The Maintenance of Sex and David Lack's Principle

Combining George C. Williams' idea that evolutionary constraints prevent asexual mutants from arising more frequently in low fecundity organisms, like mammals and birds, with an earlier one by David Lack that the brood size of these organisms has an optimum, and producing larger broods reduces their fitness, leads to a novel hypothesis about the maintenance of sex in them. All else equal, the eggs of an asexual mutant female should simply start developing without fertilisation, and there is no reason to assume that they would stop doing so after the optimal number of offspring has been produced. Without a way to control their reproductive output, asexual mutants should over-reproduce and suffer a cost of doing so. Experimental studies suggest that the cost of enlarged broods could limit the advantage of asexual mutants considerably. Moreover, research discovered that increased reproductive effort reduces immune functions of low fecundity organisms. This offers a surprising synthesis between Williams' constraint and Hamilton's parasite hypothesis on maintaining sex in low fecundity organisms: Compromised immune functions of asexual hosts may render them susceptible rather than adaptation on the side of parasites to overcome host resistance.

Using David Lack’s Observations of Finch Beak Size to Teach Natural Selection & the Nature of Science

One of the key aspects of natural selection is competition, yet the concept of competition is not necessarily emphasized in explanations of natural selection. Because of this, we developed an activity for our class that focuses on competition and provides an example of the effects of competition on natural selection. This hands-on activity models the field study completed by David Lack on Darwin’s finches. By using this historical study, we also give students an example of the nature-of-science concept of multiple methods. Although this activity was created for a college introductory biology course, it is appropriate for high school. We also provide an additional objective for upper-level ecology and evolution courses.

David Lack and the birth of radar ornithology

The use of radar to detect ships and aircraft became a key part of Britain's defence in the early part of the Second World War, but not all echoes were those of operational targets. David Lack, of the Army Operational Research Group, showed that many unexplained echoes came from flying birds, despite critics at the time. Careful observation combined with experiments provided observers with means of differentiating birds from boats and aircraft. Lack went on to use his wartime experience to launch the science of radar ornithology during the 1950s, which formed the basis of a development that continues to the present day with a range of more sophisticated radar equipment.

How slow breeding can be selected in seabirds: testing Lack's hypothesis

The historical debate of the 1960s between group and individual selection hinged on how the slow breeding of seabirds could be explained. While this debate was settled by the ascendance of individual selection, championed by David Lack, explanations for slow breeding in seabirds remain to be tested. We examined the slowest breeding of these birds, the albatrosses and petrels (order Procellariiformes), using analyses that statistically controlled for variations in body size and phylogeny. Incubation and fledging periods appeared strongly correlated, but this turned out to be largely explained by phylogeny. Nonetheless, developmental and reproductive rates were associated with the distance to the foraging range, as predicted under the hypothesis of ecological constraints on breeding pairs, and these results were independent of body size and phylogeny. Slower breeding in these seabirds appeared associated with the rigors of farther pelagic feeding, as Lack originally hypothesized.