Abstract
Understanding the hierarchy of populations from the scale of metapopulations to mesopopulations and member local populations is fundamental to understanding the population dynamics of any species. Jellyfish by definition are planktonic and it would be assumed that connectivity would be high among local populations, and that populations would minimally vary in both ecological and genetic clade-level differences over broad spatial scales (i.e., hundreds to thousands of km). Although data exists on the connectivity of scyphozoan jellyfish, there are few data on cubozoans. Cubozoans are capable swimmers and have more complex and sophisticated visual abilities than scyphozoans. We predict, therefore, that cubozoans have the potential to have finer spatial scale differences in population structure than their relatives, the scyphozoans. Here we review the data available on the population structures of scyphozoans and what is known about cubozoans. The evidence from realized connectivity and estimates of potential connectivity for scyphozoans indicates the following. Some jellyfish taxa have a large metapopulation and very large stocks (>1000 s of km), while others have clade-level differences on the scale of tens of km. Data on distributions, genetics of medusa and polyps, statolith shape, elemental chemistry of statoliths and biophysical modelling of connectivity suggest that some of the ~50 species of cubozoans have populations of surprisingly small spatial scales and low levels of connectivity. Despite their classification as plankton, therefore, some scyphozoans and cubozoans have stocks of small spatial scales. Causal factors that influence the population structure in many taxa include the distribution of polyps, behavior of medusa, local geomorphology and hydrodynamics. Finally, the resolution of patterns of connectivity and population structures will be greatest when multiple methods are used.
Highlights
Some scyphozoan jellyfishes lack a polyp phase and are holoplanktonic (e.g., Pelagia noctiluca and Periphylla spp.). Their entire lifecycle is completed in the plankton, where their planula larvae develop into ephyrae which develop into medusae
It prefers shallow algal beds of Sargassum and the have examined the role of polyps in determining the abundance of medusa and, abundance of medusae is role highest in
It is clear that despite the classification of scyphozoan and cubozoan jellyfish as plankton, many of them are highly mobile and demonstrate orientation behavior that can result in restricted distributions
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Many general paradigms on jellyfish are based on scyphozoans For this true (genetic) diversity likely being double [15]. There may be anti-tropical d biogeographic range of the three described species of Chironex are likely to be composed butions of a species where metapopulations are found in both hemispheres, but are q of multiple stocks (Figure 1). Ecological interactions are likely among individuals from different local populations through the movement of adults or early life history stages, so genetic connectivity would be assumed. It would be assumed that connectivity would be high among local jellyfish populations and that populations would vary little in both ecological and genetic clade-level differences over broad spatial scales (i.e., hundreds to thousands of km). Predictions for population structures of jellyfish based on passive dispersal are likely to be highly inaccurate
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