Héctor Reyes-Bonilla

Host-symbiont recombination versus natural selection in the response of coral-dinoflagellate symbioses to environmental disturbance.

Mutualisms between reef-building corals and endosymbiotic dinoflagellates are particularly sensitive to environmental stress, yet the ecosystems they construct have endured major oscillations in global climate. During the winter of 2008, an extreme cold-water event occurred in the Gulf of California that bleached corals in the genus Pocillopora harbouring a thermally ‘sensitive’ symbiont, designated Symbiodinium C1b-c, while colonies possessing Symbiodinium D1 were mostly unaffected. Certain bleached colonies recovered quickly while others suffered partial or complete mortality. In most colonies, no appreciable change was observed in the identity of the original symbiont, indicating that these partnerships are stable. During the initial phases of recovery, a third species of symbiont B1Aiptasia, genetically identical to that harboured by the invasive anemone, Aiptasia sp., grew opportunistically and was visible as light-yellow patches on the branch tips of several colonies. However, this symbiont did not persist and was displaced in all cases by C1b-c several months later. Colonies with D1 were abundant at inshore habitats along the continental eastern Pacific, where seasonal turbidity is high relative to offshore islands. Environmental conditions of the central and southern coasts of Mexico were not sufficient to explain the exclusivity of D1 Pocillopora in these regions. It is possible that mass mortalities associated with major thermal disturbances during the 1997–1998 El Niño Southern Oscillation eliminated C1b-c holobionts from these locations. The differential loss of Pocillopora holobionts in response to thermal stress suggests that natural selection on existing variation can cause rapid and significant shifts in the frequency of particular coral–algal partnerships. However, coral populations may take decades to recover following episodes of severe selection, thereby raising considerable uncertainty about the long-term viability of these communities.

Coral reefs of the Pacific coast of México

ABSTRACT Coral reefs and communities of the Pacific coast of Mexico have been studied since the 19th Century, but considered as rare, and of little importance. Nevertheless, new discoveries during the last decade have brought a renewed interest into these systems. Due to differences in the biological characteristics and composition of the coral communities, the reefs of the west coast of Mexico are naturally divided into three groups: those of the Gulf of California, the Revillagigedo Archipelago, and the tropical Mexican Pacific. In the Gulf, there are abundant coral patches, but only three structures that can be considered reefs; one of them, Cabo Pulmo (23°N), is the most studied reef on the west coast of the country. Frameworks are small, communities are dominated by Pocillopora spp., and zonation is weak. The oceanic Revillagigedo Archipelago (18°N) has fringing reefs in Clarion and Socorro, where pocilloporids prevail in shallow water and massive species in deeper areas. Reefs can attain 3 m in thickness, and present the highest coral species richness in western Mexico (18 taxa). The tropical Pacific shows the best reef development in Mexico at Nayarit (21°N) and Oaxaca (15°N); coral cover is high but diversity is low, because the well-consolidated frameworks are mostly composed of Pocillopora spp. Between these reef areas, long tracts of sandy beaches hinder coral settlement and growth, but some small and isolated communities exist. Along the Pacific coast of Mexico, natural perturbations are common and affect reefs in different ways, depending on their geographic position. Corallivores and bioeroders are widespread, but few studies have been conducted to determine their importance on coral communities. The sea star Acanthaster, Lithophaga bivalves and the urchins Eucidaris and Diadema appear to be the most important species, but because of their low abundance and the high coral cover, accretion seems to be higher than erosion or predation, resulting in net positive growth of reefs. On the other hand, oceanographic and atmospheric events such as hurricanes and the El Nino-Southern Oscillation are suggested to be much more important in determining coral abundance and community structure in Mexico, both on short- and long-term scales. However, their effects are not catastrophic. Human-induced perturbations (in particular fisheries, tourism and sedimentation) are still very localized and of relatively low scale, but they may turn into demanding problems in the coming years because of the lack of official and public attention to the Pacific reefs, the slow implementation of management plans and other protective procedures, and the economic need to develop Mexicos west coastal areas.

Spring “bleaching” among Pocillopora in the Sea of Cortez, Eastern Pacific

A mild bleaching event was observed among Pocillopora spp. in the southern Gulf of California in the spring of 2006. Uniform bleaching occurred in numerous colonies on the upper portions of their branches. Most (∼90%) colonies that exhibited bleaching contained a species of endosymbiotic dinoflagellate, Symbiodinium C1b-c, which differed from the Symbiodinium D1 found inhabiting most unbleached colonies. Analysis of chlorophyll fluorescence, indicated a decline in photosystem II photochemical activity, especially among colonies populated with C1b-c. By early August, most affected colonies had recovered their normal pigmentation and fluorescence values were once again high for all colonies. No mortality was observed among tagged bleached colonies nor did symbiont species composition change during recovery. This unusual episode of bleaching did not appear to be a response to thermal stress, but may have been triggered by high levels of solar radiation during a period of unseasonally high water clarity in the early spring.

Reproduction of the Cortes Geoduck Panopea globosa (Bivalvia: Hiatellidae) and Its Relationship with Temperature and Ocean Productivity

ABSTRACT This article describes the timing of gametogenic development and spawning in a population of geoduck clams, Panopea globosa (Dall 1898), from the Upper Gulf of California and its relationship to temperature changes and primary productivity. Clams were collected monthly over 1 year (March 2008 to March 2009), and salinity, dissolved oxygen, and substrate type were recorded during each survey. Standard histological analyses and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Satellite data for temperature and chlorophyll were gathered to test a general conceptual planktonic larval development model. The results demonstrated that reproductive activity was triggered by a steep decrease in temperature 4 months prior to the peak of productivity. Thus, larval development matches favorable conditions, as predicted by Cushings Match—Mismatch Hypothesis.

Genetic Connectivity Patterns of Corals Pocillopora damicornis and Porites panamensis (Anthozoa: Scleractinia) along the West Coast of Mexico

Abstract: Genetic connectivity was studied in two scleractinian corals, Pocillopora damicornis (branching and broadcast spawner) and Pontes panamensis (massive and brooding type), along the Pacific coast of Mexico. Allelic diversity between adults and juveniles, the latter recruited after the El Niño—Southern Oscillation (ENSO) 1997–1998 event, was determined, and level of genetic connectivity among populations was assessed. There were no significant differences in allelic diversity between adults and juveniles from the same location. Seascape spatial genetic analysis suggested two or three clusters, depending on the species: (1) Bahías de Huatulco, (2) south of the Baja California Peninsula and Bahía de Banderas, and (3) locations in the Gulf of California. The most important barrier to gene flow was detected between Bahía de Banderas and Bahías de Huatulco and corresponds with a major coastal stretch of sandy beaches and lagoons. Moderate to high gene flow was found inside and at the entrance of the Gulf of California (Nem = 62–250), possibly favored by seasonal circulation patterns and sexual reproduction. In contrast, low gene flow was observed between southern populations and the rest of coastal Mexico (Nem < 1.7) based on high local recruitment and habitat discontinuity. A close genetic relationship of corals from the southern part of the Baja California Peninsula and severely damaged Bahía de Banderas coral communities confirmed that exchange of propagules could have taken place between the localities after the ENSO 1997–1998 event. Despite different reproductive strategies, both species showed similar patterns, suggesting the importance of surficial currents and habitat discontinuity to predict connectivity among coral reefs.

Testing the genetic predictions of a biogeographical model in a dominant endemic Eastern Pacific coral (Porites panamensis) using a genetic seascape approach

The coral fauna of the Eastern Tropical Pacific (ETP) is depauperate and peripheral; hence, it has drawn attention to the factors allowing its survival. Here, we use a genetic seascape approach and ecological niche modeling to unravel the environmental factors correlating with the genetic variation of Porites panamensis, a hermatypic coral endemic to the ETP. Specifically, we test if levels of diversity and connectivity are higher among abundant than among depauperate populations, as expected by a geographically relaxed version of the Abundant Center Hypothesis (rel-ACH). Unlike the original ACH, referring to a geographical center of distribution of maximal abundance, the rel-ACH refers only to a center of maximum abundance, irrespective of its geographic position. The patterns of relative abundance of P. panamensis in the Mexican Pacific revealed that northern populations from Baja California represent its center of abundance; and southern depauperate populations along the continental margin are peripheral relative to it. Genetic patterns of diversity and structure of nuclear DNA sequences (ribosomal DNA and a single copy open reading frame) and five alloenzymatic loci partially agreed with rel-ACH predictions. We found higher diversity levels in peninsular populations and significant differentiation between peninsular and continental colonies. In addition, continental populations showed higher levels of differentiation and lower connectivity than peninsular populations in the absence of isolation by distance in each region. Some discrepancies with model expectations may relate to the influence of significant habitat discontinuities in the face of limited dispersal potential. Environmental data analyses and niche modeling allowed us to identify temperature, water clarity, and substrate availability as the main factors correlating with patterns of abundance, genetic diversity, and structure, which may hold the key to the survival of P. panamensis in the face of widespread environmental degradation.

Waterbirds of the Lagoon Complex Magdalena Bay-Almejas, Baja California Sur, Mexico

Abstract The spatial distribution of avifauna was documented in Magdalena Bay, the largest coastal wetland on the Pacific coast of the Baja California peninsula. An inventory of waterbirds in the three wetland zones of Magdalena Bay-Almejas, Baja California Sur was conducted by boat. Composition, abundance, and distribution of species were determined in 12 coastal censuses conducted from February 2002 to February 2003. A total of 207,383 individuals of 80 species and 20 families were recorded. Seven listed species breed in the wetland. Only ten out of 80 species were very common, while the others were occasional along the coastline. Guilds with highest populations were pelicans and allies (54%), followed by shorebirds (23%), and gulls, terns and skimmers (14%). The highest richness of 63 species was recorded in the Santo Domingo Channel in autumn. In contrast, the highest abundance (50,082) was recorded in fall in Magdalena Bay. Migratory birds explained spatial and temporal changes in richness, while resident pelicans and allies explain abundance variations. The highest species richness was observed in mangrove zones, particularly in the Santo Domingo Channel. Therefore, this habitat together with breeding and gathering places used for other activities, should be primary targets for future management and conservation initiatives.

Eastern Pacific Coral Reef Provinces, Coral Community Structure and Composition: An Overview

Advances in our knowledge of eastern tropical Pacific (ETP) coral reef biogeography and ecology during the past two decades are briefly reviewed. Fifteen ETP subregions are recognized, including mainland and island localities from the Gulf of California (Mexico) to Rapa Nui (Easter Island, Chile). Updated species lists reveal a mean increase of 4.2 new species records per locality or an overall increase of 19.2 % in species richness during the past decade. The largest increases occurred in tropical mainland Mexico, and in equatorial Costa Rica and Colombia, due mainly to continuing surveys of these under-studied areas. Newly discovered coral communities are also now known from the southern Nicaraguan coastline. To date 47 zooxanthellate scleractinian species have been recorded in the ETP, of which 33 also occur in the central/south Pacific, and 8 are presumed to be ETP endemics. Usually no more than 20–25 zooxanthellate coral species are present at any given locality, with the principal reef-building genera being Pocillopora, Porites, Pavona, and Gardineroseris. This compares with 62–163 species at four of the nearest central/south Pacific localities. Hydrocorals in the genus Millepora also occur in the ETP and are reviewed in the context of their global distributions. Coral community associates engaged in corallivory, bioerosion, and competition for space are noted for several localities. Reef framework construction in the ETP typically occurs at shallow depths (2–8 m) in sheltered habitats or at greater depths (10–30 m) in more exposed areas such as oceanic island settings with high water column light penetration. Generally, eastern Pacific reefs do not reach sea level with the development of drying reef flats, and instead experience brief periods of exposure during extreme low tides or drops in sea level during La Nina events. High rates of mortality during El Nino disturbances have occurred in many ETP equatorial areas, especially in Panama and the Galapagos Islands during the 1980s and 1990s. Remarkably, however, no loss of resident, zooxanthellate scleractinian species has occurred at these sites, and many ETP coral reefs have demonstrated significant recovery from these disturbances during the past two decades.

Integrating genetic, phenotypic and ecological analyses to assess the variation and clarify the distribution of the Cortes geoduck ( Panopea globosa )

The Cortes geoduck ( Panopea globosa ) has been considered a Gulf of California (GC) endemic but anecdotal and unpublished evidence has suggested its presence in Bahia Magdalena (BM), on the Pacific coast of southern Baja California. Establishing the identity of geoduck clams and their distribution limits is not only of clear biological significance to understand their structural and functional variation, but is also of consequence for their conservation and management, given the multi-million dollar fishery they support in north-west Mexico. We analysed Panopea clams from Mexican populations, including BM, using an integrative approach including genetics, morphometrics, and an ecological niche model. Our genetic results (restriction fragment length polymorphisms of nuclear ribosomal DNA and mtDNA cytochrome c oxidase subunit I sequences) clearly identify BM geoducks as P. globosa , implying a significant geographical range expansion outside of the GC and refuting its status as endemic to the Gulf. On the other hand, clams from BM were phenotypically different (shell significantly higher) from other Mexican P. globosa and Panopea generosa specimens, which may account for the confusion in their morphological identification. The ecological niche model for P. globosa , integrating ecological and distributional data from the GC, revealed a very low probability (

Fishes of Clipperton Atoll, Eastern Pacific: Checklist, Endemism, and Analysis of Completeness of the Inventory

Abstract: An updated checklist of cartilaginous and bony fishes from reefs and nearby areas around Clipperton Atoll (eastern Pacific) is presented. The register was compiled from field surveys between 1997 and 2012, an exhaustive literature review, and consultation of museum collections and databases. Records were then used to assess completeness of the local fish inventory using six nonparametric rarefaction formulations. A total of 197 species in 62 families was recorded, and of these 106 correspond to reef fishes; most of these are immigrants from the eastern and central Pacific, and only seven species were identified as endemics of the atoll. Estimated level of endemism in reef species (6.6%) is high for the eastern Pacific as a whole but intermediate when compared with data for other oceanic islands of the same region. From nonparametric tests it was estimated that expected number of reef fishes present at Clipperton is 110 + 4 species, and because the difference from the reported number from this new checklist was not significant, we suggest that the current listing is practically complete. Comparisons of completeness of the inventory at Clipperton (~95%) with that reported for fish fauna of the eastern Pacific and worldwide revealed that quality of the current inventory is remarkably high, even in spite of the geographic isolation of the atoll and the still limited scientific data.