Demographic changes in Pleistocene sea turtles were driven by past sea level fluctuations affecting feeding habitat availability

Pleistocene environmental changes are generally assumed to have dramatically affected species’ demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120–14 thousand years ago; kya) and assessed correlations with past changes in genetic diversity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow marine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diversity, which gradually declined to ~1/4th of present-day levels during the Last Glacial Maximum (LGM; 26–19 kya). Shallow marine habitat availability and genetic diversity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation between Pleistocene environmental changes, habitat availability and species’ demography, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling the potential environmental drivers of past demographic changes, which highlights the need for integrative approaches. Our conclusions underline the role of habitat availability on species’ demography and biodiversity, and that the consequences of ongoing habitat loss should not be underestimated

Traditional and non-traditional educational outcomes:Trade-off or complementarity?

Recently, schools have increasingly been charged with enhancing non-traditional academic competencies, in addition to traditional academic competencies. This article raises the question whether schools can implement these new educational goals in their curricula and simultaneously realise the traditional ones or whether a trade-off between educational goals occurs in schools. It is argued that this question centres on the issue of whether the development of traditional and non-traditional competencies is complementary or competitive. By reviewing the literature and by conducting multivariate multilevel analysis on data gathered in 26 secondary schools in The Netherlands, the article addresses the probability of occurrence of school trade-off between educational outcomes. Results of our analyses do not unambiguously support the occurrence of trade-off, nor the proposition that traditional and non-traditional competencies are complementary. It is concluded that both trade-off and complementarity may occur, depending on specific school conditions

Hawksbill turtle ddRAD raw sequencing data

Pleistocene environmental changes are generally assumed to have dramatically affected species’ demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120 – 14 thousand years ago; kya) and assessed correlations with past changes in genetic diversity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow marine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diversity, which gradually declined to ~1/4th of present-day levels during the Last Glacial Maximum (LGM; 26 – 19 kya). Shallow marine habitat availability and genetic diversity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation between Pleistocene environmental changes, habitat availability and species’ demography, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling the potential environmental drivers of past demographic changes, which highlight the need for integrative approaches. Our conclusions underline the role of habitat availability on species’ demography and biodiversity, and that the consequences of ongoing habitat loss should not be underestimated.,The dataset consists of two gzipped FASTQ files that raw Illumina sequencing data (ddRADs) obtained from 55 hawksbill turtles (Eretmochelys imbricata).,Please see the published manuscript and accompanying supplementary material for a detailed description of the methods and steps required to analyze the raw data.