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Ophiuroidea (Echinodermata) diversity partitioning across the eastern tropical Pacific
Abstract
Despite the high relevance of echinoderms in the Southern Mexican Pacific coral reef systems, there is no detailed analysis of
their regional diversity. Based on records from field surveys and literature, this work analyzed for the first time the echinoderm
species composition in coral reef systems in the Southern Mexican Pacific, evaluating their richness and distribution patterns. Fifty-two species represent the region (six Asteroidea, eight Echinoidea, 15 Ophiuroidea, and 23 Holothuroidea), a more
significant number than other coral reef systems in the Mexican Pacific and Central America. New records are presented at
the region, zone, and site level. At the zone level, the highest species richness occurred in Huatulco (52 species), followed by
Ixtapa (45), Acapulco and Puerto Ángel (33), and Puerto Escondido (23). At the site level, La Entrega had the highest number of species (32), while various sites in Acapulco had <10 species. The species richness in the region showed considerably high representativeness since the non-parametric estimators suggested a potential increase of ~10% more species; a more significant percentage is expected in the Acapulco zone (47.5%). All echinoderms had 100% representativeness at the class level, except for Holothuroidea. It is recommended to use as many sampling methods and as many substrates as possible during different seasons and time days to contribute to increasing representativeness. Acapulco had an average taxonomic distinctness different from that predicted by regional models and an echinoderm assemblage more dissimilar from the other areas. The latter may be the product of the scarce sampling effort carried out in Acapulco and probably because it has one of the most degraded coral reef systems within the study area.
... For example, in the Gulf of California, Mesocentrotus franciscanus and Strongylocentrotus purpuratus are exploited for human consumption (e.g., Cota et al., 1996;Palleiro-Nayar et al., 2013). Despite the above, in the phylum Echinodermata only the class Ophiuroidea has been studied regarding its broad-scale distribution patterns (e.g., Stöhr et al., 2012;O'Hara et al., 2017;Bribiesca-Contreras et al., 2019;Granja-Fernández et al., 2023). ...
... In the eastern tropical Pacific, few works have studied broad scale biodiversity patterns, but stand out the papers of Maluf (1988aMaluf ( ,1988b, Pérez-Rufaza et al. (2013), and Granja-Fernández et al. (2023) which highlight: 1) Differences in sampling effort and methods explain species richness, for example, higher species richness in areas where more investigation has been carried out (e.g., the Gulf of California, Panamá, and Galápagos); and 2) Oceanographic conditions, coastline length of the study area, dispersal, and environmental heterogeneity explain spatial distribution patterns. Unfortunately, most studies include all shallow and deep-water echinoderms in their analysis, except for the work of Granja-Fernández et al. (2023). ...
... In the eastern tropical Pacific, few works have studied broad scale biodiversity patterns, but stand out the papers of Maluf (1988aMaluf ( ,1988b, Pérez-Rufaza et al. (2013), and Granja-Fernández et al. (2023) which highlight: 1) Differences in sampling effort and methods explain species richness, for example, higher species richness in areas where more investigation has been carried out (e.g., the Gulf of California, Panamá, and Galápagos); and 2) Oceanographic conditions, coastline length of the study area, dispersal, and environmental heterogeneity explain spatial distribution patterns. Unfortunately, most studies include all shallow and deep-water echinoderms in their analysis, except for the work of Granja-Fernández et al. (2023). Specifically, in the Mexican Pacific, Echinoidea has been addressed in numerous taxonomic papers and species checklists (e.g., Solís-Marín et al., 2005;Honey-Escandón et al., 2008;Granja-Fernández et al., 2021). ...
... At local and mesoscale, abundance, diversity, and species composition in reef-related mollusks and decapods relate to changes in live coral coverage or whether they were associated with corals, sand, or rock within the reef system (Barrientos-Luján et al., 2021;Alonso-Domínguez et al., 2022). Finally, some studies conducted in the Mexican Pacific and Central America have inferred that temporal but also spatial patterns observed in decapods, mollusks, and echinoderms may have resulted from environmental drivers related to upwelling (October to April) and non-upwelling seasons, and temperature and primary productivity modifications across large-scale environmental gradients (Abele 1976;Alvarado and Vargas-Castillo 2012;Barrientos-Luján et al., 2017;Granja-Fernández et al., 2023). ...
... En México, incluso se han descrito nuevas especies recientemente, como una proveniente de Oaxaca (Breedy et al., 2012). También es de particular interés la asociación que tienen las gorgonias con moluscos, crustáceos y equinodermos (Sánchez et al., 2016(Sánchez et al., , 2019Granja-Fernández et al., 2023). En ningún ejemplar del Templo Mayor se encontraron organismos asociados a las gorgonias. ...
Antecedentes.
Desde 1978 se han realizado estudios en las más de 200 ofrendas descubiertas en la zona arqueológica del Templo Mayor de Tenochtitlan, en donde se han encontrado una gran diversidad de objetos culturales, así como restos de seres humanos, plantas y animales, incluidas varias especies de corales. Las ofrendas 178 y 179 fueron descubiertas en 2019 y por el tipo de material, pero principalmente por la cantidad de ejemplares, su proceso de excavación y revisión ha sido minucioso y lento, incluso continua actualmente en la Ofrenda 178.
Objetivos.
En este trabajo se describen los corales blandos depositados en estas dos ofrendas.
Métodos.
La excavación, extracción, limpieza y preservación de los corales se realizó de acuerdo con el protocolo del Proyecto Templo Mayor. Debido al estado de conservación de los ejemplares, y a los efectos de 500 años de enterramiento, la identificación taxonómica se realizó considerando las características morfológicas externas.
Resultados.
Hasta el momento en las dos ofrendas se han encontrado cuatro especies de gorgonias del género Pacifigorgia (Cnidaria: Anthozoa: Octocorallia: Gorgoniidae), que actualmente tienen distribución en la costa del Pacífico mexicano. En la Ofrenda 178 se registraron tres especies, mientras que en la Ofrenda 179 se registraron las cuatro especies.
Conclusiones.
Lo relevante de estas ofrendas, en particular la Ofrenda 178, es la inusitada cantidad de corales inhumados, ya que contienen más de 150 colonias enteras y casi 300 lotes de fragmentos, para un total y nueva cifra récord de 454 corales, número nunca reportado anteriormente en ninguna ofrenda registrada en el corazón de la antigua ciudad de Tenochtitlan en los últimos 45 años de excavaciones. Debido a que las exploraciones arqueológicas de ofrendas al pie del recinto sagrado siguen en curso, es previsible que el número de especies y ejemplares de corales aumente en un futuro próximo.
We reconstructed the mitochondrial phylogeny of the species of the brittle star genus Ophioderma, using sequences of the Cytochrome Oxidase I gene (COI) to address four questions: (i) Are the species of Ophioderma described on morphological evidence reflected in mitochondrial genealogy? (ii) Which species separated from which? (iii) When did speciation events occur? (iv) What is the rate of COI evolution in ophiuroids? We found that most of the 22 described species we sampled coincide with monophyletic clusters of COI sequences, but there are exceptions, most notably in the eastern Pacific, in which three undescribed species were indicated. The COI phylogeny lacks resolution in the deeper nodes, but it does show that there are four species pairs, the members of which are found on either side of the central American Isthmus. Two pairs with a genetic distance of ~ 4% between Atlantic and Pacific members were probably split during the final stages of Isthmus completion roughly 3 million years ago. The rate of divergence provided by these pairs allowed the calibration of a relaxed molecular clock. Estimated dates of divergence indicate that the lineages leading to extant species coalesce at times much older than congeneric species in other classes of echinoderms, suggesting that low extinction rates may be one of the reasons that ophiuroids are species-rich. The mean rate of COI substitution in Ophioderma is three times slower than that of echinoids. Conclusions of previous mitochondrial DNA studies of ophiuroids that relied on echinoid calibrations to determine divergence times need to be revised.
Introduction:
The study of the marine diversity of the North Pacific of Costa Rica began with isolated foreign expeditions in the 1930s and was systematically developed in the mid-1990s by the Center for Research in Marine Sciences and Limnology, Universidad de Costa Rica, as consequence there are now a total of 1 479 reported species in this region.
Objective:
Present an update to the echinoderm richness of the Guanacaste Conservation Area.
Methods:
We sampled 25 localities exhaustively and estimated similarity between sites based on the family richness and environmental heterogeneity.
Results:
We found 61 taxa, which represent 26 % of the echinoderm reported species for the country’s Pacific coast. Of these, 43 species are new records for the Guanacaste Conservation Area, and seven for Costa Rica and Central American Pacific coasts. We found three morpho-species that do not match to available descriptions of the Eastern Tropical Pacific echinoderm species. We also found the holothuroid Epitomapta tabogae, and the ophiuroid Ophioplocus hancocki, previously thought endemic to Panama and the Galapagos Islands, respectively. The proximity of the sampled sites and the redundancy of certain families may explain why we did not find important differences among localities.
Conclusions:
The echinoderm richness of this conservation area is at least 20 % higher than previously reported, reaching similar levels to those in other high diversity sites of the Eastern Tropical Pacific.
Introducción:
La bahía de Chamela está ubicada en la parte central de la costa del estado de Jalisco, México y es un importante área natural protegida. Pese a ello, el estudio de los equinodermos en la zona es incipiente.
Objetivo:
Proporcionar una lista de verificación actualizada, descripciones de las especies y una clave taxonómica de los ofiuroideos de la bahía de Chamela.
Métodos:
Recolectamos en la bahía de 1998 a 2018, y también analizamos información de la literatura y especímenes en colecciones científicas internacionales.
Resultados:
se reportan 19 especies de ofiuroides para el área de estudio, distribuidas en dos órdenes, siete familias y 11 géneros. Ocho de estos corresponden a nuevos registros para el área y tres posiblemente representan nuevas especies. La biodiversidad de ofiuroideos en la bahía de Chamela representa el 15.2% de las especies de ofiuroides del Pacífico mexicano y el 73% de Jalisco. El número de equinodermos conocidos en la bahía de Chamela aumenta a 48 especies.
Conclusiones:
Se presenta el listado más completo de la clase Ophiuroidea en la bahía de Chamela, Jalisco. La información proporcionada se puede utilizar para otras áreas del Pacífico oriental. La bahía de Chamela es importante en términos de riqueza de especies debido a su heterogeneidad ambiental y numerosas islas.
The widespread Ophioderma hendleri sp. nov., from the Eastern Tropical Pacific (Mexico to Colombia) is distinguished from its congeners by having radial shields covered by granules, naked adoral shields, up to 11 arm spines, and by its brown and beige coloration. Ophioderma hendleri sp. nov. belongs to the group of species with naked adoral shields (i.e., O. pentacanthum H.L. Clark, 1917, O. variegatum Lütken, 1856), and it has frequently been misidentified as O. panamense Lütken, 1859 or O. variegatum. Therefore, the main aim of the present work was to describe Ophioderma hendleri sp. nov. and differentiate it from its congeners. The original description of O. panamense was incomplete; thus, we provide a redescription. Due to the confusion in previous designations of its type material, we designate a lectotype and paralectotype of O. variegatum. Finally, we expand the distribution range of O. pentacanthum to Cocos Island, Costa Rica. With this work, the total number of valid species of Ophioderma Müller & Troschel, 1840 in the world increases to 33 and in the Eastern Pacific to nine species.
The distance travelled by marine larvae varies by seven orders of magnitude. Dispersal shapes marine biodiversity, and must be understood if marine systems are to be well managed. Because warmer temperatures quicken larval development, larval durations might be systematically shorter in the tropics relative to those at high latitudes. Nevertheless, life history and hydrodynamics also covary with latitude—these also affect dispersal, precluding any clear expectation of how dispersal changes at a global scale. Here we combine data from the literature encompassing >750 marine organisms from seven phyla with oceanographic data on current speeds, to quantify the overall latitudinal gradient in larval dispersal distance. We find that planktonic duration increased with latitude, confirming predictions that temperature effects outweigh all others across global scales. However, while tropical species have the shortest planktonic durations, realized dispersal distances were predicted to be greatest in the tropics and at high latitudes, and lowest at mid-latitudes. At high latitudes, greater dispersal distances were driven by moderate current speed and longer planktonic durations. In the tropics, fast currents overwhelmed the effect of short planktonic durations. Our results contradict previous hypotheses based on biology or physics alone; rather, biology and physics together shape marine dispersal patterns. Analysing data on egg size and planktonic duration from >750 marine species with a larval period, the authors show that temperature, life-history and oceanographic processes interact to shape peaks of dispersal at low and high latitudes.
Extracting meaningful information from community data is among the most challenging tasks of community ecology. Whereas presence-absence data matrices are commonly used in different analytical frameworks, we argue that the conceptual distinction among community patterns (on which inference is made), pairwise pattern components (PPCs, which reflect the unique response of communities for pairs of sites), and measures (which quantify a relevant property of PPCs), liberates our field from the possible misinterpretation of results derived from existing approaches. The novel concept suggested here is the PPC, which can be efficiently used to identify response types of communities, thereby shortening the list of potential explanatory processes. Consequently, the introduction of PPCs supports the analysis of real data sets and links patterns to ecological hypotheses. Based on PPCs, we proposed a new partitioning of beta diversity (SET framework) into intersection (I) of nestedness and beta diversity and the relative complement (RC) of nestedness in beta diversity. We performed an algebraic assessment of three existing partitioning frameworks of beta diversity: the BAS (Baselga, 2010, Global Ecology and Biogeography), POD (Podani and Schmera, 2011 Oikos) and SET (present paper). We found that when a community pattern is anti-nested, which is characterized by the presence of both Replacement and Richness difference PPCs, the BAS framework falsely indicates a 100% share of replacement from beta diversity. In contrast, the POD and SET partitioning procedures detect the presence and the proper size of PPCs for all types of community patterns. In conclusion, we argue that breaking down community patterns into PPCs and then quantifying the importance of these PPCs form a straightforward strategy to extract information from community data under a broad range of circumstances.
Understanding the distribution of life's variety has driven naturalists and scientists for centuries , yet this has been constrained both by the available data and the models needed for their analysis. Here we compiled data for over 67,000 marine and terrestrial species and used artificial neural networks to model species richness with the state and variability of climate , productivity, and multiple other environmental variables. We find terrestrial diversity is better predicted by the available environmental drivers than is marine diversity, and that marine diversity can be predicted with a smaller set of variables. Ecological mechanisms such as geographic isolation and structural complexity appear to explain model residuals and also identify regions and processes that deserve further attention at the global scale. Improving estimates of the relationships between the patterns of global biodiversity, and the environmental mechanisms that support them, should help in efforts to mitigate the impacts of climate change and provide guidance for adapting to life in the Anthropocene.
Aim
Mining and petroleum industries are exploring for resources in deep seafloor environments. Lease areas are often spatially aggregated and continuous over hundreds to thousands of kilometres. Sustainable development of these resources requires an understanding of the patterns of biodiversity at similar scales, yet these data are rarely available for the deep sea. Here, we compare biodiversity metrics and assemblage composition of epibenthic megafaunal samples from deep‐sea benthic habitats from the Great Australian Bight (GAB), a petroleum exploration zone off southern Australia, to similar environments off eastern Australia.
Location
The Great Australian Bight (34–36°S, 129–134°E) and south‐eastern (SE) and north‐eastern (NE) Australian continental margins (23–42°S, 149–155°E) in depths of 1,900–5,000 m.
Methods
A species–sample matrix was constructed from invertebrate and fish megafauna collected from beam trawl samples across regions at lower bathyal (1,900–3,200 m) and abyssal (>3,200 m) depths, and analysed using multivariate, rarefaction and model‐based statistics. We modelled rank abundance distributions (RAD) against environmental factors to identify drivers of abundance, richness and evenness.
Results
Multivariate analyses showed regional and bathymetric assemblage structure across the region. There was an almost complete turnover of sponge fauna between the GAB and SE. SE samples had the highest total faunal abundance and species richness. RAD models linked total abundance and species richness to levels of carbon flux. Evenness was associated with seasonality of net primary production.
Conclusions
Significant assemblage structure at regional scales is reported for the first time at lower bathyal and abyssal depths in the southern Indo‐Pacific region along latitudinal and longitudinal gradients. The GAB fauna was distinct from other studied areas. Relatively high species richness, previously reported from the GAB continental shelf, did not occur at lower bathyal or abyssal depths. Instead, the abundance, richness and evenness of the benthic fauna are linked to surface primary production, which is elevated off SE Australia.
The largest and commercially appealing mineral deposits
can be found in the abyssal sea floor of the Clarion-Clipperton Zone (CCZ), a
polymetallic nodule province, in the NE Pacific Ocean, where experimental
mining is due to take place. In anticipation of deep-sea mining impacts, it
has become essential to rapidly and accurately assess biodiversity. For this
reason, ophiuroid material collected during eight scientific cruises from
five exploration licence areas within CCZ, one area being protected from mining
(APEI3, Area of Particular Environmental Interest) in the periphery of CCZ
and the DISturbance and re-COLonisation (DISCOL) Experimental Area (DEA),
in the SE Pacific Ocean, was examined. Specimens were genetically analysed
using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI).
Maximum-likelihood and neighbour-joining trees were constructed, while four
tree-based and distance-based methods of species delineation (automatic barcode gap discovery, ABGD; barcode index numbers, BINs;
general mixed Yule–coalescent, GMYC; multi-rate Poisson tree process, mPTP) were employed to propose secondary species hypotheses (SSHs)
within the ophiuroids collected. The species delimitation analyses'
concordant results revealed the presence of 43 deep-sea brittle star SSHs,
revealing an unexpectedly high diversity and showing that the most
conspicuous invertebrates in abyssal plains have been so far considerably
underestimated. The number of SSHs found in each area varied from five (IFREMER area) to 24 (BGR (Federal Institute for Geosciences and Natural Resources,
Germany) area) while 13 SSHs were represented by
singletons. None of the SSHs were found to be present in all seven areas while
the majority of species (44.2 %) had a single-area presence (19 SSHs).
The most common species were Ophioleucidae sp. (Species 29), Amphioplus daleus (Species 2)
and Ophiosphalma glabrum (Species 3), present in all areas except APEI3. The biodiversity
patterns could be mainly attributed to particulate organic carbon (POC) fluxes that could explain the
highest species numbers found in BGR (German contractor area) and UKSRL (UK Seabed Resources Ltd, UK
contractor area) areas. The five exploration contract areas belong to a
mesotrophic province, while conversely the APEI3 is located in an
oligotrophic province, which could explain the lowest diversity as well as
very low similarity with the other six study areas. Based on these results
the representativeness and the appropriateness of APEI3 to meet its purpose
of preserving the biodiversity of the CCZ fauna are questioned. Finally,
this study provides the foundation for biogeographic and functional analyses
that will provide insight into the drivers of species diversity and its role
in ecosystem function.
Our knowledge of the distribution and evolution of deep-sea life is limited, impeding our ability to identify priority areas for conservation¹. Here we analyse large integrated phylogenomic and distributional datasets of seafloor fauna from the sea surface to the abyss and from equator to pole of the Southern Hemisphere for an entire class of invertebrates (Ophiuroidea). We find that latitudinal diversity gradients are assembled through contrasting evolutionary processes for shallow (0–200 m) and deep (>200 m) seas. The shallow-water tropical–temperate realm broadly reflects a tropical diversification-driven process that shows exchange of lineages in both directions. Diversification rates are reversed for the realm that contains the deep sea and Antarctica; the diversification rates are highest at polar and lowest at tropical latitudes, and net exchange occurs from high to low latitudes. The tropical upper bathyal (200–700 m deep), with its rich ancient phylodiversity, is characterized by relatively low diversification and moderate immigration rates. Conversely, the young, specialized Antarctic fauna is inferred to be rebounding from regional extinctions that are associated with the rapid cooling of polar waters during the mid-Cenozoic era.
Gobies are the most diverse marine fish family. Here, we analysed the gamma-diversity (γ-diversity) partitioning of gobiid fishes to evaluate the additive and multiplicative components of α and β-diversity, species replacement and species loss and gain, at four spatial scales: sample units, ecoregions, provinces and realms. The richness of gobies from the realm Eastern Tropical Pacific (ETP) is represented by 87 species. Along latitudinal and longitudinal gradients, we found that the γ-diversity is explained by the β-diversity at both spatial scales, ecoregions and provinces. At the ecoregion scale, species are diverse in the north (Cortezian ecoregion) and south (Panama Bight ecoregion) and between insular and coastal ecoregions. At the province scale, we found that the species turnover between the warm temperate Northeast Pacific (WTNP), Tropical East Pacific (TEaP) and the Galapa-gos Islands (Gala) was high, and the species nestedness was low. At the ecoregion scale, historical factors, and phylogenetic factors have influenced the hotspots of gobiid fish biodiversity , particularly in the Cortezian, Panama Bight and Cocos Island ecoregions, where species turnover is high across both latitudinal and longitudinal gradients. At the provincial level, we found that the contributions of the β-diversity from north to south, in the WTNP, TEaP and Gala were high, as result of the high number of unique species. Species turnover was also high at this scale, with a low contribution from species nestedness that was probably due to the low species/gene flow within the provinces. These results highlight the importance and successful inclusion of a cryptobenthic fish component in ecological and biogeographical studies.
There are many marine protected areas (MPAs) containing coral reef aggregations in the eastern Pacific region. However, the connectivity of corals between MPAs is still poorly known, especially in the Marine Conservation Corridor of the Eastern Tropical Pacific (MCCETP). Here, we assess the potential connectivity of corals across equatorial eastern Pacific MPAs through a Lagrangian particle-tracking algorithm coupled offline with an ocean-circulation numerical model. Connectivity metrics and graph theory were used to analyze the networks and highlight those MPAs that are critical for maintaining the connectivity of corals across the region. Our results show that the equatorial eastern Pacific MPAs form a relatively well-connected network, at least 40% of coral larvae released per year end up within the boundaries of an MPA. MPAs like Malpelo and Gorgona islands included in the MCCETP were found to be critical for connectivity of corals because of their high betweenness centrality and potential role as stepping-stones between coastal MPAs and offshore MPAs such as the Galapagos Islands. Two pelagic larval duration (PLD) scenarios (40 and 130 days) indicate a quasi-unidirectional larval flow from coastal MPAs toward oceanic MPAs, where the only resilient MPAs (Coiba and Malpelo islands) depend mostly on subsidiary recruitment from MPAs located along the coast of Costa Rica, Panama and Colombia. In the two PLD scenarios, Cocos Island maintains a very low resilience potential. Our results indicate the imperative need to include coastal MPAs in the MCCETP network initiative, since connectivity and resilience of coral reefs in the equatorial eastern Pacific region rely heavily on coastal MPAs.
The Central Mexican Pacific is an oceanographic transitional region with complex habitats and important conservation areas, but knowledge of its Ophiuroidea fauna is limited. A total of 61 localities on a variety of substrata were sampled between 2008 and 2014 using different methodology techniques. Twenty-four species were collected and members of the families Ophiocomidae, Ophiotrichidae and Ophiactidae were the most widespread. The new records of 28 species have relevance in terms of filling distribution gaps along the Mexican Pacific or extending their geographical distribution ranges. This considerable number can be attributed to a higher number of prospected localities and the diversification of collecting methods. An updated checklist from the study area is provided, including previous literature re- cords and those found during this work, summarising 57 species. Islas Marías was the area with the highest number of species and with the highest value of taxonomic distinctness, which can be explained since these islands are considered as stepping stones for the dispersal of species in the Mexican Pacific. Despite the important diversity and composition of ophiuroids in our study area, a sample-based rarefaction curve suggests that at least 104 species can inhabit the area, so we recommend conducting more research in the region.
The ENSO observing system in the tropical Pacific plays an important role in monitoring ENSO and helping improve the understanding and prediction of ENSO. Occurrence of ENSO has been explained as either a self-sustained and naturally oscillatory mode of the coupled ocean-atmosphere system or a stable mode triggered by stochastic forcing. In either case, ENSO involves the positive ocean-atmosphere feedback hypothesized by Bjerknes. After an El Niño reaches its mature phase, negative feedbacks are required to terminate growth of the mature El Niño anomalies in the central and eastern Pacific. Four negative feedbacks have been proposed: reflected Kelvin waves at the ocean western boundary, a discharge process due to Sverdrup transport, western Pacific wind-forced Kelvin waves, and anomalous zonal advections. These negative feedbacks may work together for terminating El Niño, with their relative importance varying with time. Because of different locations of maximum SST anomalies and associated atmospheric heating, El Niño events are classified as eastern and central Pacific warming events. The identification of two distinct types of El Niño offers a new way to examine global impacts of El Niño and to consider how El Niño may respond and feedback to a changing climate. In addition to interannual variations associated with ENSO, the tropical Pacific SSTs also fluctuate on longer timescales. The patterns of Pacific Decadal Variability (PDV) are very similar to those of ENSO. When SST anomalies are positive in the tropical eastern Pacific, they are negative to the west and over the central North and South Pacific, and positive over the tropical Indian Ocean and northeastern portions of the high-latitude Pacific Ocean. Many mechanisms have been proposed for explaining PDV. Changes in ENSO under global warming are uncertain. Increasing greenhouse gases change the mean states in the tropical Pacific, which in turn induce ENSO changes. Due to the fact that the change in mean tropical condition under global warming is quite uncertain, even during the past few decades, it is difficult to say whether ENSO will intensify or weaken, but it is very likely that ENSO will not disappear in the future.
Macro- and meiobenthos contribute substantially to the diversity of marine habitats and should account for a significant fraction of the diversity in coral reefs. The aims of the present study are to characterize macro- and meiobenthic communities in a Caribbean coral reef and to analyze the effects of habitat type on the α-, β-, and γ-diversity of free-living nematodes. Two reef sites with four habitat types each were selected: seagrass bed, bare sand, coral rubble, and algal turf. Habitats within sites were adjacent to each other and characterized by their physical architecture, hydrodynamic regime, and foundation species. The diversity of marine communities was high, with eight phyla represented in the macrobenthos and 18 phyla in the meiobenthos. The structure of macrobenthos was strongly associated with the habitat type. This relationship was weaker for meiobenthos, which is likely related to ecological drift, hydrodynamic regime, and macrobenthic influence. The nematode species richness was high at both studied scales: α-diversity ranged from 31 to 83 species per habitat and γ-diversity for the whole reef was 156 ± 4 species. The nematode assemblages consisted of few dominant and many rare species, which is typical of hyperdiverse faunas. The β-diversity was large in the reef with few shared species and the presence of distinctive nematode assemblages adapted to the physical architecture and food availability of each habitat. The results imply that the physical structure and heterogeneity of the coral reef habitats are important for maintaining the high diversity of small invertebrates, especially regarding the richness and turnover of nematode species.
The fauna of three sites in the Clipperton-Clarion Fracture Zone Region of the North Pacific Ocean were evaluated as part of multiple programs supported by the US National Oceanic and Atmospheric Administration. These localities (Site A in the west and Site C and a prospective reserve area 2893-2561 km to the east) cover the range of depths and productivity observed for the region. Macrofauna densities varied with productivity, with Site A with the lowest densities and the reserve area with the highest densities. Species diversities of Polychaeta, Isopoda and Tanaidacea showed differing trends compared to export productivity, using a bootstrapped lognormal method to estimate total species. Polychaeta had the highest estimated species at the high productivity reserve site and the lowest values at the low productivity site A. Tanaidacea had similar trend to that of the polychaetes. Isopoda showed an opposite species-productivity trend, with highest estimated species at the low productivity site A and lowest values at the high productivity reserve site. Polychaetes were most similar between sites, while isopod similarities were low. Tanaid similarities between sites A and C resembled the polychaetes value. Species turnover for isopods was high, but much less so for polychaetes and tanaids, and may be related to the dispersal potential for each taxocene. Beta diversity predicts that the average isopod species in the CCFZ has a range of approximately 2200 km2 while a polychaete species range might exceed 10,000km2. Data from a single taxocene cannot be used as a proxy for the entire deep-sea fauna because each group has its own ecological and evolutionary responses, as well as its own history.
Benthic ecological surveys using standardized methods are crucial for assessing changes associated with several threats in the Southern Ocean. The acquisition of data on assemblage structure over a variety of spatial scales is important to understand the variation of biodiversity patterns. During the ANT XXIX/3 (PS81) expedition of RV Polarstern, three different regions at the tip of the Antarctic Peninsula were sampled: the northwestern Weddell Sea, the Bransfield Strait, and the northern boundary of the South Shetland Archipelago in the Drake Passage. The aim of this study was to characterize the distribution and biodiversity patterns of ophiuroid assemblages in these regions and depths. We quantified different community parameters in terms of the number of species, abundance, and biomass. Additionally, we calculated various components of species diversity (alpha, beta, and gamma diversity) over the three regions. Based on the benthic surveys, we collected 3331 individuals that were identified to species level (17 species). Overall, species diversity, as measured based on rarefaction, species richness and evenness estimators, was higher in the Bransfield Strait compared to the Weddell Sea and Drake Passage. Two deep stations in the Weddell Sea showed high dominance only of Ophionotus victoriae. Significant differences in the patterns of alpha diversity were found among the regions but not between depth zones, whereas beta diversity showed no differences. Regarding the resemblance among the ophiuroid assemblages of each region, there was a significant gradient from east to west with a maximum distance between the stations in the Drake Passage and the Weddell Sea. This study provides a baseline for detecting potential effects related to climate change, and it furnishes a basis for the implementation of monitoring schemes of Antarctic assemblages.
Collected and/or discusses the 530 species known from the entire Gulf: 22 Penaeoidea, 112 Caridea, 13 Thalassinidea, six Palinura, 108 Anomura, and 269 Brachyura. For each species, the following information was obtained and analyzed: 1) a list of all reported collecting localities; 2) for non-endemics, the range outside the Gulf (thoughout the E Pacific); and 3) the principal habitats, including depth ranges for offshore species. Gulf of California species were found in the following habitats: coastal lagoons/estuaries, 43 species (8.1%); sandy beaches, 12 species (2.3%); rocky shores, including coral reefs, 142 species (26.8%); continental shelf, 318 species (60.1%). The last are stratified bathymetrically: shore to 40 m, 162 species; 40-90 m, 131 species; >90 m, 25 species. Some 75.7% of the Gulf of California's decapod species show a clear tropical affinity. The endemic component varies from 11% (S Gulf only) and 17% (C Gulf only) to 22% (N Gulf only) and is 15.3% for the entire Gulf. If endemic is defined as restricted to an extended Cortez Province, including the Cabo San Lucas-Magdalena Bay portion of Baja California, the percentage of endemism increases to 17.5%. A larger Mexican Province should be considered, from Magdalena Bay and the whole Gulf of California south to a southern limit yet to be defined. -from Author
Despite the important effort of knowing the Ophiuroidea diversity in the Mexican Pacific, some mistakes in the taxonomic nomenclature have pervaded through time. In order to clarify the latter, a checklist based on literature review of brittle stars from the Mexican Pacific is provided. We reviewed a total of 105 references that in total summarized 125 species of brittle stars from the Mexican Pacific (112) and the Gulf of California (97), belonging to two orders, 16 families and 50 genera. These records are higher than those reported on previous studies carried out in the area. México is the country with the highest number of brittle stars reported in the Tropical Eastern Pacific; this may be due to its exceptional oceanographic conditions, location and coastline extension. However, a total of 27 species reported in the literature were considered doubtful due to their general distributions and were not included in the checklist. Of the reported species, 35 have their type locality in the Mexican Pacific, corroborating the importance of the country in the Tropical Eastern Pacific in terms of Echinodermata diversity.
The echinoderms of the Southern Mexican Pacific have been studied for three centuries, but discrepancies
in the nomenclature of some species have pervaded through time. The objective of this work is to present the first updated checklist of all valid species and synonyms, and a historical review of the study of the echinoderms of the Southern Mexican Pacific is also presented. The checklist is based on an exhaustive published literature search and records of specimens deposited in museum and curated reference collections. There are 162 species of echinoderms in the Southern Mexican Pacific from 96 genera, 54 families and 20 orders. The State of Guerrero presented a total of 135 species, Oaxaca 94 and Chiapas 15. We updated the list and added five new records of the species (Microphiopholis platydisca, Ophiostigma tenue, Arbacia stellata, Thyone bidentata, Chiridota rigida) for the Southern Mexican Pacific and one for the Mexican Pacific (Encope laevis). This checklist expands the number of species known for the study area; nevertheless studies suggest that still more species are yet to be discovered
I examine the natural barriers to distribution and colonization that have shaped the Galapagos marine invertebrate biota. While diversity is high for some groups, such as hydroids and bryozoans, it is low for many others. Porcelain crabs and molluscs are examples with reduced or unbalanced representation in Galapagos, resulting from their dependency on dispersal of relatively short-lived planktonic larvae by ocean currents and on habitat limitations in Galapagos. Because Galapagos shorelines are predominantly rocky, without the wide expanses of silt typical of much of the Ecuadorian mainland that are favored by infaunal bivalves, gastropod diversity in Galapagos far exceeds that of bivalves. Nearly all hermatypic corals in Galapagos are members of the Panamic province; none is endemic to Galapagos. This suggests that colonization occurred by larval dispersal from there. The ahermatypic (azooxanthellate) coral fauna of Galapagos, with 43 species, is richer and more diverse than the hermatypic corals, with 29% of the shallow-water ahermatypes endemic and the remainder with Panamic, Indo-Pacific, and cosmopolitan affinities. The 73 verified species of Galapagos shallow-water echinoderms are dominated by Panamic species, with additional affinities to the Indo-Pacific and the California province; 8% are cosmopolitan and 8% endemic. With species richness roughly equivalent to that of Pacific Colombia, Galapagos echinoderm representation is not depauperate, but is sufficiently distinctive to characterize it as an isolated, insular biota. Hydroids and bryozoans, two groups with high diversity in Galapagos, accomplish long-distance transport mainly as adults on floating debris and hulls of ships, rather than by the free-swimming reproductive stage. Endemism among marine invertebrates averages 18.3 %, but varies widely among major taxa, from 0% for reef corals to 71% for gorgonians. Unlike the Galapagos terrestrial biota, in which endemic genera are common, the absence of endemic genera among marine invertebrates may be attributed to low isolation arising from greater dispersal and gene flow in the marine environment.
The conservation and sustainable use of marine resources is a highlighted goal in a growing number of
national and international policy agendas. Unfortunately, efforts to assess progress, as well as to
strategically plan and prioritize new marine conservation measures, have been hampered by the lack of a
detailed and comprehensive biogeographic system to classify the oceans. Here we report on a new global
system for coast and shelf areas the Marine Ecoregions of the World (MEOW) a nested system of 12
realms, 62 provinces and 232 ecoregions. This system provides considerably better spatial resolution than
previous global systems, while preserving many common elements, and can be cross-referenced to many
regional biogeographic classifications. The designation of terrestrial ecoregions has revolutionized priority
setting and planning for land conservation; we anticipate similar benefits from the creation of a coherent
and credible marine system.
Ophiuroid assemblages were successfully predicted from current museum sample data using presence-only modeling techniques and a multivariate classification on the resulting species occurrence probabilities across the Coral and Tasman Seas (20-37°S, 148-172°E). The classification involves two-stages. The first uses a non-hierarchical clustering technique to reduce the number of data points (map-pixels) to a manageable number that can be analysed in a second stage with a hierarchical classification method. For both steps, the Bray-Curtis similarity statistic is used.
The benefits of this model-then-classify approach were:
1. It did not rely on consistent sampling techniques. Sample data contributed information to the species distribution patterns regardless of how or when it was collected.
2. It did not depend on accurate absence data. Rarely can we have confidence that a species is truly absent from a given area. This is especially true for large-scale studies, where the pixel resolution is on a scale of square kilometers.
3. Direct multivariate analysis of species occurrence probabilities was threshold independent (ie an arbitrary threshold did not have to be set to distinguish a ‘presence’ from an ‘absence’).
4. A two step classification preserved the benefit of a hierarchical classification (ie an explicit hierarchical breakdown of classes) while analysing very large datasets.
5. The Bray-Curtis similarity index is commonly used in ecological studies to reduce the emphasis on joint absences (eg it was not significant if a deep-sea species was absent from both tropical and temperate littoral areas).
The environmental predictors that contributed most to the species models were depth and seafloor temperate, and to a lesser extent nitrate, oxygen and sea-surface temperature. Productivity and surface current velocity were not emphasized.
The resulting maps of ophiuroid assemblages across the study area primarily reflect different depth strata, forming distinct classes at littoral, shelf, upper slope and mid-slope depths and only differentiating into distinct temperate and tropical clusters in shallow water (littoral and shelf depths) along the Australian coastal margin. The temperate New Zealand fauna only partially extends into the SE corner of the study area.
Lord Howe and Norfolk Islands support distinct complexes of tropical, temperate and endemic species, in part reflecting the influence of the East Australia Current. There are a few endemic echinoderms known from both islands, although these are relatively uncommon and may eventually be found elsewhere. The bases of these islands support similar species to habitats with similar depth and environmental profiles elsewhere, including other seamounts in the region and rocky habitats along the continental margins.
3
Both the Lord Howe Rise and Norfolk Ridges exhibit a north-south transition of species, however, this is less dramatic than for the Australian continental margin. This is in part due to the lack of shallow water habitat along these ridges. Latitudinal gradients are more prominent in shallow water within the study area.
Seamounts within the study areas rarely did not appear to contain more endemic ophiuroid species than similar areas along the continental margins. Instead the majority of species on seamounts appear similar to those occurring elsewhere at similar depths and seafloor temperatures. This suggests that species disperse to these seamounts from surrounding habitat regularly enough to prevent allopatric speciation. These conclusions need to be confirmed by genetic data as cryptic speciation is common in echinoderms. However, it is likely that seamounts have accumulated distinct assemblages of species over time depending on their location, form, depth and age. Seamounts do not show the consistency and specialisation of seafloor assemblages to be considered a single unit for management purposes such as marine-park planning. Until we understand more about the ecological and historical factors that structure seafloor assemblages, ‘seamounts’ should be evaluated independently to ascertain their conservation status.
This study emphasizes the tropical affinities of many ophiuroid species that live across the Tasman and Coral Seas. This differs from a preliminary pattern for fish described from the NORFANZ expedition in 2003 which emphasized 1) the southern affinities of many fish species, and 2) possible areas of endemism on the Middlesex Bank, Lord Howe Island, Norfolk Island, Norfolk Ridge, Wanganella Bank and Reinga Ridge. However, both ophiuroids and fish were primarily structured by depth
There are numerous and important coral reefs in the Mexican Pacific, but scarce studies of brittle stars conducted in these ecosystems. In this regard, this work provides the first annotated checklist of brittle stars associated with coral communities and reefs in the Mexican Pacific and an illustrated key to identify the species. We also provide taxonomic descriptions, spatial and bathymetric distributions and some important remarks of the species. We report a total of 14 species of brittle stars belonging to nine genera and seven families. Ophiocnida hispida in Jalisco, Ophiophragmus papillatus in Guerrero, and Ophiothrix (Ophiothrix) spiculata and Ophiactis simplex in Colima are new distribution records. The record of O. papillatus is remarkable because the species has not been reported since its description in 1940. The brittle stars collected in this study, represent 22.2% of the total species previously reported from the Mexican Pacific. Presently, anthropogenic activities on the coral reefs of the Mexican Pacific have increased, thus the biodiversity of brittle stars in these ecosystems may be threatened.
Island biogeographic studies traditionally treat single islands as units of analysis. This ignores the fact that most islands are spatially nested within archipelagos. Here, we took a fundamentally different approach and focused on entire archipelagos using species richness of vascular plants on 23 archipelagos worldwide and their 174 constituent islands. We assessed differential effects of biogeographic factors (area, isolation, age, elevation), current and past climate (temperature, precipitation, seasonality, climate change velocity) and intra-archipelagic spatial structure (archipelago area, number of islands, area range, connectivity, environmental volume, inter-island distance) on plant diversity. Species diversity of each archipelago (γ) was additively partitioned into α, β, nestedness and replacement β-components to investigate the relative importance of environmental and spatial drivers. Multiple regressions revealed strong effects of biogeography and climate on α and γ, whereas spatial factors, particularly number of islands, inter-island distance and area range, were key to explain β. Structural equation models additionally suggested that γ is predominantly determined by indirect abiotic effects via its components, particularly β. This highlights that β and the spatial arrangement of islands are essential to understand insular ecology and evolution. Our methodological framework can be applied more widely to other taxa and archipelago-like systems, allowing new insights into biodiversity origin and maintenance.
We investigated the current patterns of diversity by country and by class of echinoderms, and analyzed their biogeographical, depth, and habitat or substratum affinities, using the database of the appendix of this book. Traditionally, the area has been divided into five biogeographical Regions and nine Provinces that cover a wide climate range. Currently, the echinoderm fauna of Latin America and Canary islands is constituted by 1,539 species, with 82 species of Crinoidea, 392 species of Asteroidea, 521 species of Ophiuroidea, 242 species of Echinoidea and 302 species of Holothuroidea. Species richness is highly variable among the different countries. The number of species for the countries is highly dependent on its coast length. The echinoderm fauna of the Panamic, Galápagos and the Chilean regions are biogeographically related. Other regions that are closely related are the Caribbean, West Indian, Lusitania and Brazilian. Cosmopolitan species are an important component in all the regions. Affinities between faunas are a consequence of the combination of climatic and trophic factors, connectivity as a function of distance, currents patterns and historical processes. Moreover, different environmental factors would be responsible for the faunal composition and species distribution at different spatial scales. The bathymetrical distribution of the echinoderm classes and the species richness varies according to the depth range and the ocean. Most species occurred at depths between 20 and 200 m. The Caribbean-Atlantic regions are richest in shallow depths, while the Pacific coast has higher values in deeper waters. The domination of each class in each substrate and habitat categories also varies differentially along each coast.
There are few environments conducive to coral growth along the Pacific coast of Nicaragua, due mostly to strong upwelling toward the south and the lack of adequate substrates toward the north. We visited 10 localities along the south coast of Nicaragua (San Juan del Sur, Rivas Department) and used a rapid assessment methodology (four 25-m long transects) to quantify the densities and diversity of coral, fishes, motile macroinvertebrates, and algae. A total of 52 fish, 11 echinoderm, 5 mollusk, 2 crustacean, 13 coral, and 39 macroalgae species were identified along the transects. The mean coral cover was 9.05% +/- 1.91, with the highest cover toward the north at Guacalito and Punta Gigante (18.50% +/- 8.68 and 16.75% +/- 5.25, respectively). The corals Pavona gigantea Verrill, 1869 and Pocillopora spp. were the main reef-builders. The area between Guacalito and Punta Gigante had the highest abundances of fishes and motile macroinvertebrates and was the most diverse site sampled within the San Juan del Sur area. We propose management action to protect the diversity and uniqueness of this region.
Recent advances in analytical methods and exploration of regional diversity patterns in greater depth than simple whole-fauna patterns may change our understanding of the determinants of latitudinal gradients in species richness. Using a comprehensive database on the geographical distributions of the large fauna of endemic shorefishes from the Tropical Eastern Pacific (TEP), we delineated latitudinal diversity gradients (LDGs) of species with different range sizes and assessed how the mid-domain effect, energy supply, environmental variability, and habitat availability predicted the various LDGs. We used statistical methods that account for spatial autocorrelation within each variable and consider collinearity among them. We found marked variation in LDGs among species with different range sizes: species with large ranges contributed the most to the convex form of the entire- fauna LDG while species with small ranges generated most deviations from that form. The mid-domain effect was the strongest determinant for the entire-fauna LDG, largely due to the strength of its effect on widespread species. Habitat variables were the best predictors for LDGs of small-range species but had no significant effects on the entire-fauna pattern. We found that any relationship between energy supply and LDGs likely is spurious and arises from statistical effects of (1) the marked spatial autocorrelation of the residuals in those relationships and (2) strong covariation between energy supply and the mid-domain effect, two factors that have never been analyzed together in marine studies (and seldom in terrestrial studies). There was no indication that environmental stability was an important LDG determinant at any level within the fauna. We found that latitudinal (Rapoport) trends in range size in this fauna arise as corollaries of the mid-domain effect. The disparate contributions of species with different range sizes to diversity patterns demonstrate the failure of traditional, whole-fauna LDGs to adequately represent all faunal components and their determinants, particularly those of small-range (and more threatened) species. We argue that, just as analyses of whole-fauna patterns within a region obscure variation in determinants among faunal components, analyses of patterns at transoceanic (multiregional) scales are likely to conceal important regional variation in determinants of diversity gra-
We examined the geographic distributions of 1135 species of resident shore fishes to assess biogeo- graphic subdivision of the Tropical Eastern Pacific (TEP), which stretches from the Gulf of California to northern Peru. Using hierarchical clustering refined by Analysis of Similarity (ANOSIM), we determined geographic groupings in the distributions of the entire fauna, of re- gional endemics and of 3 functional (habitat) groups of species. We also examined the distributions of local en- demics throughout the TEP and how differences in fau- nal size versus faunal composition among sites con- tribute to the subdivision pattern. Our results indicate that: (1) the continental coast contains 2 provinces, the Cortez (Gulf of California and lower Pacific Baja) and the Panamic (southward), each of which has a peak in abun- dance of local endemics and of overall species richness; (2) the northern and southern boundaries of the TEP are located near Magdalena Bay on Baja California (~25° N) and the southern shore of the Gulf of Guayaquil (~4° S), respectively; and (3) the 5 oceanic islands/archipelagos collectively represent a third, Ocean Island Province. Relative to mainland areas, the fauna of the ocean is- lands is smaller, has a different functional-group compo- sition, and includes more transpacific species and more highly localized endemics. The 3-province pattern prob- ably developed in response to the formation of the Gulf of California, the rise of the Isthmus of Panama, immigra- tion from the north, south and west to the TEP, and dif- fering environmental conditions between and within provinces. In contrast, barriers to dispersal within this geographically simple region are weak and likely had much less influence.
We describe a new species of ophiodermatid brittle star from the Eastern Pacific: Ophioderma occultum sp. nov. This species has been mistakenly recorded since 1899 as a colour phase of one of its congeners, Ophioderma panamense. However, the integrative use of morphological and molecular data, and comparison with type material of other Eastern Pacific Ophioderma, led to its differentiation as a novel species. Ophioderma occultum sp. nov. is characterised by having radial shields and adoral shields covered with granules, dorsal arm plates divided typically into two pieces, and a particular colour pattern: a dark grey to brown body, and arms with subtle lighter transverse bands and parallel longitudinal white bands over some median and distal segments. Molecular information based on the mitochondrial genes cytochrome oxidase subunit I (COI) and 16S also supported the species’ validity, coinciding with the morphological observations. In particular, the molecular marker 16S had not been used before for species delimitation in this genus and was proven here to be resolutive. In contrast to most species of Ophioderma from the area, Ophioderma occultum sp. nov. shows a restricted distribution to the northern Mexican Pacific (Gulf of California and islas Revillagigedo). This new
species is the 10th Ophioderma described from the Eastern Pacific and the 34th worldwide.
Ophiuroidea are one of the most diverse classes among extant echinoderms, characterized by their flexible arms composed of a series of ossicles called vertebrae, articulating with each other proximally and distally. Their arms show a wide range of motion, important for feeding and locomotion, associated with their epizoic and non-epizoic lifestyles. It remains to be explored to what degree the phenotypic variation in these ossicles also reflects adaptations to these lifestyles, rather than only their phylogenetic affinity. In this study, we analyzed the 3D shape variation of six arm vertebrae from the middle and distal parts of an arm in 12 species, belonging to the intertidal, subtidal and bathyal zones and showing epizoic and non-epizoic behaviors. A PERMANOVA indicated a significant difference in ossicle morphology between species and between lifestyles. A principal component analysis showed that the morphology of epizoic ophiuroids is distinct from non-epizoic ones; which may reflect variation in arm function related to these different lifestyles. The Phylogenetic MANOVA and phylogenetic signal analysis showed that shape variation in the vertebral articulation seems to reflect ecological and functional adaptations, whereas phylogeny controls more the lateral morphology of the vertebrae. This suggests a convergent evolution through ecological adaptation to some degree, indicating that some of these characters may have limited taxonomic value.
While the Ophiuroidea of Peruvian waters have long been studied, there exists inconsistencies regarding taxonomy and spatial distribution records. Based on literature review and museum records, we provide an updated checklist of the ophiuroids accompanied by the first geographical distribution analysis. Peruvian waters host 36 species of Ophiuroidea (three doubtful), yet 15 previous records of species are considered invalid for the area. We recorded five new records of species for Peru: Amphiodia oerstedi, Diopederma daniana, Ophiocomella alexandri, Ophiolepis crassa, and Ophiophthalmus normani. Peruvian maritime area is divided into four areas: The Tropical Eastern Pacific area where 16 species of ophiuroids occur, the Transition Zone with 13 species, the Warm Temperate Southeastern Pacific with nine species, and the Deep Zone with 14 species. We found significant differences in species composition among areas (except among the Eastern Pacific and the Transitional Zone), and each of them is represented by particular species. According to the rarefaction curve, the inventory of ophiuroids for the country is not yet complete; therefore, we suggest performing more expeditions along the Peruvian waters focusing mainly on the deep zones which remain relatively unexplored to date.
Aim
Biogeographic barriers emerged in the tropical oceans as continental masses moved with plate tectonics, and as the tropics contracted to lower latitudes from the late Eocene. These barriers have shaped tropical marine biodiversity. We characterize large‐scale diversity patterns for tropical brittle stars and investigate the effect of biogeographic barriers on these in space and time.
Location
Shallow‐water (<200 m) tropical oceans.
Taxon
Tropical shallow‐water brittle stars (class Ophiuroidea).
Methods
We integrate phylogenetic and biogeographic modelling to test and quantify the biogeographic structuring across the major ocean basins for five families of brittle stars. These are well‐sampled in our phylogenies (173 species) and represent an important component of the brittle star fauna of tropical shallow waters. We define major bioregions based on patterns of compositional and phylogenetic beta diversity.
Results
We find congruence between patterns of shared ancestry of regions and inferred biogeographic histories. Biogeographic reconstructions show that faunal patterns reflect the emergence of biogeographic barriers in the tropical world, with evidence of vicariant events driven by the opening of the Atlantic Ocean, the narrowing of the Tethyan Seaway and the rise of the Isthmus of Panama.
Main conclusions
Biogeographic barriers almost completely isolated regional faunas. However, divergence age estimates predate the onset of the different barriers, suggesting that changes associated with the gradual emergence of the barriers had a strong effect on the evolutionary history of tropical shallow‐water brittle stars. Limited, very recent, bi‐directional dispersal was detected across the East Pacific Barrier, which is otherwise an important barrier for dispersal of brittle stars.
Brittle-stars in the family Ophiocomidae are large and colourful inhabitants of tropical shallow water habitats across the globe. Here we use targeted capture and next-generation sequencing to generate robust phylogenomic trees for 39 of the 43 species in order to test the monophyly of existing genera. The large genus Ophiocoma, as currently constituted, is paraphyletic on our trees and required revision. Four genera are recognised herein: an expanded Ophiomastix (now including Ophiocoma wendtii, O. occidentalis, O. endeani, O. macroplaca, and Ophiarthrum spp), Ophiocomella (now including the non-fissiparous Ophiocoma pumila, aethiops and valenciae) and Breviturma (now including Ophiocoma pica, O. pusilla, O. paucigranulata and O. longispina) and a restricted Ophiocoma. The resulting junior homonym Ophiomastix elegans is renamed O. brocki. The genus Ophiomastix exhibits relatively high rates of morphological disparity compared to other lineages. Ophiomastix flaccida and O. (formerly Ophiarthrum) pictum have divergent mitochondrial genomes, characterised by gene-order rearrangements, strand recoding, enriched GT base composition, and a corresponding divergence of nuclear mitochondrial protein genes. The new phylogeny indicates that larval and developmental transitions occurred rarely. Larval culture trials show that species with abbreviated lecithotrophic larval development occur only within Ophiomastix, although the possible monophyly of these species is obscured by the rapid early radiation within this genus. Asexual reproduction by fission is limited to one species-complex within Ophiocomella, also characterised by elevated rates of allelic heterozygosity, and which has achieved a relatively rapid global distribution. The crown ages of the new genera considerably predate the closure of the Tethyan seaway and all four are distributed in both the Atlantic and Indo-Pacific Oceans. Two species pairs appear to reflect the closure of the Panama Seaway, although their fossil-calibrated node ages (12-14 ± 6 my), derived from both concatenated sequence and multispecies coalescent analyses, considerably predate the terminal closure event. Ophiocoma erinaceus has crossed the East Pacific barrier and is recorded from Clipperton Island, SW of Mexico.
During the Nineteenth and early Twentieth Centuries several renowned researchers—e.g., C. Darwin, J. Dana, A. Agassiz, A.E. Verrill, and T.W. Vaughan—remarked on the absence of coral reefs in the eastern tropical Pacific (ETP), concluding this was due mainly to the influence of cool currents and upwelling centers. From later surveys in southern Mexico in the 1920s (R.H. Palmer), and the Allan Hancock Expeditions across the eastern tropical Pacific in the 1930s (C. Wyatt Durham), workers began to recognize the presence of modest structural coral reef development at several sites in the ETP. A new era of coral reef studies began in the 1970s, and has increased in pace and intellectual depth to the present. This latest surge in coral science was a result of locally active researchers, especially in Mexico, Costa Rica, Panama, and Colombia, and more recently in Ecuador and Chile. Progress in coral research in El Salvador and Nicaragua was thwarted from the 1970s to the early 1990s because of political turmoil and violence in this sector of the eastern Pacific. The establishment of national research funding agencies in Latin American countries, such as CONACYT (Mexico), CONICIT (Costa Rica), COLCIENCIAS (Colombia), and FONDECYT (Chile), has greatly benefitted coral reef research as well as scholarship opportunities for resident students to pursue advanced studies in marine science. The availability of vessels to support research in remote areas and at offshore sites has also facilitated ETP coral studies. Contrary to early views, structural coral reefs were discovered in major upwelling centers—southern Mexico (Huatulco), Costa Rica (Guanacaste), and Panama (Gulf of Panama). The number of known coral species approximately doubled from the late 1940s to 2000, from 60 (total scleractinians) and <20 (reef-building or zooxanthellate corals) to >120 and >40 species, respectively. Additionally, reports of the appearance or disappearance of extralimital coral species (e.g., in the genera Montipora, Siderastrea, Acropora, and Millepora) have added to the excitement and adventure of eastern Pacific studies. On site observations during two very strong El Niño-Southern Oscillation (ENSO) disturbances, 1982–83 and 1997–98, demonstrated that acute temperature stress can cause widespread coral bleaching and mortality and interference with reef growth. More recently, ETP waters have been found to have low pH and aragonite saturation state, which can also weaken carbonate structures and interfere with reef development. Recognizing the economic, scientific, and esthetic value of ETP coral reefs, several national and international agencies are now supporting coral research, which will have a salutary effect in increasing our knowledge and understanding of these long-neglected ecosystems.
There are nearly 200 species of echinoderms reported from the Galápagos Islands and Galápagos Ridge, including five crinoids, 44 asteroids, 74 ophiuroids, 37 echinoids, and 38 holothurians. This is nearly one-third of all echinoderm species known from the central eastern Pacific (CEP) between 34°30′N and 18°S (Maluf, 1988a). Seventy percent of all CEP families, and 45% of all CEP genera are recorded from the Galápagos. Holothurians are the most poorly represented class. In fact, two orders (Apodida and Molpadiida) containing five families and 14 CEP genera, as well as one large family in the Dendrochirotida (Cucumariidae) with ten CEP genera, are not reported from the Galápagos.
To design robust protected area networks, accurately measure species losses, or understand the processes that maintain species diversity, conservation science must consider the organization of biodiversity in space. Central is beta-diversity - the component of regional diversity that accumulates from compositional differences between local species assemblages. We review how beta-diversity is impacted by human activities, including farming, selective logging, urbanization, species invasions, overhunting, and climate change. Beta-diversity increases, decreases, or remains unchanged by these impacts, depending on the balance of processes that cause species composition to become more different (biotic heterogenization) or more similar (biotic homogenization) between sites. While maintaining high beta-diversity is not always a desirable conservation outcome, understanding beta-diversity is essential for protecting regional diversity and can directly assist conservation planning.
Various authors have suggested that the Islas Marias archipelago, Mexico, may play a significant biogeographic role in the dispersal of Indo Pacific coral species into the Eastern Pacific; however, the coral communities of this archipelago have received scarce attention to date. Here, we first addressed coral community structure across the islands and, by employing ordination analysis, minimum spanning tree and particle-tracking experiments, used this information to evaluate the relevance of the archipelago for coral dispersal. Twenty-four coral communities were recorded in the archipelago. Coral cover varied significantly among islands: Maria Cleofas had large values (38.5%), intermediate values were observed for Maria Madre (26.5%) and Maria Magdalena (22.84%), and relatively low values were recorded for San Juanito (18.5%). Coral communities mainly consisted of Pocillopora (57.3%) and Porites (25.5%) species, while species of Pavona (16%) and Psammocora (0.6%) made relatively minor contributions. Thirteen stony coral species were identified in the archipelago; of these Psammocora profundacella and Pavona duerdeni represent new records. Ordination analysis, minimum spanning tree and particle-tracking experiments suggested similar connecting paths in the studied area; in general, the Islas Marias stands as a route for coral dispersal of Indo Pacific species into the Northeastern Pacific. In a regional context, the Islas Marias has three major biogeographic implications to coral dispersal: (i) the archipelago stands as a major stepping stone for the transport of species and individuals among the Revillagigedo archipelago, the Gulf of California and the tropical Mexican Pacific; (ii) the Islas Marias may play a seminal role in maintaining the genetic connectivity between southern and northern coral populations along the Mexican Pacific and (iii) because of its relatively pristine status and low levels of human impact, the archipelago may potentially serve as a source of coral propagules for ecosystem recovery in the Gulf of California and along the Pacific coast of the Mexican mainland following natural and/or human induced perturbations.
The eastern tropical Pacific includes 28 million km2 of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.
This paper presents a complete list of hermatypic coral species, analyzes the biodiversity lev& and describes