11th ICRS Abstract book - Nova Southeastern University

14-21
Same, Same, But Different: Comparing Population Genetic Structures Of Two
Species Of Coral (Pocillopora Damicornis & Platygyra Daedalea) In The Western
Indian Ocean
Petra SOUTER* 1
1 Australian Institute of Marine Science, Towsville MD, Australia
Improved management of coral reefs is vital, and information regarding levels of genetic
diversity and scales of connectivity are factors that need to be considered when
developing efficient management plans. This study was implemented in a geographic
area where such knowledge is yet scarce but increasingly important.
Samples of Pocillopora damicornis were collected from 29 sites along the coast of East
Africa; from Malindi in Kenya, to Mtwara in Tanzania, spanning a distance of over 800
km. Over 60% of all pair-wise comparisons showed a significant genetic differentiation,
indicating predominant localised recruitment. The species exhibited mixed modes of
reproduction, with 4 populations being dominated by asexual clones and another 3
populations showing signs of mixed sexual and asexual reproduction. All clonal
genotypes were found to be homozygotes for a specific, and otherwise rare allele at one
of the studied microsatellite loci. This finding indicates that asexual reproduction is
genetically, rather than environmentally determined and that its prevalence is determined
by the successful recruitment of clonal genotypes and their potential selective advantage
within a given population.
Platygyra daedalea was sampled from 10 sites, mostly in Kenya. Genetic diversity was
found to be low for this species, especially in near shore lagoonal waters. Populations
sampled on reef-slopes and on the islands of Zanzibar and Mafia in Tanzania, were found
to be significantly more genetically diverse, albeit not as diverse as populations studied
on the GBR. The results indicate limited migration from the more diverse reef-slope
populations into the lagoons, whereas the lagoonal populations were found to be largely
panmictic.
Interestingly, both species show a clear divergence between populations north and south
of Mtwapa creek, indicating a dispersal barrier at this location resulting in significantly
different and isolated coral populations in Northern Kenya.
14-22
Rapid Long-Distance Dispersal Of Pelagic Reef-Fish Larvae: Implications For
Connectivity Models
Benjamin VICTOR* 1
1 Ocean Science Foundation, Irvine, CA
There is a dearth of direct information on long-range connectivity among reef fish
populations. This is mostly because little is known about the potential for distant
dispersal of pelagic reef fish larvae on the scale of hundreds to thousands of kilometers. I
collected a large sample of larvae in the open ocean along the equator about 1,000 km
from the coast of Ecuador. The larvae were identified using mtDNA barcoding and the
sequences revealed that the sample included a significant complement of the regional
shore and reef-fish community, including pomacentrids, labrids, gobiids, blenniids,
serranids, chaetodontids and holocentrids. In addition, freshwater eleotrid larvae were
present that occur only on mainland South America. Barcoding sequences identified a
microdesmid species endemic to Colombia as well as the Baja California razorfish
Xyrichtys mundiceps (Baja California is more than 2,000 km from the collection site).
Daily otolith increments from the reef fish larvae revealed that the ages of the youngest
larvae converged on about 3 weeks. Given the origin of the larvae was at least as far as
Colombia and likely from the Panama Bight, a surprisingly-high estimate of the rate of
dispersal is obtained, about 70 km per day. This estimate is well higher than the usual
South Equatorial Current velocity of 30 cm/s and indicates that the capacity of shorefish
larvae to disperse far offshore in significant numbers may well be underestimated in
connectivity models.
Oral Mini-Symposium 14: Reef Connectivity
14-23
Contrasting Patterns of Population Structure and Dispersal for the Giant Barrel Sponge
(Xestospongia muta) within the Florida Reef Tract and Caribbean
Vince RICHARDS* 1 , Kevin FELDHEIM 2 , Mahmood SHIVJI 1
1 The National Coral Reef Institute, Oceanographic Center, Nova SE University, Florida 33004
USA, Dania Beach, FL, 2 Field Museum, Chicago, Illinois 60605 USA, Chicago, IL
Sponges are one of the dominant fauna on Florida and Caribbean reefs, with species diversity
often exceeding that of scleractinian corals. Despite their importance as structural components
and habitat providers on reefs, their dispersal dynamics are little understood. We utilized eight
microsatellite markers to study the population structure and migration patterns of the giant
barrel sponge (Xestospongia muta), a widespread species throughout Florida and the Caribbean.
Bayesian multilocus genotype analyses clustered 157 samples from the Bahamas, Honduras,
and the US Virgin Islands into three distinct groups. 159 samples from nine locations within
284 km of the Florida reef tract (Key Largo to the Dry Tortugas) formed a fourth group.
Population structure among the four groups was high (FST = 0.155; P = 0.001), with no recent
migration among the groups. In contrast, high levels of migration were detected within the
Florida reef tract. Reefs in the Upper Keys (Long Key) appear to be sources of larvae to reefs in
the north (Key Largo) and also to reefs in the south (Key West and the Dry Tortugas). This
pattern of migration closely matches current pathways within the South Florida recirculation
system, suggesting that currents play an important role in dispersing X. muta larvae within the
Florida reef tract. Although there was an overall lack of isolation by distance among the four
groups, a significant correlation between genetic and geographic distance was found among the
Florida sampling sites indicating that mating within the reef tract is not random. Asexual
reproduction appears not to be the cause as only 1.3% of individuals in Florida shared the same
genotype (1.6% overall). Rather, limited larval dispersal along the reef tract and among
Caribbean locations has probably led to inbreeding within reefs, explaining the significant
deficit in heterozygosity detected (FIS = 0.219; P = 0.001).
14-24
Genetic Population Structure Of Coral Reef Fauna In The Indo-Malay Archipelago:
Implications For Connectivity And Conservation
Marc KOCHZIUS* 1 , Janne TIMM 2 , Agus NURYANTO 2,3 , Wiebke KRÄMER 4 , Leyla
KNITTWEIS 5 , Lemia HAMID 2 , Janet HAUSCHILD 2 , Stina KIRCHHOFF 2 , Inga MEYER-
WACHSMUTH 2 , Christian SEIDEL 2 , Patrick MESTER 2
1 Biotechnology and Molecular Genetics, University of Bremen, 28357 Bremen, Germany,
2 Biotechnology and Molecular Genetics, University of Bremen, 28359 Bremen, Germany,
3 Faculty of Biology, Jenderal Soedirman University, Purwokerto 53122, Indonesia, 4 Marine
Botany, University of Bremen, 28359 Bremen, Germany, 5 Centre for Tropical Marine Ecology,
Bremen, Germany
Even though the Indo-Malay Archipelago hosts the world’s greatest diversity of marine shallow
water species, studies on the genetic population structure and gene flow of marine organisms
within this area are rather rare. Consequently, not much is know about connectivity of marine
populations in the Indo-Malay Archipelago, despite the fact that such information is important
to understand evolutionary and ecological processes in the centre of marine biodiversity.
Therefore, the genetic population structure of several groups of coral reef organisms, such as
fish, bivalves, gastropods, echinoderms, and corals was studied in the framework of the
German-Indonesian research programme SPICE (Science for the Protection of Indonesian
Coastal Marine Ecosystems). Most of the studied species show a complex genetic population
structure characterised by restricted gene flow between some sites and panmixing between
others, which can be attributed to the geological history and prevailing current regimes in the
Indo-Malay Archipelago. The major observed genetic differentiation between the Indian Ocean
and Western Pacific is most probably due to historical isolation by sea level changes, whereas
current oceanographic conditions facilitate connectivity along the ITF on the one hand and
separation at sometimes very small scales on the other hand. Prevailing current regimes at the
western coast of Sumatra as well as the Halmahera eddy off north-western New Guinea prevent
connectivity of populations in the Eastern Indian Ocean and Western Pacific to the central Indo-
Malay Archipelago, maintaining the historical separation caused by sea level fluctuations.
These factors cause vicariance between populations, which can lead to allopatric speciation,
suggesting that the Indo-Malay Archipelago is a centre-of-evolutionary-radiation. These large
scale genetic breaks as well as small scale genetic differentiations should be considered in
conservation efforts and the spatial arrangement of marine protected areas.
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