Review Questions

7.1. Only 0.06 % of described insect species are classified by the IUCN as threatened. Why do we nevertheless have reason to fear that we are on the brink of a sixth mass extinction?

7.2. Why does a reduction in population size lead to a simultaneous reduction in genetic diversity and an increase in inbreeding.

7.3. Add either " or # to each boxed variable in the following flow charts to show how different factors can influence the increment in inbreeding over time. Note that not all variables are included in each flow chart - you are asked to comment on the effects of a few key variables.

Population bottleneck

Gene flow i

Ne i

Polygynous mating system*

Small Ne i

Selection i Drift

*From Chapter 6

Is purging more likely to reduce inbreeding depression that is caused by dominance or by overdominance?

7.5. Fledgling survival within a population of blue tits (Parus major) was found to be 80.5 % for the offspring of unrelated parents and 60 % for the offspring of related parents. What is the impact of inbreeding depression on offspring survival in this population?

7.6. What three aspects of population genetics are of particular relevance to successful genetic restoration programmes?

7.7. In the 1940s, land iguanas (Conolophus subcristatus) were extirpated from Isla Baltra on the Galapagos archipelago. Historical records show that some iguanas were moved from Baltra to nearby Isla Seymour Norte in the 1930s, an island that previously had lacked land iguanas. As part of a proposed translocation programme, biologists compared mitochondrial haplotypes from current populations with Isla Baltra specimens that had been collected in the 1940s to determine whether it would be appropriate to restock Isla Baltra using iguanas from Seymour Norte (Hofkin et al., 2003). The six haplotypes that they found were distributed across the archipelago as follows:

Figure 7.13 Distribution of land iguana haplotypes (H2-H7) in past and current populations in the Galápagos archipelago. White islands have always lacked land iguana populations, grey islands represent extirpated populations, and hatched islands represent extant populations. Note that the current population on Seymour Norte is not native, and the Baltra haplotypes date from the 1940s (there is currently no population on Baltra)

Figure 7.13 Distribution of land iguana haplotypes (H2-H7) in past and current populations in the Galápagos archipelago. White islands have always lacked land iguana populations, grey islands represent extirpated populations, and hatched islands represent extant populations. Note that the current population on Seymour Norte is not native, and the Baltra haplotypes date from the 1940s (there is currently no population on Baltra)

On the basis of this haplotype distribution, what would be the most conservative approach to follow when translocating iguanas from Seymour Norte to Baltra?

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