Food-web structure in relation to environmental gradients and predator-prey ratios in tank-bromeliad ecosystems

Little is known of how linkage patterns between species change along environmental gradients. The small, spatially discrete food webs inhabiting tank-bromeliads provide an excellent opportunity to analyse patterns of community diversity and food-web topology (connectance, linkage density, nestedness) in relation to key environmental variables (habitat size, detrital resource, incident radiation) and predators: prey ratios. We sampled 365 bromeliads in a wide range of understorey environments in French Guiana and used gut contents of invertebrates to draw the corresponding 365 connectance webs. At the bromeliad scale, habitat size (water volume) determined the number of species that constitute food-web nodes, the proportion of predators, and food-web topology. The number of species as well as the proportion of predators within bromeliads declined from open to forested habitats, where the volume of water collected by bromeliads was generally lower because of rainfall interception by the canopy. A core group of microorganisms and generalist detritivores remained relatively constant across environments. This suggests that (i) a highly-connected core ensures food-web stability and key ecosystem functions across environments, and (ii) larger deviations in food-web structures can be expected following disturbance if detritivores share traits that determine responses to environmental changes. While linkage density and nestedness were lower in bromeliads in the forest than in open areas, experiments are needed to confirm a trend for lower food-web stability in the understorey of primary forests

Ants mediate the structure of phytotelm communities in an ant-garden bromeliad

The main theories explaining the biological diversity of rain forests often confer a limited understanding of the contribution of interspecific interactions to the observed patterns. We show how two-species mutualisms can affect much larger segments of the invertebrate community in tropical rain forests. Aechmea mertensii (Bromeliaceae) is both a phytotelm (plant-held water) and an ant-garden epiphyte. We studied the influence of its associated ant species (Pachycondyla goeldii and Camponotus femoratus) on the physical characteristics of the plants, and, subsequently, on the diversity of the invertebrate communities that inhabit their tanks. As dispersal agents for the bromeliads, P. goeldii and C. femoratus influence the shape and size of the bromeliad by determining the location of the seedling, from exposed to partially shaded areas. By coexisting on a local scale, the two ant species generate a gradient of habitat conditions in terms of available resources (space and food) for aquatic invertebrates, the diversity of the invertebrate communities increasing with greater volumes of water and fine detritus. Two-species mutualisms are widespread in nature, but their influence on the diversity of entire communities remains largely unexplored. Because macroinvertebrates constitute an important part of animal production in all ecosystem types, further investigations should address the functional implications of such indirect effects

An annotated list of the centipedes (Chilopoda) in the National Collection of Arachnids, Instituto de Biología, Universidad Nacional Autónoma de México : Addendum: Scutigeromorpha and Scolopendromorpha

This addendum to “An annotated list of the centipedes (Chilopoda) in The National Collection of Arachnids (Colección Nacional de Arácnidos, CNAN), Instituto de Biología, Universidad Nacional Autónoma de México” (México City), is based on new samples deposited in the last three years. It updates the preliminary list of 197 samples determined to genus and/or species. In this paper a total of 132 samples were added: Scutigeromorpha, 27; and Scolopendromorpha, 105. It also provides new state distribution records for Dendrothereua linceci (Wood, 1867), Scolopendra morsitans Linnaeus, 1758, S. polymorpha Wood, 1861, Rhysida immarginata (Porat, 1876), Scolopocryptops melanostomus Newport, 1845, Newportia spinipes Pocock, 1896, and Ectonocryptoides quadrimeropus Shelley and Mercurio, 2005.Adiciones a la “Lista anotada de ciempiés (Chilopoda) de la Colección Nacional de Arácnidos (CNAN) del Instituto de Biología de la Universidad Nacional Autónoma de México” (Ciudad de México), se realizaron a partir de la revisión de nuevas muestras depositadas en los últimos tres años. Con estas adiciones se actualiza la lista preliminar de 197 muestras determinadas a nivel de género y/o especie. En este trabajo se adicionan en total 132 muestras: Scutigeromorpha, 27; y Scolopendromorpha, 105. También se proporcionan nuevos registros de distribución estatal para Dendrothereua linceci (Wood, 1867), Scolopendra morsitans Linnaeus, 1758, S. polymorpha Wood, 1861, Rhysida immarginata (Porat, 1876), Scolopocryptops melanostomus Newport, 1845, Newportia spinipes Pocock, 1896, y Ectonocryptoides quadrimeropus Shelley y Mercurio, 2005

Arboreal frogs, tank bromeliads and disturbed seasonal tropical forest

We investigated the relationship between arboreal frogs, tank bromeliads and landscape transformation in tropical forests of southeastern Campeche, Mexico. We surveyed frogs in six distinct habitats: slash and burn agriculture, seasonally flooded forest (bajo), aquatic habitats (lagoons and small ponds), second growth upland forest, primary forest and creek habitat using both systematic and non-systematic surveys. The highest species richness of frogs was documented in primary forest and small ponds. In contrast, no frogs were recorded in second growth forest. Similarly, tank bromeliads (Aechmea bracteata) were completely absent from early successional stages and were almost twice as abundant in seasonally flooded forest as in upland forest. The vertical distribution of A. bracteata differed between forest types, and they significantly more abundant in larger diameter trees. We examined 60 tank bromeliads during the peak of the dry season to test their use as refugia by frogs. Approximately 27% of tank bromeliads sampled had arboreal frogs belonging to three species, but 9 species have been recorded as occasional users of bromeliads in the region. There were significantly more frogs on large than on medium-sized bromeliads, and frogs were more abundant on bromeliads higher on host trees, particularly those above 3 m in height. Our results suggest that the loss of tank bromeliads from drier and less structurally complex habitats created by slash and burn agriculture and selective logging results in loss of refugia for arboreal frogs in this seasonal tropical forest. We suggest that Aechmea bracteata be a keystone species in seasonal tropical forest

Isthmohyla zeteki

Number of Pages: 3Integrative BiologyGeological Science

Multiple anti-predator mechanisms in the red-spotted Argentina Frog (Amphibia: Hylidae)

Anurans employ a wide variety of anti-predator mechanisms to defend themselves. In casque-headed hylids, defence is thought to be a complex combination of several anti-predator mechanisms. However, the defence traits of only a few species are known; some hypotheses have yet to be addressed, whereas others, already tested in some species, need to be tested in additional taxa. The anti-predator mechanism of the casque-headed frog, Argenteohyla siemersi, is described here. It is a complex mechanism consisting of (1) behavioural and ecological traits, including secretive and semi-phragmotic habits and posture; (2) morphological features, including cryptic and aposematic colourations, a skull covered with bony dermal spines and protuberances that are associated with two types of granular venom glands; and (3) physiological and chemical traits, such as a highly lethal skin secretion. Our results are compared with those of previous studies of defence mechanisms in casque-headed frogs in an effort to understand the mechanisms and evaluate their potential phylogenetic signal in this group of anurans.Fil: Cajade, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas, Naturales y Agrimensura. Departamento de Biología; ArgentinaFil: Hermida, Gladys Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Piñeiro, Jose Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas, Naturales y Agrimensura. Departamento de Biología; ArgentinaFil: Regueira, Eleonora. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Alcalde, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Fusco, Luciano Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Departamento de Bioquímica; ArgentinaFil: Marangoni, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas, Naturales y Agrimensura. Departamento de Biología; Argentin

An annotated list of the centipedes (Chilopoda) in the National Collection of Arachnids, Instituto de Biología, Universidad Nacional Autónoma de México

The National Collection of Arachnids, Instituto de Biología, Universidad Nacional Autónoma de México (México City) houses 476 chilopod samples, of which 197 are determined to genus and/or species. These are documented here and represent several new state records. Topotypes of eight species of centipedes described by R. V. Chamberlin also documented.La Colección Nacional de Arácnidos, del Instituto de Biología de la Universidad Nacional Autónoma de México (Ciudad de México), resguarda 476 muestras de quilópodos, de los que 197 están determinadas a nivel de género y/o especie. Algunas de estas muestras corresponden a nuevos registros estatales. Se documentan los topotipos de ocho especies de ciempiés descritos por R. V. Chamberlin

Aquatic invertebrate communities in tank bromeliads: how well do classic ecological patterns apply?

Tank bromeliads (Bromeliaceae) often occur in high densities in the Neotropics and represent a key freshwater habitat in montane forests, housing quite complex invertebrate communities. We tested the extent to which there are species richness–altitude, richness–environment, richness–size, richness–habitat complexity and richness–isolation relationships for the aquatic invertebrate communities from 157 bromeliads in Cusuco National Park, Honduras. We found that invertebrate species richness and abundance correlated most strongly, and positively, with habitat size, which accounted for about a third of the variance in both. Apart from bromeliad size (equivalent of the species– area relationship), we found remarkably little evidence of classic biogeographic and ecological relationships with species richness in this system. Community composition correlated with altitude, bromeliad size and position, though less than 20% of the variation was accounted for by the tested variables. The turnover component of dissimilarity between the communities correlated with altitude, while the nestedness-resultant component was related to bromeliad size. The unexplained variance could reflect a large stochastic component in the system, associated with the ephemerality of the habitat patches (both the plants themselves and the fluctuations in their water content) and stochasticity due to the dispersal dynamics in the system. We conclude that there is a small contribution of classic biogeographic factors to the diversity and community composition of aquatic invertebrates communities in bromeliads. This may be due to the highly dynamic nature of this system, with small patch sizes and high emigration rates. The patterns may mostly be driven by factors affecting colonisation success

Environmental control of the microfaunal community structure in tropical bromeliads.

Ecological communities hosted within phytotelmata (plant compartments filled with water) provide an excellent opportunity to test ecological theory and to advance our understanding of how local and global environmental changes affect ecosystems. However, insights from bromeliad phytotelmata communities are currently limited by scarce accounts of microfauna assemblages, even though these assemblages are critical in transferring, recycling, and releasing nutrients in these model ecosystems. Here, we analyzed natural microfaunal communities in leaf compartments of 43 bromeliads to identify the key environmental filters underlying their community structures. We found that microfaunal community richness and abundance were negatively related to canopy openness and vertical height above the ground. These associations were primarily driven by the composition of amoebae and flagellate assemblages and indicate the importance of bottom-up control of microfauna in bromeliads. Taxonomic richness of all functional groups followed a unimodal relationship with water temperature, peaking at 23-25°C and declining below and above this relatively narrow thermal range. This suggests that relatively small changes in water temperature under expected future climate warming may alter taxonomic richness and ecological structure of these communities. Our findings improve the understanding of this unstudied but crucial component of bromeliad ecosystems and reveal important environmental filters that likely contribute to overall bromeliad community structure and function.This research was funded by Natural Sciences and Engineering Research Council of Canada (NSERC) and the Swiss National Science Foundation (SNF)