Reproduction in Urbanised Coastal Waters: Shallow-Water Sea Anemones (Entacmaea quadricolor and Stichodactyla haddoni) Maintain High Genetic Diversity and Panmixia

Abstract

Sea anemones are sedentary marine animals that tend to disperse via planktonic larvae and are predicted to have high population connectivity in undisturbed habitats. We test whether two sea anemone species living in two different tidal zones of a highly disturbed marine environment can maintain high genetic connectivity. More than 1000 loci with single-nucleotide polymorphisms (SNPs) were obtained with double-digest RADseq for 81 Stichodactyla haddoni and 99 Entacmaea quadricolor individuals to test for population genetic structure. We find evidence that both species predominantly propagate via sexual reproduction, and asexual reproduction is limited. We observe panmixia that indicates the absence of effective dispersal barriers for these species living in a highly anthropogenically disturbed environment. This is positive news for both species that are also found in the aquarium trade. More fundamentally, our results suggest that inhabiting different parts of a shallow reef may not affect a species’ population connectivity nor favour asexual reproduction.

Megacolonies: an alternative social organization in anemonefishes?

“…The formation of large clusters could then result from a higher larval settlement. Field monitoring and genetic surveys [74] of anemones clusters could help answer the following questions: are clusters composed of different genotypes, and if so, which factors are triggering higher larval recruitment (hydrodynamic, substrate type, light, conspecific density, etc.)? Or are they composed of clones, and are these anemone species more prone to clonal duplication, or do some environmental conditions enhance clonality over sexual reproduction?…”