Network-based methods are being actively developed to respond to the needs for operational assessments of the degree of landscape connectivity and of the impact of landscape changes in ecological flows and related ecological processes. Among these, a recent paper by Matisziw and Murray (2009) presented the C index as an adequate and advantageous way of ranking habitat patches by their importance for the maintenance of landscape connectivity. We show that this index is equivalent and conveys the same information in undirected graphs as a previously described index, the landscape coincidence probability (LCP), which can be readily computed in any landscape network through the Conefor Sensinode software package. We slightly generalize the LCP definition for cases involving asymmetric dispersal, which makes LCP compatible with C and maintains the equivalency between both indices in directed graphs. We place LCP and C in a broader context of other existing indices and ongoing developments and describe how some of these may be better suited for the analysis of the connectivity in landscape networks and their changes. We conclude by highlighting the need (1) to go beyond the identification of unobstructed movement paths or habitat components (sets of interconnected patches) when pursuing the most appropriate landscape connectivity indices and (2) for increased efforts in assessing and reporting the potential overlaps, coincidences and synergies between the available approaches in order to guide the final user and facilitate index selection in a densely populated metric space.
Authors:Lydia Gil, S. Saura, Arantxa Echegaray, Felisa Martinez, I. de Blas, A. Akourki, Noelia Gonzalez, E. Espinosa and A. Josa
The present study evaluated the effect of supplementing the medium used to mature equine oocytes in vitro with oestrous mare serum (EMS) or horse follicular fluid (HFF). To this end, 144 ovaries were obtained from mares aged 16-21 months and transported to the laboratory in Dulbecco's phosphate buffered saline (D-PBS) at 30°C. Oocytes were harvested from the ovaries by slicing, and then selected for in vitro maturation (IVM) according to the number of cumulus cell layers and the characteristics of the cytoplasm. The selected oocytes were washed three times in TCM199 medium plus HEPES (TCM-199H) or in the same medium plus glutamine (TCM-199G), then matured in vitro in six study groups established according to the in vitro maturation (IVM) treatment to see possible interactions between HEPES and glutamine on other supplements: Ten percent EMS was added to two of these media (TCM-199H+EMS and TCM-199G+EMS) and 10% HFF was added to the media in two other groups (TCM-199H+HFF and TCM-199G+HFF). IVM was performed at 38.5°C for 40 h in a controlled atmosphere (5% CO2, 95% relative humidity). The findings indicate that the presence of EMS or HFF in the TCM-199H medium gives rise to the best results in terms of the proportions of oocytes reaching maturity (37.7% and 36.8%, respectively). The values obtained with EMS and HFF were statistically similar to each other but differed from the other treatments. The media containing glutamine led to the highest proportions of degenerated oocytes.
Authors:A. Gil-Tena, J. Nabucet, C. Mony, J. Abadie, S. Saura, A. Butet, F. Burel and A. Ernoult
Over the last 30 years, ecological networks have been deployed to reduce global biodiversity loss by enhancing landscape connectivity. Bird species dwelling in woodland habitats that are embedded in agriculture-dominated landscapes are expected to be particularly sensitive to the loss of connectivity. This study aimed to determine the role of landscape connectivity in woodland bird species richness, abundance, and community similarity in north-east Brittany (north-west France). An exhaustive woodland selection protocol was carried out to minimize the effects of woodland size on the response variables. Connectivity of the woodland and forest network in the study area was evaluated using graph-theory, accounting for matrix permeability, and a characteristic median natal dispersal distance at the community level based on the bird species pool recorded in the sampled woodlands. Information-theoretic model selection, controlling for woodland size in all the cases, depicted the response of woodland birds at the community level to the connectivity of agriculture-dominated landscapes. On average, the sampled woodlands (n = 25) contained 15.5 ± 2.4 bird species, with an abundance of 25.1 ± 3.9, and had highly similar bird communities (species composition and proportion); eight species represented 57% of total abundance and were present in at least 22 woodlands. The performance of models improved when using effective, rather than Euclidean, interpatch distances in the connectivity assessment. Landscape connectivity was only significantly related to similarity of proportional species composition. Large woodlands contained communities with more similar species proportions in an inhospitable agricultural landscape matrix than in a more permeable one. Woodland size was the most relevant factor determining species abundance, indicating that the bird population sizes are primarily proportional to the local habitat availability. Connectivity in relation to landscape matrix permeability did not seem to induce the flow of woodland-dependent bird species that are dominant in the community but rather of matrix-dwelling bird species that are less dependent on woodland patch area. In conclusion, both habitat conservation and restoration (i.e., amount and quality), in combination with permeable landscape structures (such as heterogeneous land cover mosaics), are advocated for community level conservation strategies.