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7 Synergies between Climate Change and Species Invasions: Evidence from Marine Systems

Ziska, L.H., Editor CAB International PDF

7

Synergies between Climate

Change and Species Invasions:

Evidence from Marine Systems

Cascade J.B. Sorte

Department of Ecology and Evolutionary Biology, University of

California, Irvine, California, USA

Abstract

The hypothesis that climate change will facilitate species invasions has recently received increasing focus in studies of marine systems. Over the past decade, approaches to testing this hypothesis have shifted from time-series observations of concomitant increases in both processes to experimental tests that are beginning to reveal the mechanisms underlying the synergies between these two aspects of global change. The results of many studies conform to expectations that under climate change, invasive species’ abundances, ranges and per capita effects – collectively indicative of invader impacts – will increase. However, there remain significant gaps in our understanding of responses to non-thermal factors (such as changes in ocean pH, dissolved oxygen and storm events) and how species-specific idiosyncrasies will manifest in changes at the community level.

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8 A Comparative Analysis of Reconstructed Jaw Musculature and Mechanics of Some Large Theropods

RALPH MOLNAR Indiana University Press ePub

Ralph E. Molnar

8.1. Illustration of the methodology for estimating the lever arm and muscle extension of the jaw muscles of Tyrannosaurus rex, using the M. adductor mandibulae externus superficialis et medialis as an example. A) First the areas of origin (dashed) and insertion of the muscles are determined (or postulated). Then a “center” of each area is estimated. This “center” is chosen subjectively, taking into account the angle of the surface with respect to the plane of the projection, the relative proportion of fibers originating from this area, and so forth. In this example, the “center” (indicated by “x”) is set in the middle of the upper lobe of the infratemporal fenestra. The apparently large area of origin of the squamosal-quadratojugal flange probably contributed relatively few fibers, as the orientation of the muscle was parallel to the surface of the flange. However, the area of origin along the dorsal margin of the infratemporal fenestra is only small in projection since it is situated nearly perpendicular to the plane of projection. Hence, this area presumably contributed more fibers to the muscle than the squamosal-quadratojugal flange, although that area appears to be the greater. B) After the “centers” have been chosen, a line is constructed from the origin “center” to the insertion “center.” The length of this line is taken as a measure of the length of the muscle fibers. The perpendicular distance from this line (OI) to the center of rotation of the quadrate condyles (r) is the lever arm for this muscle at this gape. The measurements were made for angles of 0°–50° of gape, with zero being taken as that gape for which the tips of several of the dentary teeth reach the ventral margin of the maxilla. C) The same for a gape of 10°. D) The same for a gape of 20°. E) Graph of extension vs. gape. The extension plotted here is the extension for zero gape subtracted from the extension for a given gape, so that the extension for zero gape is zero. This graph therefore represents the relation of gape to the length of the muscle extended beyond its (presumed rest) length with the mouth closed. The units of the abscissa are centimeters times 0.2: the reason for this unconventional unit is that the measurements were made on a one-fifth scale projection of the skull. The points on this graph labeled B, C, and D are likewise derived from the extensions illustrated in parts (B), (C), and (D), respectively. F) Graph of the lever arm versus gape. This graph is constructed from the lengths of the lever arms as shown in (B), (C), and (D). The abscissa represents the lever arm, and the ordinate the gape. The units of the axes of this graph are the same as those of the previous graph. The points on the graph labeled B, C, and D are derived from the lever arms illustrated in parts (B), (C), and (D), respectively.

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Evolution/Classification: AP Biology

Ace Academics Ace Academics ePub
Medium 9780253009289

6 Mineral Marketplaces, Arbitrage, and the Production of Difference

Elizabeth Emma Ferry Indiana University Press ePub

6 MINERAL MARKETPLACES, ARBITRAGE, AND THE PRODUCTION OF DIFFERENCE

In November 1977, a prospector named Felix Esquivel entered the Ojuela mine in Mapimí, Durango, Mexico, and discovered a pocket of over twenty specimens of legrandite (a zinc arsenate). He and his brother sold them to a dealer, Jack Amsbury, via his Mexican agent Shorty Bonilla, for 48,000 old pesos, or approximately $4,000. Amsbury, with the help of Gene Schlepp, a Tucson dealer, resold the best piece (later christened the Aztec Sun) from the pocket (figure 6.1) to Miguel Romero for $30,000. Felix Esquivel reported to us that the buyer (he did not remember who) did periodically pay him 1,000 new pesos—between $60 and $100, depending on the year—as further remuneration. Romero held onto it for the rest of his life, planning to donate it with the rest of his collection to the University of Arizona Mineral Museum, where the best of his collection was on loan for many years (see chapter 4). In 2008, his heirs sold it to a Lebanese collector for something in the neighborhood of $1.7 million.

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8 How Can We Cover Millions of Hectares with Conservation Agriculture in Africa?

Kassam, A.H. CABI PDF

8 

How Can We Cover Millions of Hectares with Conservation

Agriculture in Africa?

Roland Bunch*

Independent consultant, Juneau, USA

8.1  Introduction

Let it be admitted from the start that Conservation Agriculture (CA) in Africa has spread faster in the past 5 years than in previous years but it is still not spreading as fast as it should. Also, the great majority of African smallholder farmers who have adopted CA use it on less than half a hectare. However, neither of these phenomena will turn CA into just a temporary fad that will die a sad and lonely death. In fact, there is evidence that CA, with a few simple improvements, could someday become the dominant way of producing food in much of the tropical world.

To achieve such a goal, we need to look at CA with a cold eye to shortcomings in some of the present practices and then find practical solutions that will: (i) significantly increase basic grain productivity; (ii) require less labour than do other farming systems; (iii) use only local resources that are plentiful; and (iv) increase net benefits for the farm family.

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