Novlttates PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET NEW YORK, N.Y

Novlttates PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET NEW YORK, N.Y

AMERICAN MUSEUM Novlttates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET NEW YORK, N.Y. 10024 U.S.A. NUMBER 2604 AUGUST 19, 1976 WILLIS J. GERTSCH AND SUSAN E. RIECHERT The Spatial and Temporal Partitioning of a Desert Spider Community, With Descriptions of New Species v " : 4>0Xvatqwqrr wfm? > w :g0 I AMERICAN MUSEUM Novitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2604, pp. 1-25, figs. 1-41, table 1 August 19, 1976 The Spatial and Temporal Partitioning of a Desert Spider Community, With Descriptions of New Species WILLIS J. GERTSCH1 AND SUSAN E. RIECHERT2 ABSTRACT The habitat of desert spiders is characterized, seasonal considerations. The remaining groups and multivariate analyses are used to assess inter- consist of species that exhibit preferences toward specific relations among spiders inhabiting a specific habitat features (grasses and shrubs). Recent lava bed area in south-central New In most, but not all cases, closely related spe- Mexico. cies are separated by spatial and temporal differ- General habitat types (i.e., lava bed, mixed ences. Factors of the physical environment are grassland, and rangeland) account for most of the thought to allow the coexistence of congeneric variability in species dispersion. The majority of Pellenes (Salticidae) and Dictyna (Dictynidae) the 90 species present in the area frequented the for which no niche partitioning is apparent. lava bed; the fewest species occupied the mixed Nine new species are described from the study grassland habitat bordering the flow. The spider area: Zorocrates karli, Theridion leviorum, Dras- community can be readily divided into eight syllus mumai, Zelotes chicano, Zelotes anglo, groups within which frequent interaction is Phidippus reederi, Phidippus volcanus, Metaphi- expected. Five of these groups are distinguished dippus shaferi, and Sitticus juniperi. by general habitat association and temporal and INTRODUCTION Ecological studies of spider communities are In the present paper we use multivariate confronted with problems concerning adequate analyses to describe a spider community in terms sampling across taxonomic lines and identifli- of the Hutchinsonian niche (differentiation in cation of an incompletely known fauna. With the habitat [Grinnel, 1924] and in diumal and exception of a few papers (Tretzel, 1955; seasonal activity pattems). The study was initi- Duffey, 1962 a, b, 1968; Luczak, 1963, 1966; ated to place a local population of the funnel- Almquist, 1973a, b; Van der Aart, 1973; web spider Agelenopsis aperta (Gertsch) in the Schaefer, 1972), our knowledge of spider com- context of its biotic environment. However, it munities is largely limited to species checklists has proven useful in the direction it provides for with accompanying notes on relative abundance future study of community structure. Principal and associated habitats. components and cluster analyses can be applied 1Curator Emeritus, Department of Entomology, the American Museum of Natural History, New York, N.Y. 2Assistant Professor of Zoology, Department of Zoology, University of Tennessee, Knoxville, Tennessee 37916. Copyright © The American Museum of Natural History 1976 ISSN 00003-00082 / Price $1.90 2 AMERICAN MUSEUM NOVITATES NO. 2604 to data sets consisting of both quantitative and coln County, New Mexico (Gallacher Cattle qualitative observations, alleviating some of the Corporation; Robert M. Shafer Ranch, T6S, biases encountered when using one sampling RiOE, Alt. 5400'; fig. 1). One study area on the technique for all groups. lava bed, one on the mixed grassland bordering The paper is divided into two sections. The the flow, and a third on surrounding rangeland first section deals with the spider community of (fig. 2). the lava bed area: where various members fit in Lava Study Area. The lava study area is repre- an environmental context and in relation to one sentative of the malpais formation that is another. In the second section we describe those believed to have been extruded around 1000 new species which are supplementary to pub- years ago (Weber, 1964). It is barren over much lished revisional studies or which will not be dealt of its surface and marked by ropy corrugations, with in revisions in the forseeable future. sink holes, and pressure ridges. Local concen- trations of shrubs occur along the flow margins ACKNOWLEDGMENTS and where cracks and crevices have permitted collection of wind-blown soil and moisture. The The field work was completed on the Robert specific plot used in this study (figs. 1 and 2), a M. Shafer Ranch, Gallacher Cattle Corporation, north-facing slope on a sunken plateau between Carrizozo, New Mexico. We are grateful for the two pressure ridges, was selected because of its cooperation of this family. We thank Ms. Cheryl high concentration of spiders. Total vegetative Hughes of the Zoology Department of the Uni- cover for the area was 78.3 percent, probably versity of Wisconsin for preparation of the draw- much higher than the average lava bed sample. ings and Dr. William G. Reeder of the same The shrub Fallugia paradoxa (D. Dondl.) Endl. department for his assistance during the course (apache-plume) dominates the study area. of the study. For loan of material and aid in (Importance value = 12.8%; Riechert, 1973.) identification of some of the difficult species, we Vegetative diversity, however, is high and other thank the following: Drs. Bruce Cutler, St. Paul, shrubs are also important, including Opuntia Minnesota; Charles Dondale, Research Branch, imbricata Engelm. (staghorn cholla), Berberis Department of Agriculture, Ottawa, Canada; haematocarpa (Fedde) Wooton (red hollygrape), Herbert Levi, Museum of Comparative Zoology, and Juniperus monosperma (Engelm.) Sarge. Harvard University, Cambridge, Massachusetts; (one-seeded juniper). Martin Muma, Silver City, New Mexico; Norman Grasses account for 43 percent of the vege- Platnick, Department of Entomology, the Ameri- tative cover on the lava bed (Riechert, 1973); can Museum of Natural History, New York; Jon dominant grasses include Muhlenbergia porten Reiskind, Department of Zoology, University of Scribn. (bush muhly), which is associated with Florida, Gainesville, Florida; and Mr. Vincent shrubs in the study area, Sporobolus cryptandrus Roth, Southwestern Research Station of the (Torr.) Gray (sand dropseed), and the Bouteloua American Museum of Natural History, Portal, grasses B. aristidoides (H.B.K.) Griseb. (needle Arizona. grama), B. curtipendula (Michx.) Torr. (side-oats Financial support to the second author during grama), and B. gracilis (H.B.K.) Lab. (blue the several years of this study was provided by grama) which are found in more open areas. the National Geographic Society (Grant nos. Mixed Grassland Study Area. The second 1090 and 1288), the American Society of study area was selected from rich grassland University Women, and the University of Wiscon- at the northern margin of the lava beds (figs. 1 sin Graduate School. Collected material is in the and 2). This grassland contains plant species Zoological Museum of the University of Wiscon- frequenting both the flow and surrounding range- sin and type specimens have been deposited in land and supports a more dense growth of vege- the American Museum of Natural History. tation than either the lava bed or rangeland. It is dominated by the grass species Sporobolus flex- STUDY AREAS uosus (Thurb.) Rydb. (mesa dropseed) (Im- Three study areas were established at the portance value = 9.39%; Riechert, 1973). This northem edge of the Carrizozo "malpais," Lin- and other grasses surround the numerous depres- 1976 GERTSCH AND RIECHERT: DESERT SPIDER COMMUNITY 3 sions found along the flow margin. The depres- two. In this area a gravel pavement is covered sions are straight-sided dirt holes averaging 15-30 with sand and sparse clumps of Muhlenbergia cm. in height and 1.4m2 in area. They probably arenicola Buckl. (Muhly). Herbs of the following result from the outwash of underground aquifer families are prevalent, especially following the tubes. Following the summer rains, three flower- summer rains: Compositae, Cruciferae, and ing herbs demonstrate increased importance in Malvaceae. Juniperus dominates a south-facing this study area.Portulaca retusa Engelm. (notched slope included within this study area. Total vege- purslane), Gutierrezia sp.' (snakeweed), and tative cover is low (14%o) and depressions are Cuscuta indecora Choisy. (dodder) often exceed lacking on the rangeland. absolute frequencies of greater than 90 percent Species lists of the vegetation of this malpais in vegetation samples collected at this time area have been made (Shields and Crispin, 1956; (Riechert, 1973). Iwen, unpubl. data) and a more detailed analysis Rangeland Study Area. Study area three is of the habitat afforded spiders in the various representative of the rangeland surrounding the areas is presented elsewhere (Riechert, 1973). Carrizozo lava bed and is adjacent to study area SECTION I: SPIDER COMMUNITY METHODS RESULTS AND DISCUSSION Field. Data were collected over a five-year Principal Components Analysis. Ninety spe- period, 1969-1974, much of which represents cies were found to frequent the malpais area. quantitative collections obtained through suction They are listed by family in the legend for figure sampling, after methods described by Turnbull 3. Figure 3 is a representation of the first two and Nicholls (1966). Relative methods

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