Elliot J. Tramer

Bio: Elliot J. Tramer is an academic researcher from University of Toledo. The author has contributed to research in topics: Habitat & Woodland. The author has an hindex of 4, co-authored 5 publications receiving 163 citations.

On Latitudinal Gradients in Avian Diversity

Abstract: Species diversity patterns exist on at least three geographical scales: (1) the diversity in a sample drawn from a single community, often called within-habitat diversity; (2) the diversity occurring in a collection of similar habitats within a given region, here referred to as between-habitat diversity; and (3) the total diversity to be found in all the available habitats in a fairly large geographical area. Whittaker (1960) has termed these categories alpha, beta, and gamma diversity, respectively. The tropics contain more bird species than other regions. This statement seems to apply to diversity on all three geographical scales, although there are some exceptions in the case of alpha diversity; i.e., Cody (1966, 1968) has demonstrated that diversity in American grasslands is a function of vegetation structure, with structurally similar grasslands having similar avian diversities at all latitudes. In

Proportions of Wintering North American Birds in Disturbed and Undisturbed Dry Tropical Habitats

Abstract: Information on the ecology of temperate-zone birds on their tropical wintering grounds is scanty. Qualitative observations indicate that temperate-zone birds are most conspicuous in man-disturbed areas or in woodlands at high elevations. Lowland rain forests apparently contain very few temperate-zone migrants (Brosset 1968; Buechner and Buechner 1970). Willis (1966) and Leck (1972a) have studied the relative impact of migrant and resident birds upon small portions of the available food resources of upland and lowland forests in Panama. Otherwise, quantitative studies of the distribution and ecological importance of temperate-zone migrants in the tropics are virtually nonexistent. In particular, it is not clear whether migrants are scarce in all successionally mature lowland habitats or whether they merely avoid tracts of humid lowland forest. This paper represents a contribution toward answering that particular question.

The gap dynamics of canopy trees of a tsuga canadensis forest community

Abstract: We examined the correlation between canopy gap formation and the initial growth of forest trees by reconstructing the gap history of a Tsuga canadensis (L.) Carr. forest community in southeastern Ohio. We cored each tree (>10 cm dbh, n = 156) in a 40 × 90 m plot and examined the cores for release events, characterized by dramatic increases in radial growth. We identified 80 former gaps in the 79 yr sample period by clustering release events in time and space. Thirteen of the 80 former gaps coincided with the initial growth of trees. These 13 gaps were usually large gaps containing few established trees or gaps undergoing repeat disturbance. Of the 36 trees >10 cm dbh that began growth during the sample, 21 (58%) began growing inside a gap within 6 yr of gap formation-three times the rate predicted by chance (p = 0.001). We also measured the distance in time and space between the first year of growth and the closest canopy gap for each tree. We called the inverse of this measure the gap affinity i...

III. Ecological Observations on Tachysphex pechumani (Hymenoptera: Crabronidae)

Abstract: This study addressed aspects of the ecology of Tachysphex pechumani (antenna-waving wasp), a rare solitary wasp. Wasps nested in compacted sand, pri- marily where vegetative cover was 5-30% and vegetation height was 0.5 to 33 cm. Miltogrammine ? ies and predators presented challenges to wasp success at the study sites. The timing and duration of T. pechumani's breeding season conformed to an apparent abundance peak of acridid grasshopper nymphs used by wasps, based on sweep-net data. Heat increased wasp activity to an upper threshold of 56 °C at the sand surface, at which temperature wasps ceased working. Weak ? ying abilities of both sexes suggested that populations were effectively isolated and vulnerable to habitat loss or fragmentation. Management for wasps should include maintenance of open sites and prohibition of sand disturbance.

LATITUDINAL GRADIENTS OF BIODIVERSITY:Pattern,Process,Scale,and Synthesis

Abstract: ▪ Abstract The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas f...

The Latitudinal Gradient in Geographical Range: How so Many Species Coexist in the Tropics

Abstract: The latitudinal gradient in species richness is paralleled by a latitudinal gradient in geographical-range size called Rapoport's rule. It is suggested that the greater annual range of climatic con...

Scale and species richness: towards a general, hierarchical theory of species diversity

Abstract: Aim Current weaknesses of diversity theory include: a failure to distinguish different biogeographical response variables under the general heading of diversity; and a general failure of ecological theory to deal adequately with geographical scale. Our aim is to articulate the case for a top-down approach to theory building, in which scale is addressed explicitly and in which different response variables are clearly distinguished. Location The article draws upon both theoretical contributions and empirical analyses from all latitudes, focusing on terrestrial ecosystems and with some bias towards (woody) plants. Methods We review current diversity theory and terminology in relation to scale of applicability. As a starting point in developing a general theory, we take the issue of geographical gradients in species richness as a main theme and evaluate the extent to which commonly cited theories are likely to operate at scales from the macro down to the local. Results A degree of confusion surrounds the use of the terms alpha, beta and gamma diversity, and the terms local, landscape and macro-scale are preferred here as a more intuitive framework. The distinction between inventory and differentiation diversity is highlighted as important as, in terms of scale of analysis, are the concepts of focus and extent. The importance of holding area constant in analysis is stressed, as is the notion that different environmental factors exhibit measurable heterogeneity at different scales. Evaluation of several of the most common diversity theories put forward for the grand clines in species richness, indicates that they can be collapsed to dynamic hypotheses based on climate or historical explanations. The importance of the many ecological/ biological mechanisms that have been proposed is evident mainly at local scales of analysis, whilst at the macro-scale they are dependent largely upon climatic controls for their operation. Local communities have often been found not to be saturated, i.e. to be non-equilibrial. This is argued, perhaps counter-intuitively, to be entirely compatible with the persistence through time of macro-scale patterns of richness that are climatically determined. The review also incorporates recent developments in macroecology, Rapoport’s rule, trade-offs, and the importance of isolation, landscape impedance and geometric constraints on richness (the mid-domain effect) in generating richness patterns; highlighting those phenomena that are contributory to the first-order climatic pattern, and those, such as the geometric constraints, that may confound or obscure these patterns. Main conclusions A general theory of diversity must necessarily cover many disparate phenomena, at various scales of analysis, and cannot therefore be expressed in a simple formula, but individual elements of this general theory may be. In particular, it appears possible to capture in a dynamic climate-based model and ‘capacity rule’, the form of the

Biological determinants of species diversity

Abstract: We consider four categories of biological mechanisms of deter- minants which cause and maintain species diversity: niche relations, habitat diver- sity, mass effects and ecological equivalency. Two of these determinants are origi- nal to this paper: mass effect, the establishment of species in sites where they cannot be self-maintaining; and ecological equivalency, the coexistence of species with effectively identical niche and habitat requirements. The mode of action and ecological implications of each biological determinant are discussed using a schematic method for measuring alpha (community), beta (differentiation), and gamma (regional) diversities. The importance of mass effects and ecological equivalency to species richness is documented with several types of field data from Israel and California, U.S.A. Floristic richness and, in particular, the richness of floristic transitions, are discussed and interpreted by use of the biological determinants of diversity. Contact transitions between distinct floras are rich predominantly because of mass effects. Transitions induced by marked environmental changes are rich because of the combined influences of habitat diversity and mass effects. The rate at which species richness increases with sample area is related to the combined effects of all four biological determinants. This complexity explains the failures of simple species-area models. The relative intensity of each determinant is related to area: niche relations are most important at within-community scales, habitat diversity most important at both within-community and land- scape scales, and ecological equivalency most important at regional scales. We suggest that understanding patterns of species diversity will be enhanced by the partitioning of total species richness into the richness caused by each of the four ecologically distinct determinants of diversity.