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1. Metapopulation dynamics of oysters: sources, sinks, and implications for conservation and restoration

   https://doi.org/10.1002/ecs2.3573  

   Theuerkauf, Seth J. ; Puckett, Brandon J. ; Eggleston, David B. ( July 2021 , Ecosphere)

   Metapopulation and source–sink dynamics are increasingly considered within spatially explicit management of wildlife populations, yet the application of these concepts has generally been limited to comparisons of the performance (e.g., demographic rates or dispersal) inside vs. outside protected areas, and at spatial scales that do not encompass an entire metapopulation. In the present study, a spatially explicit, size‐structured matrix model was applied to simulate the dynamics of an Eastern oyster (Crassostrea virginica) metapopulation in the second largest estuary in the United States—the Albemarle‐Pamlico Estuarine System in North Carolina. The model integrated larval dispersal simulations with empirical measures of oyster demographic rates to simulate the dynamics of the entire oyster metapopulation consisting of 646 reefs and five reef types: (1) restored subtidal reefs closed to harvest (i.e., sanctuaries or protected areas;n = 14), (2) restored subtidal reefs open to harvest (n = 53), (3) natural subtidal reefs open to harvest (n = 301), (4) natural intertidal reefs open to harvest (n = 129), and (5) oyster reefs on manmade, hard structures such as seawalls (n = 149). Key findings included (1) an overall stable, yet slightly declining oyster metapopulation, (2) variable reef type‐specific population trajectories, largely dependent on spatiotemporal variation in larval recruitment, (3) a greater relative importance of inter‐reef larval connectivity on metapopulation dynamics than local larval retention processes, and (4) spatiotemporal variation in the source–sink status of reef subpopulations wherein subtidal sanctuaries and reefs located in the northeastern portion of the estuary were frequent sources. From a management perspective, continued protection of oyster sanctuaries is warranted. Sanctuaries represented only 6.2% of the total reef area, however, they harbored 19% (± 2%) of all oysters and produced 25% (± 6%) of all larvae settling within the metapopulation. Additional management priorities should focus on restoration or conservation of subpopulations that serve as frequent source subpopulations (including those with poor demographic rates, but high connectivity potential), and management of harvest from sink subpopulations. The application of a source–sink framework and similar integrated modeling approach could inform management of oysters in other systems, as well as other species that exhibit similar metapopulation characteristics.

    

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2. Quantifying dispersal variability among nearshore marine populations

   https://doi.org/10.1111/mec.15732  

   Catalano, Katrina A. ; Dedrick, Allison G. ; Stuart, Michelle R. ; Puritz, Jonathan B. ; Montes, Jr., Humberto R. ; Pinsky, Malin L. ( December 2020 , Molecular Ecology)

   Dispersal drives diverse processes from population persistence to community dynamics. However, the amount of temporal variation in dispersal and its consequences for metapopulation dynamics is largely unknown for organisms with environmentally driven dispersal (e.g., many marine larvae, arthropods and plant seeds). Here, we used genetic parentage analysis to detect larval dispersal events in a common coral reef fish,Amphiprion clarkii, along 30 km of coastline consisting of 19 reef patches in Ormoc Bay, Leyte, Philippines. We quantified variation in the dispersal kernel across seven years (2012–2018) and monsoon seasons with 71 parentage assignments from 791 recruits and 1,729 adults. Connectivity patterns differed significantly among years and seasons in the scale and shape but not in the direction of dispersal. This interannual variation in dispersal kernels introduced positive temporal covariance among dispersal routes that theory predicts is likely to reduce stochastic metapopulation growth rates below the growth rates expected from only a single or a time‐averaged connectivity estimate. The extent of variation in mean dispersal distance observed here among years is comparable in magnitude to the differences across reef fish species. Considering dispersal variation will be an important avenue for further metapopulation and metacommunity research across diverse taxa.

    

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3. What makes urban parks good for California quail? Evaluating park suitability, species persistence, and the potential for reintroduction into a large urban national park

   https://doi.org/10.1111/1365-2664.14045  

   Iknayan, Kelly J. ; Wheeler, Megan M. ; Safran, Samuel M. ; Young, Jonathan S. ; Spotswood, Erica N. ( October 2021 , Journal of Applied Ecology)

   Preserving and restoring wildlife in urban areas benefits both urban ecosystems and the well‐being of urban residents. While urban wildlife conservation is a rapidly developing field, the majority of conservation research has been performed in wildland areas. Understanding the applicability of wildland science to urban populations and the relative importance of factors limiting species persistence are of critical importance to identifying prescriptive management strategies for restoring wildlife to urban parks.

   We evaluated how habitat fragmentation, habitat quality and mortality threats influence species occupancy and persistence in urban parks. We chose California quailCallipepla californicaas a representative species with potential to respond to urban conservation. We used publicly available eBird data to construct occupancy models of quail in urban parks across their native range, and present an application using focal parks interested in exploring quail reintroduction.

   Urban parks had a 0.23 ± 0.02 probability of quail occupancy, with greater occupancy in larger parks that were less isolated from potential source populations, had higher shrub cover and had lower impervious cover. Less isolated parks had higher colonization rates, while larger parks had lower extinction rates. These results align with findings across urban ecology showing greater biodiversity in larger and more highly connected habitat patches.

   A case study highlighted that interventions to increase effective park size and improve connectivity would be most influential for two highly urban focal parks, while changes to internal land cover would have a relatively small impact. Low joint extinction probability in the parks (0.010 ± 0.013) indicated reintroduced populations could persist for some time.

   Synthesis and applications. We show how eBird data can be harnessed to evaluate the responsiveness of wildlife to urban parks of variable size, connectivity and habitat quality, highlighting what management actions are most needed. Using California quail as an example, we found park size, park isolation and presence of coyotes are all important drivers of whether quail can colonize and persist in parks. Our results suggest reintroducing quail to parks could be successful provided parks are large enough to support quail, and management actions are taken to enhance regional connectivity or periodic assisted colonization is used to supplement local populations.

    

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4. MetaIPM: Placing integral projection models into a metapopulation framework

   https://doi.org/10.1111/2041-210X.14156  

   Erickson, Richard A. ; Peirce, James P. ; Sandland, Greg J. ; Thompson, Hannah M. ; Coulter, Alison A. ; Glover, David C. ( June 2023 , Methods in Ecology and Evolution)

   Metapopulation models include spatial population dynamics such as dispersion and migration between subpopulations. Integral projection models (IPMs) can include demographic rates as a function of size. Traditionally, metapopulation models do not included detailed populaiton models such as IPMs. In some situations, both local population dynamics (e.g. size‐based survival) and spatial dynamics are important.

   We present a Python package,MetaIPM, which places IPMs into a metapopulation framework, and allow users to readily construct and apply these models that combine local population dynamics within a metapopulation framework.

   MetaIPMincludes an IPM for each subpopulation that is connected to other subpopulations via a metapopulation movement model. These movements can include dispersion, migration or other patterns. The IPM can include for size‐specific demographic rates (e.g. survival, recruitment) as well as management actions, such as length‐based harvest (e.g. gear specific capture sizes, varying slot limits across political boundaries). The model also allows for changes in metapopulation connectivity between locations, such as a fish passage ladders to enhance movement or deterrents to reduce movement. Thus, resource managers can useMetaIPMto compare different management actions such as the harvest gear type (which can be length‐specific) and harvest locations.

   We demonstrate howMetaIPMmay be applied to inform managers seeking to limit the spread of an invasive species in a system with important metapopulation dynamics. Specifically, we compared removal lengths (all length fish versus longer fish only) for an invasive fish population in a fragmented, inland river system.MetaIPMallowed users to compare the importance of harvesting source populations away from the invasion front, as well as species at the invasion front. The model would also allow for future comparisons of different deterrent placement locations in the system.

   Moving beyond our example system, we describe howMetaIPMcan be applied to other species, systems and management approaches. TheMetaIPMpackages includes Jupyter Notebooks documenting the package as well as a second set of JupyterNotebooks showing the application of the package to our example system.

    

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5. The rescue effect and inference from isolation–extinction relationships

   https://doi.org/10.1111/ele.13460  

   Van Schmidt, Nathan D. ; Beissinger, Steven R. ; Chase, ed., Jonathan ( January 2020 , Ecology Letters)

   The rescue effect in metapopulations hypothesises that less isolated patches are unlikely to go extinct because recolonisation may occur between breeding seasons (‘recolonisation rescue’), or immigrants may sufficiently bolster population size to prevent extinction altogether (‘demographic rescue’). These mechanisms have rarely been demonstrated directly, and most evidence of the rescue effect is from relationships between isolation and extinction. We determined the frequency of recolonisation rescue for metapopulations of black rails (Laterallus jamaicensis) and Virginia rails (Rallus limicola) from occupancy surveys conducted during and between breeding seasons, and assessed the reliability of inferences about the occurrence of rescue drawn from isolation–extinction relationships, including autologistic isolation measures that corrected for unsurveyed patches and imperfect detection. Recolonisation rescue occurred at expected rates, but was elevated during periods of disturbance that resulted in non‐equilibrium metapopulation dynamics. Inferences from extinction–isolation relationships were unreliable, particularly for autologistic measures and for the more vagile Virginia rail.

    

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