Phylogeny, biogeography and methodology: a meta-analytic perspective on heterogeneity in adult marine turtle survival rates

Abstract

Comparative syntheses of key demographic parameters are critical not only for identifying data gaps, but also for evaluating sources of heterogeneity among estimates. Because demographic studies frequently exhibit heterogeneity, evaluating sources of heterogeneity among estimates can inform biological patterns and conservation actions more broadly. 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. Fifty-nine studies from five marine turtle species met the minimum selection criteria for inclusion in our meta-analysis. 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). 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. 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.

Survival and breeding interval of an endangered marine vertebrate, the leatherback turtle Dermochelys coriacea, in French Guiana

“…Thorson et al (2012), using a large data set from 1965 to 2009 in South Africa, corrected for metal mark loss, based on a subsample of individuals also having a PIT tag and assuming no loss of a PIT tag. Pfaller et al (2018, their Fig. 1) report for this study an average survival estimate equal to 0.82 (95% CI: 0.74− 0.88).…”

“…The absence of correction for PIT tag loss may explain the fairly low survival estimate. The other estimates reported by Pfaller et al (2018) (Spotila et al 2000, Tomillo 2007 are based on enumeration rather than CMR analysis and are, not surprisingly, quite low with wide CIs.…”

“…The meta-analysis of sea turtle survival by Pfaller et al (2018) gathers all published estimates of survival of adult female leatherbacks and provides a sound basis for discussing survival.…”

Covariates streamline age‐specific early life survival estimates of two chelonian species

“…Much is likely a consequence of inherent interspecific differences; in juvenile tortoises survival estimates range from eight to 90%, whereas in juvenile sea turtles they almost always exceed 70% (Table 1). Perhaps even more importantly, the plethora of methodological approaches (last column, Table 1) likely contributes largely to this variation (see also Pfaller et al, 2018).…”

Effect of pelagic longline bait type on species selectivity: a global synthesis of evidence

“…The speciesspecific samples sizes were too small to consider potentially informative covariates. We therefore only used random-effects models rather than fixed-or mixed-effects or meta-regression models that have been used in other recent ecological meta-analyses (e.g., Gilman et al 2016b;Pfaller et al 2018;Musyl and Gilman 2019).…”