Latitudinal variation in monthly-scale reproductive synchrony among Acropora coral assemblages in the Indo-Pacific

Jessica Bouwmeester,Michael L Berumen,Alasdair J Edwards,Andrew G Bauman,Andrew H Baird,James R Guest

doi:10.1007/s00338-021-02129-3

Abstract

Early research into coral reproductive biology suggested that spawning synchrony was driven by variations in the amplitude of environmental variables that are correlated with latitude, with synchrony predicted to break down at lower latitudes. More recent research has revealed that synchronous spawning, both within and among species, is a feature of all speciose coral assemblages, including equatorial reefs. Nonetheless, considerable variation in reproductive synchrony exists among locations and the hypothesis that the extent of spawning synchrony is correlated with latitude has not been formally tested on a large scale. Here, we use data from 90 sites throughout the Indo-Pacific and a quantitative index of reproductive synchrony applied at a monthly scale to demonstrate that, despite considerable spatial and temporal variation, there is no correlation between latitude and reproductive synchrony. Considering the critical role that successful reproduction plays in the persistence and recovery of coral reefs, research is urgently needed to understand the drivers underpinning variation in reproductive synchrony.

Highlights

Many plants and animals breed seasonally during periods that are likely optimal for fertilisation success and the early development of offspring
Early research into coral reproductive biology suggested that spawning synchrony was driven by variations in the amplitude of environmental variables that are correlated with latitude, with synchrony predicted to break down at lower latitudes
No relationship was found between latitude and Acropora coral reproductive synchrony at the lunar month level

Summary

Introduction

Many plants and animals breed seasonally during periods that are likely optimal for fertilisation success and the early development of offspring. In addition to reproductive seasonality, many species exhibit marked reproductive synchrony, i.e. reproduction occurring in tighter temporal clusters than would be expected by seasonality alone (Ims 1990a). Some examples include species of mast-seeding bamboos, which will grow during a species-specific period of between 3 and 120 years, before reproducing synchronously (Janzen 1976), and the Pacific Ridley turtle, which lays eggs during synchronous mass nestings called ‘‘arribadas’’ involving tens of thousands of individuals (Hughes and Richard 1974). In addition to high reproductive synchrony within species, spawning events involving multiple species occur in fishes (Whaylen et al 2004; Heyman and Kjerfve 2008), polychaetes (Hardege 1999), echinoderms (Himmelman et al 2008) and frogs (Wilczynski et al 1993). Intra-specific synchrony is likely highly adaptive for sessile, broadcast spawning marine invertebrates as a way to maximise fertilisation

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