DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.      

A collection of strains containing genetically linked alternating antibiotic resistance elements for genetic mapping of Escherichia coli.

We present a collection of 182 isogenic strains containing genetically linked antibiotic resistance elements located at approximately 1-min intervals around the Escherichia coli chromosome. At most positions both Tn10 (Tetr) and TN10kan (Kanr) elements are available, so that the collection contains a linked set of alternating antibiotic resistance markers. The map position of each insertion has been aligned to the E. coli genetic map as well as to the Kohara ordered clone bank. These strains are designed to be used in a rapid two-step mapping system in E. coli. In the first step, the mutation is localized to a 5- to 15-min region of the chromosome by Hfr mapping with a set of Hfr strains containing either Tn10 or Tn10kan elements located 20 min from their respective origins of transfer. In the second step, the mutation is localized to a 1-min region by P1 transduction, with a collection of isogenic insertion strains as donors. We discuss the uses of this collection of strains to map and eventually to clone a variety of mutations in E. coli.     

Evolution of major pattern models and processes of alluvial forest of the Rhine in the rift valley (France/Germany)

In the rift valley (North-East of France/South-West of Germany), the Rhine runs freely for 300 km from South to North. The absence of natural obstacles allows the development of a very regular profile of the river. We have therefore an opportunity to study very gradual modifications of the alluvial forest communities of the fluvial corridor from upstream to downstream, according to the gradual evolution of the ecological factors, related to slope decrease and hydrological modifications.We describe, from Basel to Mainz:

How greater mouse-eared bats deal with ambiguous echoic scenes

Echolocating bats have to assign the received echoes to the correct call that generated them. Failing to do so will result in the perception of virtual targets that are positioned where there is no actual target. The assignment of echoes to the emitted calls can be ambiguous especially if the pulse intervals between calls are short and kept constant. Here, we present first evidence that greater mouse-eared bats deal with ambiguity by changing the pulse interval more often, in particular by reducing the number of calls in the terminal group before landing. This strategy separates virtual targets from real ones according to their change in position. Real targets will always remain in a constant position, and virtual targets will jitter back and forth according to the change in the time interval.     

Spectral call features provide information about the aggression level of greater mouse-eared bats (Myotis myotis) during agonistic interactions

Bats rely heavily on acoustic signals in order to communicate with each other in a variety of social contexts. Among those, agonistic interactions and accompanying vocalizations have received comparatively little study. Here, we studied the communicational behaviour between male greater mouse-eared bats (Myotis myotis) during agonistic encounters. Two randomly paired adult males were placed in a box that allowed us to record video and sound synchronously. We describe their vocal repertoire and compare the acoustic structure of vocalizations between two aggression levels, which we quantified via the bats’ behaviour. By inspecting thirty, one-minute long encounters, we identified a rich variety of social calls that can be described as two basic call types: echolocation-like, low-frequency sweeps and long, broadband squawks. Squawks, the most common vocalization, were often noisy, i.e. exhibited a chaotic spectral structure. We further provide evidence for individual signatures and the presence of nonlinear phenomena in this species’ vocal repertoire. As the usage and acoustic structure of vocalizations is known to encode the internal state of the caller, we had predicted that the spectral structure of squawks would be affected by the caller’s aggression level. Confirming our hypothesis, we found that increased aggression positively correlated with an increase in call frequency and tonality. We hypothesize that the extreme spectral variability between and within squawks can be explained by small fluctuations in vocal control parameters (e.g. subglottal pressure) that are caused by the elevated arousal, which is in turn influenced by the aggression level.