Interference Competition in a Tropical Ripple Bug (Hemiptera: Veliidae)

We examine and assess deterministic chaos as an observable. First, we present the development of model ecological systems. We illustrate how to apply the Kolmogorov theorem to obtain limits on the parameters in the system, which assure the existence of either stable equilibrium point or stable limit cycle behavior in the phase space of two-dimensional (2D) dynamical systems. We also illustrate the method of deriving conditions using the linear stability analysis. We apply these procedures on some basic existing model ecological systems. Then, we propose four model ecological systems to study the dynamical chaos (chaos and intermittent chaos) and cycles. Dynamics of two predation and two competition models have been explored. The predation models have been designed by linking two predator–prey communities, which differ from one another in one essential way: the predator in the first is specialist and that in the second is generalist. The two competition models pertain to two distinct competition processes: interference and exploitative competition. The first competition model was designed by linking two predator–prey communities through inter-specific competition. The other competition model assumes that a cycling predator–prey community is successfully invaded by a predator with linear functional response and coexists with the community as a result of differences in the functional responses of the two predators. The main criterion behind the selection of these two model systems for the present study was that they represent diversity of ecological interactions in the real world in a manner which preserves mathematical tractability. For investigating the dynamic behavior of the model systems, the following tools are used: (i) calculation of the basin boundary structures, (ii) performing two-dimensional parameter scans using two of the parameters in the system as base variables, (iii) drawing the bifurcation diagrams, and (iv) performing time series analysis and drawing the phase space diagrams. The results of numerical simulation are used to distinguish between chaotic and cyclic behaviors of the systems.The conclusion that we obtain from the first two model systems (predation models) is that it would be difficult to capture chaos in the wild because ecological systems appear to change their attractors in response to changes in the system parameters quite frequently. The detection of chaos in the real data does not seem to be a possibility as what is present in ecological systems is not robust chaos but short-term recurrent chaos. The first competition model (interference competition) shares this conclusion with those of predation ones. The model with exploitative competition suggests that deterministic chaos may be robust in certain systems, but it would not be observed as the constituent populations frequently execute excursions to extinction-sized densities. Thus, no matter how good the data characteristics and analysis techniques are, dynamical chaos may continue to elude ecologists. On the other hand, the models suggest that the observation of cyclical dynamics in nature is the most likely outcome.

ABSTRACTDensity‐dependent processes are important for a fundamental understanding of population regulation, as well as for understanding responses to and recovery from stressors. While exploitative competition is well‐studied, interference competition is rather difficult to investigate, but it has been regularly observed to occur in many aquatic insect populations. We conducted laboratory experiments with the non‐biting midge Chironomus riparius (Diptera: Chironomidae) to investigate the impact of different combinations of food supply and larval densities on development and mortality at a constant temperature of 20°C. The chosen two‐factorial experimental design allowed a separate evaluation of exploitative (food) and interference (mortality) competition across a gradient of larval densities. The use of different vessel sizes between 50 cm2 and 600 cm2 made it possible to quantify the functional response at different food densities. To test mechanistic explanations for the statistically significant empirical relationships found in this study and to predict density‐dependent processes, we used a dynamic process‐oriented modeling approach. We extended a recently developed DEB‐IBM full life cycle model for C. riparius and successfully applied it under variable food conditions at the population level under laboratory conditions. Our study showed that chironomid development and reproduction are primarily dependent on food supply, whereas larval density drives the density‐dependent mortality rate. The interaction of food availability and interference competition determined the effective mortality over time. Killing by conspecifics was the most likely mechanism responsible for the intraspecific mortality of the larval stages. Combining data generated using a tailor‐made experimental design with a mechanistic model provided insights into and quantified regulation mechanisms of chironomid populations, allowing future uses of this information in the context of population‐level risk assessment from exposure to chemicals.

Cyperus herndoniae is described, illustrated, and compared to its nearest relative, C. distans. It is known from collections from Guanacaste Province, Costa Rica, and Chiapas, Mexico. During the course of my work on Cyperus in Costa Rica and Panama, an undescribed species was noted from two collections made by R. L. Wilbur in Guanacaste Province. Later, a third collection made by D. E. Breedlove in Chiapas, Mexico, was detected. Cyperus herndoniae Tucker, sp. nov., fig. 1.-TYPE: Costa Rica, Guanacaste, local in ditch at the entrance of the Santa Rosa National Park, 21 Jul 198 1, Wilbur 31825 (holotype: DUKE; isotypes: CR, F, GH, MO). Rhizoma ascendens, ad 2 cm longa. Radii simplices. Spiculae linearilanceolatae, 8-16 mm longae, 1.5-2.1 mm latae. Squamae divaricatae, ellipticae, 3-3.2 mm longae, 1.5-1.9 mm latae. Achaenium trigonum, oblongum, 2-2.2 mm longum, 0.6-0.7 mm latum. Affinis Cypero distanti L.f. Culms single or 2-3 together, 30-75 cm tall, trigonous, smooth; basally indurate. Rhizomes up to 2 cm long, turning upward. Roots fibrous. Leaves 1-4, 20-40 cm long, 2-3 mm wide, margins scabrellate. Inflorescence bracts 3-6, 2-25 cm long, 1-6 mm wide, borne horizontally, margins scabrellate. Rays (4-)6-8, up to 5 cm long, unbranched. Spikes ovoid to hemispherical, (5-)15-35 mm long, 17-45 mm wide; rachis 3-12 mm long. Spikelets (10-)25-50 per spike, linear-lanceolate, compressed, 816 mm long, 1.5-2.1 mm wide; rachilla slightly flexuous, its wings hyaline, 0.3-0.4 mm wide. Scales 4-12 per spikelet, elliptic, 3-3.2 mm long, 1.3-1.9 mm wide, obtuse, mucronulate, borne divaricately on the rachilla, laterally 2-3-nerved, brown to stramineous, the margins hyaline, the keel 3-nerved, greenish. Stamens 3; filaments ribbonlike, 3.5-4 mm long; anthers oblong, 0.9-1.1 mm long. Styles 0.4-0.7 mm long; stigmatic branches 3, 2.5-3 mm long. Achenes trigonous, oblong, 2-2.2 mm long, 0.6-0.7 mm wide, apiculate, slightly stipitate, angles rounded, faces flat to slightly convex, finely papillose, brown. Distribution. Roadsides, wet marshy depressions, and low flats from sea level to 700 m. Flowering and fruiting specimens have been collected in Jul, Aug, and Sep. Specimens examined. Costa Rica. Guanacaste: just outside Santa Rosa National Park, Wilbur 30970 (DUKE); 14 km S of La Cruz, Wilbur 30928B (DUKE); about 18 km N of

Overview.- The role of national institutions and international cooperation in the development of the geological sciences in the Central American-Caribbean region.- The known and potential resource base for economic development in the Central American-Caribbean region.- Geodynamic map of Costa Rica.- Central America and the north Caribbean: Resource implications inferred from paleomagnetic data and plate tectonic history.- The status of mineral production in the Caribbean Basin countries.- Circum-Caribbean sedimentary basin development and timing of hydrocarbon maturation as a function of Caribbean Plate tectonic evolution.- The human and economic losses of selected natural disasters in Latin America, 1970-1987.- Central American resource studies.- Petroleum Resources.- Caribbean region: Perspectives on petroleum.- Sedimentary basins of Costa Rica: Late Mesozoic-Cenozoic evolution and hydrocarbon potential.- An integrated geological and geophysical interpretation of the San Carlos basin, Costa Rica.- Preliminary tectonic outline of northern Guatemala.- The Coban Formation in the Peten basin, Guatemala.- The petroleum potential of the Netherlands Antilles.- Sedimentary basins and petroleum potential of Puerto Rico.- An oil and gas assessment of the U. S. continental slope in the Gulf of Mexico.- The perpetual mystery of petroleum migration.- Summary of working group session on petroleum resources.- Coal and Peat Resources.- Coal in the Central American-Caribbean region.- Exploration, development, and utilization of coal in Costa Rica.- Coal resources of the Baja Talamanca area of Costa Rica.- A mining design project for the Zent coal, Limon, Costa Rica.- Utilizing coal in the cement industry in Costa Rica.- Coal districts of Venezuela.- Status of coal exploration in the Atlantic coast of Colombia.- Opportunities for collaborating in utilization of clean coal technologies.- Peat deposits of Central America and the Caribbean region.- Deposits of peat in Costa Rica.- Economics of selected energy applications of peat in Panama and Costa Rica.- Recommendations of the working group on coal and peat.- Geothermal Resources.- Status and geologic setting of geothermal fields in Central America, Mexico, and the Caribbean.- Seismological studies at the Miravalles geothermal project.- Geophysical exploration of Las Pailas geothermal field, Rincon de la Vieja, Guanacaste Province, Costa Rica.- Momotombo geothermal field.- Current status of geothermal activities in Guatemala.- Geothermal prefeasibility studies in Honduras.- Prefeasibility geothermal assessment of Platanares, Department of Copan, Honduras.- An economic prefeasibility study of geothermal energy development at Platanares, Honduras.- Application of geothermal energy to mineral processing: Cyanide heap-leaching of low-grade gold ore.- Environmental impacts associated with geothermal exploration, development, and power generation.- Summary and recommendations of the working group on geothermal resources.- Industrial Minerals and Metallic Mineral Resources.- The outlook for volcanic-hosted gold deposits in the Republic of Costa Rica.- Origin of gold from the Golfo Dulce placer province, southern Costa Rica.- Nickel potential of the Caribbean Plate and adjacent regions.- The Jamaican bauxite industry: Glimpses into its past, present, and future.- Mineral-energy resources in the Dominican Republic.- Selected precious-metal occurrences in the Lesser Antilles.- Biogeochemistry for future mineral resource exploration programs in the Central American-Caribbean region.- Industrial minerals-Key to economic development.- The occurrence, production, and trade of non-metallic industrial minerals in Costa Rica.- A provisional study of Costa Rican diatomites as raw materials for filter-aids.- Summary and recommendations of the minerals working group.- Water Resources.- The distinctive hydrology of tropical islands.- A Quaternary volcanic aquifer system in Central America: Key factors in groundwater potential and protection.- Structure and depositional patterns and their influence on the hydraulic conductivity of fan-deltas in southern Puerto Rico.- Karst localities in Costa Rica and their geologic background.- Summary statement for hydrology session working group.- Geologic Hazards.- Landslides on the Panama Canal.- Geologic hazards in Honduras.- Extent and social-economic significance of slope instability in the island of Hispaniola.- Use of seismic refraction techniques for investigating recent landslides in a tropical rain forest in Puerto Rico.- Report of the working group on natural hazards.

Costa Rica is known as a verdant, tropical paradise with rich rainforests, abundant wildlife, striking mountains and volcanoes, and picturesque beaches. However, the perceived abundance of Costa Rica’s water resources is only true for part of the country. The same geography and climate that bring abundant precipitation to most of southern Costa Rica and its Caribbean coast also leave the northern Pacific province of Guanacaste with substantially less rainfall and even periods of severe drought. This case study focuses on Guanacaste province, which is a major tourist destination as well as one of the country’s most productive agricultural regions. Water from the lush Caribbean slopes of the Lake Arenal region is transported across the continental divide through extensive infrastructure projects. Passing through the semi-arid regions of Guanacaste, hydroelectric power generation, extensive irrigated agriculture, and tourism development use most of the water, supporting a rapidly growing regional economy but leaving increasingly less water for environmental flows. This case study introduces students to “nexus thinking” to explore the multiple and overlapping water, energy, and food (WEF) demands and ecological challenges present in Guanacaste province. Each sector and its interconnections with other sectors are examined in turn through introductory lectures, and enriched by WEF systems thinking activities and class discussions. At the conclusion of this case study curriculum, students will be able to identify and characterize points of intersection, i.e., the nexus, of WEF supply and demand, and trade-offs that exist between WEF resources and biodiversity conservation.

In Guanacaste Province, Costa Rica there are 13 species of Centris (Hymenoptera: Apidae) of which six are referred to as lodger or cavity-nesting bees. Here we describe nests of these six lodger bees, five of which have been found to nest in holes bored into wooden stick “trap nests”. Although the nests of three of these five have been described from Brazil (C. bicornuta, C. analis and C. vittata), the nests of these same species from Guanacaste Province, Costa Rica have some differences that may be due to resource availability. We also describe nests of two additional species of lodger bees (C. nitida and C. trigonoides) from trap nests in Guanacaste. In addition, one nest is described of the remaining lodger bee in Guanacaste (C. lutea) that was fortuitously discovered. We also provide information to help identify nests of each species of lodger Centris from Guanacaste after nests are complete and sometimes after the mature bees have emerged and dispersed.

We examined the structure of the community of epiphytes growing on Crescentia alata trees in Santa Rosa National Park, Costa Rica. Four orchid species were dominant in this community, showing a distinct order of colonization of the calabash trees, with Oncidium cebolleta colonizing first, Encyclia cordigera second, Brassavola nodosa third, and Laelia rubescens fourth. We were unable to find any differentiation of the locations of these species based on the physical characteristics of the sites. It is hypothesized that the colonization pattern observed is due to the quantity of propagules produced by each species. THE NUMBER OF SPECIES found in a community is determined by five major factors-the time for colonization, the distance over which colonizers must travel, the number of potential colonizers, the size of the area to be colonized, and the biotic interactions between colonizers (MacArthur and Wilson 1967). Two approaches have been used to determine the effects of these factors upon the community organization of oceanic islands (e.g., Diamond 1969, Simberloff and Wilson 1969) and a variety of island-like situations (e.g., Vuilleumier 1970, Brown 1971, Culver, Holsinger, and Baroody 1973, Opler 1974). One approach applied to both plant (Johnson, Mason, and Raven 1965) and animal (Hamilton, Barth, and Rubinoff 1964, Wilson and Taylor 1967) communities has been to use correlative techniques to describe the patterns of species number and distribution from to on a large geographical scale. The second approach, applied exclusively to animal communities, has been to manipulate the five factors experimentally (e.g., Simberloff and Wilson 1969, Addicott 1974, Schoener 1974). In this paper we describe the community structure of plants occurring on a local scale using correlative techniques and suggest that this system is one in which experimental work on the relative roles of these five factors in determining community structures may be performed. STUDY AREA AND METHODS Individual Crescentia alata HBK, the calabash tree (Bignoniaceae), constitute an island-like situation for epiphytic plants. The calabash tree is an ideal epiphyte host because its soft, deep bark provides easy anchorage for epiphytes and recess for humus accumulations (Pittendrigh 1948). The study site, a 10 ha calabash orchard in Santa Rosa National Park, Guanacaste Province, Costa Rica, has been described by Janzen et al. (1980). It is surrounded by dry, deciduous thorn-forest, the dominant vegetation type in this region (Holdridge 1967). No individual calabash tree at this site is located more than 100 m from the edge of the thorn-forest. The spherical canopies of the calabash trees range from 0.5 to 7.5 m radius. Since trees are spaced at least 5 m apart, canopies of individuals rarely intertwine. Each calabash tree was considered an island which may be colonized by epiphytic plants: one cactus species, three bromeliads, and five species of orchids. Nomenclature is that of Janzen and Liesner ( 1980). We measured the canopy radius of a randomly chosen calabash tree and recorded the species of epiphytes present (sample sizes are indicated in figure 1). Canopy radius was used because it was both easily measured and accurate with repetition. The existence of a species-area relationship was investigated by means of regression analysis using a logarithmic curve fit after making a scatter plot of the data. To explore the temporal pattern of colonization, we calculated the percent occurrence of each epiphytic species in one-species, two-species, three-species, etc. communities. To study the role of biotic interactions, we contrasted the relative abundance of each epiphytic species on small trees (less than 2 m canopy radius) with that on large trees (greater than 4 m canopy radius). To obtain these numbers, at least two branches were randomly chosen on a minimum of five inBIOTROPICA 14(2): 137-14

Spatial Distribution of Pit-making Ant Lion Larvae (Neuroptera: Myrmeleontidae): Density Effects

Interference competition is ubiquitous in nature. Yet its effects on resource exploitation remain largely unexplored for species that compete for dynamic resources. Here, I present a model of exploitative and interference competition with explicit resource dynamics. The model incorporates both biotic and abiotic resources. It considers interference competition both in the classical sense (i.e. each species suffers a net reduction in per capita growth rate via interference from, and interference on, the other species) and in the broad sense (i.e. each species suffers a net reduction in per capita growth rate via interference from, but can experience an increase in growth rate via interference on, the other species). Coexistence cannot occur under classical interference competition even when the species inferior at resource exploitation is superior at interference. Such a trade-off can, however, change the mechanism of competitive exclusion from dominance by the superior resource exploiter to a priority effect. Now the inferior resource exploiter can exclude the superior resource exploiter provided it has a higher initial abundance. By contrast, when interference is beneficial to the interacting species, coexistence is possible via a trade-off between exploitation and interference. These results hold regardless of whether the resource is biotic or abiotic, indicating that the outcome of exploitative and interference competition does not depend on the exact nature of resource dynamics. The model makes two key predictions. First, species that engage in costly interference mechanisms (e.g. territoriality, overgrowth or undercutting, allelopathy and other forms of chemical competition) should not be able to coexist unless they also engage in beneficial interference mechanisms (e.g. predation or parasitism). Second, exotic invasive species that displace native biota should be superior resource exploiters that have strong interference effects on native species with little or negative cost. The first prediction provides a potential explanation for patterns observed in several natural systems, including plants, aquatic invertebrates and insects. The second prediction is supported by data on invasive plants and vertebrates.

Sustainability of Costa Rica’s water supply under climate change scenarios

Many ecological models treat exploitative competition in isolation from interference competition. Corresponding theory centers around the R* rule, according to which consumers that share a single limiting resource cannot coexist. Here we model motile consumers that directly interfere while handling resources, mechanistically capturing both exploitative and interference competition. Our analytical coexistence conditions show that interference competition readily promotes coexistence. In contrast to previous theory, coexistence does not require intraspecific interference propensities to exceed interspecific interference propensities or for interference behaviors to carry a direct (rather than merely an opportunity) cost. The underlying mechanism of coexistence can resemble the hawk-dove game, the dominance-discovery trade-off (akin to the competition-colonization trade-off), or a novel trade-off we call the "dove-discovery trade-off," depending on parameter values. Competitive exclusion via the R* rule occurs only when differences in exploitative abilities swamp other differences between species, and it occurs more easily when differences in R* reflect different search speeds than when they reflect different handling times. Our model provides a mathematically tractable framework that integrates exploitative and interference competition and synthesizes previous disparate models.

The foraging behavior of three colonies each of two species of leaf-cutting ants (Atta colombica and Atta cephalotes) was studied for a year in the seasonal evergreen forest of Guanacaste Province, Costa Rica. Foraging was predominantly nocturnal during the season and diurnal during the season, probably induced by seasonal changes in rain patterns, insolation, and vegetative cover. Largest quantities of vegetation were harvested at the beginning of the and seasons, in correlation with peaks in the number of plant species producing new leaves or flowering. Colonies harvested new leaves or flowers (especially during the season) as they became available. Though large amounts of mature leaves were available to them throughout the year, during the season the ants cut the mature leaves of a limited number of host plant species. It is proposed that Atta ants select new leaves, flower parts, and mature leaves of certain plant species because of their suitability for the growth of their fungus gardens and therefore the colony. ALTHOUGH THE EFFECTS OF SEASONALITY on temperate-zone biological communities are well known, the consequences of seasonal weather patterns on plants and animals in the tropics have only begun to be documented. Unlike temperate areas, variation in temperature is minimal. Seasonality is primarily manifested by distribution patterns of rainfall, and is expressed in terms of dry and rainy seasons. So-called rain forests usually have short seasons which appear to require little adjustment by organisms. In other areas the season is severe and lasts up to six months. To survive, plants and animals have evolved life-histories which enable them to avoid or even take advantage of the season (Fleming, Hooper, and Wilson 1972; Janzen 1967, 1970, 1973; Janzen and Schoener 1968; Wolf 1970). The season is a particular challenge to colonies of leaf-cutting ants (species of Atta). Leaf-cutters feed upon a fungus which they culture in their nest using leaves and other vegetative matter which they cut as a substrate for the fungus. Since most trees drop their leaves during the season, and herbaceous plants become inactive or die, the amount of potential harvest decreases greatly. As humidity drops and direct insolation increases, not only do conditions for foraging become unfavorable, but it becomes difficult to maintain the proper microclimate within the nest for growth of the fungus. Finally, species of Atta in the Guanacaste Province of Costa Rica mature reproductives during the season which are very large and make substantial demands on the fungus gardens. Mating flights occur at the start of the season (Rockwood 1972, 1973). The season may not be the only difficult season for leaf-cutters. During periods of heavy or continuous rainfall, foraging may be impossible or very difficult for several days. A number of workers are lost during each rainstorm (Rockwood, unpublished field observations; Weber 1972), and whole colonies may be lost during floods (Rockwood 1973). Since previous studies on leaf-cutter foraging have usually been of short duration (Cherrett 1968; Lugo et al. 1973), the effects of seasonality have been only briefly discussed in the literature (Weber 1972; Moser 1963, 1967; Lewis et al. 1974a, 1974b). This paper presents the results of a year's study and examines the effects of seasonality on the foraging of two species of leaf-cutting ants (A. colomnbica Guer. and A. cephalotes L.) in the highly seasonal Guanacaste Province of Costa Rica.

Frugivorous Bats, Seed Shadows, and the Structure of Tropical Forests

Predation on Scheelea Palm Seeds by Bruchid Beetles: Seed Density and Distance from the Parent Palm

Chapter 16 - Miravalles Power Station Guanacaste Province, Costa Rica