I use molecular genetic techniques to study ecological and evolutionary questions in marine animals endemic to the Coral Triangle, the area with the highest marine biodiversity in the world.  My research on endangered giant clam species is broadly-focused around (1) larval dispersal and population connectivity and (2) marine conservation in these endangered species.

Limited genetic connectivity in the giant boring clam, Tridacna crocea

        DeBoer, TS, MD Subia, Ambariyanto, MV Erdmann, K Kovitvongsa, and PH Barber. 2008.                                                                 Phylogeography and limited genetic connectivity in the endangered giant boring clam across the Coral Triangle. Conservation Biology 22 (5): 1255-1266.     Abstract

Concordant phylogeographic patterns in three sympatric sister-species of giant clams

The fossil record shows that modern Tridacnid lineages were present in the Indo-West Pacific by the late Miocene, prior to the extreme sea level fluctuations during the Pleistocene.  Therefore, all extant species of Tridacna experienced sea level fluctuations, and any evolutionary consequences, independently. A detailed analysis of phylogeographic patterns in these sympatric species can serve as a robust comparative test of the effects of sea level fluctuations, and resulting restricted gene flow, on phylogeographic patterns in the hyper-diverse region of the Coral Triangle. We collected mtDNA cytochrome c oxidase I sequence data from 745 T. crocea, 488 T. maxima, and 400 T. squamosa from 57 locations in Indoensia and the Philippines. Results forthcoming.

Symbiodinium and giant clams (genus: Tridacna): Patterns of distribution across three host species in the biodiverse Bird’s Head region of the Coral Triangle

The formation and persistence of modern coral reefs depends largely on organisms that host dinoflagellate algal symbionts from the genus Symbiodinium. Numerous studies have documented ecologically important differences among Symbiodinium types and many host species are able to maintain associations with multiple symbiont types simultaneously, which may permit rapid adaptation to local environmental change. This study focused on Symbiodinium diversity in giant clams (genus Tridacna) from the biodiverse Bird’s Head region of Indonesia. The goals of this study were to (a) describe Symbiodinium diversity in natural populations of giant clams, and (b) determine the relationships between Symbiodinium diversity and host species, host genotype, and host environment. Twelve unique Symbiodinium types were identified in 250 host individuals from three Tridacnid species, based on denaturing gradient gel electrophoresis (DGGE) and sequencing of internal transcribed spacer-2 (ITS-2) rDNA. All types were from Clades A, C, and D and were detected in each of the three host species.  Individuals with multiple symbionts from different clades were common (42% of all individuals). Symbiont type and host species were significantly associated. T. crocea associated more often with Clade C and less frequently with Clade D symbionts than if associations were random. T. squamosa associated more frequently with Clade D and less with Clade C. T. maxima associations with all clades did not differ from random expectations, but sample sizes were low. Twenty four data loggers recorded water temperature at 3 meters within the study area. Symbiont types were not randomly distributed in the study area. Instead clams sampled from the warmer waters of the Bay of Cenderawasih had a greater proportion of Clade C symbionts and fewer Clade A symbionts than clams outside the bay in neighboring Raja Ampat.  This is consistent with previous research indicating Clade C types may be more heat tolerant than Clade A. These results point to the possibility that giant clams may associate with different symbiont types based on local environmental conditions. Further research is necessary to understand the implications of climate change on internationally protected giant clams and their symbionts.

Modern gene flow and genetic connectivity in Tridacna crocea inferred from 9 new microsatellite markers

Recent studies of connectivity in marine populations have suggested that larval retention and local recruitment are more common than previously considered. Here I use rapidly evolving molecular markers to investigate the scale of connectivity and patterns of recruitment in the boring giant clam (Tridacna crocea), a broadcast spawner with a pelagic larval stage.