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Item Regional patterns of mtDNA diversity in Styela plicata, an invasive ascidian, from Australian and New Zealand marinas(CSIRO PUBLISHING, 7/03/2013) Torkkola J; Riginos C; Liggins LThe ascidian Styela plicata is abundant in harbours and marinas worldwide and has likely reached this distribution via human-mediated dispersal. Previous worldwide surveys based on mitochondrial cytochrome oxidase one (COI) sequences have described two divergent clades, showing overlapping distributions and geographically widespread haplotypes. These patterns are consistent with recent mixing among genetically differentiated groups arising from multiple introductions from historically distinct sources. In contrast, a study of Australian S. plicata using nuclear markers found that population differentiation along the eastern coast related to geographic distance and no evidence for admixture between previously isolated genetic groups. We re-examined the genetic patterns of Australian S. plicata populations using mtDNA (CO1) to place their genetic patterns within a global context, and we examined New Zealand populations for the first time. We found that the haplotypic compositions of Australian and New Zealand populations are largely representative of other worldwide populations. The New Zealand populations, however, exhibited reduced diversity, being potentially indicative of a severely bottlenecked colonisation event. In contrast to results from nuclear markers, population differentiation of mtDNA among Australian S. plicata was unrelated to geographic distance. The discrepancy between markers is likely to be a consequence of non-equilibrium population genetic processes that typify non-indigenous species. © 2013 CSIRO.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 The short-lived neon damsel Pomacentrus coelestis: implications for population dynamics.(2017-05) Kingsford MJ; O'Callaghan MD; Liggins L; Gerlach GDaily increments of Pomacentrus coelestis, an abundant and well-studied fish, were validated for the life of the fish and depending on the location, age-maxima were estimated to be 127-160 days on reefs separated by tens to hundreds of kilometres on the Great Barrier Reef. This contrasts with congeners and other damselfishes that live for 5 years or more. Otoliths of P. coelestis were thinner and had different patterns of banding when compared with relatively long-lived congeners. It is suggested that banding patterns in P. coelestis may be related to patterns of maturation and spawning. The consequences of a short life would have a great influence on the population dynamics of this widespread species. Further, the demographics and habitat preferences of this species suggest rapid colonization and establishment of breeding populations that would quickly change the relative abundance of sympatric fishes.Item Origin and post-colonization evolution of the Chatham Islands skink (Oligosoma nigriplantare nigriplantare).(WILEY-BLACKWELL, 2008-07) Liggins L; Chapple DG; Daugherty CH; Ritchie PAIsland ecosystems provide an opportunity to examine a range of evolutionary and ecological processes. The Chatham Islands are an isolated archipelago situated approximately 800 km east of New Zealand. Geological evidence indicates that the Chatham Islands re-emerged within the last 1-4 million years, following a prolonged period of marine inundation, and therefore the resident flora and fauna is the result of long-distance overwater dispersal. We examine the origin and post-colonization evolution of the Chatham Islands skink, Oligosoma nigriplantare nigriplantare, the sole reptile species occurring on the archipelago. We sampled O. n. nigriplantare from across nine islands within the Chatham Islands group, and representative samples from across the range of its closest relative, the New Zealand mainland common skink (Oligosoma nigriplantare polychroma). Our mitochondrial sequence data indicate that O. n. nigriplantare diverged from O. n. polychroma 5.86-7.29 million years ago. This pre-dates the emergence date for the Chatham Islands, but indicates that O. n. nigriplantare colonized the Chatham Islands via overwater dispersal on a single occasion. Despite the substantial morphological variability evident in O. n. nigriplantare, only relatively shallow genetic divergences (maximum divergence approximately 2%) were found across the Chatham Islands. Our analyses (haplotypic diversity, Phi(ST), analysis of molecular variance, and nested clade phylogeographical analysis) indicated restricted gene flow in O. n. nigriplantare resulting in strong differentiation between islands. However, the restrictions to gene flow might have only arisen recently as there was also a significant pattern of isolation by distance, possibly from when the Chatham Islands were a single landmass during Pleistocene glacial maxima when sea levels were lower. The level of genetic and morphological divergence between O. n. nigriplantare and O. n. polychroma might warrant their recognition as distinct species.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 A novel widespread cryptic species and phylogeographic patterns within several giant clam species (Cardiidae: Tridacna) from the Indo-Pacific Ocean.(PUBLIC LIBRARY SCIENCE, 2013) Huelsken T; Keyse J; Liggins L; Penny S; Treml EA; Riginos CGiant clams (genus Tridacna) are iconic coral reef animals of the Indian and Pacific Oceans, easily recognizable by their massive shells and vibrantly colored mantle tissue. Most Tridacna species are listed by CITES and the IUCN Redlist, as their populations have been extensively harvested and depleted in many regions. Here, we survey Tridacna crocea and Tridacna maxima from the eastern Indian and western Pacific Oceans for mitochondrial (COI and 16S) and nuclear (ITS) sequence variation and consolidate these data with previous published results using phylogenetic analyses. We find deep intraspecific differentiation within both T. crocea and T. maxima. In T. crocea we describe a previously undocumented phylogeographic division to the east of Cenderawasih Bay (northwest New Guinea), whereas for T. maxima the previously described, distinctive lineage of Cenderawasih Bay can be seen to also typify western Pacific populations. Furthermore, we find an undescribed, monophyletic group that is evolutionarily distinct from named Tridacna species at both mitochondrial and nuclear loci. This cryptic taxon is geographically widespread with a range extent that minimally includes much of the central Indo-Pacific region. Our results reinforce the emerging paradigm that cryptic species are common among marine invertebrates, even for conspicuous and culturally significant taxa. Additionally, our results add to identified locations of genetic differentiation across the central Indo-Pacific and highlight how phylogeographic patterns may differ even between closely related and co-distributed species.Item skelesim: an extensible, general framework for population genetic simulation in R.(2017-01) Parobek CM; Archer FI; DePrenger-Levin ME; Hoban SM; Liggins L; Strand AESimulations are a key tool in molecular ecology for inference and forecasting, as well as for evaluating new methods. Due to growing computational power and a diversity of software with different capabilities, simulations are becoming increasingly powerful and useful. However, the widespread use of simulations by geneticists and ecologists is hindered by difficulties in understanding these softwares' complex capabilities, composing code and input files, a daunting bioinformatics barrier and a steep conceptual learning curve. skelesim (an R package) guides users in choosing appropriate simulations, setting parameters, calculating genetic summary statistics and organizing data output, in a reproducible pipeline within the R environment. skelesim is designed to be an extensible framework that can 'wrap' around any simulation software (inside or outside the R environment) and be extended to calculate and graph any genetic summary statistics. Currently, skelesim implements coalescent and forward-time models available in the fastsimcoal2 and rmetasim simulation engines to produce null distributions for multiple population genetic statistics and marker types, under a variety of demographic conditions. skelesim is intended to make simulations easier while still allowing full model complexity to ensure that simulations play a fundamental role in molecular ecology investigations. skelesim can also serve as a teaching tool: demonstrating the outcomes of stochastic population genetic processes; teaching general concepts of simulations; and providing an introduction to the R environment with a user-friendly graphical user interface (using shiny).Item Cryptic speciation in pan-tropical sea urchins: a case study of an edge-of-range population of Tripneustes from the Kermadec Islands.(20/07/2017) Bronstein O; Kroh A; Tautscher B; Liggins L; Haring ETripneustes is one of the most abundant and ecologically significant tropical echinoids. Highly valued for its gonads, wild populations of Tripneustes are commercially exploited and cultivated stocks are a prime target for the fisheries and aquaculture industry. Here we examine Tripneustes from the Kermadec Islands, a remote chain of volcanic islands in the southwest Pacific Ocean that mark the boundary of the genus' range, by combining morphological and genetic analyses, using two mitochondrial (COI and the Control Region), and one nuclear (bindin) marker. We show that Kermadec Tripneustes is a new species of Tripneustes. We provide a full description of this species and present an updated phylogeny of the genus. This new species, Tripneustes kermadecensis n. sp., is characterized by having ambulacral primary tubercles occurring on every fourth plate ambitally, flattened test with large peristome, one to two occluded plates for every four ambulacral plates, and complete primary series of interambulacral tubercles from peristome to apex. It appears to have split early from the main Tripneustes stock, predating even the split of the Atlantic Tripneustes lineage. Its distinction from the common T. gratilla and potential vulnerability as an isolated endemic species calls for special attention in terms of conservation.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 Evidence of cryptic species in the blenniid Cirripectesalboapicalis species complex, with zoogeographic implications for the South Pacific(Pensoft Publishers, 20/12/2018) Delrieu-Trottin E; Liggins L; Trnski T; Williams JT; Neglia V; Rapu-Edmunds C; Planes S; Saenz-Agudelo PRapa Nui, commonly known as Easter Island (Chile), is one of the most isolated tropical islands of the Pacific Ocean. The island location of Rapa Nui makes it the easternmost point of the geographic ranges for many western Pacific fish species that are restricted to the subtropical islands south of 20°S latitude. The blenniid fish species Cirripectesalboapicalis has been thought to have one of the most extensive geographic distribution ranges among these southern subtropical fish species, extending from the southern Great Barrier Reef to Rapa Nui. A phylogenetic analysis was conducted to determine the taxonomic status of the species. The results provide genetic evidence that suggests that this formerly South Pacific-wide species comprises at least three cryptic species with allopatric geographic distributions. The analyses reveal the geographic distributions of these clades and their genetic relationships with each other, and with other species within the genus Cirripectes. The processes that culminated in the current geographic distribution of this species complex and the zoogeographic implications of this finding for the South Pacific region are discussed.