David L. Pearson

Vertical Stratification of Birds in a Tropical Dry Forest

to birds through the use of quantitative measurements. Stratification as used in this paper does not imply the presence of discrete layers of vegetation, each containing its own distinct and unique fauna. Stratification refers here to the distribution of bird species in relation to the vertical distribution of the foliage. Among the terrestrial animals in which stratification has been investigated are the leaf hoppers (Adams 1941), mosquitoes (Bates 1944; Snow 1955; Haddow et al. 1964), ants (Wilson 1959), spiders (Gibson 1947), various arthropods (Fichter 1939), and mammals (Harrison 1962; Napier 1966). Because of their extreme vertical mobility, birds are especially sensitive to vertical stratification of vegetation and, because of their size and activity, lend themselves well to observation. Studies of bird stratification have been conducted in relation to morphological adaptations (Dilger 1956), social patterns (Moynihan 1962), nest site (Tur6ek 1951), territory maintenance (Kendeigh 1947), predator avoidance (Dunlavy 1935), and food (Colquhoun and Morley 1943; Hartley 1953; Slud 1960; Pielowski 1961; Harrison 1962). Recent studies of species diversity (MacArthur et al. 1962; MacArthur 1964; MacArthur et al. 1966; Recher 1969) have also been concerned with vertical stratification of birds.

THE RELATION OF FOLIAGE COMPLEXITY TO ECOLOGICAL DIVERSITY OF THREE AMAZONIAN BIRD COMMUNITIES

The relation between foliage complexity and bird species diversity has been studied by several investigators. Some (MacArthur and MacArthur 1961, MacArthur et al., 1962, Recher 1969, Karr 1971, Karr and Roth 1971) found that the complexity of the vertical distribution of leaves, as measured by foliage height diversity ( FHD ) , was a good predictor of bird species diversity (BSD). Other investigators (Terborgh 1967, Balda 1969, Lovejoy 1972) have found little correlation between FHD and BSD. BSD, as measured by a statistic derived from information theory, necessitates knowledge of the number of individuals of each species as well as number of species. In mature tropical forests, estimates of population size are difficult because such a large proportion of the bird species do not typically occur in low strata where they can be readily netted and marked. Orians ( 1969) avoided this problem in Costa Rican forests by comparing only the number of bird species (bird species richness, BSR) to FHD. He suggested that the range of resource types permanently above threshold values in tropical forests was the major factor determining bird species richness. However, in all these relations between foliage complexity and the number of bird species inhabiting the foliage, the assumption is made that the community is in an equilibrium or saturated state, that is, new species can enter the community only if they exclude a species already present. The Amazon Basin presents a distinct difficulty in applying FHD-BSD (BSR) correlations. Due to numerous historical changes in climate, continuous forest apparently alternated with forest islands (refugia) surrounded by non-forest vegetation throughout the Pleistocene and post-Pleistocene (Haffer 1969, Vanzolini 1973). It is now generally recognized that islands with similar habitat harbor different numbers of species depending on the area and distance of the island from the mainland species pool (MacArthur and Wilson 1967). Island-like effects are also recognized for continental habitats that occur in patches

A Pantropical Comparison of Bird Community Structure on Six Lowland Forest Sites

Because of the large number of coexisting species, tropical lowland birds probably exhibit the most complex array of ecological interactions of any bird community in the world. Ecological studies in Australia (Kikkawa 1968), Sarawak (Fogden 1972), Malaya (Harrison 1962), Gabon (Brosset 1974), Panama (Karr 1971, Willis 1974), Costa Rica (Orians 1969), Brazil (Lovejoy 1974), and Western Amazonia (Pearson 1971, 1975a, 1977) have begun the work of defining and interpreting general ecological patterns among birds inhabiting these forests. Only within the last few years, however, have theories and generalizations been tested by comparing lowland forest avifaunas between Old World and New World sites (Amadon 1973, Karr 1975, 1976a, 1976b, Karr and James 1975). If similar (or dissimilar) patterns of avian species assemblages relative to foliage, climate, and biotic interactions are found, generalizations about community structure are refined. Using similar-sized study plots in Old World and New World tropical lowland forests, I examine some of the major biotic factors involved in the evolution and present state of avian community structure on these sites by comparing: 1) historical factors and island or island-like effects; 2) seasonality of rainfall and its effect on insect and fruit abundance; 3) habitat heterogeneity; and 4) the influence of avian and non-avian competition.

A test for the adequacy of bioindicator taxa: Are tiger beetles (Coleoptera: Cicindelidae) appropriate indicators for monitoring the degradation of tropical forests in Venezuela?

Abstract Indicator species can be a valuable tool for conservation research. Their use has been divided in two categories: inventory studies and monitoring studies. Tiger beetles (Coleoptera: Cicindelidae) have been identified as appropriate indicators for inventory studies. Here we test their value as potential bioindicators for monitoring habitat degradation in Venezuela. We analyze the general habitat associations of 47 of the 51 species of this insect family known to occur in Venezuela. We also analyze the assemblage patterns of forest-floor dwelling species associated with contiguous forest patches of primary and secondary forest in two sites. At the family level, tiger beetles occupy most of the major habitat types of Venezuela, but individual species tend to be restricted to one or two habitats. Forest-floor species assemblages change significantly with the degree of forest disturbance, and each stage of disturbance is characterized by a particular subset of species. Species associated with intermediate levels of disturbance show larger habitat breadth than those located at the extremes of the spectrum. The results of this study provide evidence that supports the use of tiger beetles as bioindicators for monitoring the degradation and regeneration of tropical forests.

Evidence for food as a limiting resource in the life cycle of tiger beetles (Coleoptera: Cicindelidae)

Using an assemblage of tiger beetles in SE Arizona, USA, as test organisms, the potential for food as a limiting resource in each of the life cycle stages was determined. Laboratory experiments established at what levels food quantity affected adults and larvae. Adult females at low feeding levels produced significantly fewer eggs and larvae than females at high feeding levels. Larvae at low feeding levels took significantly longer to pass through all three larval stages, and their pupae and emergent adults were significantly smaller than those individuals raised at higher feeding levels. Large adults survived longer than small adults when deprived of food. Small adult females produced fewer eggs and larvae at low feeding levels than larger conspecific females at the same feeding levels. Field observations established that the feeding levels of wild larvae and adults in several habitats over five years was lower than the level which produced maximum offspring and survival in the laboratory, except on permanent pond edges where food was abundant. Year to year fluctuations in food availability indicated that food in some habitats was more likely limiting in some years than others.

Two-year study of male orchid bee (Hymenoptera: Apidae: Euglossini) attraction to chemical baits in lowland south-eastern Perú

Machos de abejas de orquideas fueron atraidos y capturados usando atrayentes quimicos parecidos a la fragancia natural de orquideas en sitios de bosque inundable y de tierra firme de la Zona Reservada de Tambopata del sureste del Peru. En total se colectaron 38 especies de abejas atraidas a los atrayentes quimicos en ambos sitios, de las cuales 11 especies fueron significativamente mas comunes en uno de los habitats que en el otro. Se encontro una gran variacion en el numero y tipos de atrayentes quimicos que atrayeron a las abejas. Dos ciclos estacionales en la abundacia de individuos y de especies de abejas fueron detectados usando los atrayentes quimicos. El mayor pico ocurrio al cabo del primer mes de la estacion lluviosa, y el menor durante la estaci´on seca. El tamano individual por especies estuvo asociado con la actividad estacional, aunque otros factores como la fenologia floral y los parasitoides tambien pudieron haber estado involucrados. El numero de especies de abejas encontrado en la Zona Reservada de Tambopata fue similar al encontrado en otras zonas boscosas de centro y este de Brasil, en Costa Rica y Panama. Esta homogeneidad en la riqueza de especies contrasta notablemente con otros grupos de insectos, tales como Odonata, Lepidoptera, Asilidae (Diptera), Tabanidae (Diptera) y Cicindelidae (Coleoptera), en cuanto a que los numeros de especies encontrados en la Zona Reservada de Tambopata son los mayores del mundo, cuando se comparan areas de tamano similar.

SPATIAL MODELING OF BUTTERFLY SPECIES RICHNESS USING TIGER BEETLES (CICINDELIDAE) AS A BIOINDICATOR TAXON

General spatial patterns of species richness can be useful when determining conservation policy. Reliable species distribution data, however, are often rare or limited to a relatively few taxa in many parts of the world, and extensive species inventories tend to be expensive and time consuming. Consequently, the use of a few rigorously selected bioindicator taxa to represent broad-based inventories has been suggested as a viable al- ternative. Because spatial dependencies (spatial autocorrelations) are likely to exist in species richness data, common statistical techniques that assume independence are inap- propriate for making cross-taxa comparisons of species ranges and distributions. We applied geostatistical methods that incorporate spatial dependencies to test the usefulness of a proposed bioindicator, tiger beetles, as a predictor of an unrelated taxon, butterflies, across North America and found a statistically significant relationship. We also showed how the application of statistical procedures that assume independence may be misleading. Finally, we showed how to make spatial predictions of species richness in intermediate areas where no sample species data are available.

Global patterns of tiger beetle species richness (Coleoptera: Cicindelidae) : their use in conservation planning

Abstract The total numbers of tiger beetles species known in 157 countries or subregions in the world are reported and updated, based on both published and unpublished information. Also reported are the numbers and rate of species endemic to each country and the species richness patterns (total surface in km 2 /number of species) of the individual countries considered. The most current publications providing new data or detailing the tiger beetles of a country or political region are provided as references. A comparison is made between the present rank order of the 30 countries with the highest number of recorded tiger beetle species and their rank order in 1992, as well as between currently known species numbers in each of the major biogeographical regions of the world and the numbers registered in 1992. These comparisons show considerable constancy in spatial patterns and reinforce the claim for taxonomic stability of tiger beetles and for their reliability for use, especially by non-scientific decision-makers in conservation policy and management plans.

Seasonal Patterns of Lowland Forest Floor Arthropod Abundance in Southeastern Peru

We conducted a 2-yr study with semi-monthly collections of forest floor arthropods and periodic monitoring of temperature, relative humidity, and soil moisture for three habitats of different soil drainage (terra firme, bamboo and flood plain) at a single site in southeastern Peru. Several diurnal and seasonal patterns of arthropod biomass occurred. All habitats followed parallel and coincident profiles of arthropod biomass through the four major seasons covered by this study (2 yr of wet and dry seasons). Biomass in wet seasons was greater than biomass in dry seasons. The strongest association between arthropod biomass and environmental measures occurred with the contemporary measurement of maximum temperature, but only two habitats, terra firme and bamboo, showed this association. The flood plain habitat showed no detectable associations between arthropod biomass and short term environmental measures. The total number of individual arthropods trapped over the 2 yr was highest for the bamboo habitat and lowest for the flood plain. The smallest overall mean individual mass was in the bamboo habitat. The highest was in the flood plain. The seasonal change in this mean individual mass value was regular for the flood plain, less regular for the bamboo habitat, and irregular for the terra firme forest. Of all the higher arthropod taxa trapped, the Coleoptera, and to a lesser extent the Collembola, exhibited consistent and distinct seasonal patterns. Other taxa such as ants, Diptera, and Orthoptera either showed seasonal patterns in one forest type or none at all.

Recovery Plan for the Endangered Taxonomy Profession

The worldwide decline in taxonomists has a broad impact on biology and society. Learning from general historical patterns of science and understanding social changes caused by growing economies, we propose changes in priorities for training taxonomists to reverse these losses. Academically trained professionals, parataxonomists (local assistants trained by professional biologists), youths educated with an emphasis on natural history, and self-supported expert amateurs are the major sources of taxonomists. Recruiting effort from each category is best determined by public attitudes toward education, as well as the availability of discretionary funds and leisure time. Instead of concentrating on descriptions of species and narrow studies of morphology and DNA, the duties of the few professional taxonomists of the future also will be to use cyberspace and a wide range of skills to recruit, train, and provide direction for expert amateurs, young students, parataxonomists, the general public, and governments.