David Wool

Bio: David Wool is an academic researcher from Tel Aviv University. The author has contributed to research in topics: Gall & Population. The author has an hindex of 24, co-authored 105 publications receiving 2250 citations. Previous affiliations of David Wool include International Center for Tropical Agriculture & University of Reading.

Interspecific competition among phloem-feeding insects mediated by induced host-plant sinks

Abstract: The role of interspecific interactions among herbivorous insects is considered to be limited, especially in specialist communities. In the current study we report on exploitative interspecific interaction between two closely related phloem—feeding species of gall—forming aphids (Homoptera; Pemphigidae; Fordinae), mediated by the supply of photoassimilates from the host plant. Geoica sp. forms a spherical gall on the leaflet midrib of Pistacia palaestina (Anacardiaceae), while Forda formicaria forms crescent—shaped galls on the leaflet margin of the same host plant. Using 14C labeling, we were able to trace the food supply (assimilated carbohydrates) from the leaves to galls of each species. We found that Geoica galls are strong sinks. These galls divert the normal phloem transport of the plant and reduce the amount of assimilates imported by F. formicaria, especially when they are located on the same leaflet. By the end of the season Geoica caused death of 84% of F. formicaria galls that were located on the same leaflet, and reduced reproductive success in the surviving galls by 20%. This is because the presence of Geoica causes early senescence (but not abscission) of the leaflet it is on (whether or not F. formicaria is present). The interaction is asymmetrical: F. formicaria did not affect reproductive output of Geoica nor did it cause visible damage to the leaflets. To our knowledge, this it the first demonstration of exploitation competition for plant assimilates between two insect—induced sinks. This exploitative competition, mediated by manipulation of plant phloem transport, stands in contrast to the absence of interference competition for galling sites between the two aphid species. Although their spatial distributions partly overlapped, the niche breadth of each species (measured from gall positions on leaves along the shoot axis) was not affected by the presence of the other. Moreover, when both species were located on the same leaf, they formed galls independently on the same or different leaflets, and there was no indication of interference competition over galling sites.

GALLING APHIDS: Specialization, Biological Complexity, and Variation

Abstract: Gall-inducing aphids are host specific in the gall stage. Most species alternate between trees (the primary host), where the gall is induced, and shrubs and grasses (secondary hosts). Parthenogenesis during most of their life cycle is interrupted by a single stage of sexual reproduction on the primary host. Apart from these general characteristics, galling aphids present some of the most complex and diverse life histories in the insect world. In this article I review the specialized characteristics of galling aphids, as well as their complex and diverse life histories, as reported in the past 20 years.

Do the Contents of Barn Owl Pellets Accurately Represent the Proportion of Prey Species in the Field

Abstract: Prey composition of Barn Owl (Tyto alba) pellets from northwestern Negev, Israel, was ex- amined. The 414 individual specimens of mammals represented by 256 pellets comprised: 9.2% Meriones sacramenti, 41.1% M. tristrami, 8.2% Gerbillus an- dersoni, 40.1% Mus musculus, and 1.4% Crocidura suaveolens. The pellets also contained some remains of insects, small specimens of the snake Ery.x jaculus, and two passerine birds. We tested whether the ob- served distribution of prey species in the 256 pellets could be obtained if owls hunted at random. Direct calculation and simulations indicate that more single- species pellets contained large mammals than would be expected from random sampling. In simulation of owls sampling at random from the database, the dis- tribution of "pellets" containing 1, 2, 3, or more prey items was similar to the observed distribution only when a cumulative weight limit for pellet ejection was set at SO-100 g. Even when Barn Owls do not hunt some species preferentially, the contents of the pellets may be biased towards larger prey. This result should be taken into consideration when accumulated pellets are used in ecological and paleontological studies to approximate the distribution of mammal prey in real communities, present or past.

Human biochemical genetics

Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Evolution and the Theory of Games

Abstract: In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

Bemisia tabaci: A Statement of Species Status

Abstract: Bemisia tabaci has long been considered a complex species. It rose to global prominence in the 1980s owing to the global invasion by the commonly named B biotype. Since then, the concomitant eruption of a group of plant viruses known as begomoviruses has created considerable management problems in many countries. However, an enduring set of questions remains: Is B. tabaci a complex species or a species complex, what are Bemisia biotypes, and how did all the genetic variability arise? This review considers these issues and concludes that there is now sufficient evidence to state that B. tabaci is not made up of biotypes and that the use of biotype in this context is erroneous and misleading. Instead, B. tabaci is a complex of 11 well-defined high-level groups containing at least 24 morphologically indistinguishable species.

Inbreeding and Extinction: Island Populations

Abstract: Island populations are more prone to extinction than mainland populations, with island endemic species having higher extinction rates than nonendemic species. Inbreeding depression is one possible expla- nation for this. Insular populations are expected to suffer increased inbreeding relative to mainland popula- tions due to bottlenecks at foundation and to lower subsequent population sizes. Inbreeding coefficients for 182 nonendemic and 28 endemic island populations were estimated from allozyme and microsatellite het- erozygosities in island and related mainland populations. Island populations were significantly inbred, with inbreeding coefficients significantly higher in endemic than nonendemic island populations. Many island populations showed levels of inbreeding associated with elevated extinction rates in domestic and laboratory species. Inbreeding depression cannot be excluded as a factor in the extinction proneness of island popula- tions.