Effect of mountain gorilla (Gorilla beringei beringei) population growth to their key food plant biomass in Volcanoes National Park, Rwanda

High densities of large herbivores can have detrimental effects on plant biomass. Understanding the relationship between animal densities and plant distribution and abundance is essential for the conservation of endangered species and ecosystems. Mountain gorilla censuses conducted for different periods in the last three decades have revealed a steady increase of gorilla population in Virunga Massif whereby the recent number of gorillas has doubled compared to their number in the 1980s. It is unclear whether the continuous population growth of the herbivorous Virunga gorilla within an isolated forest ‘island’ has been affecting gorilla food plant biomass. This study investigated the effect of varying mountain gorilla densities on the biomass of the five key food plant species (Galium spp., Carduus nyassanus, Peucedanum linderi, Rubus spp., Laportea alatipes) that make up >70% of the mountain gorilla diet. We used plant biomass data collected in a central part of the Virunga massif, commonly known as Karisoke sector from 2009 to 2011, and GPS records of gorilla groups ranging in the same area nine months prior biomass assessment. Gorilla densities were estimated using the Kernel Utilization Distribution (KDE) analysis (functions: ‘kernelUD’ and ‘getvolumeUD’) from the Adehabitat package in R software, which provides the probability density of gorilla occurrence at each coordinate (x, y) of the study area. Analyses using GLMs suggest that gorilla densities (a proxy of previous gorilla utilization intensity) did neither affect the total biomass of key food plant species nor the biomass of each key food plant species (p>0.05). These results may indicate that current revisit rates of feeding sites by gorillas allow for complete plant regeneration, and no signs of overharvesting. Alternatively, feeding sites characterized by very high biomass may be preferred by gorillas and remain sites with the highest biomass even after being frequently used by gorillas. Findings also suggest that carrying capacity of the gorilla population in the study areas may not yet be reached if food is the driving constraint. However, monitoring of the relationship between gorilla densities and food plant biomass must continue while the Virunga population continues growing. Future studies also need to incorporate other sympatric large herbivores in the Virungas who share food plants with mountain gorillas.Keywords: habitat use, gorilla density, plants biomas

Selective neck dissection in surgically treated head and neck squamous cell carcinoma patients with a clinically positive neck: Systematic review

Contains fulltext : 191258.pdf (publisher's version ) (Closed access)Adequate treatment of lymph node metastases is essential for patients with head and neck squamous cell carcinoma (HNSCC). However, there is still no consensus on the optimal surgical treatment of the neck for patients with a clinically positive (cN+) neck. In this review, we analyzed current literature about the feasibility of selective neck dissection (SND) in surgically treated HNSCC patients with cN + neck using the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. From the reviewed literature, it seems that SND is a valid option in patients with cN1 and selected cN2 neck disease (non-fixed nodes, absence of palpable metastases at level IV or V, or large volume ->3 cm-multiple lymph nodes at multiple levels). Adjuvant (chemo) radiotherapy is fundamental to achieve good control rates in pN2 cases. The use of SND instead a comprehensive neck dissection (CND) could result in reduced morbidity and better functional results. We conclude that SND could replace a CND without compromising oncologic efficacy in cN1 and cN2 cases with the above-mentioned characteristics