Wilfredo H. Uy

Habitat Use by Fishes in Coral Reefs, Seagrass Beds and Mangrove Habitats in the Philippines

Understanding the interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas. To elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats, and between natural and transplanted mangroves, visual censuses were conducted semiannually at two sites in the Philippines during September and March 2010–2012. In total, 265 species and 15,930 individuals were recorded. Species richness and abundance of fishes were significantly higher in coral reefs (234 species, 12,306 individuals) than in seagrass (38 species, 1,198 individuals) and mangrove (47 species, 2,426 individuals) habitats. Similarity tests revealed a highly significant difference among the three habitats. Fishes exhibited two different strategies for habitat use, inhabiting either a single (85.6% of recorded species) or several habitats (14.4%). Some fish that utilized multiple habitats, such as Lutjanus monostigma and Parupeneus barberinus, showed possible ontogenetic habitat shifts from mangroves and/or seagrass habitats to coral reefs. Moreover, over 20% of commercial fish species used multiple habitats, highlighting the importance of including different habitat types within marine protected areas to achieve efficient and effective resource management. Neither species richness nor abundance of fishes significantly differed between natural and transplanted mangroves. In addition, 14 fish species were recorded in a 20-year-old transplanted mangrove area, and over 90% of these species used multiple habitats, further demonstrating the key role of transplanted mangroves as a reef fish habitat in this region.

The Kuroshio Current influences genetic diversity and population genetic structure of a tropical seagrass, Enhalus acoroides

Information on genetic diversity and differentiation of seagrass populations is essential for the conservation of coastal ecosystems. However, little is known about the seagrasses in the Indo‐West Pacific Ocean, where the worlds highest diversity of seagrasses occurs. The influence of sea currents on these populations is also unknown. We estimated the genetic diversity and population genetic structure and identified reproductive features in Enhalus acoroides populations from the Yaeyama Islands, Hainan Island and the Philippines. The Philippines are situated at the centre of the E. acoroides range, Yaeyama and Hainan are peripheral populations, and the Yaeyama population is at the northern limit of the species range. The powerful Kuroshio Current flows from the Philippines to Yaeyama. Genetic analyses using nine microsatellite markers indicated that reproduction of E. acoroides is mostly sexual. Clonal diversity does not decrease in northern populations, although genetic diversity does. However, the genetic diversity of the Yaeyama populations is greater than that of the Hainan populations. Significant genetic differentiation among most populations was evident; however, the Yaeyama and north‐east Philippines populations were genetically similar, despite being separated by ~1100 km. An assignment test suggested that recruitment occurs from the north‐east Philippines to Yaeyama. The strong current in this region is probably responsible for the extant genetic diversity and recruitment patterns.

Genetic diversity and structure of the tropical seagrass Cymodocea serrulata spanning its central diversity hotspot and range edge

Abstract Persistence of populations at their distributional ranges relies on local population dynamics and the fitness of species with low dispersal potential. We analyzed the population genetic diversity and structure of a tropical seagrass species, Cymodocea serrulata, at 34 sites spanning Philippine (diversity hotspot) and Ryukyu Islands (northern limit of distribution) populations using microsatellite (SSR) markers. Seagrass populations in the diversity hotspot are hypothesized to contain higher genetic diversity and clonal richness than those resulting from expansion or geographic range limits. We tested this hypothesis by comparing the genetic diversity, genetic structure and clonal richness of C. serrulata populations in the Philippines and Ryukyu Islands. C. serrulata populations showed decreased genetic diversity and clonal richness at their northern limit. Clonal reproduction predominated at the northern limit, while sexual reproduction prevailed in the diversity hotspot. Decreased genetic diversity and clonal richness at the northern limit may be the consequence of drift resulting from founder effect, reduced habitat, sea surface temperature and low gene flow and/or natural selection across life stages, wherein clonal reproduction confers greater environmental fitness. Analysis of molecular variance (AMOVA) and the fixation index, FST, showed significant genetic differentiation within and among geographic populations. STRUCTURE analysis revealed that the Ryukyu Islands populations were mosaics of genets from the eastern Philippines, likely carried by the Kuroshio Current.

17-year change in species composition of mixed seagrass beds around Santiago Island, Bolinao, the northwestern Philippines

Effects of fish culture can alter the adjacent ecosystems. This study compared seagrass species compositions in 2012 with those in 1995, when fish culture was less intensive compared to 2012 in the region. Observations were conducted at the same four sites around Santiago Island, Bolinao: (1) Silaqui Island, (2) Binaballian Loob, (3) Pislatan and (4) Santa Barbara, and by using the same methods as those of Bach et al. (1998). These sites were originally selected along a siltation gradient, ranging from Site 1, the most pristine, to Site 4, a heavily silted site. By 2012, fish culture had expanded around Sites 2, 3 and 4, where chlorophyll a (Chl a) was greater in 2012 than in 1995 by one order of magnitude. Enhalus acoroides and Cymodocea serrulata, which were recorded in 1995, were no longer present at Site 4, where both siltation and nutrient load are heavy.

Development of microsatellite markers in a tropical seagrass Syringodium isoetifolium (Cymodoceaceae)

Nine microsatellite markers of a tropical seagrass species, Syringodium isoetifolium, were developed to investigate genetic diversity and genetic connectivity. The number of alleles detected per locus ranged from two to 16, and the observed and expected heterozygosities ranged from 0.00 to 1.00 and 0.12 to 0.91, respectively. The markers described here are sufficiently polymorphic and informative to investigate the genetic diversity, genetic connectivity and genetic structure of S. isoetifolium.

Development of novel microsatellite markers in a tropical seagrass, Enhalus acoroides

Using the dual-suppression polymerase chain reaction technique, 12 novel polymorphic nuclear microsatellite DNA markers were isolated from the tropical seagrass Enhalus acoroides. The isolated markers provided the polymorphisms of 2–13 alleles per locus in 3 populations located in Japan, China, and the Philippines. The values of the expected heterozygosity fell in the following ranges: 0.000–0.693 (Japan), 0.000–0.623 (China), and 0.000–0.765 (Philippines). Compared to the Philippines population (1 monomorphic locus), a relatively higher proportion of the SSR loci did not show polymorphism in the marginal habitats of E. acoroides (5 loci in Japan; 5 loci in China). These markers may be useful for population and conservation genetics of E. acoroides.

Isolation and characterization of novel microsatellite markers for Cymodocea serrulata (Cymodoceaceae), a seagrass distributed widely in the Indo-Pacific region

Cymodocea serrulata is a tropical seagrass species distributed widely in the Indo-Pacific region. We developed 16 novel microsatellite (simple sequence repeat) markers for C. serrulata using next-generation sequencing for use in genetic studies. The applicability of these markers was attested by genotyping of 40 individuals collected from a natural population in the Philippines. Of the 16 loci, 15 showed polymorphism. For the 15 polymorphic markers, the number of alleles per locus ranged from two to seven, and the observed and expected heterozygosities ranged from 0.131–1.000 and 0.124–0.788, respectively. These markers are useful tools for elucidating genetic diversity, connectivity, and structure in this foundational coastal species.

Development of novel microsatellite markers for Cymodocea rotundata Ehrenberg (Cymodoceaceae), a pioneer seagrass species widely distributed in the Indo-Pacific

Genetic diversity and population genetic structure are key components of seagrass resilience and contribute to an understanding of its conservation and management. We isolated 29 polymorphic microsatellite (SSR) markers from a widely distributed pioneer seagrass, Cymodocea rotundata, by two methods; next generation sequencing and compound SSR marker isolation. Twenty-nine markers had 2–14 alleles per locus, and the observed and expected heterozygosity ranged from 0 to 0.688, and 0.113 to 0.770, respectively. These loci will facilitate investigation of the genetic diversity and population genetic connectivity and structure of C. rotundata.

Variation in macrofaunal communities of sea grass beds along a pollution gradient in Bolinao, northwestern Philippines

This study examined the variation of macrofaunal communities in sea grass beds along a pollution gradient in Bolinao, northwestern Philippines. We established four stations and compared the diversity and abundance of macrofauna between them. The Shannon diversity index in the least polluted station was more than twice higher than that in the most polluted one. Abundance was more than thrice higher in the most polluted station. The species composition generally varied, with community difference explained largely by the predominance of the filter-feeding bivalve Gafrarium pectinatum and polychaete Capitella capitata. Species heterogeneity was reduced along the pollution gradient by approximately 19% from the least polluted to the most polluted station. This reduction indicates biodiversity alteration, which has a significant impact on ecosystem functioning. Aspects of species heterogeneity should be considered in environmental impact assessments and the management of coastal areas encountered with anthropogenic disturbances.

Development of microsatellite markers for Thalassia hemprichii (Hydrocharitaceae), a widely distributed seagrass in the Indo-Pacific

Nine microsatellite markers of a widely-distributed seagrass, Thalassia hemprichii, were developed to investigate genetic diversity and genetic connectivity. The number of alleles detected per locus ranged from 3 to 26, and the expected and observed heterozygosities ranged from 0.00 to 1.00 and 0.00 to 0.87, respectively. The markers described here are sufficiently polymorphic and informative to investigate the genetic diversity, genetic connectivity and genetic structure of T. hemprichii.