Evolution and measurement of species diversity

I. the origin of species by means of natural selection

Regional differences in species number have puzzled naturalists ince the early 1800's, and explanations account for a large part of modern ecological research. Two venerable observations form the cornerstone of our knowledge on the subject: The number of species within a taxonomic group tends to increase with decreasing latitude (see Fischer 1960; Pianka 1966); and the number of species within a taxonomic group tends to increase with increasing area (see Preston 1960, 1962; Williams 1964; MacArthur and Wilson 1967; Simberloff 1972). Despite early research on the latter trend (the species-area relationship), ecologists have studied it intensely only in the last 50 yr. The relationship was originally envisioned as an empirical tool and used in three principle ways: (1) to determine optimal sample size and sample number, (2) to determine the minimum area of a \"community,\" and (3) to predict the number of species in areas larger than those sampled. All three uses are discussed by Kilburn (1966). More recently interest in the species-area relationship has focused on mechanistic explanations, its precise mathematical descriptions, and interpretations of parameters derived from these mathematical descriptions. Williams (1964) and Preston (1960, 1962) have proposed that the exponential and power function models (\"exponential model\" throughout his paper also refers to the species/log area transformation, and \"power function\" also refers to the log species/log area transformation) of the species-area relationship result from the way in which individuals are distributed among species. Williams' (1964) exponential model, which emphasizes habitat heterogeneity, was considered important by many plant ecologists but is now largely ignored. Preston's (1960, 1962) power function model was based on the assumption of a dynamic equilibrium of species exchanges between islands in an archipelago. This assumption led to the equation of the power function model with the idea of a dynamic equilibrium as expounded by MacArthur and Wilson (1963, 1967), such that an adequate fit of this model to observed species numbers has been viewed as support of the equilibrium hypothesis (Grant 1970; Diamond 1973; Simpson 1974). The interplay of the equilibrium hypothesis and the power function model of the species-area relationship has led to interpretation of the slope and intercept of the power function model exclusively in the context of the equilibrium hypothesis. In particular, specific values of the slope of the power function are often construed to * Order of authorship determined by the toss of a coin. t Present address: Department of Biology, University of South Florida, Tampa, Florida 33620. Am. Nat. 1979. Vol. 113, pp. 791-833. c) 1979 by The University of Chicago. 0003-0147/79/1306-0002$03.26

/pdf/the-statistics-and-biology-of-the-species-area-relationship-442cynzyis.pdf

The statistics and biology of the species-area relationship

Cell differentiation is based almost certainly on the regulation of gene activity, so that for each state of differentiation a certain set of genes is active in transcription and other genes are inactive. The establishment of this concept (1) has depended on evidence
indicating that the cells of an organism generally contain identical genomes (2). Direct support for the idea that regulation of gene activity underlies cell differentiation
comes from evidence that much of the genome in higher cell
types is inactive (3) and that different ribonucleic acids (RNA) are synthesized in different cell types (4).

http://science.sciencemag.org/content/sci/165/3891/349.full.pdf

Gene Regulation for Higher Cells: A Theory

We have provided a historical perspective on a body of steroid receptor research dealing with the structure and physiological significance of the untransformed 9S receptor that has often confused both novice and expert investigators. The frequent controversies and equivocations of earlier studies were due to the fact that the native, hormone-free state of these receptors is a large multiprotein complex that resisted description for many years because of its unstable and dynamic nature. The untransformed 9S state of the steroid and dioxin receptors has provided a unique system for studying the function of the ubiquitous, abundant, and conserved heat shock protein, hsp90. The hormonal control of receptor association with hsp90 provided a method of manipulating the receptor heterocomplex in a manner that was physiologically meaningful. For several steroid receptors, binding to hsp90 was required for the receptor to be in a native hormone-binding state, and for all of the receptors, hormone binding promoted dissociation of the receptor from hsp90 and conversion of the receptor to the DNA-binding state. Although the complexes between tyrosine kinases and hsp90 were discovered earlier, the hormonal regulation or steroid receptor association with hsp90 permitted much more rapid and facile study of hsp90 function. The observations that hsp90 binds to the receptors through their HBDs and that these domains can be fused to structurally different proteins bringing their function under hormonal control provided a powerful linkage between the hormonal regulation of receptor binding to hsp90 and the initial step in steroid hormone action. Because the 9S receptor hsp90 heterocomplexes could be physically stabilized by molybdate, their protein composition could be readily studied, and it became clear that these complexes are multiprotein structures containing a number of unique proteins, such as FKBP51, FKBP52, CyP-40, and p23, that were discovered because of their presence in these structures. Further analysis showed that hsp90 itself exists in a variety of native multiprotein heterocomplexes independent of steroid receptors and other 'substrate' proteins. Cell-free systems can now be used to study the formation of receptor heterocomplexes. As we outlined in the scheme of Fig. 1, the multicomponent receptor-hsp90 heterocomplex assembly system is being reconstituted, and the importance of individual proteins, such as hsp70, p60, and p23, in the assembly process is becoming recognized. It should be noted that our understanding of the mechanism and purpose of steroid receptor heterocomplex assembly is still at an early stage. We can now speculate on the roles of receptor-associated proteins in receptor action, both as individuals and as a group, but their actual functions are still vague or unknown. We can make realistic models about the chaperoning and trafficking of steroid receptors, but we don't yet know how these processes occur, we don't know where chaperoning occurs in the cell (e.g. Is it limited to the cytoplasm? Is it a diffuse process or does chaperoning occur in association with structural elements?), and, with the exception of the requirement for hormone binding, we don't know the extent to which the hsp90-based chaperone system impacts on steroid hormone action. It is not yet clear how far the discovery of this hsp90 heterocomplex assembly system will be extended to the development of a general understanding of protein processing in the cell. Because this assembly system is apparently present in all eukaryotic cells, it probably performs an essential function for many proteins. The bacterial homolog of hsp90 is not an essential protein, but hsp90 is essential in eukaryotes, and recent studies indicate that the development of the cell nucleus from prokaryotic progenitors was accompanied by the duplication of genes for hsp90 and hsp70 (698). (ABSTRACT TRUNCATED)

/pdf/steroid-receptor-interactions-with-heat-shock-protein-and-1iq19twpoc.pdf

Steroid receptor interactions with heat shock protein and immunophilin chaperones.

Variation in numbers of land plant species on islands in the Galapagos Archipelago can be predicted on the basis of elevation, area of the adjacent island, distance from the nearest island, and distance from the center of the archipelago, but not on the basis of the area of the host island. Multiple linear regression (y = bx1 + bx2 . . .) gives better "goodness of fit" than curvilinear analysis (y = bxz). The variation in number of species on large islands can be predicted more accurately than the variation on small ones. Ecologic diversity and isolation are the natural regulators of species abundance.

https://science.sciencemag.org/content/sci/142/3599/1575.full.pdf

Species Abundance: Natural Regulation of Insular Variation

Nonhistone acidic proteins were isolated, by equilibrium density centrifugation in 4 M cesium chloride, from the chromatin isolated and purified from the uterus of the ovariectomized rat or from calf endometrium. Evidence is presented to show (1) that arginine-rich histones are more effective inhibitors of chromatin-directed RNA synthesis in vitor than lysine-rich histones, (2) that the nonhistone acidic proteins of chromatin do not inhibit the synthesis of RNA directed by chromatin in vitro, (3) that added nonhistone acidic chromatin proteins effect a restoration of histone-inhibited RNA synthesis directed by chromatin in vitro, and (4) that the synthesis of nonhistone acidic chromatin proteins is under estrogen control in the uterus, but not in the liver. It is concluded that a major feature of the early action of estrogen in the uterus of the ovariectomized rat is the stimulation of synthesis and the accumulation in the interphase chromosomes of nonhistone acidic proteins which counter the inhibitory effect of histone on transcription by RNA polymerase. Presumably this would permit more and perhaps a new synthesis of RNA programmed for transport to the cytoplasm.

Role of chromatin in estrogen action in the uterus. II. Hormone-induced synthesis of nonhistone acidic proteins which restore histone-inhibited DNA-dependent RNA synthesis.

The environmental control of insular variation in bird species abundance

Regulation by estrogen of organ-specific synthesis of a nuclear acidic protein

It is now clearly established that genetic transcription in the mammalian uterus is regulated by the ovarian hormone estradiol-17f3 (for reviews see ref. 1). Stimulation of nuclear RNA synthesis in vivo has been found to be one of the earliest biochemical responses of the uterus of the ovariectomized or immature rat to a single injection of the hormone. This stimulation has been demonstrated for nuclear RNA rapidly labeled in vivo,2 for RNA synthesis assayed in vitro in isolated nuclei,2b 3 and by the assay in vitro of RNA synthesis directed by isolated chromatin and catalyzed by added RNA polymerase.4a The question thus arises: Through what molecular mechanisms of activity or synthesis does estradiol-17f3 result in an increase in the genetic material available for transcription in the uterus? In an attempt to obtain information of possible value in answering this question, we have undertaken an investigation of the role of uterine chromatin in the early action of the hormone in the ovariectomized rat. We find an early stimulatory effect on the nuclear synthesis and accumulation of chromatin-associated RNA. This effect is manifest 15 minutes after hormone treatment and occurs either prior to or simultaneously with a stimulation of the template activity of the isolated and purified chromatin. We further find that at two minutes after treatment in vivo H3-estradiol-17,3 is bound to the isolated chromatin. The time course for the amount of binding of the hormone in vivo parallels nicely the time course for the hormonal stimulation in vivo of the template activity of the chromatin, both parameters being maximal at eight hours after treatment. We conclude that estrogen regulates the chemical composition as well as the template capacity of uterine chromatin. The causal relations between these changes in template capacity, chemical composition, and binding of hormone remain to be unraveled. Materials and Methods.-The intact and ovariectomized adult rats used and their management for hormone treatment were as previously described.2 The remaining details of experimentation were as follows or appear in the text and relevant figures and tables. Preparation of purified chromatin: Chromatin was isolated and purified according to two methods. Method 1 was a modification of the procedure of Marushige and Bonner.5 About 250 mg of minced uterine tissue or 5 gm of minced liver was homogenized at -100C in 10 ml of saline-ethylenediaminetetraacetate (EDTA) (0.05 31 NaCi, 0.016 31 Na2 EDTA (pH 8.0)). The Ultra Turrax Tp 20/2 tissue disintegrator (Brinkman Instruments) was operated for 30 sec at 110 v and then for 2 min at 60 v. The following preparative steps were at 20C. The homogenate was filtered through four layers of nylon bolting cloth (110-mesh) and centrifuged at 1500 X g for 15 min. The filtrate was washed twice by sedimentation in 12 ml of the saline-EDTA and then twice in 12 ml of tris buffer (0.05 A!, pH 8.0). The sediment was then suspended in 12 ml of the tris buffer by homogenization in a Dounce homogenizer (Kontes Glass Co.) and centrifuged at 10,000 X g for 15 min. The pellet was suspended in 5 ml of the tris buffer, stirred for 30 min by a

The role of chromatin in estrogen action in the uterus, I. The control of template capacity and chemical composition and the binding of H3-estradiol-17 beta.

Terrell H. Hamilton

Papers

Species Abundance: Natural Regulation of Insular Variation

Role of chromatin in estrogen action in the uterus. II. Hormone-induced synthesis of nonhistone acidic proteins which restore histone-inhibited DNA-dependent RNA synthesis.

The environmental control of insular variation in bird species abundance

Regulation by estrogen of organ-specific synthesis of a nuclear acidic protein

The role of chromatin in estrogen action in the uterus, I. The control of template capacity and chemical composition and the binding of H3-estradiol-17 beta.