Size and density of East Greenland polar bear (Ursus maritimus) skulls: Valuable bio-indicators of environmental changes?

There is an increasing interest in assessing the relationship between climatic oscillations, environmental contaminants and the modelling of animal physiological and morphological responses. We therefore undertook a study of skull condylobasal length (CBL; reflecting body size) and bone mineral density (BMD) in 87 East Greenland male polar bears (Ursus maritimus) sampled in the time period of 1892–2010. The purpose of the study was to investigate if these measures are potential candidates as indicators for stress associated with climate change and long-range transported toxic industrial chemicals. The analyses showed that both BMD and CBL in polar bears sampled in period 4 (1999–2010, n = 57) were significantly lower when compared with period 2 (1920–1936, n = 19) (both p < 0.02). Groups of persistent organohalogen contaminants (PCBs [polychlorinated biphenyls], DDT [dichlordiphenyltrichlorethane], HCH [hexachlorocyclohexane], HCB [hexachlorobenzene], chlordanes, dieldrin, PBDEs [polybrominated diphenyl ethers]) were measured in period 4 and multiple regression analyses controlling for age showed that dieldrin had a significant negative effect on BMD (p = 0.03, n = 52) while significant positive correlations with CBL were found for DDT, dieldrin and PBDE (all p < 0.05, n = 52). When testing the correlation with the North Atlantic Oscillation climate index no significant relationship was found for BMD (p = 0.97, r = −0.01, n = 27) nor CBL (p = 0.31, r = −0.2, n = 27). We therefore suggest that BMD and body size have decreased in East Greenland polar bear males over the past 120 years and that exposure to organohalogen contaminants may explain the BMD reductions. It is, however, not entirely clear if and how climatic oscillations affected the reductions in body size and BMD mainly because of the limited sample size in period 2 and lower mean age in period 4. Therefore, precautions should be taken towards a final conclusion on BMD and CBL as bioindicators for climate oscillations and exposure to toxic environmental chemicals. It is recommended that the sampling and archiving of East Greenland polar bear skulls continue in order to further explore how CBL and BMD reflect individual and population response upon exposure to environmental stress.     

Latitudinal variation in litter size of polar bears: ecology or methodology?

I used data reported in the scientific literature to examine latitudinal variation in litter size of polar bears in 18 different populations. No relationship was found between litter size and latitude using non-weighted regression. Regression weighted by sample size indicated a negative relationship with latitude. However, sampling biases caused by latitudinal differences in the timing of sampling and cub mortality after den emergence could produce a latitudinal cline. Stratifying analyses by sampling area, at dens or away from dens, revealed no latitudinal trend in litter size. Observed differences in litter size among populations may result from variation in demography and ecosystem productivity that is not simply related to latitude. I conclude that available data do not provide support for a biologically significant latitudinal cline in polar bear litter size. Accepted: 25 May 1999     

Could brown bears (Ursus arctos) have survived in Ireland during the Last Glacial Maximum?

Brown bears are recorded from Ireland during both the Late Pleistocene and early–mid Holocene. Although most of the Irish landmass was covered by an ice sheet during the Last Glacial Maximum (LGM), Irish brown bears are known to have hybridized with polar bears during the Late Pleistocene, and it is suggested that the Irish brown bear population did not become extinct but instead persisted in situ through the LGM in a southwestern ice-free refugium. We use historical population modelling to demonstrate that brown bears are highly unlikely to have survived through the LGM in Ireland under any combination of life-history parameters shown by living bear populations, but instead would have rapidly become extinct following advance of the British–Irish ice sheet, and probably recolonized Ireland during the end-Pleistocene Woodgrange Interstadial from a closely related nearby source population. The time available for brown bear–polar bear hybridization was therefore restricted to narrow periods at the beginning or end of the LGM. Brown bears would have been extremely vulnerable to extinction in Quaternary habitat refugia and required areas substantially larger than southwestern Ireland to survive adverse glacial conditions.     

Parallel speciation or long‐distance dispersal? Lessons from seaweeds (Fucus) in the Baltic Sea

Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long‐distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra‐ and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergström & L. Kautsky) and F. vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (F_ST = 0.15–0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.     

Avoidance of aposematic prey in European tits (Paridae): learned or innate?

Predators may either learn to avoid aposematic prey or may avoidit because of an innate bias. Learned as well as innate avoidancehas been observed in birds, but the existing evidence is basedon experiments with rather few unrelated model species. We comparedthe origin of avoidance in European species of tits (Paridae).First, we tested whether wild-caught birds (blue tits, greattits, crested tits, coal tits, willow tits, and marsh tits)avoid aposematic (red and black) adult firebugs Pyrrhocorisapterus (Heteroptera) more than nonaposematic (brown painted)ones. Larger proportion of birds avoided aposematic than brown-paintedfirebugs in majority of species (except coal tits). Second,we tested whether naive hand-reared birds of 4 species (bluetits, great tits, crested tits, and coal tits) attack or avoidaposematic and nonaposematic firebugs, both novel for them.Behavior of the naive blue tits and coal tits was similar tothat of the wild-caught birds; majority of them did not attackthe firebugs. Contrastingly, the naive great tits and crestedtits behaved differently than the wild-caught conspecific adults;majority of the wild-caught birds avoided the aposematic firebugs,whereas the naive birds usually did not show any initial avoidanceand had to learn to avoid the aposematic prey. Our results showthat the origin of avoidance may be different even in closelyrelated species. Because blue tits and coal tits avoided notonly aposematic firebugs but also their brown-painted form,we interpret their behavior as innate neophobia rather thaninnate bias against the warning coloration.     

The evolution of ecological specialization in southern African ungulates: competition‐ or physical environmental turnover?

Using long‐term diet reconstructions spanning the past one million years, we contrast hypotheses that biotic interactions versus physical environmental changes are primary drivers of evolutionary turnover in mammals. We use stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope ratios in tooth enamel carbonate to trace herbivore niche shifts through the Late Quaternary Land Mammal Ages (LMAs) of grassland savannas in the South African interior (Cornelian‐1.0 to 0.6 Ma; Florisian‐500 to 10 ka; and Holocene/modern). Data reveal niche separation amongst closely related coeval taxa, and dispersals through time into empty niche spaces following extinctions. This suggests a primary role of competitive exclusion and niche displacement for speciation and extinctions in these early grassland environments. However, niche changes through time show a similar trend in many taxa, entailing increased δ¹³C (elevated C₄ grass consumption) from the Cornelian to the Florisian, and from the Florisian to the Holocene/modern, and elevated δ¹⁸O in Holocene/modern taxa that reflect global aridification around the terminal Pleistocene. Commonality in isotopic trends implies universal environmental forcing of ecological, and ultimately macroevolutionary, turnover. Yet some taxa shift from a mixed C₃/C₄ diet in the Florisian to a near‐pure C₃ diet today. Indeed, we find that while δ¹³C data are normally distributed for Cornelian fossils, non‐normal distributions characterize more recent time intervals. Such distributions are in line with the bimodal distribution of δ¹³C and diet in contemporary African ungulates. Thus, while environmental forcing did not, by necessity, lead to increases in C₄ intake, the results show changes from mixed to more specialized diets. We propose that this niche specialization was a function of long‐term exposure to C₄ grasslands, consistent with predictions that relatively high metabolic demands of C₄ grazing in subtropical environments forced the differentiation of herbivores into one of two highly specialized feeding niches, i.e. C₃ browsing or C₄ grazing.     

Year-round acoustic detection of bearded seals (Erignathus barbatus) in the Beaufort Sea relative to changing environmental conditions, 2008–2010

Bearded seals (Erignathus barbatus) are pan-Arctic pinnipeds that are often seen in association with pack ice, and are known for their long, loud trills, produced underwater primarily in the spring. Acoustic recordings were collected from August 2008 to August 2010 at two locations and a single year (2008–2009) at a third location, in the western Beaufort Sea. Three recorders in 2008–2009 had a 30 % duty cycle and a bandwidth of 10–4,096 Hz. One recorder in 2009–2010 had a 45 % duty cycle and a bandwidth of 10–4,096 Hz and the second had a 20 % duty cycle and bandwidth of 10–8,192 Hz. Spectrograms of acoustic data were examined for characteristic patterns of bearded seal vocalizations. For each recorder, the number of hours per day with vocalizations was compared with in situ water temperature and satellite-derived daily sea ice concentrations. At all sites, bearded seals were vocally active year-round. Call activity escalated with the formation of pack ice in the winter and the peak occurred in the spring, coinciding with mating season and preceding breakup of the sea ice. There was a change in the timing of seasonal sea ice formation and retreat between the two consecutive years that was reflected in the timing of peak bearded seal call activity. This study provides new information on fall and winter bearded seal vocal behavior and the relationship between year-round vocal activity and changes in annual sea ice coverage and in situ water temperature.     

Trophic matches and mismatches: can polar bears reduce the abundance of nesting snow geese in western Hudson Bay?

Climate change driven advances in the date of sea ice breakup will increasingly lead to a loss of spring polar bear foraging opportunities on ringed seal pups creating a phenological trophic ‘mismatch’. However, the same shift will lead to a new ‘match’ between polar bears and ground nesting birds. This new match will be especially prevalent along the Cape Churchill Peninsula of western Hudson Bay where both polar bears and nesting snow geese are abundant. Easily foraged goose eggs will provide at least some of the earlier arriving polar bears with compensation for the energy deficit accrued through lost seal hunting opportunities. We examine the potential impact of changes in the extent and pattern of polar bear egg predation on snow goose abundance using projection models that account not only for increases in the temporal overlap of the two species but also for autocorrelation and stochasticity in the processes underlying polar bear onshore arrival and snow goose incubation. Egg predation will reduce reproductive output of the nesting lesser snow geese and, under all but trivial rates, will lead to a reduction in the size of their nesting population on the Cape Churchill Peninsula. Stochasticity associated with the asymmetrical advances in polar bear onshore arrival and the snow goose incubation period will lead to periodic mismatches in their overlap. These, in turn, will allow snow goose abundance to increase periodically. Climate driven changes in trophic matches and mismatches may reduce snow goose numbers but will not eliminate this over‐abundant species that poses a threat to Arctic landscapes.     

Split‐root systems applied to the study of the legume‐rhizobial symbiosis: What have we learned?

Split‐root system (SRS) approaches allow the differential treatment of separate and independent root systems, while sharing a common aerial part. As such, SRS is a useful tool for the discrimination of systemic (shoot origin) versus local (root/nodule origin) regulation mechanisms. This type of approach is particularly useful when studying the complex regulatory mechanisms governing the symbiosis established between legumes and Rhizobium bacteria. The current work provides an overview of the main insights gained from the application of SRS approaches to understand how nodule number (nodulation autoregulation) and nitrogen fixation are controlled both under non‐stressful conditions and in response to a variety of stresses. Nodule number appears to be mainly controlled at the systemic level through a signal which is produced by nodule/root tissue, translocated to the shoot, and transmitted back to the root system, involving shoot Leu‐rich repeat receptor‐like kinases. In contrast, both local and systemic mechanisms have been shown to operate for the regulation of nitrogenase activity in nodules. Under drought and heavy metal stress, the regulation is mostly local, whereas the application of exogenous nitrogen seems to exert a regulation of nitrogen fixation both at the local and systemic levels.     

The hemolymph proteome of the honeybee: Gel‐based or gel‐free?

The honeybee has an invaluable economic impact and is a model for studying immunity, development and social behavior. The recent sequencing and annotation of the honeybee genome facilitates the study of its hemolymph, which reflects the physiological condition and mediates immune responses. We aimed at making a proteomic reference map of honeybee hemolymph and compared gel‐free and gel‐based techniques. One hundered and four 2‐DE spots corresponding to 62 different proteins were identified. Eight identical 2‐DLC experiments resulted in the identification of 32 unique proteins. One repeat was clearly not representative for the potential of the given 2‐DLC setup. Only 27% of the identified hemolymph proteins were found by both techniques. In addition, we found proteins of three different viruses which creates possibilities for biomarker design. Future hemolymph studies will benefit from this work.     

Isotopic Composition of Blood of Polar Bears (<Emphasis Type=Italic>Ursus maritimus</Emphasis>) of the Kara–Barents Sea Population

The data on the content of carbon and nitrogen isotopes in the blood samples of polar bears obtained in the present study confirm that polar bears in the Taimyr region (and the Kara–Barents sea population in general) are partly dependent on the resources of terrestrial origin. However the “terrestrial carbon” evidently reaches bears’ tissues indirectly, via marine food webs utilizing organic carbon brought into the polar basin by Siberian rivers.     

Rare or just unknown? The occurrence of the giant devil ray (Mobula mobular) in the Adriatic Sea

The presence of the giant devil ray (Mobula mobular) in the Adriatic Sea was evaluated based on new records collected through field research, information from interviews with fisherman and marine biology experts, and a review of existing data from the literature and Internet sources. Presented are 14 new records of 20 individual giant devil rays collected between 2008 and 2011, doubling the number of animals recorded in the Adriatic in the previous 125 years. In total, 28 records of 42 giant devil rays exist for the Adriatic to date. The cryptic life history of the species, its pelagic distribution and lack of systematic data collection have resulted in a low number of historical records. The results suggest that the species is not as rare as previously considered. Occurring mainly in the central and southern Adriatic Sea from early spring to early autumn, its appearance coincides with the general increase in local prey abundance. Interaction with fisheries is identified as a source of potential mortality, and the monitoring of multi‐gear schemes should be carried out at the regional level. Further research on the distribution and abundance of the giant devil ray is crucial for the elaboration of any effective conservation strategy for this endangered species.     

Heterogeneity in shore flies – the case of Glenanthe Haliday (Diptera: Ephydridae) in the Old World

Old World species of the genus Glenanthe are treated comprehensively with an emphasis on the unusually diverse morphological heterogeneity discovered in structures of the male terminalia. As perspective for this treatment, the tribe Lipochaetini, in which Glenanthe is placed, is characterized and discussed, and an annotated key to the four included genera is provided to facilitate their identification. Glenanthe is demonstrated to be a monophyletic lineage within Lipochaetini. Seven Old World species of Glenanthe are now known, including two new Afrotropical species as follows (type locality in parenthesis): G. namibia n. sp. (Namibia. Mukwe: Divuju: Okavango River [18°04’04”S, 21°28’51”E] and G. danielssoni n. sp. (Republic of South Africa. Cape Province: De Hoop Nature Reserve [34°27’S, 28°25’E]. The identity of G. fuscinervis Becker, revised status (raised from synonymy with G. ripicola (Haliday)), is clarified, and found to be conspecific with Hydrina ochracea Oldenberg, which is recognized as a junior synonym. Papp’s synonymy of Glenanthe fasciventris Becker with Hydrellia (Glenanthe) ripicola Haliday is confirmed, and herein we relegate G. iranica Canzoneri & Rampini also as junior synonym of G. ripicola. The remarkable diverse structures of the male terminalia of all included species are described and illustrated and distribution maps are also provided.     

Trophic control of mesopredators in terrestrial ecosystems: top‐down or bottom‐up?

It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.