Selecting habitat to what purpose? The advantage of exploring the habitat-fitness relationship

Measures of reproductive success have been recognized in many fields as essential tools to assess the status of populations, species, and communities. However, difficulties in gathering data on reproductive success often prevent researchers from taking advantage of the information offered by those measures. For example, most of habitat selection studies do not include reproductive success in their analysis even though doing so would highly improve our understanding of the habitat selection process. In our study, we aimed to assess to what extent habitat selection choices made by adult individuals are directed to increase their annual reproductive success. We tested this idea by first developing habitat selection models and then relating the results of those models to two measures of reproductive success. Using wolves, Canis lupus, as the study species, we determined that not all habitat selection choices performed by adult wolves were related to their annual reproductive success. The results varied also in relation to the measure of reproductive success used in the analysis and other individual-, group-, and population-level factors. Likely, adult female wolves select habitat characteristics to increase not only their annual reproductive success but also their lifetime reproductive success, for example, by ensuring their own survival and reproductive abilities in subsequent years. Our study suggests that a variety of motivations may govern habitat choices performed by adult individuals and including different measures of fitness in habitat selection studies can improve our understanding of these complex processes

Long-Term Trends and Role of Climate in the Population Dynamics of Eurasian Reindeer

Temperature is increasing in Arctic and sub-Arctic regions at a higher rate than anywhere else in the world. The frequency and nature of precipitation events are also predicted to change in the future. These changes in climate are expected, together with increasing human pressures, to have significant impacts on Arctic and sub-Arctic species and ecosystems. Due to the key role that reindeer play in those ecosystems, it is essential to understand how climate will affect the region's most important species. Our study assesses the role of climate on the dynamics of fourteen Eurasian reindeer (Rangifer tarandus) populations, using for the first time data on reindeer abundance collected over a 70-year period, including both wild and semi-domesticated reindeer, and covering more than half of the species' total range. We analyzed trends in population dynamics, investigated synchrony among population growth rates, and assessed the effects of climate on population growth rates. Trends in the population dynamics were remarkably heterogeneous. Synchrony was apparent only among some populations and was not correlated with distance among population ranges. Proxies of climate variability mostly failed to explain population growth rates and synchrony. For both wild and semi-domesticated populations, local weather, biotic pressures, loss of habitat and human disturbances appear to have been more important drivers of reindeer population dynamics than climate. In semi-domesticated populations, management strategies may have masked the effects of climate. Conservation efforts should aim to mitigate human disturbances, which could exacerbate the potentially negative effects of climate change on reindeer populations in the future. Special protection and support should be granted to those semi-domesticated populations that suffered the most because of the collapse of the Soviet Union, in order to protect the livelihood of indigenous peoples that depend on the species, and the multi-faceted role that reindeer exert in Arctic ecosystems

Retention and excretion of microplastics by Yellow Mealworm (Tenebrio molitor) larvae reared on an amino formaldehyde polymer microbeads contaminated substrate

Yellow mealworm (Tenebrio molitor L., TM), one of the main cultured insect species, is used for feed and food. Larval stages of this species can be reared on several substrates, including grains and industrial by-products. However, this species may potentially accumulate contaminants from the substrate, including microplastics (MPs), which may represent a potential hazard for its utilization in food chain. Evidences for plastic degradation by mealworms have been reported, while there are few information about the retention of microplastics in the body and tissues of this species. The aim of the present study was to assess whether TM larvae reared on a MPs-contaminated substrate were able to retain MPs in body tissues and to evaluate the retention and excretion rate after fasting for 24 and 48 hours. For this purpose, fluorescent amino formaldehyde polymer microbeads (1-5 μm) were used to simulate a MPs contamination in the substrate used for larvae rearing. A relevant concentration of MPs were found in the gut and were associated with ingested feed. However, microscopic analyses indicated that the gut acts as a simple transit site and a barrier towards MPs migration in tissues. A marked reduction of MPS content was highlighted in larvae after fasting, even though a 48-hours fasting period was not sufficient to completely depurate insect gut from MPs. Results obtained in the present study suggest that the polymer microbeads used are recalcitrant to digestion by TM larvae, and show the relevant ability of depuration from MPs of this species. Taken together the results showed the suitability of TM to be reared on MPs contaminated substrates since larvae survival and growth resulted not hampered by the MPs presence and open cues on the fasting period able to completely depurate insect body from MPs residues

Interannual variability: A crucial component of space use at the territory level

© 2015 by the Ecological Society of America. Interannual variability in space use and how that variation is influenced by density-dependent and density-independent factors are important processes in population ecology. Nevertheless, interannual variability has been neglected by the majority of space use studies. We assessed that variation for wolves living in 15 different packs within Yellowstone National Park during a 13-year period (1996-2008). We estimated utilization distributions to quantify the intensity of space use within each pack\u27s territory each year in summer and winter. Then, we used the volume of intersection index (VI) to quantify the extent to which space use varied from year to year. This index accounts for both the area of overlap and differences in the intensity of use throughout a territory and ranges between 0 and 1. The mean VI index was 0.49, and varied considerably, with ;20% of observations (n = 230) being \u3c 0.3 or \u3e 0.7. In summer, 42% of the variation was attributable to differences between packs. These differences can be attributable to learned behaviors and had never been thought to have such an influence on space use. In winter, 34% of the variation in overlap between years was attributable to interannual differences in precipitation and pack size. This result reveals the strong influence of climate on predator space use and underlies the importance of understanding how climatic factors are going to affect predator populations in the occurrence of climate change. We did not find any significant association between overlap and variables representing density-dependent processes (elk and wolf densities) or intraspecific competition (ratio of wolves to elk). This last result poses a challenge to the classic view of predator-prey systems. On a small spatial scale, predator space use may be driven by factors other than prey distribution

Appendix A. Number of seasons (divided by pack) for which we had sufficient sample size to estimate Utilization Distributions.

Number of seasons (divided by pack) for which we had sufficient sample size to estimate Utilization Distributions

Appendix C. Mean pack size tends to increase with total population density for the Northern Range wolf population (1996–2011).

Mean pack size tends to increase with total population density for the Northern Range wolf population (1996–2011)

Appendix B. Standardized regression coefficients for two models, each aiming to predict the volume of intersection in summer.

Standardized regression coefficients for two models, each aiming to predict the volume of intersection in summer