Facilitation and plant phenotypic evolution.

While antagonistic interactions between plants have been a major topic of eco-evolutionary research, little evidence exists on the evolution of positive plant interactions (i.e., plant facilitation). Here, we first summarize the existing empirical evidence on the role of facilitation as a selection pressure on plants. Then, we develop a theoretical eco-evolutionary framework based on fitness-trait functions and interaction effectiveness that provides predictions for how facilitation-related traits may evolve. As evolution may act at levels beyond the individual (such as groups or species), we discuss the subject of the units of evolutionary selection through facilitation. Finally, we use the proposed formal evolutionary framework for facilitation to identify areas of future research based on the knowledge gaps detected.

Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments.

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within-microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub-communities in severe environments, as demonstrated by increasing phylo-beta diversity. Thus, foundation species functioned as micro-refugia by facilitating less stress-tolerant lineages in severe environments, erasing a global productivity - phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.

Medial capsular recession for severe varus deformities.

Medial capsular recession is an effective method of correcting preoperative fixed varus knee deformities at the time of total knee arthroplasty. If the flexion and extension spaces are properly balanced and filled, knee stability is achievable. Sixty-eight knees that had medial capsular recession were followed for at least 2 years after surgery, 19 of them for more than 10 years, with a mean follow-up period of 4.8 years. Of these knees, 73% had less than 5 degrees of postoperative varus/valgus instability with no deterioration during the follow-up period. Attenuation or rupture of the medial flap occurred in only two knees. There was no statistical difference in ultimate range of motion, alignment, or presence of bone-cement radiolucencies between knees with medial recession and those without medial recession.