Extended M1 sum rule for excited symmetric and mixed-symmetry states in nuclei

A generalized M1 sum rule for orbital magnetic dipole strength from excited symmetric states to mixed-symmetry states is considered within the proton-neutron interacting boson model of even-even nuclei. Analytic expressions for the dominant terms in the B(M1) transition rates from the first and second $2^+$ states are derived in the U(5) and SO(6) dynamic symmetry limits of the model, and the applicability of a sum rule approach is examined at and in-between these limits. Lastly, the sum rule is applied to the new data on mixed-symmetry states of 94Mo and a quadrupole d-boson ratio $nd(0^+_1)/nd(2^+_2) \approx 0.6$ is obtained in a largely parameter-independent wayComment: 19 pages, 3 figures, Revte

Biological and trophic consequences of genetic introgression between endemic and invasive Barbus fishes.

Genetic introgression with native species is recognized as a detrimental impact resulting from biological invasions involving taxonomically similar invaders. Whilst the underlying genetic mechanisms are increasingly understood, the ecological consequences of introgression are relatively less studied, despite their utility for increasing knowledge on how invasion impacts can manifest. Here, the ecological consequences of genetic introgression from an invasive congener were tested using the endemic barbel populations of central Italy, where the invader was the European barbel Barbus barbus. Four populations of native Barbus species (B. plebejus and B. tyberinus) were studied: two purebred and two completely introgressed with alien B. barbus. Across the four populations, differences in their biological traits (growth, body condition and population demographic structure) and trophic ecology (gut content analysis and stable isotope analysis) were tested. While all populations had similar body condition and were dominated by fish up to 2 years of age, the introgressed fish had substantially greater lengths at the same age, with maximum lengths 410-460 mm in hybrids versus 340-360 mm in native purebred barbel. The population characterized by the highest number of introgressed B. barbus alleles (81 %) had the largest trophic niche and a substantially lower trophic position than the other populations through its exploitation of a wider range of resources (e.g. small fishes and plants). These results attest that the genetic introgression of an invasive congener with native species can result in substantial ecological consequences, including the potential for cascading effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s10530-021-02577-6

How Do They Do It? – Understanding the Success of Marine Invasive Species

From the depths of the oceans to the shallow estuaries and wetlands of our coasts, organisms of the marine environment are teeming with unique adaptations to cope with a multitude of varying environmental conditions. With millions of years and a vast volume of water to call their home, they have become quite adept at developing specialized and unique techniques for survival and – given increasing human mediated transport – biological invasions. A growing world human population and a global economy drives the transportation of goods across the oceans and with them invasive species via ballast water and attached to ship hulls. In any given 24-hour period, there are about 10,000 species being transported across different biogeographic regions. If any of them manage to take hold and establish a range in an exotic habitat, the implications for local ecosystems can be costly. This review on marine invasions highlights trends among successful non-indigenous species (NIS), from vectors of transport to ecological and physiological plasticity. Apart from summarizing patterns of successful invasions, it discusses the implications of how successfully established NIS impact the local environment, economy and human health. Finally, it looks to the future and discusses what questions need to be addressed and what models can tell us about what the outlook on future marine invasions is

Colonisation of ephemeral forest habitats by specialised species: beetles and bugs associated with recently dead aspen wood

The most appropriate strategy for preserving fragmented populations depends on a species’ ability to colonise distant habitat patches. Insects associated with early decay stages of dead wood are expected to have a high capacity to colonise new habitat patches. To study the dispersal ranges of beetles (Coleoptera) and flat bugs (Hemiptera: Aradidae) dependent on recently dead aspen (Populus tremula) wood in Finland, we set out 58 piles of recently cut aspen logs at various distances up to 1.6 km from forests that contained a high density of old aspen trees. We captured insects by trunk window-traps, and counted beetles’ exit holes. Habitat connectivity was measured in terms of the amount of suitable aspen-wood in the surrounding environment, with the closest dead wood items up-weighted by a negative-exponential function. The log-piles attracted many saproxylic insects including four red-listed aspen-specialist species. The exposure of log-piles to the sun, and high levels of habitat connectivity increased the species richness of aspen-specialists, whereas bark peeling by moose decreased richness. The spatial scale at which species richness had its strongest response to habitat was 93 m. Among individual species there was a wide variability in spatial scale of response. This study supports the view that conservation efforts in boreal forests should be concentrated on sites where colonisation by target species is most likely. Restoration of habitat by re-locating logs may be useful at localities with a rich and specialised fauna but which have too low rate of formation of dead wood by natural processes