Journal Articles
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Item Evaluating edge-of-range genetic patterns for tropical echinoderms, Acanthaster planci and Tripneustes gratilla, of the Kermadec Islands, southwest Pacific(ROSENSTIEL SCH MAR ATMOS SCI, 1/01/2014) Liggins L; Gleeson L; Riginos CEdge-of-range populations are often typified by patterns of low genetic diversity and high genetic differentiation relative to populations within the core of a species range. The "core-periphery hypothesis," also known as the "central-marginal hypothesis," predicts that these genetic patterns at the edge-of-range are a consequence of reduced population size and connectivity toward a species range periphery. It is unclear, however, how these expectations relate to high dispersal marine species that can conceivably maintain high abundance and high connectivity at their range edge. In the present study, we characterize the genetic patterns of two tropical echinoderm populations in the Kermadec Islands, the edge of their southwest Pacific range, and compare these genetic patterns to those from populations throughout their east Indian and Pacific ranges. We find that the populations of both Acanthaster planci (Linnaeus, 1758) and Tripneustes gratilla (Linnaeus, 1758) are represented by a single haplotype at the Kermadec Islands (based on mitochondrial cytochrome oxidase C subunit I). Such low genetic diversity concurs with the expectations of the "core-periphery hypothesis." Furthermore, the haplotypic composition of both populations suggests they have been founded by a small number of colonists with little subsequent immigration. Thus, local reproduction and self-recruitment appear to maintain these populations despite the ecologically marginal conditions of the Kermadec Islands for these tropical species. Understanding rates of self-recruitment vs reliance on connectivity with populations outside of the Kermadec Islands has implications for the persistence of these populations and range stability of these echinoderm species.© 2014 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.Item Seascape features, rather than dispersal traits, predict spatial genetic patterns in co-distributed reef fishes(Wiley, 2015) Liggins L; Treml EA; Possingham HP; Riginos CAim: To determine which seascape features have shaped the spatial genetic patterns of coral reef fishes, and to identify common patterns among species related to dispersal traits [egg type and pelagic larval duration (PLD)]. Location: Indian and Pacific Oceans, including the Indo-Australian Archipelago. Methods: We sampled coral reef fishes with differing dispersal traits (Pomacentrus coelestis, Dascyllus trimaculatus, Hailchoeres hortulanus and Acanthurus triostegus) and characterized spatial (mtDNA) genetic patterns using AMOVA-clustering and measures of genetic differentiation. Similarity in the spatial genetic patterns among species was assessed using the congruence among distance matrices method and the seascape features associated with the genetic differentiation of each species were identified using multiple regression of distance matrices (MRDM) and stepwise model selection. Results: Similar spatial genetic patterns were found for P. coelestis and H. hortulanus, despite their differing egg type (benthic versus pelagic). MRDM indicated that geographical distance was underlying their correlated genetic patterns. Species with pelagic eggs (A. triostegus and H. hortulanus) also had correlated patterns of genetic differentiation (Dest); however, a common underlying seascape feature could not be inferred. Additionally, the common influence of the Torres Strait and the Lydekker/Weber's line was identified for the genetic patterns of differentiation for P. coelestis and A. triostegus, despite their differing dispersal traits, and the uncorrelated spatial genetic patterns of these species. Main conclusions: Our study demonstrates the value of a quantitative, hypothesis-testing framework in comparative phylogeography. We found that dispersal traits (egg type and PLD) did not predict which species had similar spatial genetic patterns or which seascape features were associated with these patterns. Furthermore, even in the absence of visually similar, or correlated spatial genetic patterns, our approach enabled us to identify seascape features that had a common influence on the spatial genetic patterns of co-distributed species.Item Return of the ghosts of dispersal past: Historical spread and contemporary gene flow in the blue sea star Linckia laevigata(ROSENSTIEL SCH MAR ATMOS SCI, 1/01/2014) Crandall ED; Treml EA; Liggins L; Gleeson L; Yasuda N; Barber PH; Wörheide G; Riginos CMarine animals inhabiting the Indian and Pacific oceans have some of the most extensive species ranges in the world, sometimes spanning over half the globe. These Indo-Pacific species present a challenge for study with both geographic scope and sampling density as limiting factors. Here, we augment and aggregate phylogeographic sampling of the iconic blue sea star, Linckia laevigata Linnaeus, 1758, and present one of the most geographically comprehensive genetic studies of any Indo-Pacific species to date, sequencing 392 base pairs of mitochondrial COI from 791 individuals from 38 locations spanning over 14,000 km. We first use a permutation based multiple-regression approach to simultaneously evaluate the relative influence of historical and contemporary gene flow together with putative barriers to dispersal. We then use a discrete diffusion model of phylogeography to infer the historical migration and colonization routes most likely used by L. laevigata across the Indo-Pacific. We show that estimates of genetic structure have a stronger correlation to geographic distances than to "oceanographic" distances from a biophysical model of larval dispersal, reminding us that population genetic estimates of gene flow and genetic structure are often shaped by historical processes. While the diffusion model was equivocal about the location of the mitochondrial most recent common ancestor (MRC A), we show that gene flow has generally proceeded in a step-wise manner across the Indian and Pacific oceans. We do not find support for previously described barriers at the Sunda Shelf and within Cenderwasih Bay. Rather, the strongest genetic disjunction is found to the east of Cenderwasih Bay along northern New Guinea. These results underscore the importance of comprehensive range-wide sampling in marine phylogeography.© 2014 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.Item Not the time or the place: the missing spatio-temporal link in publicly available genetic data.(Blackwell Publishing Ltd, 2015-08) Pope LC; Liggins L; Keyse J; Carvalho SB; Riginos CGenetic data are being generated at unprecedented rates. Policies of many journals, institutions and funding bodies aim to ensure that these data are publicly archived so that published results are reproducible. Additionally, publicly archived data can be 'repurposed' to address new questions in the future. In 2011, along with other leading journals in ecology and evolution, Molecular Ecology implemented mandatory public data archiving (the Joint Data Archiving Policy). To evaluate the effect of this policy, we assessed the genetic, spatial and temporal data archived for 419 data sets from 289 articles in Molecular Ecology from 2009 to 2013. We then determined whether archived data could be used to reproduce analyses as presented in the manuscript. We found that the journal's mandatory archiving policy has had a substantial positive impact, increasing genetic data archiving from 49 (pre-2011) to 98% (2011-present). However, 31% of publicly archived genetic data sets could not be recreated based on information supplied in either the manuscript or public archives, with incomplete data or inconsistent codes linking genetic data and metadata as the primary reasons. While the majority of articles did provide some geographic information, 40% did not provide this information as geographic coordinates. Furthermore, a large proportion of articles did not contain any information regarding date of sampling (40%). Although the inclusion of spatio-temporal data does require an increase in effort, we argue that the enduring value of publicly accessible genetic data to the molecular ecology field is greatly compromised when such metadata are not archived alongside genetic data.Item Building a global genomics observatory: Using GEOME (the Genomic Observatories Metadatabase) to expedite and improve deposition and retrieval of genetic data and metadata for biodiversity research.(2020-11) Riginos C; Crandall ED; Liggins L; Gaither MR; Ewing RB; Meyer C; Andrews KR; Euclide PT; Titus BM; Therkildsen NO; Salces-Castellano A; Stewart LC; Toonen RJ; Deck JGenetic data represent a relatively new frontier for our understanding of global biodiversity. Ideally, such data should include both organismal DNA-based genotypes and the ecological context where the organisms were sampled. Yet most tools and standards for data deposition focus exclusively either on genetic or ecological attributes. The Genomic Observatories Metadatabase (GEOME: geome-db.org) provides an intuitive solution for maintaining links between genetic data sets stored by the International Nucleotide Sequence Database Collaboration (INSDC) and their associated ecological metadata. GEOME facilitates the deposition of raw genetic data to INSDCs sequence read archive (SRA) while maintaining persistent links to standards-compliant ecological metadata held in the GEOME database. This approach facilitates findable, accessible, interoperable and reusable data archival practices. Moreover, GEOME enables data management solutions for large collaborative groups and expedites batch retrieval of genetic data from the SRA. The article that follows describes how GEOME can enable genuinely open data workflows for researchers in the field of molecular ecology.Item Larval traits show temporally consistent constraints, but are decoupled from postsettlement juvenile growth, in an intertidal fish(John Wiley and Sons, Inc on behalf of the British Ecological Society, 8/08/2018) Thia JA; Riginos C; Liggins L; Figueira WF; McGuigan K1. Complex life cycles may evolve to dissociate distinct developmental phases in an organism's lifetime. However, genetic or environmental factors may restrict trait independence across life stages, constraining ontogenetic trajectories. Quantifying covariance across life stages and their temporal variability is fundamental in understanding life-history phenotypes and potential distributions and consequences for selection. 2. We studied developmental constraints in an intertidal fish (Bathygobius cocosensis: Gobiidae) with a discrete pelagic larval phase and benthic juvenile phase. We tested whether traits occurring earlier in life affected those expressed later, and whether larval traits were decoupled from postsettlement juvenile traits. Sampling distinct cohorts from three annual breeding seasons afforded tests of temporally variability in trait covariance. 3. From otoliths (fish ear stones), we measured hatch size, larval duration, pelagic growth (larval traits) and early postsettlement growth (juvenile trait) in 124 juvenile B. cocoensis. We used path analyses to model trait relationships with respect to their chronological expression, comparing models among seasons. We also modelled the effect of season and hatch date on each individual trait to quantify their inherent variability. 4. Our path analyses demonstrated a decoupling of larval traits on juvenile growth. Within the larval phase, longer larval durations resulted in greater pelagic growth, and larger size-at-settlement. There was also evidence that larger hatch size might reduce larval durations, but this effect was only marginally significant. Although pelagic and postsettlement growth were decoupled, pelagic growth had postsettlement consequences: individuals with high pelagic growth were among the largest fish at settlement, and remained among the largest early postsettlement. We observed no evidence that trait relationships varied among breeding seasons, but larval duration differed among breeding seasons, and was shorter for larvae hatching later within each season. 5. Overall, we demonstrate mixed support for the expectation that traits in different life stages are independent. While postsettlement growth was decoupled from larval traits, pelagic development had consequences for the size of newly settled juveniles. Temporal consistency in trait covariances implies that genetic and/or environmental factors influencing them were stable over our three-year study. Our work highlights the importance of individual developmental experiences and temporal variability in understanding population distributions of life-history traits.Item Vicariance and dispersal across an intermittent barrier: Population genetic structure of marine animals across the Torres Strait land bridge(SPRINGER, 1/12/2011) Mirams AGK; Treml EA; Shields JL; Liggins L; Riginos CBiogeographic barriers, some transitory in duration, are likely to have been important contributing factors to modern marine biodiversity in the Indo-Pacific region. One such barrier was the Torres Strait land bridge between continental Australia and New Guinea that persisted through much of the late Pleistocene and separated Indian and Pacific Ocean taxa. Here, we examine the patterns of mitochondrial DNA diversity for marine animals with present-day distributions spanning the Torres Strait. Specifically, we investigate whether there are concordant signatures across species, consistent with either vicariance or recent colonization from either ocean basin. We survey four species of reef fishes (Apogon doederleini, Pomacentrus coelestis, Dascyllus trimaculatus, and Acanthurus triostegus) for mtDNA cytochrome oxidase 1 and control region variation and contrast these results to previous mtDNA studies in diverse marine animals with similar distributions. We find substantial genetic partitioning (estimated from F-statistics and coalescent approaches) between Indian and Pacific Ocean populations for many species, consistent with regional persistence through the late Pleistocene in both ocean basins. The species-specific estimates of genetic divergence, however, vary greatly and for reef fishes we estimate substantially different divergence times among species. It is likely that Indian and Pacific Ocean populations have been isolated for multiple glacial cycles for some species, whereas for other species genetic connections have been more recent. Regional estimates of genetic diversity and directionality of gene flow also vary among species. Thus, there is no apparent consistency among historical patterns across the Torres Strait for these co-distributed marine animals. © 2011 Springer-Verlag.