Colin J. Limpus

Global population structure and natural history of the green turtle chelonia mydas in terms of matriarchal phylogeny

To address aspects of the evolution and natural history of green turtles, we assayed mitochondrial (mt) DNA genotypes from 226 specimens representing 15 major rookeries around the world. Phylogenetic analyses of these data revealed (1) a comparatively low level of mtDNA variability and a slow mtDNA evolutionary rate (relative to estimates for many other vertebrates); (2) a fundamental phylogenetic split distinguishing all green turtles in the Atlantic‐Mediterranean from those in the Indian‐Pacific Oceans; (3) no evidence for matrilineal distinctiveness of a commonly recognized taxonomic form in the East Pacific (the black turtle C.m. agassizi or C. agassizi); (4) in opposition to published hypotheses, a recent origin for the Ascension Island rookery, and its close genetic relationship to a geographically proximate rookery in Brazil; and (5) a geographic population substructure within each ocean basin (typically involving fixed or nearly fixed genotypic differences between nesting populations) that suggests a strong propensity for natal homing by females. Overall, the global matriarchal phylogeny of Chelonia mydas appears to have been shaped by both geography (ocean basin separations) and behavior (natal homing on regional or rookery‐specific scales). The shallow evolutionary population structure within ocean basins likely results from demographic turnover (extinction and colonization) of rookeries over time frames that are short by evolutionary standards but long by ecological standards.

Mitochondrial DNA control region polymorphisms: genetic markers for ecological studies of marine turtles.

We describe a rapid and sensitive method for the detection of population‐specific genetic markers in mitochondrial DNA (mtDNA) and the use of such markers to analyse population structure of marine turtles. A series of oligonucleotide primers specific for the amplification of the mtDNA control region in Cheloniid turtles were designed from preliminary sequence data. Using two of these primers, a 384–385‐bp sequence was amplified from the 5′ portion of the mtDNA control region of 15 green turtles Chelonia mydas from 12 different Indo‐Pacific rookeries. Fourteen of the 15 individuals, including some with identical whole‐genome restriction fragment patterns, had sequences that differed by one or more base substitutions. Analysis of sequence variation among individuals identified a total of 41 nucleotide substitutions and a 1‐bp insertion/deletion. Comparison with evidence from whole‐genome restriction enzyme analysis of the same individuals indicated that this portion of the control region is evolving approximately eight times faster than the average rate and that the sequence analysis detected approximately one fifth of the total variation present in the genome. Restriction enzyme analysis of amplified products from an additional 256 individuals revealed significant geographic structuring in the distribution of mtDNA genotypes among five of the 10 rookeries surveyed extensively. Additional geographic structuring of genotypes was identified through denaturing gradient gel electrophoresis (DGGE) of amplified products. Only two of the 10 rookeries surveyed could not be differentiated, indicating that the Indo‐Pacific C. mydas include a number of genetically differentiated populations, with minimal female‐mediated gene flow among them. Important applications for genetic markers in the conservation and management of marine turtles include the identification of appropriate demographic units for research and management (i.e. genetically discrete populations) and assessment of the composition of feeding and harvested populations.

Trends in the abundance of sea turtles resident in southern Great Barrier Reef waters

Abstract A mark-recapture study was used to estimate trends in annual abundance of green and loggerhead turtles resident in southern Great Barrier Reef (sGBR) waters between 1985–1992. Abundance was derived using a Horvitz–Thompson type estimator based on sex- and ageclass-specific recapture probabilities conditioned on annual sampling effort. The resident green turtle population increased over the 8 years by 11% pa and comprised 1300 individuals in 1992. The female nesting population also increased but more slowly at 3% pa and has continued to do so. The increase may be due to favourable environmental conditions affecting breeding behaviour. On the other hand, the resident loggerhead population declined at 3% pa and comprised

GLOBAL PHYLOGEOGRAPHY OF THE LOGGERHEAD TURTLE (CARETTA CARETTA ) AS INDICATED BY MITOCHONDRIAL DNA HAPLOTYPES

Restriction‐site analyses of mitochondrial DNA (mtDNA) from the loggerhead sea turtle (Caretta caretta) reveal substantial phylogeographic structure among major nesting populations in the Atlantic, Indian, and Pacific oceans and the Mediterranean sea. Based on 176 samples from eight nesting populations, most breeding colonies were distinguished from other assayed nesting locations by diagnostic and often fixed restriction‐site differences, indicating a strong propensity for natal homing by nesting females. Phylogenetic analyses revealed two distinctive matrilines in the loggerhead turtle that differ by a mean estimated sequence divergence p = 0.009, a value similar in magnitude to the deepest intraspecific mtDNA node (p = 0.007) reported in a global survey of the green sea turtle Chelonia mydas. In contrast to the green turtle, where a fundamental phylogenetic split distinguished turtles in the Atlantic Ocean and the Mediterranean Sea from those in the Indian and Pacific oceans, genotypes representing the two primary loggerhead mtDNA lineages were observed in both Atlantic–Mediterranean and Indian‐Pacific samples. We attribute this aspect of phylogeographic structure in Caretta caretta to recent interoceanic gene flow, probably mediated by the ability of this temperate‐adapted species to utilize habitats around southern Africa. These results demonstrate how differences in the ecology and geographic ranges of marine turtle species can influence their comparative global population structures.

The genetic structure of Australasian green turtles (Chelonia mydas): exploring the geographical scale of genetic exchange

Ecological and genetic studies of marine turtles generally support the hypothesis of natal homing, but leave open the question of the geographical scale of genetic exchange and the capacity of turtles to shift breeding sites. Here we combine analyses of mitochondrial DNA (mtDNA) variation and recapture data to assess the geographical scale of individual breeding populations and the distribution of such populations through Australasia. We conducted multiscale assessments of mtDNA variation among 714 samples from 27 green turtle rookeries and of adult female dispersal among nesting sites in eastern Australia. Many of these rookeries are on shelves that were flooded by rising sea levels less than 10 000 years (c. 450 generations) ago. Analyses of sequence variation among the mtDNA control region revealed 25 haplotypes, and their frequency distributions indicated 17 genetically distinct breeding stocks (Management Units) consisting either of individual rookeries or groups of rookeries in general that are separated by more than 500 km. The population structure inferred from mtDNA was consistent with the scale of movements observed in long‐term mark–recapture studies of east Australian rookeries. Phylogenetic analysis of the haplotypes revealed five clades with significant partitioning of sequence diversity (Φ = 68.4) between Pacific Ocean and Southeast Asian/Indian Ocean rookeries. Isolation by distance was indicated for rookeries separated by up to 2000 km but explained only 12% of the genetic structure. The emerging general picture is one of dynamic population structure influenced by the capacity of females to relocate among proximal breeding sites, although this may be conditional on large population sizes as existed historically across this region.

Chapter 2 Vulnerability of Marine Turtles to Climate Change

Marine turtles are generally viewed as vulnerable to climate change because of the role that temperature plays in the sex determination of embryos, their long life history, long age-to-maturity and their highly migratory nature. Extant species of marine turtles probably arose during the mid-late Jurassic period (180-150 Mya) so have survived past shifts in climate, including glacial periods and warm events and therefore have some capacity for adaptation. The present-day rates of increase of atmospheric greenhouse gas concentrations, and associated temperature changes, are very rapid; the capacity of marine turtles to adapt to this rapid change may be compromised by their relatively long generation times. We consider the evidence and likely consequences of present-day trends of climate change on marine turtles. Impacts are likely to be complex and may be positive as well as negative. For example, rising sea levels and increased storm intensity will negatively impact turtle nesting beaches; however, extreme storms can also lead to coastal accretion. Alteration of wind patterns and ocean currents will have implications for juveniles and adults in the open ocean. Warming temperatures are likely to impact directly all turtle life stages, such as the sex determination of embryos in the nest and growth rates. Warming of 2 degrees C could potentially result in a large shift in sex ratios towards females at many rookeries, although some populations may be resilient to warming if female biases remain within levels where population success is not impaired. Indirectly, climate change is likely to impact turtles through changes in food availability. The highly migratory nature of turtles and their ability to move considerable distances in short periods of time should increase their resilience to climate change. However, any such resilience of marine turtles to climate change is likely to be severely compromised by other anthropogenic influences. Development of coastlines may threaten nesting beaches and reproductive success, and pollution and eutrophication is threatening important coastal foraging habitats for turtles worldwide. Exploitation and bycatch in other fisheries has seriously reduced marine turtle populations. The synergistic effects of other human-induced stressors may seriously reduce the capacity of some turtle populations to adapt to the current rates of climate change. Conservation recommendations to increase the capacity of marine turtle populations to adapt to climate change include increasing population resilience, for example by the use of turtle exclusion devices in fisheries, protection of nesting beaches from the viewpoints of both conservation and coastal management, and increased international conservation efforts to protect turtles in regions where there is high unregulated or illegal fisheries (including turtle harvesting). Increasing research efforts on the critical knowledge gaps of processes influencing population numbers, such as identifying ocean foraging hotspots or the processes that underlie the initiation of nesting migrations and selection of breeding areas, will inform adaptive management in a changing climate.

Diet selection by immature green turtles, Chelonia mydas, in subtropical Moreton Bay, south-east Queensland

Diet selection by immature green turtles (Chelonia mydas) in Flathead Gutter, Moreton Bay, was determined by examining food ingested in relation to food availability (measured as vegetation composition and abundance within the feeding site). Food composition was sampled by oesophageal lavage. Turtles were repeatedly located over a 10-week period by means of sonic telemetry and visual identification. The number of resightings indicated that these turtles remained within their feeding grounds for at least short periods of time. Immature green turtles fed on both seagrass and algal species. However, most fed selectively on algae, primarily Gracilaria sp. Food items consumed frequently by these turtles were analysed for total nitrogen, gross energy and neutral detergent fibre levels. There was a negative correlation between fibre level and the preferred food species, where the more frequently selected species had lower levels of fibre. The preferred species also had higher nitrogen levels.

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.

Hazards Associated with the Consumption of Sea Turtle Meat and Eggs: A Review for Health Care Workers and the General Public

Sea turtle products (e.g., meat, adipose tissue, organs, blood, eggs) are common food items for many communities worldwide, despite national regulations in some countries prohibiting such consumption. However, there may be hazards associated with this consumption due to the presence of bacteria, parasites, biotoxins, and environmental contaminants. Reported health effects of consuming sea turtles infected with zoonotic pathogens include diarrhea, vomiting, and extreme dehydration, which occasionally have resulted in hospitalization and death. Levels of heavy metals and organochlorine compounds measured in sea turtle edible tissues exceed international food safety standards and could result in toxic effects including neurotoxicity, kidney disease, liver cancer, and developmental effects in fetuses and children. The health data presented in this review provide information to health care providers and the public concerning the potential hazards associated with sea turtle consumption. Based on past mortality statistics from turtle poisonings, nursing mothers and children should be particularly discouraged from consuming all sea turtle products. We recommend that individuals choose seafood items lower in the food chain that may have a lower contaminant load. Dissemination of this information via a public health campaign may simultaneously improve public health and enhance sea turtle conservation by reducing human consumption of these threatened and endangered species.

Ontogenetic Dietary Partitioning by Crocodylus johnstoni during the Dry Season

We examined size-related dietary patterns in a Queensland population of the Australian freshwater crocodile (Crocodylus johnstoni). In three consecutive dry seasons, we stomach flushed crocodiles (n = 324) to record the numerical frequency and percent occurrence of prey items. Prey included spiders, aquatic insects, terrestrial insects, shrimp, fish, anurans, turtles, snakes, mammals, and birds. The diet of C. johnstoni showed ontogenetic shifts as the cranium broadened and once body size exceeded 60 cm SVL. With increasing crocodile size, the ingestion of spiders, insects, and anurans declined strongly whereas the consumption of fish, turtles, and snakes increased strongly. Shrimp were eaten at low and variable levels by all size classes of crocodile. The low overall prevalence of mammals and birds suggested that they were consumed opportunistically by the larger crocodiles. With increasing crocodile size, there were overall increases in prey richness and significant declines in realized dietary niche, dietary breadth, and mean number of prey items per crocodile. There were no significant changes in dietary diversity, evenness, or number of equally common prey species.