Commonness, rarity, and intraspecific variation in traits and performance in tropical tree seedlings

Abstract

One of the few rules in ecology is that communities are composed of many rare and few common species. Trait-based investigations of abundance distributions have generally focused on species-mean trait values with mixed success. Here, using large tropical tree seedling datasets in China and Puerto Rico, we take an alternative approach that considers the magnitude of intraspecific variation in traits and growth as it relates to species abundance. We find that common species are less variable in their traits and growth. Common species also occupy core positions within community trait space indicating that they are finely tuned for the available conditions. Rare species are functionally peripheral and are likely transients struggling for success in the given environment. The work highlights the importance of considering intraspecific variation in trait-based ecology and demonstrates asymmetry in the magnitude of intraspecific variation among species is critical for understanding of how traits are related to abundance.

Do community-weighted mean functional traits reflect optimal strategies?

“…Our results are consistent with another recent study (involving tree seedlings in China and Puerto Rico) that examined the relationship between local abundance and the deviation of species trait values from the local CWM [24]. In that study, abundance was higher for species whose trait values were closer to the local CWM for a majority of univariate traits studied.…”

“…Additionally, disequilibrium dynamics (e.g. source-sink populations) could lead to the local occurrence of functional types with inferior fitness [24]. Other mechanisms that could contribute to the maintenance of local functional diversity are, however, not entirely consistent with the CWM-optimality hypothesis.…”

Functional Rarity: The Ecology of Outliers

“…Complementing this, quantifying functional rarity must include the extent to which species traits, used as proxies to represent functions, trophic links and niche axes [42][43][44][45][46][47], are more or less distinct or redundant within local communities or larger-scale species assemblages [40,48,49] (Box 1).…”

“…For example, the recent awareness that intra-specific functional variability can have important impacts not only on local adaptation but also on community assembly and ecosystem functioning [51][52][53] has led to increased measurement of traits of individuals within species at different locations [54], as well as the development of new diversity metrics [55,56]. Our framework can be easily extended to include intra-specific variability, as functional rarity can be calculated at the individual level [48]. This can be further extended to lower levels of integration such as genotypes, genes or transcriptomes as well.…”

Functional trait shifts after disturbance reveal broad‐scale variability in temperate forest regional recruitment processes

“…The studies so far have focused on extant adult trees (Schamp & Aarssen, ; Wonkka, Lafon, Hutton, & Joslin, ; Giehl & Jarenkow, ; Wilfahrt, White, Collins, & Tuttle, ), which reveals traits conferring tolerance to disturbance, as opposed to recruitment ability following disturbance. Although recruitment into later age classes and its contribution to trait patterns in forests is slow (Muscarella et al., ), the trait composition of juveniles in post‐disturbance communities can nonetheless indicate future community composition of mature trees (Pacala et al., ; Umaña, Zhang, Cao, Lin, & Swenson, ). This study makes use of a continental‐scale tree database with repeated surveys of permanent plots in the eastern temperate forests of the US to reveal patterns of tree seedling functional traits in response to forest disturbances.…”