ABSTRACT
Fine-scale population structure of two anemones (Stichodactyla gigantea and Heteractis
magnifica) in Kimbe Bay, Papua New Guinea.
Anemonefish are one of the main groups that have been used over the last decade to
empirically measure larval dispersal and connectivity in coral reef populations. A few
species of anemones are integral to the life history of these fish, as well as other obligate
symbionts, yet the biology and population structure of these anemones remains poorly
understood. The aim of this study was to measure the genetic structure of these anemones
within and between two reefs in order to assess their reproductive mode and dispersal
potential. To do this, we sampled almost exhaustively two anemones species
(Stichodactyla gigantea and Heteractis magnifica) at two small islands in Kimbe Bay
(Papua New Guinea) separated by approximately 25 km. Both the host anemones and the
anemonefish are heavily targeted for the aquarium trade, in addition to the populations
being affected by bleaching pressures (Hill and Scott 2012; Hobbs et al. 2013; Saenz-
Agudelo et al. 2011; Thomas et al. 2014), therefore understanding their biology is crucial
for better management strategies. Panels of microsatellite markers were developed for
each species using next generation sequencing tools. Clonality analyses confirm six pairs
of identical genotypes for S. gigantea (n=350) and zero for H. magnifica (n=128),
indicating presence/absence of asexual reproduction in this region. S. gigantea showed
low structure between islands (FST= 0.003, p-value= 0.000), however, even if the
majority of the individuals were unrelated (r~0), 81 families that shared 50% of their
genetic material formed from two to four members were found. Out of these families,
45% were found with individuals only within Tuare Island, 11% only in Kimbe Island,
and 44% were sharing individuals among islands. In comparison, H. magnifica showed
no structure (FST= 0.002, p-value= 0.278), mean relatedness indicated the majority of
individuals were unrelated, and 31 families were identified. Families again consisted
from two to four members and were found within Kimbe Island 90% of the time, and
shared between islands the remaining 10%. Results show the first genetic evidence of
their reproductive characteristics, high levels of connectivity among islands and
significant levels of genetic relatedness among individuals within islands.
