Boundary-crossing identities for diffusions having the time-inversion property

We review and study a one-parameter family of functional transformations, denoted by (S (β)) β∈ℝ, which, in the case β<0, provides a path realization of bridges associated to the family of diffusion processes enjoying the time-inversion property. This family includes Brownian motions, Bessel processes with a positive dimension and their conservative h-transforms. By means of these transformations, we derive an explicit and simple expression which relates the law of the boundary-crossing times for these diffusions over a given function f to those over the image of f by the mapping S (β), for some fixed β∈ℝ. We give some new examples of boundary-crossing problems for the Brownian motion and the family of Bessel processes. We also provide, in the Brownian case, an interpretation of the results obtained by the standard method of images and establish connections between the exact asymptotics for large time of the densities corresponding to various curves of each family

Global research priorities for sea turtles : informing management and conservation in the 21st century

Over the past 3 decades, the status of sea turtles and the need for their protection to aid population recovery have increasingly captured the interest of government agencies, non-governmental organisations (NGOs) and the general public worldwide. This interest has been matched by increased research attention, focusing on a wide variety of topics relating to sea turtle biology and ecology, together with the interrelations of sea turtles with the physical and natural environments. Although sea turtles have been better studied than most other marine fauna, management actions and their evaluation are often hindered by the lack of data on turtle biology, human&ndash;turtle interactions, turtle population status and threats. In an effort to inform effective sea turtle conservation a list of priority research questions was assembled based on the opinions of 35 sea turtle researchers from 13 nations working in fields related to turtle biology and/or conservation. The combined experience of the contributing researchers spanned the globe as well as many relevant disciplines involved in conservation research. An initial list of more than 200 questions gathered from respondents was condensed into 20 metaquestions and classified under 5 categories: reproductive biology, biogeography, population ecology, threats and conservation strategies

Conservation and dynamics of microsatellite loci over 300 million years of marine turtle evolution

Microsatellite loci consisting of (CA)(n) repetitive arrays were obtained from three species of marine turtle, and primers were designed to test for polymorphism within species and the persistence of microsatellites across species. Homologous loci were found in each test of six marine species within two families (Cheloniidae and Dermochelyidae), as well as in a freshwater species (Emydidae, Trachemys, scripta), which indicates a conservation of flanking sequences spanning approximately 300 million years of divergent evolution. The persistence of homologous microsatellites across marine turtles was confirmed by direct sequencing of loci across species and by the discovery of polymorphism in 24 of 30 cross species tests. The conservation of flanking sequences could be due to a slow rate of base substitution in turtle nuclear DNA, as previously reported for mtDNA. In contrast, the presence of up to 25 alleles per locus per species indicates that the replication slippage events responsible for changes in allele length operate as in mammals. Comparisons of alleles among species revealed that alleles of the same length may not be homologous due to mutations within the flanking sequences. Levels of heterozygosity were consistently higher in species from which the primers were designed, which suggests problems with cross-species comparisons of variability. Within species, microsatellite variation between divergent populations was consistent with results from previous mtDNA studies indicating the usefulness of microsatellites for comparing male- versus female-mediated gene flow

Conservation implications of internesting habitat use by Loggerhead Turtles Caretta caretta in Woongarra Marine Park, Queensland, Australia

We studied internesting habitat use by Loggerhead Turtles Caretta caretta with radio telemetry and by visual sightings of paint-marked turtles in Woongarra Marine Park, adjacent to the major mainland nesting rookery in Queensland. A high concentration of females occurs within the Park during the early phase of the internesting period as ovulation and shelling of eggs occur. From 36-72 hr following oviposition, activity ranges and swimming rates were greatly reduced. About day 9 after oviposition, turtles resumed higher swimming rates and wider activity ranges and were as likely to be outside protected management zones as within. Movements were generally within 10 km north or south of the rookery, limited to 1-2 km of the coast rather than offshore oriented and were independent of currents. A different pattern was exhibited after the final nest of the season: females departed the region quickly, with little of the localized movement characteristic of the internesting period. Over 89% of the nesting females were susceptible to trawling at some time during their internesting period as they swam outside the Protected Management Area. The likelihood of turtle-trawler interactions along the Woongarra coast and the potential of turtle excluder devices (TEDs) as a conservation measure are discussed. TED use provides a broadly applicable management option that can be combined with spatially or temporally restricted trawling zones

Mating system, multiple paternity and effective population size in the endemic flatback turtle (Natator depressus) in Australia

In recent years, genetic studies have been used to investigate mating systems of marine turtles, but to date no such research has been conducted on the flatback turtle (Natator depressus). This study investigates paternity of flatback turtle clutches at two rookeries in Queensland, Australia; Peak Island (Keppel Bay), and Mon Repos (Bundaberg). In the 2004–2005 nesting season, tissue samples were taken from either single or multiple clutches (n = 16) of nesting females (n = 8) representing a sampling effort ranging from 25% to 50% offspring per nest. Determination of the extent of multiple paternity was done using a comparative approach that included initial inferences based on observed alleles, Chi-square tests for deviations from Mendelian expectations, and three software programs (PARENTAGE1.0, GERUD2.0 and MER3.0). Results varied depending on the approach, but by calculating a consensus value of the output from these different methods, the null hypothesis of single paternity could be rejected in at least 11 of the 16 clutches (69%). Multiple paternity was thus observed in the clutches of six of nine females (67%), with two or three fathers being the most likely outcome. Analyses of successive clutches illustrated that paternal contribution to clutch fertilization can vary through time, as observed for two females. This first evidence regarding the mating system of flatback turtles indicates that multiple paternity is common in this species and that the observed frequency of multiple paternity is among the higher values reported in marine turtle species. Application of these results to estimates of effective population size (N e) suggests that population size may have been relatively stable over long periods. Continued monitoring of population dynamics is recommended to ensure that future changes in the east coast can be detected

Evidence for transoceanic migrations by loggerhead sea turtles in the southern Pacific Ocean

Post-hatchling loggerhead turtles (Caretta caretta) in the northern Pacific and northern Atlantic Oceans undertake transoceanic developmental migrations. Similar migratory behaviour is hypothesized in the South Pacific Ocean as post-hatchling loggerhead turtles are observed in Peruvian fisheries, yet no loggerhead rookeries occur along the coast of South America. This hypothesis was supported by analyses of the size-class distribution of 123 post-hatchling turtles in the South Pacific and genetic analysis of mtDNA haplotypes of 103 nesting females in the southwest Pacific, 19 post-hatchlings stranded on the southeastern Australian beaches and 22 post-hatchlings caught by Peruvian longline fisheries. Only two haplotypes (CCP1 93% and CCP5 7%) were observed across all samples, and there were no significant differences in haplotype frequencies between the southwest Pacific rookeries and the post-hatchlings. By contrast, the predominant CCP1 haplotype is rarely observed in North Pacific rookeries and haplotype frequencies were strongly differentiated between the two regions (Fst=0.82; p=<0.00001). These results suggest that post-hatchling loggerhead turtles emerging from the southwest Pacific rookeries are undertaking transoceanic migrations to the southeastern Pacific Ocean, thus emphasizing the need for a broader focus on juvenile mortality throughout the South Pacific to develop effective conservation strategies