In this work, we quantified the differences in the bird assemblage structure between seasons in two Mediterranean habitat types (small wetlands and oak forests) using a diversity/dominance approach (Whittaker plots). Small wetland assemblages showed the higher slopes in Whittaker plots for breeding species; oak forest assemblages showed the higher slope for wintering species. When we compared seasonal assemblages between the two habitat types, only the breeding species showed significant differences in the slopes of lines. When we compared the three seasonal-related assemblages (migrants, wintering and passage species) inside each habitat type, we observed significant differences in small wetlands, but not in oak woodlands. Our data suggest that season associated to habitat type could be considered an important factor affecting the structure of bird assemblages. Small Mediterranean wetlands are characterized by seasonally specific structural disturbances and changes in resource and niche availability that may be more abrupt when compared to forest habitats. These changes allow the coexistence of a higher number of individuals and species, so significantly affecting the line slopes between seasonal-related assemblages. During the spring, breeding species are less represented in small wetlands due to their less stratified vegetation, when compared to oak forests. Instead, oak forests are resource poor and less dynamic environments, especially in winter (high slope in tendency line) where only sedentary generalist species could persist. We stimulate the use of diversity/dominance approaches to detect seasonal and habitat differences among animal assemblages.
Roberto Isotti, Corrado Battisti and Luca Luiselli
Amos Bouskila, Emmanuel Lourie, Shiri Sommer, Han de Vries, Zef M. Hermans and Machteld van Dierendonck
Relatedness is likely to affect the decisions of animals regarding their affiliations with conspecifics. Social network analysis provides tools to describe the social structure of animals. Here, we investigate the social network of a population of 27 unmanaged Konik horses in the Blauwe Kamer Nature Reserve, in the Netherlands. We test three hypotheses: (1) that related individuals will have stronger associations; (2) that individuals with low values of average relatedness to their neighbors in the network will have more links and (3) homophily, the tendency of individuals to associate with similar others, will lead to stronger associations among individuals of similar sex, reproductive state, age and rank in the social network. We videotaped 22 horses (excluding foals) and their interactions. Relatedness was calculated from the pedigree, which was based on parentage, determined by DNA analysis. The social network was based on spatial proximity data. There was no significant influence of relatedness on strength of associations in the network or an influence of age- or rank-homophily. We argue that the lack of a relatedness effect is not likely to have been caused by an inability to detect kinship. Strength of associations in the social network was significantly affected by the tendency of the horses to associate with individuals of the same sex and the same reproductive state. This social network pattern is not common in mammals, and the study of unexplained variation in choice and strength of associations may have important implications for other equids increasingly confined to reserves worldwide.
Marco Scotti and Ferenc Jordán
Rarity of species is often considered to set priorities for biodiversity conservation. Less abundant species are expected to be at higher risk of extinction and make significant contribution to food web functioning. However, the relationship between species abundance and position in food webs is still unclear. Here we tested possible correlations between species abundance and structural position in Prince William Sound food web. Species abundance was inferred from biomass data and structural position was characterized by 13 centrality indices.
We found that less abundant species have higher trophic positions and display more generalist feeding strategies. However, positive correlations link most of the centrality indices to population size. Thus, being locally rare translates into more peripheral food web positions and implies marginal roles in the spread of indirect effects. Species characterized by largest population size are responsible for the transfer of largest amounts of biomass and regulate the transmission of indirect effects. Less abundant species are of marginal structural importance and are exposed to impacts mediated by larger populations. In Prince William Sound ecosystem, rarity is associated with critical food web positions and does not simply reflect a marginal contribution to biodiversity.
We suggest that knowing the food web position of rare species might help to formulate more effective, system-level solutions for their conservation, rather than simply focusing on the direct treatment of symptoms.
Anatoly Bobrov, Vasiliy D. Kravchenko and Günter C. Müller
Tannins, which are polyphenols present in various plants, have anti-nutritional activity; however, their negative effects are mitigated by the presence of tannin-degrading microorganisms in the gastrointestinal tract of animals. This has never been investigated in the plateau zokor (Myospalax baileyi) – the predominant small herbivore in the alpine meadow ecosystem of Qinghai Province, China – which consumes tannin-rich herbaceous plants. Tannase activity in the feces of the plateau zokor increased from June to August corresponding to the increase in hydrolyzable tannin concentrations in plants during this period, and three tannin-degrading facultative anaerobic strains (designated as E1, E2, and E3) were isolated from the cecum of these animals. Sequencing of the 16S rDNA gene identified isolates of strain E1 as belonging to the genus Enterococcus, and E2 and E3 to the genus Bacillus. All of the bacteria had cellulose-degrading capacity. This study provides the first evidence of symbiotic bacterial strains that degrade tannic acid and cellulose in the cecum of plateau zokor.
Arthur A. Owiny
Understanding the process of community reassembly is crucial for the conservation of biodiversity and rehabilitation of ecosystems. This study tested whether tree communities in logged forests follow an equilibrium (deterministic) or non-equilibrium (stochastic) model of succession. We assessed reassembly of tree communities in different size classes along a successional gradient consisting of nine differently aged successional forests, namely, four regenerating former clear-cuts (9–19 years), three selectively logged (42–43 years) and two primary forests (PFs) in Kibale National Park, Uganda. The results show that the forests are converging and undergoing reassembly towards PFs. The species composition of seedlings, saplings and poles declined in similarity to the PF with age but that of mature trees in the different successional stages increased towards the PFs. These differences in tree species composition among the different size classes might be due to dominance of some particular species. Recovery of tree species density, diversity and dominance in all the size classes showed directional patterns as predicted by the deterministic model of succession. Compared to other variables, tree species density and diversity in selectively logged forests recovered relatively faster and was equivalent to or higher than that of PFs at 43 years. The results of the present study indicate that community reassembly in smaller sized trees followed a stochastic model of succession. However, as trees matured, they conform to the deterministic model of succession.
T. Mieczan, M. Tarkowska-Kukuryk, W. Płaska and J. Rechulicz
Most ecological research has hitherto focused more on sea and lake ecosystems than on peatland habitats. The primary objectives of this paper were to analyse the ciliate, rotifer, cladoceran, copepod and insect assemblages in a horizontal lagg and an open peat bog, and to assess the influence of physical and chemical parameters on their communities. Sampling was done in a transitional bog from May to October 2012 in a transect comprising the lagg and the open peatbog. The first two axes of a principal component analysis accounted for 49.8% of the total variance in the composition of the faunal communities studied. The distribution of samples in ordination space suggested that the habitats are distributed along the gradient of water level and the gradients of total organic carbon and nutrients. Assemblages of all groups investigated showed a strong compositional gradient correlated with surface water and phosphates. However, species composition of ciliates and rotifers was explained by conductivity and/or chlorophyll-a concentration. The results suggest that the lagg zone of a bog can function as an ecotone, with significantly greater species richness and abundance of faunal communities.
Editors Israel Journal of Ecology and Evolution
Rainee L. Kaczorowski, Gali Blumenfeld, Avi Koplovich and Shai Markman
Floral color is an important cue that converged in many ornithophilous flowers and can be used by nectarivorous birds to make foraging decisions. Wild ornithophilous flowers are frequently red, although they are more often yellow in Israel. The Palestine sunbird (Nectarinia osea) is the only nectarivorous bird in Israel and surrounding Mediterranean areas. Given the prevalence of yellow flowers in their habitats (along with sunbirds' expected sensitivity increase in this region of color vision), we predicted that Palestine sunbirds prefer yellow food sources over red. We examined sunbird foraging behavior when they were presented simultaneously with a yellow and red feeder, each containing the same quantity and quality of food. We investigated whether sunbirds had a side bias in the color preference experiment, but also in a separate experiment where both feeders were white. Sunbirds did not exhibit a significant color bias, while they did have a significant preference for a particular side of the cage. Location appears to be a more important cue than color to Palestine sunbirds, likely because location can offer information on the most rewarding plants and recently depleted flowers. However, color may still provide useful information that could influence foraging decisions in different contexts.
Giuliano Fanelli and Corrado Battisti
Hemeroby is a concept widely employed in assessment of the effect of human activities on vegetation. In this study, we apply the concept to a set of bird species occurring in a Mediterranean remnant wetland. The aim was to obtain an average hemeroby index for two seasonally related bird assemblages (i.e. breeding and wintering) based on the information related to two levels of plant hemeroby. In a grid of 47 cells 100×100 m-wide, we sampled the fine-grained distribution of plant communities (Braun-Blanquet method/cell) in parallel with birds (point count method; one point count/cell), assigning an independent score of hemeroby to plants and birds on a scale from I to V, from pristine habitats with a lack of natural and/or anthropogenic disturbance (score = I) to completely artificial habitats (score = V). Whereas bird species ranged from categories II to V, vegetation types spanned only the categories III and IV. Therefore, bird species showed a higher variability in hemeroby.
By comparing hemeroby scores, we can deduce the effect that the vegetation disturbance may have on bird species. The mean hemeroby for breeding birds, calculated on all the species occurring in a determined plant hemeroby category, is not significantly different between sites with higher (= IV) and lower (= III) plant hemeroby (i.e. higher and lower level of disturbance). The mean hemeroby of the wintering birds was significantly different in the two levels of plant hemeroby (i.e. higher vs. lower hemeroby). Our data suggest that only the wintering birds had a hemeroby distribution pattern related to that of the plants, while the distribution of breeding birds showed no association, i.e. they appear in similar distribution in both plant hemeroby classes. This pattern may reflect the characteristics of the habitat types in relation to bird seasonality: a large section of wintering bird species are strictly water-related, linked to habitats with low plant hemeroby, so appearing more sensitive to change in plant hemeroby when compared to breeding species. Although explorative, our data may be useful in wildlife management, implying that in wetland–grassland mosaics the more sensitive wintering bird species are suitable as indicators aimed to test the effect of natural and anthropogenic disturbances.
Xin Dai, Yan-Qi Zhang, Lian-Yu Jiang, Fei Yuan, Ai-Qin Wang, Wan-Hong Wei and Sheng-Mei Yang
Limited information is available about how mammalian browsing activity influences the dynamic defense mechanisms of plants. Here, we aimed to clarify the response mechanism of a herbaceous plant (Chinese lyme grass, Leymus chinensis) to browsing by a mammalian herbivore (Brandt's vole, Lasiopodomy brandtii). We used high-performance liquid chromatography and spectrophotometry to investigate changes in the concentrations of 6-MBOA, total phenol and condensed tannin in Chinese lyme grass seedlings with respect to its ontogeny and different types of damage treatments. 6-MBOA concentrations were higher on day 7 and day 8 than on days 12 and 17 after seedling germination. The concentrations of total phenol and condensed tannin were higher on day 12 than on days 7 and 8 after seedling germination. Compared to the control, higher 6-MBOA concentrations were obtained in the salivation, gnawing and artificial cutting treatment groups. The response of 6-MBOA was delayed in the artificial cutting group compared to the salivation and gnawing groups. In contrast, the concentrations of total phenol and condensed tannin were higher in the artificial cutting and control groups compared to the salivation and gnawing groups. 6-MBOA concentration was negatively correlated with total phenol concentration. The results indicated that 6-MBOA concentration decreased with seedling ontogeny, and that it could be induced by Brandt's vole saliva. In conclusion, our study verified the hypothesis that the browsing by Brandt's vole induces the dynamic defenses of L. chinensis.