Spatiotemporal dynamics of plant diversity and endemism during primary succession on an oceanic-volcanic island

Questions How does the diversity of native, endemic and alien plant species, as well as the diversity of plant life forms, change during primary succession on lava flows of an oceanic-volcanic island? How do environmental factors such as moisture and soil properties alter diversity during primary succession? Location La Palma, Canary Islands. Methods We recorded vascular plants and bryophytes in 210 plots on a chronosequence of nine lava flows spanning approx. 6,000 years and covering an elevational range of 1,100 m. In a subset (n = 78 plots) we collected and analyzed soil samples for soil nitrogen and plant-available phosphorus. We used generalized linear models, variance partitioning and structural equation models (SEMs) to analyze the data. Results Species richness, endemic richness and alien richness increased with time. Natives dominated during early successional stages, whereas endemics and aliens increased with time. At early successional stages, vascular plants and bryophytes had an equal contribution to the species pool, while vascular plants increased up to an 80% contribution at later stages. In the variance partitioning and SEMs, time was the only consistent factor influencing different aspects of diversity during succession (species richness, endemic richness and percent endemism). Only for percent endemism did soil attributes have a substantial impact. Conclusion Primary succession on lava flows on La Palma shows a pattern of increasing overall diversity, endemism and alien richness with time. Time is the only factor consistently explaining diversity and endemism, indicating that environmental influences such as climate and soil properties do not substantially alter them during primary succession. Our study contributes to understanding how different facets of diversity assemble through time by using an understudied, yet important island system, and, for the first time, specifically addresses how endemics contribute to the process of primary succession.