Population structure and quantitative characteristics of Tetracentron sinense (Trochodendraceae) in Leigong Mountain Nature Reserve, China

Background: Knowledge of plant population structure facilitates conservation, management, and utilization of endangered plants. Research question: What is the current status of the natural populations of Tetracentron sinense in Leigong Mountain Nature Reserve (LMNR) and what future population development trends can be predicted? Studied species: Tetracentron sinense Study site and period of research: T. sinense populations in LMNR in China in 2018. Methods: The population structure and quantity dynamics of four typical patches were studied using static life tables, survival curves, survival analyses, and time series analyses. Results: The age structures of the T. sinense populations were spindle-shaped, with few seedlings and saplings, and Deevey type II and Ⅲ survival curves. The mortality rate (qx) of each patch increased quickly, and then plateaued, finally increasing again. Survival rate (Sx) showed a contrary trend to qx. Trends in cumulative mortality rate (F(i)), killing power (Kx), mortality density (f(ti)), and hazard rate (λ(ti)) with increasing age class were similar: increasing at a younger age, gradually stabilizing in middle age, and then increasing slightly in older age. The number of individuals in these T. sinense populations was predicted to decrease sharply in future, with younger individuals being seriously deficient. The results showed that the natural populations of T. sinense in the LMNR were relatively stable but were in an early stage of decline. Conclusions: The lack of younger individuals might reflect a bottleneck for regeneration of T. sinense populations, leading to a decline in population size.

Plant population structure and insect herbivory on Solanum mauritianum Scopoli (Solanaceae) in southern Brazil: a support to biological control

Solanum mauritianum Scopoli (Solanaceae), a native Brazilian shrub, has become naturalized and invasive in several countries. In South Africa, where invasions are severe, herbivorous insects that attack S. mauritianum in its native area have been considered for introduction as biological control agents. To assess the action of such herbivores on the plant, studies were carried out on a population of S. mauritianum in an area undergoing regeneration in southern Brazil. An analysis of the structure of that population was performed, as well as of herbivory by insects, in particular of Anthonomus (Curculionidae). The population structure showed an "inverted J" pattern in diameter classes, but not in height classes. Individual plants showed an aggregate distribution. The damage caused by Anthonomus did not amount to the loss of a large leaf area, but since it was inflicted on young leaves and in a large proportion, could lead to the survival decrease.