy matter in fragmented habitats?

We studied genetic variation and structure in 24 populations of Primula veris, a distylous self-incompatible perennial herb that in Flanders (northern Belgium) occurs in fragmented habitats of the intensively used agricultural landscape. Distyly, which favours cross-fertilization, is characterized in this species by two genetically determined floral morph types (‘pin’ or ‘thrum’). Using 30 allozyme loci, we investigated within-population and within-morph genetic variation and structure in relation to distyly (stochastic morph bias and pin frequency), demography (population size, plant density), and evidence of recent bottlenecks. No significant relationship was found between genetic patterns and stochastic morph bias. However, F_IS values were lower when pin frequency increases in the population. This may be explained by the partial self-compatibility of the pin morph, which, in conditions of pollination disruption, as observed for P. veris in fragmented habitats, may favour intra-pin outcrosses and increase mating opportunities in the population. A lower within-population structure can be expected because of a higher density of compatible mates and more random matings. Pin and thrum individuals showed similar levels of genetic variation. Three populations revealed a significant genetic differentiation between pin and thrum morphs (F_ST0.049), as a result of recent bottlenecks, spatial segregation of the morphs and/or disturbance of demographic processes. From our findings, we may hypothesize future changes in population mating processes in fragmented habitats, which might lead to pin excesses. However, due to slowing down life-history traits (long-lived perenniality and clonality), and demographic stochasticity randomly changing morph frequency, this may take time before being expressed. Evaluating the impact of morph frequencies on population dynamics is therefore essential for implementing conservation strategies of heterostylous plant species.     

How to regulate a gene: to repress or to activate?

Gene-expression responses to an input can depend on growth conditions; in this issue, Sasson et al. (2012) show that this dependence is lower when the input results in a high degree of promoter occupancy.     

Disgust sensitivity relates to affective responses to – but not ability to detect – olfactory cues to pathogens

Hundreds of studies have assessed variation in the degree to which people experience disgust toward substances associated with pathogens, but little is known about the mechanistic sources of this variation. The current investigation uses olfactory perception and threshold methods to test whether it is apparent at the cue-detection level, at the cue-interpretation level, or both. It further tests whether relations between disgust sensitivity and olfactory perception are specific to odors associated with pathogens. Two studies (N's = 119 and 160) of individuals sampled from a Dutch university each revealed that pathogen disgust sensitivity relates to valence perceptions of odors found in pathogen sources, but not to valence perceptions of odors not associated with pathogens, nor to intensity perceptions of odors of either type. Study 2, which also assessed olfactory thresholds via a three-alternative forced-choice staircase method, did not reveal a relation between pathogen disgust sensitivity and the ability to detect an odor associated with pathogens, nor an odor not associated with pathogens. In total, results are consistent with the idea that pathogen disgust sensitivity relates to how olfactory pathogen cues are interpreted after detection, but not necessarily to the ability to detect such cues.     

Instructions to Authors

Acta Biochimica et Biophysica Sinica (ABBS) is a scientific journal publishing monthly research papers, short communications and minireviews in biochemistry, molecular biology and biophysics. Research papers and short communications should report original work not published or considered for publication elsewhere. Minireviews should provide a concise introduction to the subject matter to inform the readers of the latest developments in a certain area.     

Instructions to Authors

Acta Biochimica et Biophysica Sinica (ABBS) is a scientific journal publishing monthly research papers, short com-munications and minireviews in biochemistry, molecular biology and biophysics. Research papers and short communi-cations should report original work not published or considered for publication elsewhere. Minireviews should provide