DOCSLIB.ORG

Ecological Convergence in a Rocky Intertidal Shore Metacommunity Despite High Spatial Variability in Recruitment Regimes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ecological Convergence in a Rocky Intertidal Shore Metacommunity Despite High Spatial Variability in Recruitment Regimes Ecological convergence in a rocky intertidal shore metacommunity despite high spatial variability in recruitment regimes Andrés U. Caro, Sergio A. Navarrete1, and Juan Carlos Castilla Center for Advanced Studies in Ecology and Biodiversity and Estación Costera de Investigaciones Marinas, Pontificia Universidad Católica de Chile, Santiago, C.P. 8331150, Chile Edited by James Hemphill Brown, University of New Mexico, Albuquerque, NM, and approved September 17, 2010 (received for review May 20, 2010) In open ecological systems, community structure can be determined Instead of parameterizing a neutral model for species that by physically modulated processes such as the arrival of individuals share and compete for a common resource within a trophic level, from a regional pool and by local biological interactions. There is as required by NTB models (1, 6, 8, 19), we start with a rocky shore debate centering on whether niche differentiation and local inter- metacommunity, composed of 15 local communities of coexisting actions among species are necessary to explain macroscopic com- species from disparate taxa at all trophic levels and exhibiting an munity patterns or whether the patterns can be generated by the astonishing diversity of modes of development (Table S1). These neutral interplay of dispersal and stochastic demography among local communities are spread over 800 km of coastline and are ecologically identical species. Here we evaluate how much of the separated by tens of kilometers (Fig. 1A), surpassing the scale of observed spatial variation within a rocky intertidal metacommunity movement of all adult mobile invertebrates. In this system, we ask along 800 km of coastline can be explained by drift in the structure to what extent large-scale spatial variation in species composition of recruits across 15 local sites. Our results show that large spatial can be predicted solely by variation in dispersal and re- changes in recruitment do not explain the observed spatial variation cruitment rates. in adult local structure and that, in comparison with the large drift in Rocky intertidal communities are formed by a large proportion structure of recruits, local adult communities converged to a com- of species with complex life cycles that include an initial pelagic mon, although not unique, structure across the region. Although larval stage that lives in the water column before settling in the there is no unique adult community structure in the entire region, adult habitat. Several studies in these communities have shown the observed variation represents only a small subset of the possible that the arrival of new individuals varies greatly from site to site, structures that would be expected from passive recruitment drift. influenced largely by local and meso-scale oceanographic pro- Thus, in this diverse system our results do not support the idea cesses, and that different species appear to be affected by different that rocky intertidal metacommunities are structured by neutral larval transport mechanisms (20–25). Therefore, recruitment var- mechanisms. iation from site to site can be independent of local adult abun- dances. This open characteristic of populations over comparatively community structure | ecological drift | neutral theory | interaction large spatial scales, together with a myriad of reproductive strat- strength | macroecology egies of component species, make rocky shore invertebrate com- munities ideal systems for examining whether variation in he extent to which the structure and diversity of natural com- recruitment of multispecific assemblages from site to site is suffi- Tmunities is determined by interactions among species, such as cient to account for among-site variation in local community predation and competition that occur at local scales, and the extent structure. Conversely, postsettlement processes could erase the to which they are the result of regional-scale processes that can be signal of dispersal and buffer against spatiotemporal variation in largely independent of species interactions are central questions in the arrival of individuals. If such processes are deterministic across ecology and are the subject of intense debate (1–4). One aspect of the metacommunity, they may create structures of adult assemb- the debate is centered on whether niche differentiation and local lages that are more convergent to a common structure than would interactions among species play a significant role in macroscopic be expected by variation in the supply of individuals. Classic studies community patterns (e.g., species diversity, species-abundance consolidating the view of local control of community structure by curves) or whether, as stated by the neutral theory of biodiversity species interactions (e.g., predation, competitive exclusion) (26– (NTB) (2), these patterns can be generated by the neutral interplay 29) have focused on relatively few sites in close proximity and on sensu of dispersal and stochastic demography among ecologically iden- a small subset of strongly interacting species or modules ( fi tical species (4–10). A related topic at the center of ecological Paine, ref. 30), making it dif cult to infer the relative importance of debate since the mid-1980s is that of “supply-side” ecology (11), these processes across space for the entire community. On the which proposes that the supply of individuals to local communities, other hand, numerous studies have demonstrated the importance a process driven largely by physical factors, can be the main de- of recruitment in determining adult abundance patterns from local to regional scales (21, 31–34). However, these studies have ex- terminant of population and community structure, challenging the – view of control by local species interactions (12–18). If recruitment amined the recruit adult relationship individually for one or a few species, with widely varying results (14, 32, 35, 36). An exception is were the main determinant of adult population abundance for most species in local communities, then community structure and its spatiotemporal variation would result from environmentally fl Author contributions: A.U.C., S.A.N., and J.C.C. designed research; A.U.C., S.A.N., and J.C.C. driven uctuations in the supply of individuals, largely un- performed research; A.U.C. and S.A.N. analyzed data; and A.U.C., S.A.N., and J.C.C. wrote correlated with local species interactions. Similarity with the NTB the paper. argument is apparent when examining large sets of species. The The authors declare no conflict of interest. fact that some static, aggregated attributes of intertidal marine This article is a PNAS Direct Submission. fi communities follow predictions based on NTB (5, 8) justi es fur- 1To whom correspondence should be addressed. E-mail: [email protected]. ther evaluation of the neutrality of spatiotemporal variation in This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. marine community structure to deterministic species interactions. 1073/pnas.1007077107/-/DCSupplemental. 18528–18532 | PNAS | October 26, 2010 | vol. 107 | no. 43 www.pnas.org/cgi/doi/10.1073/pnas.1007077107 Downloaded by guest on September 26, 2021 A TEM ARR GUA PTA MOL MON CUR SEITIS QUY QUI SAL Fig. 1. Spatial variability in rates of re- cruitment and adult abundance in the meta- EN community. (A) Location of local intertidal ES communities along central Chile. (Left) The red graph shows the daily average recruitment CRU for all species per site (mean ± SE). Sites are MAT sorted from north to south, as in the map (Right). (Center) The blue graph shows adult PIC average abundance (individuals per square 0,0 0,2 0,4 0,6 0 200 400 600 800 1000 meter) at the same sites. (B) Relationship be- Recruitment rate Adults Abundance tween the dissimilarity in the recruit and adult assemblages at a given site obtained through PCA ordinations and the average recruitment rates of species at that site. Relationship with entire dataset averaged per site (three sam- B C pling dates for adults, 8 y of sampling for recruits). (C) The same relationship analyzed separately for two periods. ●, adults measured in 2006 and recruitment rates recorded in 2005. ○, adults measured in 2007 and re- cruitment rates recorded in 2005. The cyan- colored quadrangles in B and C show the dis- persion of recruit–adult distances across the region. The shape and lower boundary slope are significantly different from random ex- pectation. ARR, Arrayán; CRU, Las Cruces; CUR, Curaumilla; EN, ECIM North; ES, ECIM South; GUA, Guanaqueros; MAT, Matanzas; MOL, Los Molles; MON, Montenar; PIC, Pichilemu; PTA, Punta de Talca; QUI, El Quisco; QUY, Quintay; ECOLOGY SAL, Salinas; TEM, Temblador. the work by Forde and Ralmondi (37), who experimentally ma- munity structure of adults results simply from spatial variation in nipulated recruitment rates of two species of rocky intertidal bar- the arrival of new individuals, before niche differentiation plays nacles to evaluate their effect on community composition, a role. The rocky intertidal abundance of adults was quantified by considering a total of five species. Their results show that in early nondestructive sampling at all study sites, including six intertidal stages of succession, variability in recruitment had significant im- microhabitats, on three different survey dates. pact on community structure, but in intermediate and final stages community structure was strongly influenced by postsettlement Results and Discussion processes that produced density-dependent
Load more

Recommended publications
  • Appendix 1 Table A1
    OIK-00806 Kordas, R. L., Dudgeon, S., Storey, S., and Harley, C. D. G. 2014. Intertidal community responses to field-based experimental warming. – Oikos doi: 10.1111/oik.00806 Appendix 1 Table A1. Thermal information for invertebrate species observed on Salt Spring Island, BC. Species name refers to the species identified in Salt Spring plots. If thermal information was unavailable for that species, information for a congeneric from same region is provided (species in parentheses). Response types were defined as; optimum - the temperature where a functional trait is maximized; critical - the mean temperature at which individuals lose some essential function (e.g. growth); lethal - temperature where a predefined percentage of individuals die after a fixed duration of exposure (e.g., LT50). Population refers to the location where individuals were collected for temperature experiments in the referenced study. Distribution and zonation information retrieved from (Invertebrates of the Salish Sea, EOL) or reference listed in entry below. Other abbreviations are: n/g - not given in paper, n/d - no data for this species (or congeneric from the same geographic region). Invertebrate species Response Type Temp. Medium Exposure Population Zone NE Pacific Distribution Reference (°C) time Amphipods n/d for NE low- many spp. worldwide (Gammaridea) Pacific spp high Balanus glandula max HSP critical 33 air 8.5 hrs Charleston, OR high N. Baja – Aleutian Is, Berger and Emlet 2007 production AK survival lethal 44 air 3 hrs Vancouver, BC Liao & Harley unpub Chthamalus dalli cirri beating optimum 28 water 1hr/ 5°C Puget Sound, WA high S. CA – S. Alaska Southward and Southward 1967 cirri beating lethal 35 water 1hr/ 5°C survival lethal 46 air 3 hrs Vancouver, BC Liao & Harley unpub Emplectonema gracile n/d low- Chile – Aleutian Islands, mid AK Littorina plena n/d high Baja – S.
    [Show full text]
  • Energy Flow Through Marine Ecosystems: Confronting Transfer Efficiency
    TREE 2756 No. of Pages 11 Trends in Ecology & Evolution Review Energy Flow Through Marine Ecosystems: Confronting Transfer Efficiency Tyler D. Eddy ,1,2,*,@ Joey R. Bernhardt ,3,4,5,@ Julia L. Blanchard,6,7 William W.L. Cheung,3 Mathieu Colléter,8 Hubert du Pontavice ,3,9 Elizabeth A. Fulton,6,10 Didier Gascuel ,9,@ Kelly A. Kearney ,11 Colleen M. Petrik ,12 Tilla Roy,13,14 Ryan R. Rykaczewski ,1,15 Rebecca Selden,16 Charles A. Stock ,17 Colette C.C. Wabnitz ,3,18,19 and Reg A. Watson 6,7 Transfer efficiency is the proportion of energy passed between nodes in food webs. Highlights It is an emergent, unitless property that is difficult to measure, and responds Transfer efficiency is a key parameter de- dynamically to environmental and ecosystem changes. Because the consequences scribing ecosystem structure and func- of changes in transfer efficiency compound through ecosystems, slight variations tion and is used to estimate fisheries production; however, it is also one of can have large effects on food availability for top predators. Here, we review the the most uncertain parameters. processes controlling transfer efficiency, approaches to estimate it, and known variations across ocean biomes. Both process-level analysis and observed macro- Questions remain about how habitats, fi scale variations suggest that ecosystem-scale transfer efficiency is highly variable, food resources, shing pressure, spatio- fi temporal scales, as well as temperature, impacted by shing, and will decline with climate change. It is important that we primary production, and other climate more fully resolve the processes controlling transfer efficiency in models to drivers impact transfer efficiency.
    [Show full text]
  • Does the Acorn Barnacle Balanus Glandula Exhibit Predictable Gradients in Metabolic Performance Across the Intertidal Zone?
    Warren J. Baker Endowment for Excellence in Project-Based Learning Robert D. Koob Endowment for Student Success FINAL REPORT Final reports will be published on the Cal Poly Digital Commons website(http://digitalcommons.calpoly.edu). I. Project Title Does the acorn barnacle Balanus glandula exhibit predictable gradients in metabolic performance across the intertidal zone? II. Project Completion Date 2/2019 III. Student(s), Department(s), and Major(s) (1) Kali Horn, Biological Sciences Department, M.S. Biological Sciences IV. Faculty Advisor and Department Kristin Hardy, Biological Sciences Department V. Cooperating Industry, Agency, Non-Profit, or University Organization(s) NA VI. Executive Summary Using funding from the Baker-Koob endowment, I successfully completed an experiment looking at metabolic variation in the common acorn barnacle, Balanus glandula, across tidal heights. We characterized the temperature profile across the zone as well to have data explicitly describing the abiotic variability from the upper intertidal zone to the low. Myself and many undergraduates collected barnacles from the top middle and bottom of the B.glandula distribution and ran the individuals through a suite of experiments to characterize the ‘metabolic phenotype’ . We defined the metabolic phenotype with a comprehensive suite of biochemical (e.g., citrate synthase and lactate dehydrogenase activity), physiological (VO2, aerobic scope) and behavioral (feeding rate) indices of metabolism. After removal from the intertidal zone, barnacles were placed in our intermittent respirometry system to calculate an average oxygen consumption rate over a 24h period. During the first two hours of the experiment, I conducted a behavioral observation to determine overall activity and feeding rate.
    [Show full text]
  • Balanus Glandula Class: Multicrustacea, Hexanauplia, Thecostraca, Cirripedia
    Phylum: Arthropoda, Crustacea Balanus glandula Class: Multicrustacea, Hexanauplia, Thecostraca, Cirripedia Order: Thoracica, Sessilia, Balanomorpha Acorn barnacle Family: Balanoidea, Balanidae, Balaninae Description (the plate overlapping plate edges) and radii Size: Up to 3 cm in diameter, but usually (the plate edge marked off from the parietes less than 1.5 cm (Ricketts and Calvin 1971; by a definite change in direction of growth Kozloff 1993). lines) (Fig. 3b) (Newman 2007). The plates Color: Shell usually white, often irregular themselves include the carina, the carinola- and color varies with state of erosion. Cirri teral plates and the compound rostrum (Fig. are black and white (see Plate 11, Kozloff 3). 1993). Opercular Valves: Valves consist of General Morphology: Members of the Cirri- two pairs of movable plates inside the wall, pedia, or barnacles, can be recognized by which close the aperture: the tergum and the their feathery thoracic limbs (called cirri) that scutum (Figs. 3a, 4, 5). are used for feeding. There are six pairs of Scuta: The scuta have pits on cirri in B. glandula (Fig. 1). Sessile barna- either side of a short adductor ridge (Fig. 5), cles are surrounded by a shell that is com- fine growth ridges, and a prominent articular posed of a flat basis attached to the sub- ridge. stratum, a wall formed by several articulated Terga: The terga are the upper, plates (six in Balanus species, Fig. 3) and smaller plate pair and each tergum has a movable opercular valves including terga short spur at its base (Fig. 4), deep crests for and scuta (Newman 2007) (Figs.
    [Show full text]
  • Alien Marine Invertebrates of Hawaii
    BARNACLE Balanus amphitrite (Darwin, 1854) Striped barnacle Phylum Arthropoda Subphylum Crustacea Class Maxillopoda Subclass Cirripedia Order Thoracica Family Balanidae Photo by R. DeFelice DESCRIPTION HABITAT Balanus amphitrite is a small, conical, sessile barnacle Very common in the intertidal fouling communities of (to about 1.5 cm diameter). Color is whitish with purple harbors and protected embayments. The live attached to or brown longitudinal stripes. Surface of test plates are any available hard surface, including rocks, pier pilings, longitudinally ribbed. The interlocking tergum and ship hull, oyster shells, and mangrove roots. scutum, the paired structures which cover the animal inside are as pictured below. A similar species, Balanus reticulatus Utinomi, is also an introduced species and commonly occurs with B. amphitrite. It also has longitudinal purple or brown stripes, but these stripes are intersected by horizontal grooves, giving the surface of the test plates a rough reticulated striation, unlike B. amphitrite. It can also be distinguished by examination of the tergum and scutum pictured below. Note the more sharply pointed apex of the tergum and the elongated and narrower tergum spur Balanus retculatus. (A) Scutum. (B) Tergum. of B. reticulatus. DISTRIBUTION HAWAIIAN ISLANDS Throughout the main Hawaiian Islands NATIVE RANGE Southwestern Pacific and Indian Ocean PRESENT DISTRIBUTION World-wide in warm and temperate seas spur MECHANISM OF INTRODUCTION Balanus amphitrite. (A) Scutum. (B) Tergum. Unintentional, as fouling on ships hulls © Hawaii Biological Survey 2001 B-35 Balanus amphitrite IMPACT REMARKS Barnacles are a serious fouling problem on ship bot- This now widespread barnacle of southern hemisphere toms, buoys, and pilings. The ecological impact of this origins was first collected in 1902 in Honolulu Harbor.
    [Show full text]
  • Balanus Trigonus
    Nauplius ORIGINAL ARTICLE THE JOURNAL OF THE Settlement of the barnacle Balanus trigonus BRAZILIAN CRUSTACEAN SOCIETY Darwin, 1854, on Panulirus gracilis Streets, 1871, in western Mexico e-ISSN 2358-2936 www.scielo.br/nau 1 orcid.org/0000-0001-9187-6080 www.crustacea.org.br Michel E. Hendrickx Evlin Ramírez-Félix2 orcid.org/0000-0002-5136-5283 1 Unidad académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México. A.P. 811, Mazatlán, Sinaloa, 82000, Mexico 2 Oficina de INAPESCA Mazatlán, Instituto Nacional de Pesca y Acuacultura. Sábalo- Cerritos s/n., Col. Estero El Yugo, Mazatlán, 82112, Sinaloa, Mexico. ZOOBANK http://zoobank.org/urn:lsid:zoobank.org:pub:74B93F4F-0E5E-4D69- A7F5-5F423DA3762E ABSTRACT A large number of specimens (2765) of the acorn barnacle Balanus trigonus Darwin, 1854, were observed on the spiny lobster Panulirus gracilis Streets, 1871, in western Mexico, including recently settled cypris (1019 individuals or 37%) and encrusted specimens (1746) of different sizes: <1.99 mm, 88%; 1.99 to 2.82 mm, 8%; >2.82 mm, 4%). Cypris settled predominantly on the carapace (67%), mostly on the gastric area (40%), on the left or right orbital areas (35%), on the head appendages, and on the pereiopods 1–3. Encrusting individuals were mostly small (84%); medium-sized specimens accounted for 11% and large for 5%. On the cephalothorax, most were observed in branchial (661) and orbital areas (240). Only 40–41 individuals were found on gastric and cardiac areas. Some individuals (246), mostly small (95%), were observed on the dorsal portion of somites.
    [Show full text]
  • The New Talent Landscape: Recruiting Difficulty and Skills Shortages (SHRM, 2016)
    THE NEW TALENT LANDSCAPE RECRUITING DIFFICULTY AND SKILLS SHORTAGES THE NEW TALENT LANDSCAPE Recruiting Difficulty and Skills Shortages A RESEARCH REPORT BY THE SOCIETY FOR HUMAN RESOURCE MANAGEMENT Media Contact USA Kate Kennedy SHRM Headquarters Phone: + 1.703.535.6260 Alexandria, VA 22314 The Society for Human Resource Management E-mail: [email protected] Phone +1.800.283.7476 (SHRM) is the world’s largest HR professional society, E-mail [email protected] representing 285,000 members in more than 165 Vanessa Hill countries. For nearly seven decades, the Society Phone: +1.703.535.6072 China has been the leading provider of resources serving E-mail: [email protected] Gateway Plaza the needs of HR professionals and advancing the Chaoyang District Online practice of human resource management. SHRM Beijing, 100027 SHRM Online: shrm.org has more than 575 affiliated chapters within the Phone +86.10.59231033 United States and subsidiary offices in China, India SHRM Research & Surveys: shrm.org/research E-mail [email protected] and United Arab Emirates. Visit us at shrm.org. SHRM Research on Twitter: @SHRM_Research India SHRM Research on LinkedIn: LinkedIn.com Gurgaon, Sector 26 SHRM Research on SHRM Connect: Haryana 122002 community.shrm.org Phone +91.12.44200243 E-mail [email protected] United Arab Emirates Dubai Knowledge Village Dubai, UAE Phone +971.050.104.6330 E-mail [email protected] 16-0156 To order printed copies of this report, visit shrmstore.shrm.org or call 1-800-444-5006. 2 About This Research Report 5 Executive Summary
    [Show full text]
  • Life History Strategies, Population Regulation, and Implications for Fisheries Management1
    872 PERSPECTIVE / PERSPECTIVE Life history strategies, population regulation, and implications for fisheries management1 Kirk O. Winemiller Abstract: Life history theories attempt to explain the evolution of organism traits as adaptations to environmental vari- ation. A model involving three primary life history strategies (endpoints on a triangular surface) describes general pat- terns of variation more comprehensively than schemes that examine single traits or merely contrast fast versus slow life histories. It provides a general means to predict a priori the types of populations with high or low demographic resil- ience, production potential, and conformity to density-dependent regulation. Periodic (long-lived, high fecundity, high recruitment variation) and opportunistic (small, short-lived, high reproductive effort, high demographic resilience) strat- egies should conform poorly to models that assume density-dependent recruitment. Periodic-type species reveal greatest recruitment variation and compensatory reserve, but with poor conformity to stock–recruitment models. Equilibrium- type populations (low fecundity, large egg size, parental care) should conform better to assumptions of density- dependent recruitment, but have lower demographic resilience. The model’s predictions are explored relative to sustain- able harvest, endangered species conservation, supplemental stocking, and transferability of ecological indices. When detailed information is lacking, species ordination according to the triangular model provides qualitative
    [Show full text]
  • Recruitment, Dispersal, and Demographic Rescue in Spatially-Structured White-Tailed Ptarmigan Populations ’
    The Condor 102:503-516 D The Cooper Ornithological Society Zoo0 RECRUITMENT, DISPERSAL, AND DEMOGRAPHIC RESCUE IN SPATIALLY-STRUCTURED WHITE-TAILED PTARMIGAN POPULATIONS ’ KATHY MARTIN Canadian Wildlife Service, 5421 Robertson Rd, RR I Delta, British Columbia, Canada, V4K 3N2, and Department of Forest Sciences, 2424 Main Mall, University of British Columbia, Vancouver, British Columbia, Canada, V6T 124, e-mail: [email protected] PETER B. STACEY Department of Biology, University of New Mexico, Albuquerque, NM 87131, e-mail: [email protected] CLAIT E. BRAUN* Colorado Division of Wildlife, 317 West Prospect Rd., Fort Collins, CO 80526, e-mail: [email protected] Abstract. We studiedrecruitment and dispersalof White-tailed Ptarmigan (Lagopus leu- curus) breeding in naturally fragmented alpine habitatsat four study sites in Colorado from 1987-1998. Almost all recruitment for both sexes, particularly females, was of birds pro- duced outside local populationsand also external to nearby studiedpopulations. Populations were more dependent on female recruitment than on male recruitment to sustainthem, and patterns of recruitment were not correlated with local survival of adults or production of young the previous year, except at one site for females. Over 95% of recruitswere yearlings. Breeding dispersal of adults, an infrequent but regular event, was also important to inter- population connectivity. Our data for multiple populationsallowed us to describemovement patterns among populations to assess consistency with conditions required for a
    [Show full text]
  • OREGON ESTUARINE INVERTEBRATES an Illustrated Guide to the Common and Important Invertebrate Animals
    OREGON ESTUARINE INVERTEBRATES An Illustrated Guide to the Common and Important Invertebrate Animals By Paul Rudy, Jr. Lynn Hay Rudy Oregon Institute of Marine Biology University of Oregon Charleston, Oregon 97420 Contract No. 79-111 Project Officer Jay F. Watson U.S. Fish and Wildlife Service 500 N.E. Multnomah Street Portland, Oregon 97232 Performed for National Coastal Ecosystems Team Office of Biological Services Fish and Wildlife Service U.S. Department of Interior Washington, D.C. 20240 Table of Contents Introduction CNIDARIA Hydrozoa Aequorea aequorea ................................................................ 6 Obelia longissima .................................................................. 8 Polyorchis penicillatus 10 Tubularia crocea ................................................................. 12 Anthozoa Anthopleura artemisia ................................. 14 Anthopleura elegantissima .................................................. 16 Haliplanella luciae .................................................................. 18 Nematostella vectensis ......................................................... 20 Metridium senile .................................................................... 22 NEMERTEA Amphiporus imparispinosus ................................................ 24 Carinoma mutabilis ................................................................ 26 Cerebratulus californiensis .................................................. 28 Lineus ruber .........................................................................
    [Show full text]
  • Talent Acquisition Technology Ecosystem
    Global Staffing and Recruitment Technology Talent Acquisition Technology Ecosystem February 15, 2018 | David Francis, Research Manager | [email protected] Talent Acquisition Technology Ecosystem | February 15, 2017 Contents Talent Acquisition Technology Ecosystem ........................................................................................................................................................... 2 Overview of an Ecosystem .................................................................................................................................................................................... 3 Systems of Record ................................................................................................................................................................................................ 8 Candidate Discovery ........................................................................................................................................................................................... 10 Candidate Assessment ........................................................................................................................................................................................ 14 Candidate Engagement ....................................................................................................................................................................................... 15 Candidate Verification .......................................................................................................................................................................................
    [Show full text]
  • Recruitment of Marine Invertebrates: the Role of Active Larval Choices and Early Mortality
    Oecologia (Berl) (1982) 54:348-352 Oer Springer-Verlag 1982 Recruitment of Marine Invertebrates: the Role of Active Larval Choices and Early Mortality Michael J. Keough and Barbara J. Downes Department of Biological Sciences, University of California, Santa Barbara, Ca 93106, USA Summary. Spatial variation in the recruitment of sessile a reflection of the limitations of the observer. The number marine invertebrates with planktonic larvae may be derived of organisms passing through the fourth phase is termed from a number of sources: events within the plankton, recruitment, while the number passing to the third phase choices made by larvae at the time of settlement, and mor- is termed settlement. Recruitment is a composite of larval tality of juvenile organisms after settlement, but before a and juvenile stages, while settlement involves only larval census by an observer. These sources usually are not distin- stages. guished. It is important to distinguish between settlement and A study of the recruitment of four species of sessile recruitment. Non-random patterns of recruitment, such as invertebrates living on rock walls beneath a kelp canopy differences in the density of recruitment with height on the showed that both selection of microhabitats by settling shore (Underwood 1979) or differences in the density of larvae and predation by fish may be important. Two micro- recruitment with patch size (Jackson 1977; Keough 1982a), habitats were of interest; open, flat rock surfaces, and small or with microhabitat, may have two causes: (1) differential pits and crevices that act as refuges from fish predators. settlement, and (2), different probabilities of early mortality The polychaete Spirorbis eximus and the cyclostome in different parts of an organism's habitat.
    [Show full text]