Functional trait divergence of juveniles and adults of nine Inga species with contrasting soil preference in a tropical rain forest

Abstract

Summary1. Community-wide studies have shown that functional traits of tropical trees vary with soiltype preference, but few have examined trait diversification among closely related taxa. In this study, we asked how functional traits of adults and saplings within a speciose genus, Inga, differ in relation to their soil-type preferences. 2. We quantified soil-type preference and functional traits of nine Inga species (Fabaceae) in the wet tropical forest at La Selva Biological Station, Costa Rica, where rich alluvial soil and less fertile residual soil of volcanic origin occur in close proximity. 3. From the extensive trail network, we randomly selected 104 trail segments, each 50 m long, along which all Inga individuals >50 cm tall were counted and identified to species. Five and three common species showed significant bias to residual or alluvial soil, respectively, while the remaining one showed no significant bias. For these nine species, we quantified five leaf traits for saplings and adults, as well as wood-specific gravity (WSG) and three seed traits. 4. For both adults and saplings, leaf mass per area (LMA) and lamina density were higher for residual-soil specialists than fertile alluvial-soil specialists. The opposite trend was found for nitrogen (N) and phosphorus (P) concentrations in leaves. Lamina thickness did not differ between soil-type preference groups. All leaf trait values except N concentration increased from saplings to adults, with adults showing larger interspecific variations in trait values than saplings. 5. Saplings and adults of the single species found on both soils had trait values intermediate between residual and alluvial-soil specialists. 6. Seed mass and seed N, as well as WSG of adults, were higher in residual-soil specialists than alluvial-soil specialists. Higher seed N indicates higher maternal investment of species growing on less fertile soil. 7. These differences in traits among closely related species across continuous soils suggest that habitat filtering has contributed to the evolution of seed, juvenile and adult traits within a speciose tropical tree genus.

Intraspecific Relationships among Wood Density, Leaf Structural Traits and Environment in Four Co-Occurring Species of Nothofagus in New Zealand

“…Plant traits can vary with ontogeny [51] and to remove size-related variation in each trait before testing for trait-trait and trait-environment correlations, we used a general linear model to determine the relationship between tree diameter at breast height and each trait within each species. The residuals from these models were used in all subsequent analyses.…”

Ontogenetic changes in the phenotypic integration and modularity of leaf functional traits

“…Similarly, lamina thickness, leaf mass per area and phosphorous concentration have been reported to increase in leaves during plant development of nine Inga species in Costa Rica (Palow, Nolting, & Kitajima, 2012); and photosynthetic rate, nitrogen content, leaf mass per area, water content, pH and vein density have been reported to vary across whole-plant ontogeny in three Helianthus species Mason, McGaughey, & Donovan, 2013).…”

“…For example, leaf area, stomatal size, conductance and photosynthetic rate have been found to increase during plant development in different Protea species (Carlson & Holsinger, ). Similarly, lamina thickness, leaf mass per area and phosphorous concentration have been reported to increase in leaves during plant development of nine Inga species in Costa Rica (Palow, Nolting, & Kitajima, ); and photosynthetic rate, nitrogen content, leaf mass per area, water content, pH and vein density have been reported to vary across whole‐plant ontogeny in three Helianthus species (Mason & Donovan, ; Mason, McGaughey, & Donovan, ). Ontogenetic changes in laminar area:perimeter ratio, specific leaf area, percent of parenchyma and stomatal length and density have been also reported in different habitats, as is the case for Lasthenia species associated with terrestrial or vernal pool habitats (Forrestel et al., ).…”

Negative relationship between interspecies spatial association and trait dissimilarity

“…However, the dependence of the species associationtrait similarity relationship on plant life stage remains somewhat unclear. To advance the understanding of demographic processes involving environmental and competitive filtering (Poorter 2007, Palow et al 2012), a comparison of the role of trait dissimilarity in shaping species association across life stages would be valuable.…”