Showing papers in "American Midland Naturalist in 1972"

Allelopathic Mechanisms of Arctostaphylos glandulosa var. zacaensis

Abstract: Arctostaphylos glandulosa var. zacaensis is a strong dominant of chaparral vegetation on Zaca Ridge in the San Rafael Mountains, California. It occurs in pure stands, sometimes openly spaced with the canopies covering 50 to 75% of the soil surface, or it may form completely closed cover. A barren soil surface, without seed- lings of any species in spite of sufficient light and soil moisture, char- acterizes the stands. Fire or artificial removal of shrubs results in growth of herbs and shrub seedlings until shrub dominance is again established. Detrimental biochemical interference (allelopathy) between Arcto- staphylos and associated plants is involved in this phenomenon. Aqueous leachate from Arctostaphylos foliar branches and from leaf litter is toxic to the growth of annual grasses. The allelopathic constituents leachable from Arctostaphylos plant organs have been identified as arbutin, hydro- quinone, and gallic, protocatechuic, tannic, vanillic, chlorogenic and p-hydroxybenzoic acids. Toxins such as p-hydroxybenzoic, p-coumaric, ferulic, syringic and o-coumaric acids are found in the soils beneath Arctostaphylos shrubs. These toxins can inhibit the germination and suppress the radicle growth of herbaceous plants at concentrations below 400 ppm; e.g., hydroquinone significantly inhibits radicle growth of Avena fatua and Bromus rigidus at a concentration of 50 ppm. Chem- ical constituents present in leaf litter appear to be more leachable after subjection to temperatures up to 160 C-resulting in increases of toxic- ity to herb growth-but are denatured at temperatures above 180 C, with complete loss of toxicity at temperatures above 200 C. Allelopathy

Interspecific Interactions and Limiting Factors of Abundance and Distribution in the Red River Pupfish, Cyprinodon rubrofluviatilis

Abstract: The Red River pupfish, Cyprinodon rubrofluviatilis, was positively associated in occurrence with Fundulus zebrinus, Hybognathus, placitus and Notropis bairdi and negatively associated with a large, predominantly fresh-water (salinity 10 ppt) where few other species occurred. An apparent lack of intrinsic limiting factors was demonstrated. The pupfish seems adapted to a broad ecological niche, creating competition with an array of fresh-water forms that are better adapted to exist in richer faunas. A W to E filter-bridge based on decreasing nurnbers of saline streams seems to be the major factor limiting eastward distribution of the pupfish. Competition and direct behavioral interaction with the pupfish seemed to be major factors depressing F. zebrinus populations in saline waters. A variety of "broad adaptations" of the pupfish may help to confer a numbers advantage over F. zebrinus, magnifying the effects of behavioral interaction. These effects may also help make the pupfish successful at moderate salinities (10-20 ppt) where there are at least 12 potentially competing species.

Fish Species Diversity in Relation to Stream Order and Physicochemical Conditions in the Plum Creek Drainage Basin

Abstract: Water and fish samples were collected at 202 sampling stations throughout the Plum Creek drainage basin in south central Texas between January and April 1968. Fish species diversity (D) was analyzed to determine its relationship to stream order and physicochemical conditions. Fluctuations in physicochemical conditions decreased as stream order increased. Twenty-seven species of fishes were collected. Minimum, maximum and mean numbers of species per stream increased as stream order increased through the first four stream orders and decreased in the fifth-order stream. Mean D values decreased from first-order to secondorder streams, then increased through fourth-order streams; and decreased again in the fifth-order stream. Cumulative D values increased through third-order streams and decreased in fourthand fifth-order streams. In general, D values for adventitious streams correlated with trends in D values for the higher order stream into which the adventitious stream flowed. The decrease in number of species and in species diversity in the fifth-order stream may have been due to migration of fishes into lower order streams for spawning purposes and/or to escape abnormally high water in the fifth-order stream. Also, increased depth and obstacles, such as logs and barbed wire, may have reduced seining efficiency in the fifth-order stream. INTRODUCTION The use of stream classification in biological studies was proposed by Abell (1961). Several methods have been proposed for the classification of streams. Such classifications have been based on varying criteria such as slope and velocity (Huet, 1959); water source (Klugh, 1923); water velocity and nature of substrate (Pearse, 1939); size of drainage basin (Thompson and Hunt, 1930); algal associations (Margalef, 1960); habitat (Odum, 1959); temperature, altitude, rainfall and permanence of water (Usinger, 1963), and stream branching (Horton, 1945). Horton's method of stream classification was used in this study because it reduces the number of environmental variables. Horton designated the smallest unbranched tributary as a first-order stream. The confluence of two first-order streams formed a second-order stream, etc. The order number for any stream was not changed by the entrance of a smaller order stream. Several mathematical expressions or diversity indices have been proposed to measure community structure (Fisher, Corbett and Williams, 1943; Preston, 1948; Simpson, 1949; Margalef, 1951; I Present address: Zoology Department, Arizona State University, Tempe 85281.

Influence of germination date on survival and seed production in a natural population of Leavenworthia stylosa.

Abstract: The influence of germination date in 1970 on survival and seed production was studied in a population of the winter annual Leavenworthia stylosa in the field. The lowest percentage of survival was in plants from July-germinating seeds, while the highest percentage was in plants from seeds that germinated in midto late September and early October. Plants from July-germinating seeds produced more fruits and seeds per plant than plants from seeds that germinated in September or October. However, since a much higher percentage of plants from seeds that germinated in September and October survived, the number of seeds produced per 100 seeds germinated was highest in these plants. The fewest seeds produced per 100 seeds germinated were in plants from seeds that germinated after 4 October.

Differential Predation by Gambusia affinis on the Eggs of Seven Species of Anuran Amphibians

Abstract: Gambusia affinis starved 1 to 4 days and offered normally deposited eggs of Acris crepitans, Bufo valliceps, Gastrophryne olivacea, Hyla chrysoscelis, Pseudacris clarki, Scaphiopus couchi, or Rana pipiens ate a significantly larger number and volume of eggs of those species which usually breed in temporary as opposed to permanent water. The differential predation seemed to result from the larger, firmer egg capsule of the permanent water breeders acting as a mechanical defense mechanism. There was no evidence of chemical repellents or toxicity in the egg species studied.

Ecological Factors Influencing the Breeding Season Schedule of Western Sandpipers (Calidris mauri) in Subarctic Alaska

Abstract: Studies of the breeding system ecology of the Western Sandpiper (Calidris mauri) were conducted in the summers of 19661969 on the Yukon-Kuskokwim Delta in western Alaska. Western Sandpipers arrive as soon as the snow begins to melt, establish territories on heath tundra, pair and nest once. Second nestings are restricted to replacement clutches. As soon as breeding is completed, the adults shift to coastal habitats, begin molt, and by early to mid-July move S on migration. Young mauri follow about 2 to 3 weeks later. After their arrival on Pacific coast feeding areas, the adults continue their prebasic molt, completing it by late October. The single nesting and early departure of Western Sandpipers from the breeding areas are related to a decreasing food supply in an otherwise favorable environment. The only other congener sympatric with mauri on the Delta, C. alfpina, follows an identical breeding schedule, but remains longer in the N, occupying riverbank and intertidal habitats, and completes its molt before migrating S in late September. This extended residence of alpina in Alaska is possible because it is able to exploit marine invertebrates there during late summer, whereas mauri apparently is not. Therefore, the changes in food abundance near the nesting areas and the lack of suitable food supply in midsummer are the primary factors influencing the scheduling of breeding season events in Western Sandpiper populations.

Aspects of Behavioral Ecology of Red-Headed and Red-Bellied Woodpeckers

Abstract: Habitat utilization of red-headed and red-bellied woodpeckers was compared. Since these species are sympatric over much of their range, an examination was made of their segregation and overlap in vertical distribution, and a temporal and spatial analysis was made of their foraging behavior, nesting habits and aggression patterns. Greatest niche segregation was found during the breeding seascn, particularly in choice of nest site and territory use. During the nonbreeding season, interspecific aggression between the two species increased as they overlapped more in various spatial and behavioral parameters. INTRODUCTION Red-headed woodpeckers (Melanerpes erythrocephalus) and redbellied woodpeckers (Centurus carolinus) are structurally and taxonomically similar species, and exist sympatrically over much of the eastern United States. This study was undertaken to compare the activities of these species and, specifically, to study the spatial, temporal and behavioral segregation that permits their coexistence. An analysis of habitat utilization was undertaken to enumerate environmental factors and more importantly, to quantify their relative importance or degree of utilization. Similar studies of patterns of habitat utilization, particularly in terms of foraging strategies, have been made in recent years by Hartley (1953), Gibb (1954), MacArthur (1958), Root (1967), Morse (1967, 1968), Sturman (1968), Jackson (1970) and Willson (1970). Temporal segregation of the two species was studied by constructing time budgets for each "morph"-red-heads, male red-bellies and female red-bellies-and investigating how partitioning of time into various behavior patterns was modified by diurnal and seasonal environmental changes. Orians (1961), Verbeek (1964), Verner (1965 ), Smith (1968), and Schartz and Zimmerman (1971) have discussed the importance of maintaining an efficient time budget in terms of reproduction and survival for several species. METHODS AND STUDY AREAS Methods.-In order to observe seasonal changes in the behavioral ecology of red-headed and red-bellied woodpeckers, this study was conducted during an entire year; however, the seasonal fluctuation of local woodpecker populations necessitated changing woods each season and decreased the reliability of seasonal comparisons. Data were continuously recorded in the field, using a time base provided by a portable, electronic metronome that was set to emit tones through an 1 Current address: 200 North Smith Road, Bloomington, Indiana 47401.

The Benthic Fauna in Four Small Southern Appalachian Streams

Abstract: Monthly quantitative samples of benthic organisms were collected from streams in four different watersheds from August 1968 through July 1969. Each of the watersheds supports one of the following types of vegetation: old-field succession, hardwood forest, white pine forest with a few hardwoods, coppice forest. The kinds of organisms in the four streams were generally similar but their relative importance varied significantly. A Duncan's multiple-range test showed significant differences in the numbers of most taxa among the watersheds. The old-field stream had the greatest abundance while the coppice stream had the greatest standing crop biomass. The white pine stream had lowest standing crops of both numbers and biomass. Most of the differences among watersheds were attributed to different inputs of allochthonous detritus.

Effect of Deficiencies of Nitrogen, Potassium and Sulfur on Chlorogenic Acids and Scopolin in Sunflower

Abstract: Helianthus annuus, an important species in the first stage of succession in infertile old-fields in Oklahoma and Kansas, was previously found to produce chlorogenic acid and scopolin which are inhibitory to many plants of the same successional stage. Consequently, investigations were made to determine effects of age and fertility on concentrations of those phenolics and related compounds in H. annuus. Concentrations of chlorogenic acid in control leaves of Helianthus annuus increased with age of the plant, and also in stems up to the 4th week of experimentation. Scopolin concentrations increased with age in old leaves and remained stable in the stems during most of the experimental treatment. Scopolin was not present in measurable amounts in young leaves or in roots. Chlorogenic acid concentrations were generally significantly higher in stems and leaves of mineral-deficient plants than in controls. Except for nitrogen-deficient plants, young leaves accumulated greater concentrations of chlorogenic acids than old leaves. Concentrations in roots were variable and no definite trends occurred. Band-510 (4-0-caffeoylquinic acid) and neochlorogenic acid were present in all plant tissues but not at all sampling times. Concentrations of both were generally higher in potassium-deficient stems, nitrogendeficient old leaves and stems, and sulfur-deficient old leaves, young leaves and stems than in controls. In addition neochlorogenic acid was generally higher in potassium-deficient young leaves than in controls. Band-510 was usually lower in concentration in nitrogen-deficient young leaves and roots, and neochlorogenic acid was generally lower in potassium-deficient roots than in controls. The concentrations of scopolin increased considerably, compared to the amounts in controls, in potassium-deficient old leaves, young leaves and stems during the last 3 weeks of treatment. In sulfur-deficient stems the scopolin concentration decreased with age but was generally not significantly different from the concentration in controls. Nitrogen deficiency decreased the concentration of scopolin in stems but had no other effects. The increased concentration of chlorogenic acids in sunflower with increase in age of plants and with mineral deficiencies probably increases the allelopathic effects of that species in the first stage of succession in infertile old-fields.

A revision of Echinochloa in the United States

Abstract: Seven U. S. species of Echinochloa are recognized, five indigenous (E. polystachya, E. muricata, E. paludigena, E. walteri, E. crus-pavonis) and two adventive or introduced (E. crusgalli and E. colonum). The indigenous species are all tetraploid (2n9= 36), whereas E. crusgalli and E. colonum appear to be represented in the United States only by hexaploid (2n54) plants. A possible exception is E. crusgalli var. oryzicola for which USA counts have not been obtained, but the two published records are of tetraploid plants. Widespread and frequent throughout much of the USA are E. crusgalli and E. muricata, two species that were treated as a single species (E. crusgalli) by Hitchcock but which are distinguished by reliable morphological characters. INTRODUCTION Echinochloa is present throughout the tropical and temperate regions: of the world. Hitchcock (1936) placed the number of species at 15; Swallen (1955), Yabuno, (1962) and Gould (1968a) estimated approximately 20, and Shaw (1966) indicated 30. However, in 1966, Yabuno revised hig species estimate to 13. Morphological, cytological, embryological and anatomical features of Echinochloa are similar to those of Panicum, and this explains why the species included in Echinochloa were first placed in Panicum. Strikingly different monographic treatments of the North American species of Echinochloa were published by Hitchcock (1920) and Wiegand (1921). Hitchcock recognized seven North American species, four native, two introduced, and one, E. crusgalli, with both native and introduced or adventive varieties. Wiegand recognized 12 species, nine native and three introduced. He also listed seven varieties for the native species in addition to the typical varieties. 'Species delimitations in our treatment are in general agreement with those of 'Chase in Hitchcock's Manual (1951) except for the reclassification of a large proportion of the plants referred by her to Echinochloa crusgalli. Echinochloa crusgalli and E. muricata have been the most controversial species in the genus. Some authors have contended that crusgalli and muricata constitute one species while others have proposed five distinct species. As concluded by Fernald (1915), Wiegand (1921), Fairbrothers (1952), Ali (1968) and others, both native and adventive populations comprise the North American "barnyard grass" complex included by Hitchcock (1920, 1935) and Chase in Hitchcock's Manual (1951) in the species E. crusgalli. As delimited in the present treatment, the native plants are referrable to E. muricata (Beauv.) Fernald var. muricata, E. muricata var. microstachya Wiegand, and E. crus-pavonis var. macera. All native plants are tetraploid (2n= 36), and these commonly grow i Technical Bulletin No. T.A. 8804, Texas Agricultural Experiment Station, College Station 77843.

Aspects of the Ecology of a Sonoran Desert Population of the Western Banded Gecko, Coleonyx variegatus (Sauria, Eublepharinae)

Abstract: A population of Coleonyx variegatus was studied during 1965-66 at a low-altitude Sonoran Desert mountain range. Seasonal activity extended from April through October, with intermittent activity during winter months. Mean distances between capture points ranged from 10.9 m for immature males to 43.7 m for immature females. Frequency of broken or regenerated tails was positively correlated with body length; in the largest size group 74.1 % were broken. Growth rates varied from 9.7 mm/month in immature lizards to no discernible growth for large adults. Gravid females were found from April through September, occurring most frequently in May and June. Two or more clutches of two eggs each are produced annually. Males had enlarged testes from April through August. Hatchlings appeared from July through November. Many individuals of both sexes reached sexual maturity when less than 1 year old, but some did not mature until their 2nd year. Males were captured more frequently than females from January through May, perhaps indicating more extensive wanderings. An estimated 66% of the population was reproductive in May, the height of the breeding season. Among five study areas, abundance was highest on a S-facing slope. Population density in one area was estimated to be 12-25 geckos/ha. INTRODUCTION The lizard subfamily Eublepharinae (family Gekkonidae) contains five genera: Aeluroscalabates Gunther, an arboreal forest gecko found in Indonesia; Eublepharis Gray, a terrestrial desert genus occurring in southwestern Asia, Hainan and Loo-Choo islands; Hemitheconyx Stejneger and Holodactylus Boettger, ground-dwelling desert genera found in West Africa and Somaliland; and Coleonyx Gray, a terrestrial genus distributed from southwestern United States to Central America (Kluge, 1967). Kluge (1962) divided Coleonyx into northern (brevis and variegatus) and southern (elegans and mitratus) species groups. Little is known of the life history of any eublepharine gecko. Inger and Greenberg (1966) described aspects of reproduction of Aeluroscalabates felinus in Borneo, but knowledge of the other Old World genera is restricted to a few scattered observations. Coleonyx has been the most intensively studied genus in the subfamily, but most published life history data are based on captive individuals of C. variegatus or miscellaneous field observations. Dixon (1970a, b, c) listed pertinent literature for Coteonyx, C. brevis and C. variegatus. In spite of the long reference list for eublepharine geckos, there has been no population study of any species; life histories of all members of the subfamily remain relatively unknown. A field study of the western banded gecko (Coleonyx variegatus Baird) was conducted at Phoenix South Mountain Park, Maricopa Co., Ariz., during 1965-66. Turner (1962), Williams (1968, 1970) and Hadley (1970) studied arthropods in the same general vicinity.

The Effects of Grazing by Snails on Community Structure of Periphyton in Laboratory Streams

Abstract: The effects of grazing by snails on community structure of periphyton were studied in laboratory streams. The levels of grazing studied caused slight reduction in standing crop, significant increase in chlorophyll a concentration, reduction in pigment diversity and no effect on species diversity. Grazing did not affect instantaneous rates of accumulation of oven-dry weight, ash-free weight, or ash-free percentage of oven-dry weight. Pigment diversity and species diversity were positively correlated. Oven-dry weight per unit chlorophyll a was reduced by grazing, but ash-free weight per unit chlorophyll a was not affected. Grazing had no effect on the percentage of chlorophyll a in ash-free weight.

A Vegetational Description of a Mid-Missouri Forest Using Gradient Analysis Techniques

Abstract: Several gradient analytical techniques were used to pro- vide rigorous ecological description of 75 forest plots in the Ashland Wild- life Area (AWA), Missouri. Tetrachoric correlation was used to construct a comparison matrix of the tree species. Gradients were then extracted from the comparison matrix using a principal components analysis. The model produced from the principal components analysis displayed vege- tational patterns evident in the area. The species principal component values were weighted, independently, by density, basal area and impor- tance value, to position the plots along the dimensions of the model. All three weighting variables yielded highly similar plot positions along a theoretical moisture gradient. Application of differential weighting to quantify direction and rate of compositional change, expressed as a vector, provided evidence that the forest composition of the Ashland Wildlife Area is becoming more mesic. A number of environmental variables were used as the third dimension on graphs of the plot posi- tions. Several environmental variables bear a definite relationship to species compositional patterns. A principal components model of the sapling and shrub species shows a few species shifting from xeric to more mesic conditions as compared to the tree model. This is verified by com- paring sapling densities of the dominant species. Acer saccharum is the leading sapling dominant in the Ashland Wildlife Area; and it appears likely that this species will eventually come to dominate the overstory of the present oak forests.

The Swamp Rabbit (Sylvilagus aquaticus) in Indiana

Abstract: Swamp-rabbit (Sylvilagus aquaticus) distribution, habitat, population characters and behavioral traits were studied in Indiana in 1968-69. Swamp rabbits were found in 25 swampy forested tracts in the six most southwestern counties. All sites were within the Southern Swamp Forest type, with the most northern site about 18 km S of Vincennes. The most frequently used winter foods were cross vine (Bignonia capreolata), sedges (Carex spp.) and poison ivy (Rhus radicans). Body characters of swamp rabbits from Indiana, Illinois, Missouri and Georgia probably follow Bergmann's Rule, but the data are not conclusive. Approximately 4050 ha of habitat remain from a presettlement area of 40,500 ha. The state population estimate was 1,000, with a probable annual successful natality of 50-55%, and an annual hunter kill of 40-45%. The mean home range on Cane Ridge was 4.4 ha, with a population density of one rabbit per 2.4 ha. Permanent nonrandom log transects can probablv be used to (1) estimate hunter kill in per cent of the population, ( 2) reveal long-term population trends, and (3) when combined with hunter rabbit-kill data, to calculate the rabbit density. INTRODUCTION The first positively identified swamp rabbits (Syivilagus aquaticus) from Indiana were reported in 1930 when four were shot in the canebrakes in Point Township, Posev Co. (Harrison and Hickie, 1931). Lyon (1936) published records for Posey and Warrick counties. In 1959, Kirkpatrick (1961) collected a swamp rabbit from Spencer Co. Specimens were obtained by T. Tichenor in the Broad Pond Swamp in Gibson Co. in 1966. In 1967, a cooperative program was established between Purdue University's Department of Forestry and Conservation and the Indiana Division of Fish and Game to determine the status of the swamp rabbit in Indiana. The objectives, of the study were: (1) to delineate the distribution of the swamp rabbit in Indiana, (2) to obtain population data and (3) to gain a more complete ecological perspective of the species.

The Origin of Houses in the Okefenokee Prairies

Abstract: About 15% of the 412,000-acre Okefenokee Swamp is open marsh dotted with various-sized clumps of trees and shrubs known locally as "houses." These houses originate from partially floating masses of peat which are called "batteries." Batteries are of three types. In one type a mass of peat breaks loose from the underlying peat bed and floats freely on the water surface. A second type is that in which an upper layer of peat partially separates from the peat bed and forms a bulge above the water surface. A third type results from bits of loose floating peat and other debris drifting to the edge of a pond or a lake and accumulating until a base forms for the growth of vegetation. The upper surface of these batteries, being at or slightly above the water surface, provides habitat for a greater variety and more profuse growth of plants than does the open marsh. Ultimately woody growth encroaches, thus forming the clumps of trees known as houses.

Habitat restriction in Giant Sequoia: the environmental control of grove boundaries.

Abstract: Present boundaries of the giant sequoia groves of the Sierra Nevada appear to be remarkably stable. The maintenance of grove boundaries is controlled by an interaction of moisture availability, temperature and the tolerances of the seedling stage of giant sequoia. Measurements of soil-moisture stress and water-potential measurements of coniferous species within the Giant Forest, the largest extant giant sequoia grove, indicate that conditions of water availability for plant growth are more favorable inside the grove than outside. Although some soils outside the grove did not reach the permanent wilting point during the summer of 1968, pressure-bomb studies have shown that significant differences in water stress do occur between grove and nongrove habitats. High levels of soil moisture appear to be maintained within the Giant Forest during the dry summer months by the input of ground water whose hypothetical origin is summer thunderstorms in the High Sierra. This ground water percolates down to lower elevations where it appears in the soil profile of the grove. Outside of the grove, there is little input of ground water during the summer months and soil moisture remains low in late summer. This percolation of highelevation ground water into the groves during the dry summer months may be the key to the continued existence of the Giant Forest.

Mound Development by a Pioneer Population of the Banner-Tailed Kangaroo Rat, Dipodomys spectabilis baileyi Goldman, in Eastern New Mexico

Abstract: The development stages of two den complexes of Dipodomys spectabilis baileyi Goldman were observed from July 1966 to November 1970 in eastern New Mexico. Each mound was observed to develop from a single burrow. The area around the initial burrow was cleared of vegetation, the number of burrow entrances increased, and characteristic mounds developed after a period of 23 to 30 months. Removal of one D. s. baileyi from each mound resulted in noticeable degradation by weathering within 1 month and very marked deterioration within 1 year. Blackwater Draw, a broad, sandy-soiled drainage basin. extending eastward across Roosevelt Co., New Mexico, into Texas, is indicated as the route of dispersal for this species.

On Objective Functions of Phytosociological Resemblance

Abstract: Different objective functions are reviewed with regard to their intrinsic properties and generic relationshiDs as they relate to the measurement of phytosociological resemblance. These functions may take the form of a distance, probability, or information. Functions of these kinds are best conceived by the phytosociologist as abstractions which are meaningful only when placed within the bounds of a given sample space. In such a space the phytosociological objects, such as the individual stands of vegetation, are represented as points whose relative spatial placement is determined by the resemblance function. The spatial configuration of points, i.e., the manner of their placement relative to one another in sample space, is referred to as sample structure in the present paper. The first part of the paper includes a discussion of the sample space and sample structure, and it also deals with the concept of stochastic and deterministic resemblance functions. This is followed by the description of the different variants of distance, a probability-type coefficient, and several information theory functions. While the distance functions here represent metric divergences, which define the relative placement of objects in sample space, a probability-type coefficient, as a probability divergence, expresses the likelihood that given objects will be more dis-

Culture an'd Larval Behavior of Photurid Fireflies

Abstract: Techniques are presented for collecting firefly larvae and for laboratory cultures providing adults in any month of the year. Tem- peratures below about 16 C prevent pupation, and constant darkness causes 90% inhibition of pupation and delays the adult eclosions that do occur. Larval body-weight frequency distributions for nine field samples, plus laboratory and field observations, suggest a 2-year life cycle for the species studied. Some aspects of larval behavior are dis- cussed in relation to light emission.

Winter Coexistence of Clethrionomys gapperi and Microtus pennsylvanicus in a Grassland Habitat

Abstract: In October 1969 numerous red-backed voles (Clethrionomys gapperi) immigrated into a field normally occupied mainly by meadow voles (Microtus pennsylvanicus), established home ranges, and survived well until February 1970, when they began to disappear. Both species were at peak populations during the winter of 1969-70, in the Pinawa, Manitoba, area. The times of immigration and emigration corresponded with the end and onset of reproductive activity in the resident Microtus. It is suggested that Clethrionomys are normally excluded from grassland habitats by reproductively active and aggressive Microtus. In winter M. pennsylvanicus is less aggressive and the species can coexist. Winter colonization, allowed by the breakdown of habitat separation due to aggressive behavior, may explain the ubiquitous presence of forest animals in the isolated groves which are common in the aspen parkland. INTRODUCTION The mechanisms which preserve habitat separation between meadow voles (Microtus) and red-backed voles (Clethrionomys) have been the subject of several recent studies (Clough, 1964; Cameron, 1964; Morris, 1969; Grant, 1969, 1970a, 1970b), but are still incompletely understood (Clough, 1964; Morris, 1969). This paper describes a temporary breakdown of habitat separation, and discusses the implications of this event to an understanding of the mechanisms which normally preserve habitat separation.

Pollen analysis of a central texas bog

Abstract: Hershop Bog, a domed-quaking peat bog, 5.4 m deep located near Ottine, Gonzales Co., Texas, has provided a pollen record dating to 12,000 BP. The pollen profile has been interpreted to indicate a definite change about 10,000 BP in the upland regional vegetation from an oak-parkland to an oak savannah, reflecting a climatic change from mesic to less mesic. After 10,000 BP, pollen of a species of Betula is no longer present in the profile, and its loss parallels a definite reduction in total arboreal pollen. Picea pollen present at 10,000-12,000 BP time interval in bogs 48 km to, the NE is absent from Hershop Bog, suggesting that the southern limit of spruce in central Texas was N of the Hershop Bog area. INTRODUCTION Late glacial and postglacial pollen records from Texas are infrequent and those which have been published are difficult to correlate because of geographic separation, differences in environments of deposition and lack of radiocarbon dating in the earlier studies. This lack of adequate palynological data has limited our understanding of late and postglacial vegetations and climates in Texas and their influences on early man, and the past and present distributions of animals and plants. An intensive search for additional pollen sites was initiated in 1967. Several archeological sites, including Bonfire Rock Shelter which has sediments dating to the late glacial, and two peat bogs deep enough to warrant study were found. Hershop Bog, the subject of this paper, is in S-central Texas about 1 mile S of the Soefje Bog studied by Graham and Heimsch (1960). Published pollen records have come from peat bogs, archeological sites and playa lake sediments. The earliest are those of Potzger and Tharp (1943, 1947, 1954) on undated peat bogs from E-central Texas. They identified pollen of Picea, Abies, Betula, Tilia, Acer, Castanea, Corylus and Alnus in the lowermost strata of Patschke Bog in Lee Co,. These pollen types were interpreted to indicate a boreal forest vegetation and a cool moist climate during the late glacial period of Texas. On the basis of the total profile, Potzger and Tharp proposed a four-stage post full-glacial climatic sequence (cool-moist, warm-dry, warm-moist and warm-dry) for central Texas. Additional profiles from the nearby Gause and Franklin bogs were interpreted by Potzger and Tharp (1954) to substantiate the climatic sequence derived from the earlier study of Patschke Bog.

Cluster Analysis of Data from Limnological Surveys of the Upper Potomac River

Abstract: In a study of data from limnological surveys of a portion of the upper Potomac River, cluster analysis and correlation coefficients have shown that redundancy exists in the data. Aquatic insects and, to a lesser extent, diatoms have distributions that most nearly represent the total biota. It is suggested that the study of these two groups and the exclusion of other algae, protozoans, other invertebrates and fish would significantly reduce the cost of such surveys without appreciably affecting the information they provide. INTRODUCTION Limnological surveys of the kind reported by Patrick, Cairns and Roback (1967) of the Savannah River between South Carolina and Georgia have typically involved study by a team of specialists of almost the entire biota, including diatoms and other algae, protozoans, aquatic insects, other invertebrates and fish, from several stations for each of several years. Such surveys are usually used to monitor a source of potential pollution, such as thermal pollution from the outfall of a power station. Because the results of limnological surveys may be used as evidence in the courts, it is imperative that standard methods be used both for the surveys themselves and for their interpretation (Patrick, 1949). Nevertheless, it is clear that a great deal of redundancy may be introduced by the study of the entire biota, so that the cost of limnological surveys could be reduced if only those groups of organisms were selected for study that have distributions that are highly correlated with other major groups. The purpose of this research was to investigate the hypothesis that data from limnological surveys typically include a great deal of redundancy. In this paper we show that this isi true, we present the results of Q-mode cluster analysis using several groups of organisms, and we indicate which groups of organisms are likely to best summarize the distribution of the total biota. We have selected for study data from limnological surveys of the upper Potomac River directed by Dr. Ruth Patrick. Cairns, Kaesler and several co-authors have studied distribution of the several groups of organisms and have described in detail the sampling procedures and methods of analysis used (Cairns and Kaesler, 1969; Roback, Cairns and Kaesler, 1969; Cairns, Kaesler and Patrick, 1970; Cairns and Kaesler, 1971; and Kaesler, Cairns and Bates,, 1971). Data from the surveys are on file as follows: protozoans, National Auxiliary Publications Service No. 00362 and No. 89021; insects, 1National Auxiliary Publications Service, 22 West 34th Street, New York, N.Y. 10001, U.S.A. Microfiche copies $1.00 per set; 8 x 11 inch photo copies $3.00 per set.

Derivation of Species Succession Vectors

Abstract: By placing size classes of individual species in sequence within a reference ordination model, a series of succession vectors is produced. These vectors show how the pattern of association of a given species changes in relation to growth. Analysis of data from 879 forest plots in northeastern Wisconsin shows some tree species entering into successional sequences in accordance with existing theory. Other species, particularly those of the xeric sand plains and poorly drained sites, are apparently as self-perpetuating as the traditional "climax" species of mesic sites. INTRODUCTION Association among biological species is the result of an interwoven complex of historical, environmental and biotic factors. The usual procedure in phytosociological ordination is to sample a number of plots and, on the basis of the correspondence of occurrence or importance, to produce an arrangement of the stands within an abstract model. The hyperspace of this model is a representation of the variability of vegetation in the landscape in that the distance between stands in the ordination is approximately proportional to their overall ecological dissimilarity. Where species rather than stands are ordered, as in this study, the distance between species in the ordination hyperspace is a measure of the dissimilarity of their pattern of occurrence or importance over the area sampled. In vegetation such as grasslands or marshes, composed of shortlived species, the relationship between distance in the ordination model and ecological similarity, and thus pattern in the landscape, is quite direct. However, in forests, where an age profile of two or more centuries is commonly included within a single sample plot, the relationship between ordination distance and ecology of the species is much more complicated. Two tree species may be significantly associated even though their entry into the sample plot has taken place at different times under distinctly different environmental conditions. Although these differences are often apparent from the age and size structure of the two populations, this information is lost when importance (i.e., occurrence, density, frequency, biomass, etc.) is the only measure used in constructing the ordination. An example of association of species having differing environmental requirements is found in the mixed pine-hardwood forests of the northern Great Lakes region. Here, Pinus strobus isi often quite highly associated with the more mesic Tsuga canadensis, Betula lutea and Acer saccharum in old-growth stands. There is usually no evidence of 1 Present address: Department of Ecology, San Diego State University, San Diego, California 92110.

A Method for Exact Testing of 2X2, 2X3, 3X3, and Other Contingency Tables, Employing Binomial Coefficients

Abstract: Procedures for the computation of the Fisher exact test of 2X2 tables by means of the alignment and multiplication of appropri- ate binomial coefficients are reviewed and extended to larger tables. The 2X3 table originally employed by Freeman and Halton to illustrate their extension of the Fisher exact test principle is reworked with bi- nomial coefficients, their result being obtained with substantially less effort. An example of the application of the method to a 3X3 table is also provided, and the procedures by which the method of binomial co- efficients may be extended to 2XC and RXC tables are outlined.

Altitudinal Zonation of Chipmunks (Eutamias): Adaptations to Aridity and High Temperature'

Abstract: Fecal, urinary and evaporative water losses were mea- sured at 15 C, 50-75% relative humidity for four species of western chipmunks (Eutamias) which are contiguously allopatric and alti- tudinally zoned on the eastern slope of the Sierra Nevada, California. Evaporative loss and hyperthermia were also studied for acute exposures to 25, 35 and 40 C. Differences in total water budgets, calculated for 35 C and 11% relative humidity are not important in determining the lines of contact, starting from the alpine and descending toward the desert, between E. alpinus and E. speciosus or between E. speciosus and E. amoenus. But they may play a role in preventing E. am,oenus from colonizing the desert sagebrush habitat occupied by E. minimus. E. minimus can be active in the open areas of the hot, arid sagebrush desert by minimizing evaporative water loss and tolerating increased body heat content; this species frequently retreats to, its burrows to un- load excess body heat. When large patches of shade are available from pifion pines the aggressively dominant E. amoenus can occupy the sage- brush habitat. Hence, in the field area of this study the line of contact between E. amoenus and E. minimus coincides with the lower limits of the pifion pine.

The Life History of Procambarus hayi

Abstract: The- life history of Procambarus hayi (Faxon) was studied for 2 years near State College, Miss. Seasonal and temporal changes within the populations were determined from periodic field samples and laboratory observations. The known geographic range of the species was defined and its preference for lentic and sluggish lotic waters was in- dicated. P. hayi bred in spring and summer and oviposited and hatched from late summer to autumn. A study of monthly ovarian egg development confirmed the period of oviposition. Oviposition and the first juvenile molts occurred within the burrow. Upon reaching the 3rd instar, juveniles became independent of the female and entered the open water from mid-September through Novem- ber. Most became adults during May and June of the following year after attaining a carapace length of 36.0 to 45.0 mm. Most crawfish reproduced 8 to 10 months after hatching, lived to reproduce again the following summer at 18 to 20 months, then died during the following autumn at approximately 24 months. A few apparently reproduced a third time and died after 36 months.