Comparing survival among species with imperfect detection using multilevel analysis of mark—recapture data: a case study on bats

For comparative demography studies, 2 prerequisites are usually needed: 1) using typical parameter values for species, 2) correctly accounting for the uncertainty in the species specific estimates. However, although within‐species variability may be essential, it is typically not considered in analytical procedures, resulting in parameter estimates that may not be representative of the species. Further, data are analysed in 2 steps, first separately for each species, then estimates are compared among species. Accounting for the uncertainty in the species specific estimates is then difficult. Here we propose the application of multilevel Bayesian models on mark—recapture (MR) data for comparative studies on survival probabilities that solves these problems. Our models account for within‐species variability in space and time in the form of random effects. Models reflecting different biological predictions related to the species’ ecology and life‐history traits may further be contrasted. To illustrate our approach, we used long‐term data from 5 temperate tree‐roosting bat species and compared their survival probabilities. Results suggest that species foraging in open space, high reproductive output and short longevity records have lower survival than species foraging at short distances, with low reproductive output and high longevity records. Multilevel models provided relatively precise estimates, away from the edges of the parameter space, even for species with low encounter rates and short study duration. This is particularly valuable for less studied taxa such as bats for which available data are often more sparse. Our approach can be easily extended to include additional groups or levels of interest and effects at the individual level (e.g. sex or age). Different hypotheses regarding differences or similarities in parameters among species can be tested through the application of different models. Overall, it offers a flexible tool to ecologists, and population and evolutionary biologists for comparative studies, explicitly accounting for multilevel structures often encountered in MR data.     

Oxygen-dependent niche formation of a pyrite-dependent acidophilic consortium built by archaea and bacteria

Biofilms can provide a number of different ecological niches for microorganisms. Here, a multispecies biofilm was studied in which pyrite-oxidizing microbes are the primary producers. Its stability allowed not only detailed fluorescence in situ hybridization (FISH)-based characterization of the microbial population in different areas of the biofilm but also to integrate these results with oxygen and pH microsensor measurements conducted before. The O₂ concentration declined rapidly from the outside to the inside of the biofilm. Hence, part of the population lives under microoxic or anoxic conditions. Leptospirillum ferrooxidans strains dominate the microbial population but are only located in the oxic periphery of the snottite structure. Interestingly, archaea were identified only in the anoxic parts of the biofilm. The archaeal community consists mainly of so far uncultured Thermoplasmatales as well as novel ARMAN (Archaeal Richmond Mine Acidophilic Nanoorganism) species. Inductively coupled plasma analysis and X-ray absorption near edge structure spectra provide further insight in the biofilm characteristics but revealed no other major factors than oxygen affecting the distribution of bacteria and archaea. In addition to catalyzed reporter deposition FISH and oxygen microsensor measurements, microautoradiographic FISH was used to identify areas in which active CO₂ fixation takes place. Leptospirilla as well as acidithiobacilli were identified as primary producers. Fixation of gaseous CO₂ seems to proceed only in the outer rim of the snottite. Archaea inhabiting the snottite core do not seem to contribute to the primary production. This work gives insight in the ecological niches of acidophilic microorganisms and their role in a consortium. The data provided the basis for the enrichment of uncultured archaea.     

Gathering Local Knowledge in Madagascar Results in a Major Increase in the Known Range and Number of Sites for Critically Endangered Greater Bamboo Lemurs (Prolemur simus)

Greater bamboo lemurs (Prolemur simus) are endemic to Madagascar and are the only recognized species within their genus. The IUCN lists the species as critically endangered, with very few confirmed distribution records and <200 individuals known in the wild. With the aim of contributing to its conservation, we attempted to find previously unknown sites containing the species. Working closely with local communities, and basing our methodology on the gathering of local knowledge, we surveyed 44 sites in and around the Ankeniheny-Zahamena Corridor. We found evidence of the presence of Prolemur simus at 18 sites. We made direct sightings at 6 sites, of a total of 65 confirmed individuals, and identified their characteristic feeding remains at the other sites. Twelve of the sites are located in midaltitude rain forest within the corridor, and 6 lie in isolated and degraded lowland areas outside the corridor. These discoveries more than double the number of sites where the species is known to occur, and extend its known range 85 km further north. We identified numerous threats to the newly discovered sites, including hunting pressure, habitat destruction, habitat disturbance, and habitat fragmentation. Demographic factors related to small population sizes and population isolation may also impact the viability of the populations. Our results illustrate the benefits of systematic gathering of local knowledge when searching for rare or secretive primates.     

Transitions in sandflat biota since the 1930s: effects of sea-level rise,eutrophication and biological globalization in the tidal bay Königshafen,northern Wadden Sea

Conspicuous macrozoobenthos and vegetation of intertidal sandflats in Königshafen (Island of Sylt, SE North Sea) were mapped in 1932, 1988 and 2008. Higher water levels since the 1930s with a concomitant increase in tidal dynamics are assumed to have weakened sediment stability. This dissolved the distinctly banded macrobenthic zonation of the 1930s. Near high water level, cyanobacterial mats with associated beetles, belts of the mudshrimp Corophium volutator and the seagrass Zostera noltii have vanished, while the range of the lugworm Arenicola marina has extended towards the shore. Near low water level, sandy elevations have become permanently submerged because a tidal creek has widened its bed. In 1988, extensive green algal mats and the almost complete absence of seagrass are attributed to peak eutrophication. This partially reversed until 2008. The mussel Mytilus edulis had strongly extended its beds along the creek in 1988. These were taken over by introduced Pacific oysters Crassostrea gigas in 2008. Also in 2008, the cordgrass Spartina anglica, another introduced species, grew into large tussocks where cyanobacterial mats and a Corophium-belt had been mapped in the 1930s. Former benthic patterns may have little chance of resurrection by conventional nature protection because these small-scale shifts represent responses to regional and global change.     

Defoliation of alders (Alnus glutinosa) affects herbivory by leaf beetles on undamaged neighbours

The effects of defoliation of alder (Alnus glutinosa) on subsequent herbivory by alder leaf beetle (Agelastica alni) were studied in ten alder stands in northern Germany. At each site, one tree was manually defoliated (c. 20% of total foliage) to simulate herbivory. Subsequent damage by A. alni was assessed on ten alders at each site on six different dates from May to September 1994. After defoliation, herbivory by A. alni increased with distance from the defoliated tree. Laboratory experiments supported the field results. Not only leaf damage in the field, but also the extent of leaf consumption in laboratory feeding-preference tests and the number of eggs oviposited per leaf in another laboratory test were positively correlated with distance from the defoliated tree. Resistance was therefore induced not only in defoliated alders, but also in their undamaged neighbours. Consequently, defoliation of alders may trigger interplant resistance transfer, and therefore reduce herbivory in whole alder stands.     

Salinity gradient shapes distance decay of similarity among parasite communities in three marine fishes

Published data were used to compare the distance decay of similarity in parasite communities of three marine fish hosts: Atlantic cod Gadus morhua, the dab Limanda limanda and the flounder Platichthys flesus in two adjacent areas that differ with respect to the strength of a salinity gradient. In the Baltic Sea, which exhibits a strong salinity gradient from its connection with the North Sea in the west to its head in the north‐east, parasite communities in all three fish hosts showed a significant decline of similarity with increasing distance. In contrast, among host populations in the North Sea, which is a fully marine environment, there was no such decline or only a weak relationship. The results suggest that environmental gradients like salinity can be strong driving forces behind patterns of distance decay in parasite communities of fishes.     

New distributional records and conservation implications for the critically endangered greater bamboo lemur Prolemur simus

To improve our knowledge of the distribution of the critically endangered greater bamboo lemur Prolemur simus, we surveyed 6 sites in eastern Madagascar. We found its characteristic feeding signs at 5 sites and made a direct sighting at one of these. One site represents a northern extension of 45 km of the known extant range of the species. Two sites are located in a forest corridor approximately halfway between the previously known southern and northern populations, therefore suggesting a broadly continuous distribution of the species within its range rather than the previously suspected distribution of two distinct populations separated by a distance of over 200 km. Our results illustrate the benefit of species-focussed surveys in determining the true distribution of endangered species, a realistic measure which is necessary in order to assess their current status and to prioritise long-term conservation interventions.     

Long-term changes of intertidal and subtidal sediment compositions in a tidal basin in the northern Wadden Sea (SE North Sea)

Wadden Sea tidal flats are highly dynamic regarding the spatial distribution and the grain size composition of their sediments. From 2003 to 2006 surface sediments have been surveyed in an intertidal and a subtidal area within the tidal inlet Königshafen (south-eastern North Sea, northern Wadden Sea, island of Sylt) with the goal to gain information on short-term development trends in the grain size composition. The average grain size (Mean) becomes finer in the sheltered part of the intertidal survey area whereas a coarsening tendency can be observed in the more exposed part of the intertidal and especially in the subtidal survey area. The trend of the most frequent grain size (first Mode) shows the same spatial distribution pattern but is far less distinct. Thus, the changing Mean must be related to an increase in the deposition of fines in the sheltered part of the intertidal Königshafen as well as a general removal of fine-grained material in the exposed intertidal and subtidal Königshafen. In order to see long-term trends the surveys of 2003–2006 were compared to earlier studies conducted in 1932/1933, 1981 and 1989. A significant depletion of mud can be observed in the entire survey area. It is concluded that primarily changed hydrodynamics that may accompany ongoing climate change are responsible for this. However, the loss of fine-grained sediments is additionally amplified by a reduced vegetation cover and coastal protection measures.