Population persistence in marine reserve networks: incorporating spatial heterogeneities in larval dispersal

Abstract

ABSTRACT:The relationship between marine reserve design and metapopulation persistence has been analyzed only for cases of spatially homogenous advective-diffusive larval dispersal. However, many coastlines exhibit more complex circulation, such as retention zones in which slower-moving currents shorten dispersal distances and larvae can accumulate. We constructed metapopulation models that incorporated 3 types of spatial variability in dispersal associated with retention zones: (A) reduction of both advective (L A ) and stochastic (L S ) length scales of dispersal within the retention zone, (B) reduction of L A only, and (C) accumulation of larvae in the retention zone, followed by redistribution along the coastline. For each scenario, we examined reserve networks with a range of size and spacing configurations. The scenarios differed in the relative number of self-persistent reserves, i.e. those which can survive in isolation, and network-persistent reserves, i.e. those which rely on connectivity through space and across generations to offset shortfalls in direct self-replenishment. When dispersal was dominated by stochastic movements (L S > L A in scenarios A and B), metapopulations typically consisted of self-persistent reserves. As dispersal became increasingly advective (L A > L S ), retention aided persistence, and network persistence became more prevalent. Persistence in scenario C decreased with the amount of redistribution. The specific patterns of persistence depended on the size and number of reserves and demographic parameters, but self-persistence was always more likely for reserves in the retention zone. Thus, placing a reserve in a retention zone to promote population persistence is advisable for all 3 dispersal scenarios.KEY WORDS: Larval dispersal · Dispersal kernel · Headland · Metapopulation · Marine reserve · Persistence · Self-recruitment Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 398: [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] 2010 ment influences metapopulation dynamics. Adequate reserve size and placement depends critically on larval dispersal patterns: reserves must be large enough or close enough together to ensure metapopulation persistence (e.g. Botsford et al. 2001, Walters et al. 2007. In this paper, we consider metapopulations made up of many discrete local populations, and define persistence in a deterministic way: when the metapopulation is near extinction, population density will tend to increase rather than decrease. Our interest is in both overall persistence (Does the metapopulation persist in at least one location?) and the spatial pattern of persistence (Where are the persistent local populations?).Recent empirical and theoretical results suggest that persistence of a metapopulation in a system of marine reserves depends on 2 mechanisms: (1) selfpersistence of local populations and (2) persistence that depends on connectivity among all or many locations in the network , Lipcius et al....

Spatially Explicit Conditions for Waterborne Pathogen Invasion

“…Possible examples include directly transmitted human diseases (i.e., pathologies that are transmitted through airborne or fecal-oral contact), in which the intertwining of mobility and social networks may play a key role in spreading the epidemic, and vector-borne/zoonotic diseases, in which spatial interactions of both host and vector/carrier populations might be relevant. In general, the mathematical framework outlined in this work can be used to approach other (apparently unrelated) topics in spatial and conservation ecology, such as the persistence of populations living in fragmented landscapes (e.g., Casagrandi and Gatto 1999Gatto , 2002Gatto , 2006, advective environments (e.g., Speirs and Gurney 2001;Pachepsky et al 2005), dendritic networks (Campbell Grant et al 2007, and webs of marine protected areas (e.g., White et al 2010;Aiken and Navarrete 2011;Watson et al 2011). In all these cases, in fact, population persistence can be established by properly accounting for the relevant spatial interactions and studying the conditions under which the extinction equilibrium becomes stable or unstable.…”

Beyond connectivity: how empirical methods can quantify population persistence to improve marine protected‐area design

“…Their analysis showed how high levels of selfrecruitment could be commonly observed in coral reef landscapes, but did not directly address whether populations would persist at each location. Earlier models have shown how persistence in MPA networks is determined by the combination of patch size, patch spacing, and dispersal distances (Botsford et al 2001, Gerber et al 2005, Moffitt et al 2009, White et al 2010a. These earlier models did not calculate openness because that specific quantity does not arise in the analysis of persistence (Appendix A).…”

“…In the context of MPA design, the self-persistence criterion suggests that, to ensure a single MPA is self-persistent, it should be in a location with high enough LEP (survival, fecundity, or both) and LR (local retention) for LEP 3 LR . 1 (White et al 2010a).…”

“…If one knows the spatial pattern of connectivity and LEP, then one can determine whether a network of MPAs should persist. This criterion is particularly important for species with moderate or large dispersal distances, because it quickly becomes impractical to design a single MPA large enough to be self-persistent , White et al 2010a). In reality, connectivity and LEP all likely vary over time.…”

“…In the last decade or so, a strong theoretical literature has emerged providing generalized design principles for MPAs in the context of population persistence (e.g., Mangel 1998, Botsford et al 2001, 2009a, Gerber et al 2003, White et al 2010a, Gru¨ss et al 2011, Blowes and Connolly 2012. This literature emphasizes that patterns of population connectivity, typically facilitated by larval dispersal in coastal currents, critically influence persistence.…”