A structured search was conducted in Google Scholar, Sea Turtle Document Library () and Sea Turtle Online Bibliography (Archie Carr Center for Sea Turtle Research, University of Florida) using the following Boolean search terms: survival, survivorship, mortality, and the names of the seven marine turtle genera. Specifically, we conducted a two-tiered literature search to compile annual survival probability estimates for adult marine turtles. We followed the PRISMA protocols for assembling a dataset suitable for meta-analytic evaluation 5, 6. We expect the findings of this synthesis to highlight the importance of evaluating sources of heterogeneity when interpreting demographic estimates 2 and directly inform efforts to identify research priorities for marine turtles globally 9, 10, 11, 12. In this case, the use of survival estimates that are lower than expected may mislead management decisions if methodological biases are not accounted for. However, if heterogeneity is also strongly influenced by methodological differences, then statistical biases related to certain methodologies introduce artificial variation and mask important biological differences. In this case, survival estimates that are lower than expected would highlight important species- or region-specific hotspots in adult mortality – areas of conservation concern. If heterogeneity is influenced by phylogeny or biogeography, then biological differences in survival among species/populations may exist. Our goal was to quantify heterogeneity among survival estimates and test how heterogeneity is influenced by (a) phylogeny, (b) biogeography and (c) methodology. In theory, because all marine turtles exhibit conserved life history patterns, including slow growth and delayed sexual maturity 8, adult survival rates should be high (>0.90) and exhibit limited natural heterogeneity among estimates. We conducted a systematic review and comprehensive meta-analysis 5, 6 of annual survival rates for adult marine turtles to generate precision-weighted, species-specific estimates and prediction intervals from existing data 7 and to explicitly model sources of heterogeneity among estimates 2. Conversely, comparative studies that fail to evaluate sources of heterogeneity risk drawing inaccurate conclusions and misleading management decisions.
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Because demographic studies frequently exhibit heterogeneity due to system-specific nature of biological phenomena 2 and study-specific differences in methodology, identifying important sources of heterogeneity can inform biological patterns and conservation actions more broadly 2, 3, 4. In this regard, comparative syntheses of similar demographic studies are critical not only for identifying data gaps, but also for evaluating sources of heterogeneity among estimates. However, estimates of key demographic parameters, such as survival and recruitment, viewed in isolation often provide limited and/or potentially biased inferences. Our results highlight the importance of evaluating sources of heterogeneity when interpreting patterns among similar demographic studies and directly inform efforts to identify research priorities for marine turtles globally.ĭemographic studies in ecology and conservation biology form the basis for assessing population viability and managing ecological risk 1. However, apparent differences attributed to biogeography (ocean basin effect) and phylogeny (family/tribe effect) were highly correlated with methodological differences in tag type, model type, habitat type and study duration, thereby confounding biological interpretations and complicating efforts to use many current survival estimates in population assessments. Heterogeneity among survival estimates was first partitioned between differences in ocean basin (Indo-Pacific versus Atlantic), then by differences among family/tribe within the Indo-Pacific (Chelonini versus Carettini and Dermochelidae). Fifty-nine studies from five marine turtle species met the minimum selection criteria for inclusion in our meta-analysis.
![comprehensive meta analysis chapter 19 comprehensive meta analysis chapter 19](https://www.bmj.com/content/bmj/367/bmj.l5342/F3.medium.jpg)
To better understand adult survival in marine turtles and avoid drawing inaccurate conclusions from current estimates, we conducted a comprehensive meta-analysis to test how heterogeneity among estimates was partitioned among phylogenetic, biogeographic and methodological factors. Because demographic studies frequently exhibit heterogeneity, evaluating sources of heterogeneity among estimates can inform biological patterns and conservation actions more broadly. Comparative syntheses of key demographic parameters are critical not only for identifying data gaps, but also for evaluating sources of heterogeneity among estimates.