La gazelle endémique (Gazella gazella farasani) favorise la dispersion de l’invasive Prosopis juliflora sur les îles Farasan, Arabie Saoudite

Invasive Prosopis juliflora dispersal on Farasan Kebir (Miharraq area, Wadi Matr) was investigated in relation to endozoochory by Farasan Gazelle (Gazella gazella farasani). A germination experiment was conducted to test defecated seed viability of competing P. juliflora and Acacia ehrenbergiana. It revealed that 0.0013 ± 0.0009 Acacia seeds per gram of faeces germinated, while the rate of germinating Prosopis seeds was higher (0.0053 ± 0.0022 seeds per gram of faeces). Dung middens with a Prosopis seedling (or a young tree nearby) were distinctly closer to the putative centre of Prosopis introduction (Al-Qisar and Miharraq villages) than middens without Prosopis, suggesting that gazelles whose home ranges (mean size, females: 2.07 km2, males: 0.71 km2) encompass the gardens edging the aforementioned villages contribute to the dispersal of this invasive species. Altogether, our results suggest that gazelles on the Farasan Islands contribute to the invasion success of Prosopis; it still needs to be investigated though to what extent also domestic livestock - in particular goats - contribute to Prosopis dispersal. Based on our present data it is recommended to reduce the number of Prosopis trees in the protected area around Wadi Matr by mechanical eliminationLa dispersion d'une plante invasive Prosopis juliflora sur Farasan Kébir (région de Miharraq, Ouadi Matr) a été étudiée en relation avec l'endozoochorie par la Gazelle de Farasan (Gazella gazella farasani). Une expérience de germination a été réalisée afin de tester la viabilité des graines de P. juliflora et d'Acacia ehrenbergiana, deux espèces concurrentes. Elle a révélé que 0,0013 ± 0,0009 graines d'Acacia par gramme de matière fécale ont germé, soit moins que pour les graines de Prosopis (0,0053 ± 0,0022 graines par gramme). Les amas de fèces avec un semis de Prosopis (ou un jeune arbre à proximité) étaient nettement plus proches du centre supposé d'introduction de Prosopis (villages de AI-Qisar et Miharraq) que les amas sans Prosopis, ce qui suggère que les gazelles, dont le domaine vital (2,07 km2 pour les femelles; 0,71 km2 pour les mâles) englobe les jardins adjacents aux villages sus-mentionnés, contribuent à la dispersion de cette espèce envahissante. Au total, nos résultats suggèrent que les gazelles des îles Farasan contribuent au succès de l'invasion de Prosopis. Il reste toutefois encore à étudier dans quelle mesure le bétail domestique, en particulier les chèvres, contribue à la dispersion de Prosopis. Sur la base des données actuelles, il est recommandé de réduire le nombre d'arbres de Prosopis par élimination mécanique dans la zone protégée autour de Ouadi Matr

RNA promotes the formation of spatial compartments in the nucleus

The nucleus is a highly organized arrangement of RNA, DNA, and protein molecules that are compartmentalized within three-dimensional (3D) structures involved in shared functional and regulatory processes. Although RNA has long been proposed to play a global role in organizing nuclear structure, exploring the role of RNA in shaping nuclear structure has remained a challenge because no existing methods can simultaneously measure RNA-RNA, RNA-DNA, and DNA-DNA contacts within 3D structures. To address this, we developed RNA & DNA SPRITE (RD-SPRITE) to comprehensively map the location of all RNAs relative to DNA and other RNAs. Using this approach, we identify many RNAs that are localized near their transcriptional loci (RNA-DNA) together with other diffusible ncRNAs (RNA-RNA) within higher-order DNA structures (DNA-DNA). These RNA-chromatin compartments span three major classes of nuclear functions: RNA processing (including ribosome biogenesis, mRNA splicing, snRNA biogenesis, and histone mRNA processing), heterochromatin assembly, and gene regulation. More generally, we identify hundreds of ncRNAs that form stable nuclear compartments in spatial proximity to their transcriptional loci. We find that dozens of nuclear compartments require RNA to guide protein regulators into these 3D structures, and focusing on several ncRNAs, we show that these ncRNAs specifically regulate heterochromatin assembly and the expression of genes contained within these compartments. Together, our results demonstrate a unique mechanism by which RNA acts to shape nuclear structure by forming high concentration territories immediately upon transcription, binding to diffusible regulators, and guiding them into spatial compartments to regulate a wide range of essential nuclear functions

Turbulence, instream wood and fish: ecohydraulic interactions under field conditions

This is the pre-peer reviewed version of the following article: Trinci, G, Harvey, GL, Henshaw, AJ, Bertoldi, W, Hölker, F. Turbulence, instream wood and fish: Ecohydraulic interactions under field conditions. Ecohydrology. 2020;e2211. https://doi.org/10.1002/eco.2211 , which has been published in final form at https://doi.org/10.1002/eco.2211. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

Does personality affect premating isolation between locally-adapted populations?

Background: One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system. Results: We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small. Conclusions: Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively

Edge Detection in Landing Budgerigars (Melopsittacus undulatus)

Background: While considerable scientific effort has been devoted to studying how birds navigate over long distances, relatively little is known about how targets are detected, obstacles are avoided and smooth landings are orchestrated. Here we examine how visual features in the environment, such as contrasting edges, determine where a bird will land. Methodology/Principal Findings: Landing in budgerigars (Melopsittacus undulatus) was investigated by training them to fly from a perch to a feeder, and video-filming their landings. The feeder was placed on a grey disc that produced a contrasting edge against a uniformly blue background. We found that the birds tended to land primarily at the edge of the disc and walk to the feeder, even though the feeder was in the middle of the disc. This suggests that the birds were using the visual contrast at the boundary of the disc to target their landings. When the grey level of the disc was varied systematically, whilst keeping the blue background constant, there was one intermediate grey level at which the budgerigar's preference for the disc boundary disappeared. The budgerigars then landed randomly all over the test surface. Even though this disc is (for humans) clearly distinguishable from the blue background, it offers very little contrast against the background, in the red and green regions of the spectrum. Conclusions: We conclude that budgerigars use visual edges to target and guide landings. Calculations of photoreceptor excitation reveal that edge detection in landing budgerigars is performed by a color-blind luminance channel that sums the signals from the red and green photoreceptors, or, alternatively, receives input from the red double-cones. This finding has close parallels to vision in honeybees and primates, where edge detection and motion perception are also largely color-blind