The Molecular Biogeography of the Indo-Pacific: Testing Hypotheses With Multispecies Genetic Patterns

Aim: To test hypothesized biogeographic partitions of the tropical Indo-Pacific Ocean with phylogeographic data from 56 taxa, and to evaluate the strength and nature of barriers emerging from this test. \u3eLocation: The Indo-Pacific Ocean. Time Period: Pliocene through the Holocene. Major Taxa Studied: Fifty-six marine species. Methods: We tested eight biogeographic hypotheses for partitioning of the Indo-Pacific using a novel modification to analysis of molecular variance. Putative barriers to gene flow emerging from this analysis were evaluated for pairwise ΦST, and these ΦST distributions were compared to distributions from randomized datasets and simple coalescent simulations of vicariance arising from the Last Glacial Maximum. We then weighed the relative contribution of distance versus environmental or geographic barriers to pairwise ΦST with a distance-based redundancy analysis (dbRDA). Results: We observed a diversity of outcomes, although the majority of species fit a few broad biogeographic regions. Repeated coalescent simulation of a simple vicariance model yielded a wide distribution of pairwise ΦST that was very similar to empirical distributions observed across five putative barriers to gene flow. Three of these barriers had median ΦST that were significantly larger than random expectation. Only 21 of 52 species analysed with dbRDA rejected the null model. Among these, 15 had overwater distance as a significant predictor of pairwise ΦST, while 11 were significant for geographic or environmental barriers other than distance. Main Conclusions: Although there is support for three previously described barriers, phylogeographic discordance in the Indo-Pacific Ocean indicates incongruity between processes shaping the distributions of diversity at the species and population levels. Among the many possible causes of this incongruity, genetic drift provides the most compelling explanation: given massive effective population sizes of Indo-Pacific species, even hard vicariance for tens of thousands of years can yield ΦST values that range from 0 to nearly 0.5

The molecular biogeography of the Indo‐Pacific: Testing hypotheses with multispecies genetic patterns

Aim: To test hypothesized biogeographic partitions of the tropical Indo‐Pacific Ocean with phylogeographic data from 56 taxa, and to evaluate the strength and nature of barriers emerging from this test. Location: The Indo‐Pacific Ocean. Time period: Pliocene through the Holocene. Major taxa studied: Fifty‐six marine species. Methods: We tested eight biogeographic hypotheses for partitioning of the Indo‐ Pacific using a novel modification to analysis of molecular variance. Putative barriers to gene flow emerging from this analysis were evaluated for pairwise ΦST, and these ΦST distributions were compared to distributions from randomized datasets and simple coalescent simulations of vicariance arising from the Last Glacial Maximum. We then weighed the relative contribution of distance versus environmental or geographic barriers to pairwise ΦST with a distance‐based redundancy analysis (dbRDA). Results: We observed a diversity of outcomes, although the majority of species fit a few broad biogeographic regions. Repeated coalescent simulation of a simple vicariance model yielded a wide distribution of pairwise ΦST that was very similar to empirical distributions observed across five putative barriers to gene flow. Three of these barriers had median ΦST that were significantly larger than random expectation. Only 21 of 52 species analysed with dbRDA rejected the null model. Among these, 15 had overwater distance as a significant predictor of pairwise ΦST, while 11 were significant for geographic or environmental barriers other than distance. Main conclusions: Although there is support for three previously described barriers, phylogeographic discordance in the Indo‐Pacific Ocean indicates incongruity between processes shaping the distributions of diversity at the species and population levels. Among the many possible causes of this incongruity, genetic drift provides the most compelling explanation: given massive effective population sizes of Indo‐Pacific species, even hard vicariance for tens of thousands of years can yield ΦST values that range from 0 to nearly 0.5

Defining Boundaries for Ecosystem-Based Management: A Multispecies Case Study of Marine Connectivity across the Hawaiian Archipelago

Determining the geographic scale at which to apply ecosystem-based management (EBM) has proven to be an obstacle for many marine conservation programs. Generalizations based on geographic proximity, taxonomy, or life history characteristics provide little predictive power in determining overall patterns of connectivity, and therefore offer little in terms of delineating boundaries for marine spatial management areas. Here, we provide a case study of 27 taxonomically and ecologically diverse species (including reef fishes, marine mammals, gastropods, echinoderms, cnidarians, crustaceans, and an elasmobranch) that reveal four concordant barriers to dispersal within the Hawaiian Archipelago which are not detected in single-species exemplar studies. We contend that this multispecies approach to determine concordant patterns of connectivity is an objective and logical way in which to define the minimum number of management units and that EBM in the Hawaiian Archipelago requires at least five spatially managed regions

Not All Larvae Stay Close to Home: Insights into Marine Population Connectivity with a Focus on the Brown Surgeonfish (Acanthurus nigrofuscus)

Recent reports of localized larval recruitment in predominately small-range fishes are countered by studies that show high genetic connectivity across large oceanic distances. This discrepancy may result from the different timescales over which genetic and demographic processes operate or rather may indicate regular long-distance dispersal in some species. Here, we contribute an analysis of mtDNA cytochrome b diversity in the widely distributed Brown Surgeonfish (Acanthurus nigrofuscus; N=560), which revealed significant genetic structure only at the extremes of the range (ΦCT=0.452; P<.001). Collections from Hawaii to the Eastern Indian Ocean comprise one large, undifferentiated population. This pattern of limited genetic subdivision across reefs of the central Indo-Pacific has been observed in a number of large-range reef fishes. Conversely, small-range fishes are often deeply structured over the same area. These findings demonstrate population connectivity differences among species at biogeographic and evolutionary timescales, which likely translates into differences in dispersal ability at ecological and demographic timescales. While interspecific differences in population connectivity complicate the design of management strategies, the integration of multiscale connectivity patterns into marine resource planning will help ensure long-term ecosystem stability by preserving functionally diverse communities

Escaping paradise: larval export from Hawaii in an Indo-Pacific reef fish, the yellow tang Zebrasoma flavescens

The depauperate marine ecosystems of the Hawaiian Archipelago share a high proportion of species with the southern and western Pacific, indicating historical and/or ongoing connections across the large oceanic expanse separating Hawaii from its nearest neighbors. The rate and direction of these interactions are, however, unknown. While previous biogeographic studies have consistently described Hawaii as a diversity sink, prevailing currents likely offer opportunities for larval export. To assess interactions between the remote reefs of the Hawaiian Archipelago and the species-rich communities of the Central and West Pacific, we surveyed 14 nuclear microsatellite loci (nDNA, n = 857) and a 614 bp segment of mitochondrial cytochrome b (mtDNA, n = 654) in the yellow tang Zebrasoma flavescens. Concordant frequency shifts in both nDNA and mtDNA reveal significant population differentiation among 3 West Pacific sites and Hawaii (nDNA F-CT\u27 = 0.116; mtDNA phi(CT) = 0.098, p \u3c 0.001). SAMOVA analyses of microsatellite data additionally indicate fine scale differentiation within the 2600 km Hawaiian Archipelago (F-SC\u27 = 0.026, p \u3c 0.001), which has implications for management of this heavily-exploited aquarium fish. Mismatch analyses indicate the oldest contemporary populations are in the Hawaiian Archipelago (ca. 318 000 yr) with younger populations in the West Pacific (91 000 to 175 000 yr). Estimates of yellow tang historical demography contradict expectations of Hawaii as a population sink and instead indicate asymmetrical gene flow, with Hawaii exporting rather than importing yellow tang larvae

Age and growth of bluespine unicornfish (Naso unicornis): a half-century life-span for a keystone browser, with a novel approach to bomb radiocarbon dating in the Hawaiian Islands

Bluespine unicornfish (Naso unicornis) from Hawaii were aged to >50 years using cross-sectioned sagittal otoliths. Fish length was a poor indicator of age because of rapid and variable early growth, exemplified by fish aged to be 4 years near maximum length. Growth was deterministic with adult ages decoupled from body length. Otolith mass and thickness were evaluated as proxies for age and both were encouraging; thickness explained more variance but mass was easier to measure. An age estimation protocol was validated through ontogeny using bomb radiocarbon (14C) dating. Use of the postbomb 14C decline period from a regional reference chronology enabled age validation of young fish – a novel approach for the Pacific Ocean. A probabilistic procedure for assigning bomb14C dates (CALIBomb) was used for the first time to determine fish birth years. The age-reading protocol was generally validated, and it was possible to describe length-at-age despite difficulties in counting otolith annuli beyond 30-40 years. Growth curves differed between the sexes, and a four-parameter generalized von Bertalanffy growth function provided the best fit

Ground-Dwelling Arthropod Communities of a Sky Island Mountain Range in Southeastern Arizona, USA: Obtaining a Baseline for Assessing the Effects of Climate Change

<div><p>The few studies that have addressed past effects of climate change on species distributions have mostly focused on plants due to the rarity of historical faunal baselines. However, hyperdiverse groups like Arthropoda are vital to monitor in order to understand climate change impacts on biodiversity. This is the first investigation of ground-dwelling arthropod (GDA) assemblages along the full elevation gradient of a mountain range in the Madrean Sky Island Region, establishing a baseline for monitoring future changes in GDA biodiversity. To determine how GDA assemblages relate to elevation, season, abiotic variables, and corresponding biomes, GDA were collected for two weeks in both spring (May) and summer (September) 2011 in the Santa Catalina Mountains, Arizona, using pitfall traps at 66 sites in six distinct upland (non-riparian/non-wet canyon) biomes. Four arthropod taxa: (1) beetles (Coleoptera), (2) spiders (Araneae), (3) grasshoppers and crickets (Orthoptera), and (4) millipedes and centipedes (Myriapoda) were assessed together and separately to determine if there are similar patterns across taxonomic groups. We collected 335 species of GDA: 192/3793 (species/specimens) Coleoptera, 102/1329 Araneae, 25/523 Orthoptera, and 16/697 Myriapoda. GDA assemblages differed among all biomes and between seasons. Fifty-three percent (178 species) and 76% (254 species) of all GDA species were found in only one biome and during only one season, respectively. While composition of arthropod assemblages is tied to biome and season, individual groups do not show fully concordant patterns. Seventeen percent of the GDA species occurred only in the two highest-elevation biomes (Pine and Mixed Conifer Forests). Because these high elevation biomes are most threatened by climate change and they harbor a large percentage of unique arthropod species (11–25% depending on taxon), significant loss in arthropod diversity is likely in the Santa Catalina Mountains and other isolated mountain ranges in the Southwestern US.</p></div

British Indian ocean territory (the Chagos archipelago) : setting, connections and the marine protected area

Coral cover throughout the Chagos archipelago is high. Coral and soft coral mortality was very severe in 1998, along with most of the ocean, but there are no direct human impacts so that soft coral and coral cover is as high as it was before the massive mortality episode. There is a very low incidence of coral disease, and there are no recorded marine invasive species, a condition which is unprecedented in coral seas. The area contains between 25 and 50 % of the reefs in the Indian Ocean in very good condition, and the area has the largest contiguous area in the world of reefs in such a state. Reasons for the good condition of Chagos reefs are likely to include remoteness from compounding human activities, but also strongly light adapted ‘Clade A’ zooxanthellae may contribute: these occur in approximately half of the shallow water Acropora colonies which are now recovering strongly. Another contributing factor may be the regular incursions of deep, cool water that rise to cover reefs, including during annual periods of greatest warming. These reefs are viewed as a ‘baseline’ or reference point for many other coral rees in the Indian Ocean

Results from SIMPER analyses, listing the six most important species according to its contribution to the dissimilarity between arthropod assemblages in adjacent biomes: DS = Desertscrub, GL = Grassland, CH = Chaparral, and PO = Pine Oak, P = Pine, MC = Mixed Conifer.

<p>Capital letters preceding species names indicate to which major arthropod group the species belongs (C-Coleoptera, A- Araneae, O-Orthoptera, M-Myriapoda).</p

Proportion of species in each taxa found in only one biome.

<p>Proportion of species in each taxa (Coleoptera, Araneae, Orthoptera, and Myriapoda) found in only one biome (presented as a proportion of the total richness).</p