In order to analyse the structure of the fish community in Cabo Pulmo Reef., 36 cylindrical stationary censuses (5 m radius, 15 min of observation time) were conducted in October 2003 (warm season) and February 2004 (cold season). To explore the relationship with depth and associated variables, we considered a shallow stratum (<5 m) and a deep stratum (>5.5 m; depth range was between 2 and 15 m). Species richness, number of individuals, and the indices of diversity (Shannon), evenness (Pielou) and taxonomic distinctness were computed for each census. A total of 8725 fish were recorded (3829 in the warm season and 4896 in the cold season), belonging to 62 species, included in 23 families. Thalassoma lucasanum and Chromis atrilobata were the dominant species (62.5% of total abundance, and occurrence of 97% and 72%, respectively). Conversely, 50 species had low relative abundance, <1% of total abundance, and a frequency of occurrence <50% of the census. None of the ecological descriptors were significantly different between seasons (P > 0.5), but richness, abundance and taxonomic differentiation were higher in the deeper zone. The analysis of similarity and ordination analysis did not show consistent clusters by season or depth, but suggest similarity among census of deeper zones. Most species preference for physical factors associated with deeper zones maybe the reason for the pattern observed in this study.

No abstract

Abstract. The influence of corallivores on coral community structure of eastern Pacific reefs has been considered less important then that of abiotic oceanographic factors. The data that support this assumption, however, are only available for Central American reefs. To assess the role of predation on hermatypic corals in a different regional reef environment, the abundance, spatial distribution and consumption rate of three corallivores: the echinoid Eucidaris thouarsii (Valenciennes), the asteroid Acanthaster planci (Linnaeus) and the teleostean fish Arothron meleagris (Bloch & Schneider), were estimated at Cabo Pulmo reef, Gulf of California, México (23°25′ N, 109°25′ W). Statistically, the abundances of the species did not change in any sections of the reef (mean values: E. thouarsii, 0.17 indiv. · m−2; A. planci, 1.9 indiv. · m−2; A. meleagris, 39 indiv. · ha−1). The average daily individual consumption rates of coral were calculated at 1.83 g CaCO3· m−2 for E. thouarsii, 118.4 cm2 for A. planci, and 16.38 g CaCO3· m−2 for A. meleagris, and were lower than those reported for Central American reefs. Considering the mean estimated carbonate production (7.9 kg CaCO3· m−2· a−1), corallivores eliminate less than 4% of the coral standing stock of Cabo Pulmo reef. The low corallivore population density and consumption rates, together with high local coral cover, indicate that corallivores are not key factors determining scleractinian abundance in this marginal reef.

Corals in the Eastern Pacific extend south from the Gulf of California to Ecuador and oceanic Chile, and west from Colombia to Clipperton Atoll. Nevertheless, large stretches of the Mexican Pacific remain fundamentally unstudied. Therefore, to assess the current conditions of coral communities, a coastal fringe ∼300 km long (17°40′ N, 101°39′ W to 16°46′ N, 99°49′ W) was surveyed within the Southern Mexican Pacific, between 2005 and 2009. Fifteen stony coral species were identified at 13 coral communities and six Pocillopora‐dominated fringing reefs, with Pocillopora verrucosa and Pocillopora damicornis the primary contributing taxa. Reef development was identified in embayments or behind rocks or islands that offered shelter from northern and northwestern winds. Observations of Pocillopora effusus, Pocillopora inflata, Porites lobata, Pavona clavus, and Pavona varians expanded the species known geographic ranges by several degrees of latitude, suggesting reef building fauna comprised a mixture of widespread and relatively rare Eastern Pacific corals. Results indicated greater live coral cover in the Ixtapa‐Zihuatanejo area (15–73%) than in the Acapulco localities, which had high algal dominance; the reefs in the latter region exhibited high erosion. Regional differences are likely the result of long‐standing anthropogenic pressures around Acapulco since 1950, when it became an important tourist destination. This paper is the first detailed report of ecologically stressed corals and coral reefs from the state of Guerrero on the Mexican Southern Pacific coast.

Mexico harbors more than 10% of the planet's endemic species. However, the integrity and biodiversity of many ecosystems is experiencing rapid transformation under the influence of a wide array of human and natural disturbances. In order to disentangle the effects of human and natural disturbance regimes at different spatial and temporal scales, we selected six terrestrial (temperate montane forests, montane cloud forests, tropical rain forests, tropical semi-deciduous forests, tropical dry forests, and deserts) and four aquatic (coral reefs, mangrove forests, kelp forests and saline lakes) ecosystems. We used semiquantitative statistical methods to assess (1) the most important agents of disturbance Electronic supplementary material The online version of this article (affecting the ecosystems, (2) the vulnerability of each ecosystem to anthropogenic and natural disturbance, and (3) the differences in ecosystem disturbance regimes and their resilience. Our analysis indicates a significant variation in ecological responses, recovery capacity, and resilience among ecosystems. The constant and widespread presence of human impacts on both terrestrial and aquatic ecosystems is reflected either in reduced area coverage for most systems, or reduced productivity and biodiversity, particularly in the case of fragile ecosystems (e.g., rain forests, coral reefs). In all cases, the interaction between historical human impacts and episodic high intensity natural disturbance (e.g., hurricanes, fires) has triggered a reduction in species diversity and induced significant changes in habitat distribution or species dominance. The lack of monitoring programs assessing before/after effects of major disturbances in Mexico is one of the major limitations to quantifying the commonalities and differences of disturbance effects on ecosystem properties.

No abstract

Summary In spite of their ecological and economic importance, reef fishes from the coast of Oaxaca, Mexico are rarely studied, therefore precluding their management and conservation. In order to identify the set of habitat characteristics/environmental conditions that predict major shifts in fish assemblages in space and time, a stationary census (5′, φ = 5 m) was conducted on a semi‐monthly basis from 2006 to 2009 at patch reefs along the coast. Habitat configuration was gathered using 25 m long point‐intersect transects (data every 25 cm), recording all underlying coral species and substrate characteristics (rocks, sand, algal mats, rubble or dead corals). Recorded were 65 452 fishes grouped in 11 orders, 36 families, 65 genera and 89 species. Labridae (nine species), Pomacentridae (eight species) and Serranidae (seven species) were the most frequent families. Abundance is severely skewed among species; four species Thalassoma lucasanum, Chromis atrilobata, Apogon pacificus and Stegastes acapulcoensis comprise nearly 59% of the fish abundance, 11 species contribute 30%, whereas most of the species (75) can be considered as rare since they contribute <1% each to the total. Species richness and family‐level assemblage composition are similar to those recorded elsewhere in the eastern Pacific. Non‐parametric multivariate analysis of variance demonstrated that changes of diversity metrics might be associated with environmental differences on the scale of hundreds of meters to kilometers, as well as coupled with major changes on oceanographic variables throughout time, exerting meaningful changes on reef‐related fish assemblages.

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.