Courtship behaviour influences social partner choice in male guppies

Although male courtship displays have evolved primarily to sexually attract females, they also generate inadvertent public information that potentially reveals the courter’s relative sexual attractiveness and the perceived quality and sexual receptivity of the female being courted to nearby eavesdropping male competitors, who in turn may use this information to bias their social partner choices. We tested this hypothesis by first presenting individual eavesdropping male guppies (Poecilia reticulata) the opportunity to simultaneously observe two demonstrator males whose courtship behaviour was manipulated experimentally to differ, following which we tested them for their preference to associate socially with either demonstrator males. Test males preferentially associated with the demonstrator male who they had previously observed courting a female over the other (non-courting) demonstrator. This social association preference was not expressed in the absence of a female to court. Our findings highlight the potential for sexual behaviour influencing male-male social associations in nature.

Potentially Mistaking Enantiomers for Different Compounds Due to the Self-Induced Diastereomeric Anisochronism (SIDA) Phenomenon

The NMR phenomenon of self-induced diastereomeric anisochronism (SIDA) was observed with an alcohol and an ester. The alcohol exhibited large concentration-dependent chemical shifts (δ’s), which initially led us to erroneously consider whether two enantiomers were in fact atropisomers. This highlights a potential complication for the analysis of chiral compounds due to SIDA, namely the misidentification of enantiomers. A heterochiral association preference for the alcohol in CDCl3 was determined by the intermolecular nuclear Overhauser effect (NOE) and diffusion measurements, the same preference as found in the solid state. The ester revealed more subtle effects, but concentration-dependent δ’s, observation of intermolecular NOE’s, as well as distinct signals for the two enantiomers in a scalemic sample all indicated the formation of associates. Intermolecular NOE and diffusion measurements indicated that homochiral association is slightly preferred over heterochiral association in CDCl3, thus masking association for enantiopure and racemic samples of equal concentration. As observed with the alcohol, heterochiral association was preferred for the ester in the solid state. The potential problems that SIDA can cause are highlighted and constitute a warning: Due care should be taken with respect to conditions, particularly the concentration, when measuring NMR spectra of chiral compounds. Scalemic samples of both the alcohol and the ester were found to exhibit the self-disproportionation of enantiomers (SDE) phenomenon by preparative TLC, the first report of SDE by preparative TLC.

Male-mediated species recognition among African weakly electric fishes

Effective communication among sympatric species is often instrumental for behavioural isolation, where the failure to successfully discriminate between potential mates could lead to less fit hybrid offspring. Discrimination between con- and heterospecifics tends to occur more often in the sex that invests more in offspring production, i.e. females, but males may also mediate reproductive isolation. In this study, we show that among two Campylomormyrus African weakly electric fish species, males preferentially associate with conspecific females during choice tests using live fish as stimuli, i.e. when all sensory modalities potentially used for communication were present. We then conducted playback experiments to determine whether the species-specific electric organ discharge (EOD) used for electrocommunication serves as the cue for this conspecific association preference. Interestingly, only C. compressirostris males associated significantly more with the conspecific EOD waveform when playback stimuli were provided, while no such association preference was observed in C. tamandua males. Given our results, the EOD appears to serve, in part, as a male-mediated pre-zygotic isolation mechanism among sympatric species. However, the failure of C. tamandua males to discriminate between con- and heterospecific playback discharges suggests that multiple modalities may be necessary for species recognition in some African weakly electric fish species.

Association theory: a new framework for analyzing social evolution

The dominant social-evolutionary paradigm implicitly equates social actions and behaviors causing associations by extrapolating from models of social actions to explain behaviors affecting association. This extrapolation occurs when models of helping behavior are applied to explain aggregation or fusion, and when models of discriminatory helping behavior are applied to explain discriminatory segregation or discriminatory rejection. Here, I outline an alternative theoretical approach that explicitly distinguishes a social action as a helping or harming behavior, and an association as the context for a social action. Based on this distinction, I define a list of terms that allows a classification of association phenomena and the conceptual framework necessary to explain their evolution. I apply the resulting theory, which I call “association theory,” to identify a series of steps common to major and minor transitions in social evolution. These steps include the evolution of association, the evolution of differential treatment, the evolution of association preference, and the evolution of genetic kin recognition. I explain how to measure the parameters of association theory and I apply the theory to test Hamilton’s rule. I evaluate the evidence for association theory, including how it resolves anomalies of a former paradigm. Finally, I discuss association theory’s assumptions, and I explain why it may become the dominant framework for analyzing social evolution.

ECHINODERMATA, Holothuria atra, IN AN INTERTIDAL SEAGRASS BED OFF THE BAMA BEACH, BALURAN NATIONAL PARK, EAST JAVA, INDONESIA

<p>The occurrence of sea cucumber, <em>Holothuria atra,</em> was assessed in the seagrass area of the Bama beach, Baluran National Park in East Java. The study investigated the frequency and early stages of seagrass association preference of <em>H. atra</em>. Survey was conducted in May 2011 using belt transect (1m x 100m with three replicates). Frequency of <em>H. atra</em> and their association with seagrass were recorded. Furthermore, length and wet weight of each individual of <em>H. atra</em> were measured. The total of 146 individuals of <em>H. atra </em>were observed in which 37.67% associated with <em>Enhalus acoroides </em>(EA), 23.29% associated with <em>Cymodocea rotundata </em>(CR), 23,29% associated with mixed seagrass species of <em>E. acoroides</em> and <em>C. rotundata, </em>and 15.75% associated with no seagrass habitats. The results suggested that small size <em>H. atra</em> might prefer to live under the taller seagrass stands such <em>E. acoroides</em>, which could be morphologically benefits the <em>H. atra</em> by providing better protection and shelter area.</p> <p>Keywords: <em>Holothuria atra</em>, <em>Enhalus acoroides</em>, <em>Cymodocea rotundata</em>, Baluran National Park</p>

ECHINODERMATA, Holothuria atra, IN AN INTERTIDAL SEAGRASS BED OFF THE BAMA BEACH, BALURAN NATIONAL PARK, EAST JAVA, INDONESIA

The occurrence of sea cucumber, Holothuria atra, was assessed in the seagrass area of the Bama beach, Baluran National Park in East Java. The study investigated the frequency and early stages of seagrass association preference of H. atra. Survey was conducted in May 2011 using belt transect (1m x 100m with three replicates). Frequency of H. atra and their association with seagrass were recorded. Furthermore, length and wet weight of each individual of H. atra were measured. The total of 146 individuals of H. atra were observed in which 37.67% associated with Enhalus acoroides (EA), 23.29% associated with Cymodocea rotundata (CR), 23,29% associated with mixed seagrass species of E. acoroides and C. rotundata, and 15.75% associated with no seagrass habitats. The results suggested that small size H. atra might prefer to live under the taller seagrass stands such E. acoroides, which could be morphologically benefits the H. atra by providing better protection and shelter area. Keywords: Holothuria atra, Enhalus acoroides, Cymodocea rotundata, Baluran National Park

The choice of bromeliads as a microhabitat by Scinax argyreornatus (Anura, Hylidae)

The association of anurans to bromeliads presents different degrees of interaction such as: eventual, obligatory and bromeligen. The frog species Scinax argyreornatus shows a regular association with these plants. The goal of this study is to characterise the degree of association between the frog S. argyreornatus to different species of bromeliads. We identified which species of bromeliad is regularly associated with S. argyreornatus and recognised which factors interfere with this association preference. We analysed the Concentration of Relative Dominance of frogs per bromeliad species. As possible criteria for frog association preference to different bromeliads species we established the analysis of leaves number, length and width, number of leaf axils, stored water in the axils, pH and relative humidity, among other organographic components. Our observations were analyzed by ANOVA followed by the Tukey test. We also evaluated the preference for association by the constancy of Bodenheimer. The correlation matrix indicated that the relative humidity is the factor responsible for the frog-bromeliads association, except for Aechmea sp.. However Aechmea sp. was the species with greater constancy of occupation followed by Quesnelia arvensis and Neoregelia johannis. According to our statistical results, Aechmea sp. and Q. arvensis are not different regarding organographic parameters, but differ from N. johannis. Our observations suggest that the bromeliads organographic structure and the relative humidity are key conditions which influence the preferences of S. argyreornatus to bromeliad species, while the other features showed no correlation.