Defaunation changes leaf trait composition of recruit communities in tropical forests in French Guiana.

Hunting impacts tropical vertebrate populations, causing declines of species that function as seed dispersers and predators, or that browse seedlings and saplings. Whether and how the resulting reductions in seed dispersal, seed predation, and browsing translate to changes in the tree composition is poorly understood. Here, we assess the effect of defaunation on the functional composition of communities of tree recruits in tropical rainforests in French Guiana. We selected eight sites along a gradient of defaunation, caused by differences in hunting pressure, in otherwise intact old-growth forests in French Guiana. We measured shifts in functional composition by comparing leaf and fruit traits and wood density between tree recruits (up to 5 cm diameter at breast height) and adults, and tested whether and how these compositional shifts related to defaunation. We found a positive relationship with defaunation for shifts in specific leaf area, a negative relationship for shifts of leaf toughness and wood density, and a weak relationship for shifts in fruit traits. Our results suggest that the loss of vertebrates affects ecological processes such as seed dispersal and browsing, of which browsing remains understudied. Even though these changes sometimes seem minor, together they result in major shifts in forest composition. These changes have long-term ramifications that may alter forest dynamics for generations.

Preferencias alimentarias de Phylloicus sp. (Trichoptera: Calamoceratidae) en un río Neotropical de la Sierra Nevada de Santa Marta, Colombia / Feeding preferences of Phylloicus sp. (Trichoptera: Calamoceratidae) in a Neotropical river of the Sierra Nevada de Santa Marta, Colombia

Introducción: En los sistemas fluviales colombianos ha sido poco estudiada la fragmentación del material alóctono por parte de los insectos acuáticos. Uno de los organismos trituradores más abundantes en las corrientes tropicales de América es el tricóptero del género Phylloicus (Calamoceratidae). Objetivo: El presente estudio tuvo como objetivo evaluar el efecto de los atributos químicos (nitrógeno, fósforo y lignina) y físicos (dureza) de las hojas de tres especies ribereñas (Ficus tonduzii, Zygia longifolia y Clusia multiflora) dominantes en la parte media del río Gaira, sobre la preferencia de hojas y el crecimiento de larvas de Phylloicus sp. Métodos: Se realizaron experimentos de multiselección de alimento en campo, en los que se ubicaron cámaras experimentales dentro del río por 21 días. Para la valoración de la calidad foliar se recolectaron hojas del río, las cuales se secaron y se pulverizaron para realizar los análisis químicos. Resultados: No se presentaron diferencias significativas en los porcentajes de lignina y fósforo entre las hojas de las tres especies de árboles, pero si en su dureza y en el contenido de nitrógeno. Las hojas de C. multiflora fueron más suaves (180.1± 53.9 g) que las de F. tonduzii (285.3 ± 88.4 g) y Z. longifolia (232.3 ± 60.8 g), pero sin diferencias entre las dos últimas especies. Las hojas de Z. longifolia también tuvieron más nitrógeno (1.9 ± 0.0%) que las de hojas de las otras especies (1 ± 0.0 %). En cuanto a la preferencia de hojas, las larvas de Phylloicus sp. utilizaron en mayor proporción las hojas de C. multiflora. Aunque las hojas de C. multiflora no tuvieron diferencias significativas en el contenido de lignina y fósforo, presentaron valores menores de dureza, lo que podría hacerlas más palatables para Phylloicus sp. Por otra parte, el crecimiento específico diario de las larvas fue mayor cuando usaron hojas de F. tonduzii. Conclusiones: Nuestros resultados parecen indicar que las hojas más preferidas no son necesariamente las de mejor calidad nutricional y sugieren que la dureza de las hojas es la variable más importante en la selección de la hojarasca por parte de las larvas de Phylloicus sp.

Introduction: Fragmentation of allochthonous material by aquatic insects is a functional process that has been little studied in Colombian rivers. One of the most abundant shredder genus in American tropical stream ecosystems is the caddisfly genus Phylloicus (Calamoceratidae). Objective: In this study we evaluate the effect of chemical (nitrogen, phosphorus and lignin) and physical (toughness) attributes of leaves of three dominant tree species (Ficus tonduzii, Zygia longifolia and Clusia multiflora) in the riverine area of the middle section of the Gaira river, on leaf preferences and larval growth of a species of Phylloicus. Methods: Multiple food selection field experiments were performed, in which experimental chambers were located in the river for twenty-one days. For the assessment of leaf quality, leaves were collected in the river, dried and pulverized to perform chemical analyzes. Results: There were no significant differences in lignin and phosphorous percentages between the leaves of the three species, but nitrogen content and leaf toughness differed among them. The leaves of C. multiflora were softer (180.1± 53.9 g) than those of F. tonduzii (285.3 ± 88.4 g) and Z. longifolia (232.3 ± 60.8 g), but without differences between the last two species. The Z. longifolia leaves also had more nitrogen (1.9 ± 0.0 %) than those of the other species (1 ± 0.0 %). Regarding leaf selection, Phylloicus sp. larvae used in greater proportion the leaves of C. multiflora. Although lignin and phosphorous differences were not significant, the leaves of C. multiflora had lower toughness, which could make them more palatable for Phylloicus sp. On the other hand, the daily specific growth of the larvae was higher when they used leaves of F. tonduzii. Conclusions: Our findings seem to indicate that the most preferred leaves were not necessarily those of better nutritional quality and suggest that leaf toughness was the most important variable in the selection of leaf litter by the larvae of Phylloicus sp.

Shredders prefer soft and fungal-conditioned leaves, regardless of their initial chemical traits / Fragmentadores preferem folhas macias e condicionadas por fungos, independente da sua qualidade química inicial

Through field and laboratory experiments we investigated the effects of leaf traits of two tree species and microbial conditioning on the abundance, biomass, and feeding preference of a typical macroinvertebrate shredder. In the field, we compared the association of Phylloicus (Calamoceratidae, Trichoptera) with two tree species commonly found in riparian zones, which are representative of high and low nutritional quality, respectively: Nectandra megapotamica and Chusquea tenella. In the laboratory, we investigated the feeding preference of Phylloicus using unconditioned leaves and leaves conditioned by aquatic fungi. The same tree species used in the field experiment were used in the laboratory. Initially, C. tenella leaves were proved to be more nutritious and softer, while N. megapotamica leaves were harder and more lignified. The shredders preferred conditioned leaf detritus of reduced toughness (field: C. tenella; laboratory: N. megapotamica, both conditioned for 14 days). These leaf traits seem to be crucial for the choice process of Phylloicus. After 14 days, N. megapotamica leaves showed a decreased toughness associated with the microbial conditioning, which explained its consumption rate by Phylloicus. In both field and laboratory experiments, we found evidence that Phylloicus is a selective feeding shredder, and that the leaf traits, especially leaf structure (e.g., leaf toughness and lignin content), determine its association and preferences.(AU)

Nós investigamos em experimento de campo e de laboratório os efeitos das características foliares e condicionamento microbiano de duas espécies de árvores na abundância, biomassa e preferência alimentar de um fragmentador típico. No experimento de campo, comparamos a associação do Phylloicus (Calamoceratidae, Trichoptera) entre duas espécies vegetais, comumente encontradas em zonas ripárias, que são representativas de alta e baixa qualidade nutricional, respectivamente: Nectandra megapotamica e Chusquea tenella. Em experimento de laboratório, investigamos a preferência alimentar de Phylloicus, usando folhas condicionadas e não condicionadas pelos fungos aquáticos. As mesmas espécies vegetais usadas no experimento de campo foram usadas em laboratório. Inicialmente, as folhas de C. tenella mostraram-se mais nutritivas e macias, enquanto que as de N. megapotamica foram mais duras e lignificadas. Os fragmentadores preferiram o detrito com menor dureza e condicionados pelos fungos (campo: C. tenella; laboratório: N. megapotamica, ambas condicionadas por 14 dias), ou seja, estes parecem ser os fatores determinantes para a escolha dos Phylloicus. Após 14 dias, as folhas de N. megapotamica apresentaram decréscimo na dureza, que está associado ao condicionamento microbiano, e que explicou o padrão de consumo por Phylloicus. Nós encontramos evidências em campo e em laboratório que os Phylloicus são seletivos em relação ao alimento e que as características foliares, especialmente relacionadas à estrutura da folha (ex. dureza foliar e lignina), determinam a associação e a preferência destes fragmentadores.(AU)

Shredders prefer soft and fungal-conditioned leaves, regardless of their initial chemical traits / Fragmentadores preferem folhas macias e condicionadas por fungos, independente da sua qualidade química inicial

Through field and laboratory experiments we investigated the effects of leaf traits of two tree species and microbial conditioning on the abundance, biomass, and feeding preference of a typical macroinvertebrate shredder. In the field, we compared the association of Phylloicus (Calamoceratidae, Trichoptera) with two tree species commonly found in riparian zones, which are representative of high and low nutritional quality, respectively: Nectandra megapotamica and Chusquea tenella. In the laboratory, we investigated the feeding preference of Phylloicus using unconditioned leaves and leaves conditioned by aquatic fungi. The same tree species used in the field experiment were used in the laboratory. Initially, C. tenella leaves were proved to be more nutritious and softer, while N. megapotamica leaves were harder and more lignified. The shredders preferred conditioned leaf detritus of reduced toughness (field: C. tenella; laboratory: N. megapotamica, both conditioned for 14 days). These leaf traits seem to be crucial for the choice process of Phylloicus. After 14 days, N. megapotamica leaves showed a decreased toughness associated with the microbial conditioning, which explained its consumption rate by Phylloicus. In both field and laboratory experiments, we found evidence that Phylloicus is a selective feeding shredder, and that the leaf traits, especially leaf structure (e.g., leaf toughness and lignin content), determine its association and preferences.

Nós investigamos em experimento de campo e de laboratório os efeitos das características foliares e condicionamento microbiano de duas espécies de árvores na abundância, biomassa e preferência alimentar de um fragmentador típico. No experimento de campo, comparamos a associação do Phylloicus (Calamoceratidae, Trichoptera) entre duas espécies vegetais, comumente encontradas em zonas ripárias, que são representativas de alta e baixa qualidade nutricional, respectivamente: Nectandra megapotamica e Chusquea tenella. Em experimento de laboratório, investigamos a preferência alimentar de Phylloicus, usando folhas condicionadas e não condicionadas pelos fungos aquáticos. As mesmas espécies vegetais usadas no experimento de campo foram usadas em laboratório. Inicialmente, as folhas de C. tenella mostraram-se mais nutritivas e macias, enquanto que as de N. megapotamica foram mais duras e lignificadas. Os fragmentadores preferiram o detrito com menor dureza e condicionados pelos fungos (campo: C. tenella; laboratório: N. megapotamica, ambas condicionadas por 14 dias), ou seja, estes parecem ser os fatores determinantes para a escolha dos Phylloicus. Após 14 dias, as folhas de N. megapotamica apresentaram decréscimo na dureza, que está associado ao condicionamento microbiano, e que explicou o padrão de consumo por Phylloicus. Nós encontramos evidências em campo e em laboratório que os Phylloicus são seletivos em relação ao alimento e que as características foliares, especialmente relacionadas à estrutura da folha (ex. dureza foliar e lignina), determinam a associação e a preferência destes fragmentadores.

Shredders prefer soft and fungal-conditioned leaves, regardless of their initial chemical traits

ABSTRACT Through field and laboratory experiments we investigated the effects of leaf traits of two tree species and microbial conditioning on the abundance, biomass, and feeding preference of a typical macroinvertebrate shredder. In the field, we compared the association of Phylloicus (Calamoceratidae, Trichoptera) with two tree species commonly found in riparian zones, which are representative of high and low nutritional quality, respectively: Nectandra megapotamica and Chusquea tenella. In the laboratory, we investigated the feeding preference of Phylloicus using unconditioned leaves and leaves conditioned by aquatic fungi. The same tree species used in the field experiment were used in the laboratory. Initially, C. tenella leaves were proved to be more nutritious and softer, while N. megapotamica leaves were harder and more lignified. The shredders preferred conditioned leaf detritus of reduced toughness (field: C. tenella; laboratory: N. megapotamica, both conditioned for 14 days). These leaf traits seem to be crucial for the choice process of Phylloicus. After 14 days, N. megapotamica leaves showed a decreased toughness associated with the microbial conditioning, which explained its consumption rate by Phylloicus. In both field and laboratory experiments, we found evidence that Phylloicus is a selective feeding shredder, and that the leaf traits, especially leaf structure (e.g., leaf toughness and lignin content), determine its association and preferences.

RESUMO Nós investigamos em experimento de campo e de laboratório os efeitos das características foliares e condicionamento microbiano de duas espécies de árvores na abundância, biomassa e preferência alimentar de um fragmentador típico. No experimento de campo, comparamos a associação do Phylloicus (Calamoceratidae, Trichoptera) entre duas espécies vegetais, comumente encontradas em zonas ripárias, que são representativas de alta e baixa qualidade nutricional, respectivamente: Nectandra megapotamica e Chusquea tenella. Em experimento de laboratório, investigamos a preferência alimentar de Phylloicus, usando folhas condicionadas e não condicionadas pelos fungos aquáticos. As mesmas espécies vegetais usadas no experimento de campo foram usadas em laboratório. Inicialmente, as folhas de C. tenella mostraram-se mais nutritivas e macias, enquanto que as de N. megapotamica foram mais duras e lignificadas. Os fragmentadores preferiram o detrito com menor dureza e condicionados pelos fungos (campo: C. tenella; laboratório: N. megapotamica, ambas condicionadas por 14 dias), ou seja, estes parecem ser os fatores determinantes para a escolha dos Phylloicus. Após 14 dias, as folhas de N. megapotamica apresentaram decréscimo na dureza, que está associado ao condicionamento microbiano, e que explicou o padrão de consumo por Phylloicus. Nós encontramos evidências em campo e em laboratório que os Phylloicus são seletivos em relação ao alimento e que as características foliares, especialmente relacionadas à estrutura da folha (ex. dureza foliar e lignina), determinam a associação e a preferência destes fragmentadores.

Leaf traits in Chilean matorral: sclerophylly within, among, and beyond matorral, and its environmental determinants.

Studies of leaf traits often focus on tradeoffs between growth and resource conservation, but little is known about variation in the mechanical traits that influence resource conservation. This study investigates how leaf mechanical traits vary across matorral vegetation in central Chile, how they correlate with environmental factors, and how these trends compare at a broader geographic scale. Leaf toughness, strength, stiffness, and associated traits were measured in five matorral types in central Chile, and relationships with soil N and P and climate variables were assessed. Trends with soil and climate were then analyzed across shrubland and woodland in Chile, Western Australia, and New Caledonia. Chilean species varied in leaf mechanics and associated traits, both within and among matorral types, with more species in sclerophyll matorral having strong, tough, and stiff leaves than in arid and littoral matorral. Overall, leaves with high leaf dry mass per area were stiffer, tougher, stronger, thicker, denser, with more fiber, lignin, phenolics and fiber per unit protein and less protein: tannin activity and N and P per mass, forming a broad sclerophylly syndrome. Mechanical traits of matorral species were not correlated with soil N or P, or predictably with climate variables, except flexural stiffness (EI W) which correlated positively with annual reference evapotranspiration (ET 0). However, soil P made strong independent contributions to variation in leaf mechanics across shrublands and woodlands of Chile, Western Australia, and New Caledonia, either separately (strength) or together with ET 0 (toughness) explaining 46-90% of variation. Hence ET 0 was predictive of EI W in Chilean matorral, whereas soil P was highly predictive of variation in leaf strength, and combined with ET 0 was highly predictive of toughness, at a broader geographic scale. The biological basis of these relationships, however, may be complex.

Leaf mechanical resistance in plant trait databases: comparing the results of two common measurement methods.

BACKGROUND AND AIMS: The influence of leaf mechanical properties on local ecosystem processes, such as trophic transfer, decomposition and nutrient cycling, has resulted in a growing interest in including leaf mechanical resistance in large-scale databases of plant functional traits. 'Specific work to shear' and 'force to tear' are two properties commonly used to describe mechanical resistance (toughness or strength) of leaves. Two methodologies have been widely used to measure them across large datasets. This study aimed to assess correlations and standardization between the two methods, as measured by two widely used apparatuses, in order to inter-convert existing data in those global datasets. METHODS: Specific work to shear (W(SS)) and force to tear (FT) were measured in leaves of 72 species from south-eastern Australia. The measurements were made including and excluding midribs. Relationships between the variables were tested by Spearman correlations and ordinary least square regressions. KEY RESULTS: A positive and significant correlation was found between the methods, but coefficients varied according to the inclusion or exclusion of the midrib in the measurements. Equations for prediction varied according to leaf venation pattern. A positive and significant (r = 0·90, P < 0·0001) correlation was also found between W(SS) values for fresh and rehydrated leaves, which is considered to be of practical relevance. CONCLUSIONS: In the context of broad-scale ecological hypotheses and used within the constraints recommended here, leaf mechanical resistance data obtained with both methodologies could be pooled together into a single coarser variable, using the equations provided in this paper. However, more detailed datasets of FT cannot be safely filled in with estimations based on W(SS), or vice versa. In addition, W(SS) values of green leaves can be predicted with good accuracy from W(SS) of rehydrated leaves of the same species.