Survive or swim: different relationships between migration potential and larval size in three sympatric Mediterranean octocorals

Katell Guizien,N Viladrich,L Bramanti,Á Martínez-Quintana

doi:10.1038/s41598-020-75099-1

Abstract

Knowledge about migration potential is key to forecasting species distributions in changing environments. For many marine benthic invertebrates, migration happens during reproduction because of larval dispersal. The present study aims to test whether larval size can be used as a surrogate for migration potential arising from larval longevity, competence, sinking, or swimming behavior. The hypothesis was tested using larvae of three sympatric gorgonian species that release brooded lecithotrophic larvae in the same season: Paramuricea clavata, Corallium rubrum and Eunicella singularis. Despite different fecundities and larval sizes, the median larval longevity was similar among the three species. Free-fall speed increased with larval size. Nevertheless, the only net sinkers were the P. clavata larvae, as swimming was more common than free fall in the other two species with larger larvae. For the other two species, swimming activity frequency decreased as larval size increased. Interestingly, maximum larval longevity was lowest for the most active but intermediately sized larvae. Larval size did not covary consistently with any larval traits of the three species when considered individually. We thus advise not using larval size as a surrogate for migration potential in distribution models. The three species exemplified that different mechanisms, i.e., swimming activity or larval longevity, resulting from a trade-off in the use of energy reserves can facilitate migration, regardless of life history strategy.

Highlights

Knowledge about migration potential is key to forecasting species distributions in changing environments
These larval traits are release timing and location, pelagic larval duration (PLD, the period of time during which larvae of a benthic species can disperse in the flow until settlement) and motility behavior that results from the balance between free fall and swimming activity[20]
Flow dispersal can delay settlement opportunities in the benthic habitat, and because dispersal distance often increases with P LD21, migration potential should instead be assessed using the upper limit of the PLD range

Summary

Introduction

Knowledge about migration potential is key to forecasting species distributions in changing environments. We advise not using larval size as a surrogate for migration potential in distribution models. Estimating offspring dispersal distance in such species is challenging because reduced larval size limits their tracking. Biophysical modeling is the only tool that enables the prediction of offspring dispersal distances in future environmental scenarios, but it requires incorporating larval traits that regulate dispersal. These larval traits are release timing and location, pelagic larval duration (PLD, the period of time during which larvae of a benthic species can disperse in the flow until settlement) and motility behavior that results from the balance between free fall and swimming activity[20]. Flow dispersal can delay settlement opportunities in the benthic habitat, and because dispersal distance often increases with P LD21, migration potential should instead be assessed using the upper limit of the PLD range

Methods

Results

Conclusion