We use population genetics theory and computer simulations to demonstrate that population bottlenecks cause a characteristic mode-shift distortion in the distribution of allele frequencies at selectively neutral loci. Bottlenecks cause alleles at low frequency (< 0.1) to become less abundant than alleles in one or more intermediate allele frequency class (e.g., 0.1-0.2). This distortion is transient and likely to be detectable for only a few dozen generations. Consequently only recent bottlenecks are likely to be detected by tests for distortions in distributions of allele frequencies. We illustrate and evaluate a qualitative graphical method for detecting a bottleneck-induced distortion of allele frequency distributions. The simple novel method requires no information on historical population sizes or levels of genetic variation; it requires only samples of 5 to 20 polymorphic loci and approximately 30 individuals. The graphical method often differentiates between empirical datasets from bottlenecked and nonbottlenecked natural populations. Computer simulations show that the graphical method is likely (P > .80) to detect an allele frequency distortion after a bottleneck of < or = 20 breeding individuals when 8 to 10 polymorphic microsatellite loci are analyzed.

In Shark Bay, wild bottlenose dolphins (Tursiops sp.) apparently use marine sponges as foraging tools. We demonstrate that genetic and ecological explanations for this behavior are inadequate; thus, ''sponging'' classifies as the first case of an existing material culture in a marine mammal species. Using mitochondrial DNA analyses, we show that sponging shows an almost exclusive vertical social transmission within a single matriline from mother to female offspring. Moreover, significant genetic relatedness among all adult spongers at the nuclear level indicates very recent coancestry, suggesting that all spongers are descendents of one recent ''Sponging Eve.'' Unlike in apes, tool use in this population is almost exclusively limited to a single matriline that is part of a large albeit open social network of frequently interacting individuals, adding a new dimension to charting cultural phenomena among animals.culture ͉ Tursiops sp. ͉ social learning ͉ tradition

It is important to detect population bottlenecks in threatened and managed species because bottlenecks can increase the risk of population extinction. Early detection is critical and can be facilitated by statistically powerful monitoring programs for detecting bottleneck-induced genetic change. We used Monte Carlo computer simulations to evaluate the power of the following tests for detecting genetic changes caused by a severe reduction in a population's effective size (Ne): a test for loss of heterozygosity, two tests for loss of alleles, two tests for change in the distribution of allele frequencies, and a test for small Ne based on variance in allele frequencies (the 'variance test'). The variance test was most powerful; it provided an 85% probability of detecting a bottleneck of size Ne = 10 when monitoring five microsatellite loci and sampling 30 individuals both before and one generation after the bottleneck. The variance test was almost 10-times more powerful than a commonly used test for loss of heterozygosity, and it allowed for detection of bottlenecks before 5% of a population's heterozygosity had been lost. The second most powerful tests were generally the tests for loss of alleles. However, these tests had reduced power for detecting genetic bottlenecks caused by skewed sex ratios. We provide guidelines for the number of loci and individuals needed to achieve high-power tests when monitoring via the variance test. We also illustrate how the variance test performs when monitoring loci that have widely different allele frequency distributions as observed in five wild populations of mountain sheep (Ovis canadensis).

We investigate the utility of hypervariable microsatellite loci to measure genetic variability remaining in the northern hairy-nosed wombat, one of Australia's rarest mammals. This species suffered a dramatic range and population reduction over the past 120 years and now exists as a single colony of about 70 individuals at Epping Forest National Park, central Queensland. Because our preliminary research on mitochondrial DNA and multilocus DNA fingerprints did not reveal informative variation in this population, we chose to examine variation in microsatellite repeats, a class of loci known to be highly polymorphic in mammals. To assess the suitability of various wombat populations as a reference for comparisons of genetic variability and subdivision we further analysed mitochondrial DNA cytochrome b sequence, using phylogenetic methods. Our results show that appreciable levels of variation still exist in the Epping Forest colony although it has only 41% of the heterozygosity shown in a population of a closely-related species. From museum specimens collected in 1884, we also assessed microsatellite variation in an extinct population of the northern hairy-nosed wombat, from Deniliquin, New South Wales, 2000 km to the south of the extant population. The apparent loss of variation in the Epping Forest colony is consistent with an extremely small effective population size throughout its 120-year decline.

Together with PAXARMS (NZ), we developed a biopsy system for small cetaceans and tested it on four populations of bottlenose dolphins (Tursiops spp.). The system consists of a modified 0.22 caliber rifle, and biopsy darts made out of polycarbonate with stainless steel biopsy tips. Animals were darted at a range of 2–15 m while travelling parallel to the vessel. Overall sampling success for obtaining biopsy samples when an animal was struck ranged from 96.6% to 100% in the four populations. However, hit rate varied for the four different populations. We did not observe a significant difference in strength of the reaction to the darting procedure when an animal was hit or missed, both among and within populations. Data from one population showed no significant difference in the reaction to biopsy sampling by four different age‐sex classes. The only factor that had a significant influence on darting success was the hit location. Furthermore, we observed a significant positive correlation between the size of the sample obtained and the reaction to biopsy sampling. Biopsy samples were sufficient for microsatellite and d‐loop analysis in 95.8% and for genetic sexing in 99% of all cases. In animals that we observed on a daily basis, wounds were healed after approximately 23 d.