Melanie Meijer Zu Schlochtern

Abstract

The monotypic soft coral genus Stragulum van Ofwegen and Haddad, 2011 (Octocorallia: Malacalcyonacea: Tubiporidae) was originally described from Brazil, southwest Atlantic Ocean. Here, we report the first records of the genus from the eastern Caribbean and the Persian Gulf in the northwest Indian Ocean. We compare the morphological features of specimens, together with molecular data from three commonly used barcoding markers (COI, mtMutS, 28S rDNA) and 308 ultraconserved elements (UCE) and exon loci sequenced using a target-enrichment approach. The molecular and morphological data together suggest that specimens from all three localities are the same species, i.e., Stragulum bicolor van Ofwegen and Haddad, 2011. It is still not possible to establish the native range of the species or determine whether it may be an introduced species due to the limited number of specimens included in this study. However, the lack of historical records, its fouling abilities on artificial substrates, and a growing number of observations support the invasive nature of the species in Brazilian and Caribbean waters and therefore suggest that it may have been introduced into the Atlantic from elsewhere. Interestingly, the species has not shown any invasive behaviour in the Persian Gulf, where it has been found only on natural, rocky substrates. The aim of the present report is to create awareness of this taxon with the hope that this will lead to new records from other localities and help to establish its native range

Abstract

Pleistocene environmental changes are generally assumed to have dramatically af-fected 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  thou-sand years ago; kya) and assessed correlations with past changes in genetic diver-sity 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 ma-rine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diver-sity, 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 diver-sity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation be-tween Pleistocene environmental changes, habitat availability and species’ demog-raphy, 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 con-sequences of ongoing habitat loss should not be underestimated.

KEYWORDS: ddRAD sequencing, demographic change, habitat availability, Pleistocene sea turtles, sea level change