11th ICRS Abstract book - Nova Southeastern University

14-41
Fine-scale Spatial Genetic Structure in the Caribbean Staghorn Coral Acropora
cervicornis
Silvia LIBRO* 1 , Steve VOLLMER 1
1 Marine Science Center, Northeastern University, Nahant, MA
Localized spatial genetic structure (SGS), i.e. the non-random association of genetic
relatedness among individuals in space, can be caused by a variety of demographic and
evolutionary processes including limited dispersal, inbreeding, and selection. SGS has
been studied extensively in plants, in order to estimate fine-scale patterns of dispersal, but
has rarely been examined in sessile marine taxa. Here we investigated the possibility that
SGS might be important in the staghorn coral Acropora cervicornis. Staghorn corals from
four populations were mapped along permanent transects and genotyped with five
microsatellite loci. Our results show that A. cervicornis exhibits localized SGS within
reefs (out to 14 meters) due to both the spatial aggregation of clones and the non-random
association of genets on reefs. We show that patches of A. cervicornis can be highly
inter-related as well with relatedness on the order of cousins. We also detected moderate
to high levels of population genetic structure among reefs over spatial scales as small as
2kms, but no evidence of isolation by distance among reefs. We suggest that the localized
SGS, high relatedness among genets within reefs, and strong population structure
between reefs is the results of rare cohort recruitment.
14-42
Understanding Patterns Of Gene Flow in Coral Reef Fishes: Multiple Species And
Multiple Scales.
Joshua DREW* 1 , Paul BARBER 2
1 Marine Program, Boston University, Woods Hole, MA, 2 Marine Program, Boston
University, Boston, MA
Understanding the spatial scales over which populations of coral reef fishes are connected
is important for elucidating evolutionary patterns as well as in setting conservation
priorities. In this presentation we compare patterns of genetic connectivity of several
common coral reef fishes over multiple spatial scales. On the finest scale, between the
islands of Fiji we see broad scale genetic homogenization with most, but not all of the
species we examine. However, on the next highest spatial scale (between Fiji and the rest
of Melanesia) we see evidence for regional endemism within five species of fishes.
Expanding further, we investigate two species of fish Amphiprion melanopus and
Pomacentrus moluccenis [Pomacentridae] whose species ranges are entirely within
Melanesia and Indonesia. Here we see evidence for restricted gene flow across the Indo-
West Pacific archipelagos ultimately leading to the evolution of peripheral populations
into reproductively isolated monophyletic clades. Finally at the largest spatial scales we
use the widely distributed species Halichoeres hortulanus [Labridae], to investigate gene
flow across the Indian and Pacific oceans, and discover significant barriers to gene flow
between these oceans occurring in the Indonesian archipelago. Our results demonstrate
that despite having pelagic larvae and the ability to distribute genes over broad
geographic differences, some coral reef fish populations are geographically structured,
but the magnitude of that structure depends on the spatial scale considered.
Oral Mini-Symposium 14: Reef Connectivity
14-43
Connectivity in A Caribbean Octocoral: A Tale Of Three Datasets
Howard LASKER* 1 , Jaret BILEWITCH 1 , Stefano GOFFREDO 2
1 Program in Evolution, Ecology and Behavior, and Dept of Geology, University at Buffalo,
Buffalo, NY, 2 Department of Evolutionary and Experimental Biology, University of Bologna,
Bologna, Italy
Characterizations of connectivity vary with the spatial and temporal scales inherent in the
techniques used to assess connectivity. The Caribbean octocoral, Pseudopterogorgia
elisabethae has been harvested on the Little Bahama Bank for over 10 years. The harvest,
which involves cropping colonies, leaves areas with reduced numbers of reproductive colonies.
This reduction in reproductive colonies should reduce local recruitment, since P. elisabethae
surface broods and has negatively buoyant planulae. We examined connectivity among
populations on the Little Bahama Bank and throughout the northern Bahamas on differing
spatial and temporal scales by comparing recruitment before and after harvesting, comparing
the population size/age structure between harvested and unharvested areas and examining
population genetic structure.
Recruitment at sites in 2004 and 2005 varied with local population density, but changes in
recruitment due to harvesting were no greater than inter-annual variation in recruitment at all
sites. However, the size structure of populations that were subjected to up to 3 episodes of
harvesting had depressed proportions of small colonies suggesting that local recruitment and the
extended depression of local recruitment affected population demographics. Microsatellite
analyses of populations on the Little Bahama Bank detected minimal population clustering but
did identify significant FST values. We found high levels of structure on larger scales. The data
suggest that in any single year recruits readily move over scales >10 -1 km. However, over the
scale of a decade and summed across harvesting encompassing several kilometers a substantial
portion of recruitment is local. Over scales of decades and 10 to >100 km there is sufficient
migration to reduce but not eliminate population genetic structure. There is limited migration
across oceanographic barriers.
14-44
Preliminary Analysis of Acropora palmata Gene Flow in Reefs of the US Virgin Islands
William SCHILL* 1 , Caroline ROGERS 2 , Erinn MULLER 3 , Anthony SPITZACK 4 , Iliana
BAUMS 5
1 Natl. Fish Health Research Laboratory, USGS-Leetown Science Center, Kearneysville, WV,
2 Virgin Islands National Park, USGS-Florida Integrated Science Center, St. John, Virgin Islands
(U.S.), 3 Florida Institute of Technology, Melbourne, FL, 4 USGS-Florida Integrated Science
Center, St. John, Virgin Islands (U.S.), 5 The Pensylvania State University, University Park, PA
Two regionally isolated populations of Acropora palmata that were previously identified are
generally demarcated by Mona Island, east of Puerto Rico. To further examine pathways of
gene flow in the eastern zone, we determined the genotype at five polymorphic microsatellite
loci of 256 colonies of Acropora palmata from six sites on St. John, and 92 additional colonies
from two sites at Buck Island/St. Croix, USVI. Data analysis using AMOVA demonstrated that
98% of the genetic variation was within collections, while 2% was among the island groupings.
Sixty-five of the 348 colonies were clonal. The incidence of clonality may be influenced by
differential spatial scales of sampling at various sites, but was lowest in samples from the South
Fore Reef of Buck Island (0 of 50 colonies), and highest at the Hawksnest Bay, St. John site (21
of 42 colonies). When clonemates were removed from the analysis, the differentiation of the
island groupings disappeared and the algorithm used by the program, structure v. 2.2, failed to
identify more than a single cluster. Pairwise population FST and RST values, however, indicated
significant differentiation for combinations of the Yawzi Point or Saltpond Bay, St. John,
collections with the two St. Croix collections. We also examined distributions of sample pairs’
relatedness. Within collections, mean relatedness was significantly higher between sample
pairs from the two St. Croix collections than between sample pairs of other collections. Thus,
the St. Croix collections seem to exhibit some cohesiveness not generally found in the St. John
collections. The Saltpond Bay collection, however, was distinct from the other five St. John
collections in that 5.5% of the possible pairings shared at least one allele at each of the five loci.
Analyses of individuals with similar genotypes suggest potential connections between reefs.
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