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Prediction of recovery times (T 50 : time required to reach 50% of the numbers reached in year 400) for all populations (ω = 10 4 ; β = 0.0001). Panels (a) to (l) show predictions for different combinations of region, larval strategy and time of larval release (April, August).
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We studied the role of oceanographic conditions and life history strategies on recovery after extinction in a metapopulation of marine organisms dispersing as pelagic larvae. We combined an age‐structured model with scenarios defined by realistic oceanographic conditions and species distribution along the Irish Sea coast (North Europe). Species lif...
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Context 1
... most simulations, tidal migration led to short recovery times (T 50 < 25 yr); under a tidal migration strategy, the effects of ω (month of release) were smaller than under other migration strategies, at both the scale of regions (Fig. 4) and within regions (Figs. 5, 6). Passive and diel migration let to regional scale variation in recovery times (Fig. 6, see also Supporting Information Figs. S4-S7) from short (Irish coast: T 50 < 5 yr) to longer times (e.g., Liverpool Bay: average T 50 = 20-40 yr and Cardigan Bay: ~ 40-70 yr both ω = 10). Taken together, tidal migration and high fecundity/larval survival (i.e., high ω) minimized the average and the spatial and temporal variability in ...
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... was also important regional scale and temporal variation in recovery times (Figs. 3, 4), driven by oceanography. The Irish coast showed consistently short recovery times (Fig. 6); that is, they were short irrespective of tidal strategy and month of larval release. By contrast, recovery in other regions was largely affected by tidal strategy and month of release. In addition, recovery times were slightly shorter in simulations of release in April as compared with those in August (Figs. 4, ...
Citations
... The average effect of each biological factor on PLD and larval transport distance was determined using a General Linear Model (GLM) in R (R Core Team, 2022). This followed recommendations by White et al. (2014) that ecologists should focus on 'biological significance' such as effect sizes, since applying significance testing is not appropriate for modelling simulation outputs (Gimeńez et al., 2020). To determine which factors were the main drivers, the residuals from each simulation were compared for the PLD and population-averaged larval transport distance. ...
Marine species with a pelagic larval phase have the potential to disperse hundreds of kilometres via ocean currents, thus connecting geographically distinct populations. Connectivity between populations therefore plays a central role in population dynamics, genetic diversity and resilience to exploitation or decline and can be an important vector in the management of fisheries. The scallop, Pecten maximus, is a valuable benthic bivalve with a variety of management measures at both regional and national scales. A bio-physical numerical model was developed to simulate and characterise the larval transport and population connectivity of scallops across commercial fishing grounds within the Irish and Celtic Seas. The model incorporated realistic oceanographic currents and known behavioural traits of P. maximus larvae including spawning times, pelagic larval duration, and vertical migration during the various developmental stages i.e., passive, active swimming, vertical migrations, since growth rates change with temperature, which varies spatially and temporally, it was used in the model to determine when an individual larva changed its behaviour. Simulations showed a high degree of connectivity between most populations, with multiple connections allowing for substantial exchanges of larvae. The exception was a population off North Cornwall that was entirely reliant on self-recruitment. A sensitivity analysis of the biological parameters suggested that ocean current patterns primarily controlled the connectivity network, but the strength of the connections was sensitive to spawning date and the specific features of diel vertical migrations. The model identified weakly connected populations that could be vulnerable to overfishing, and populations that are ‘strong connectors’ and a vital source of larvae to maintain the metapopulation. Our approach highlights the benefits of characterising population connectivity as part of an effective management strategy for sustainable fisheries.
... Synergistic impacts (the result of stressors interacting and producing a greater effect than the cumulative or individual effects) of climate change vary across life stages with the tendency that early life stages are more sensitive and less tolerant to environmental stressors than adults (Kikkawa et al., 2003;Ishimatsu et al., 2004;Kurihara, 2008). Understanding the synergistic effects of OA and warming on larval development is critical to predict how climate change will influence larval survival, dispersal and hence, population connectivity (Cowen and Sponaugle, 2009;Giménez et al., 2020). This is particularly important for the future of commercially important and vulnerable species, like crustaceans, which have complex life cycles and undergo distinct ontogenetical changes. ...
Climate change combined with anthropogenic stressors (e.g. overfishing, habitat destruction) may have particularly strong effects on threatened populations of coastal invertebrates. The collapse of the population of European lobster (Homarus gammarus) around Helgoland constitutes a good example and prompted a large-scale restocking program. The question arises if recruitment of remaining natural individuals and program-released specimens could be stunted by ongoing climate change. We examined the joint effect of ocean warming and acidification on survival, development, morphology, energy metabolism and enzymatic antioxidant activity of the larval stages of the European lobster. Larvae from four independent hatches were reared from stage I to III under a gradient of 10 seawater temperatures (13–24°C) combined with moderate (∼470 µatm) and elevated (∼1160 µatm) seawater pCO2 treatments. Those treatments correspond to the shared socio-economic pathways (SSP), SSP1-2.6 and SSP5-8.5 (i.e. the low and the very high greenhouse gas emissions respectively) projected for 2100 by the Intergovernmental Panel on Climate Change. Larvae under the elevated pCO2 treatment had not only lower survival rates, but also significantly smaller rostrum length. However, temperature was the main driver of energy demands with increased oxygen consumption rates and elemental C:N ratio towards warmer temperatures, with a reducing effect on development time. Using this large temperature gradient, we provide a more precise insight on the aerobic thermal window trade-offs of lobster larvae and whether exposure to the worst hypercapnia scenario may narrow it. This may have repercussions on the recruitment of the remaining natural and program-released specimens and thus, in the enhancement success of future lobster stocks.
... Metapopulations studies suggest that network topology can affect metapopulation-wide extinction probabilities (Adler & Nuernberger, 1994;Campbell Grant, 2011), persistence (Grilli et al., 2015;Kininmonth et al., 2010), recovery time (Giménez et al., 2019), as well as the distribution of abundance among patches (Altermatt & Fronhofer, 2017). For metacommunities, topology can mediate the effects of dispersal on local diversity (Economo & Keitt, 2010) and drive patterns of α and β diversity (Seymour et al., 2015). ...
... First, to produce empirical information on networks of a size that is difficult to study in the field and that is in the range of real metapopulations, and second to allow our experimental networks-that were constrained to two adjacent well plates-to be connected by a comparable number of links. This number also falls within the range of field studies addressing networks of local populations (Giménez et al., 2019;Rozenfeld et al., 2008). ...
Biological populations are rarely isolated in space and instead interact with others via dispersal in metapopulations. Theory predicts that network connectivity patterns can have critical effects on network robustness, as certain topologies, such as scale‐free networks, are more tolerant to disturbances than other patterns. However, at present, experimental evidence of how these topologies affect population dynamics in a metapopulation framework is lacking.
We used experimental metapopulations of the aquatic protist Paramecium tetraurelia to determine how network topology influences occupation patterns.
We created metapopulations engineered to be comparable in linkage density, but differing in their degree distribution. We compared random networks to scale‐free networks by evaluating local population occupancy and abundance throughout 18–30 protist generations. In parallel, we used simulations to explore differences in patch occupation patterns among topologies.
Our experimental results highlighted the importance of the balance between dispersal and extinction in the interaction with spatial network topology. Under low dispersal conditions, random metapopulations of P. tetraurelia reached higher abundance and higher occupancy (proportion of occupied patches) compared to scale‐free systems in both experimental and simulated systems. Under high dispersal conditions, we did not detect differences between types of metapopulations. Increasing patch degree (i.e. number of connections per patch) reduced the probability of extinction of local populations in both types of networks.
We suggest the interaction between colonization/extinction rates and network topology alters the likelihood of rescue effects which results in differential patterns of occupancy and abundance in metapopulations.
... Spatially realistic models have shown that, besides patch quality, the spatial network structure (topology) has strong effects on patch occupancy 14 , species persistence 15 and species recovery 16 . In addition to network topology, predictions from spatial realistic models critically depend on the implementation of the dispersal process and its dependency on patch characteristics, as well as species specific dispersal abilities. ...
Meta-population and -community models have extended our understanding regarding the influence of habitat distribution, local patch dynamics, and dispersal on species distribution patterns. Currently, theoretical insights on spatial distribution patterns are limited by the dominant use of deterministic approaches for modeling species dispersal. In this work, we introduce a probabilistic, network-based framework to describe species dispersal by considering inter-patch connections as network-determined probabilistic events. We highlight important differences between a deterministic approach and our dispersal formalism. Exemplified for a meta-population, our results indicate that the proposed scheme provides a realistic relationship between dispersal rate and extinction thresholds. Furthermore, it enables us to investigate the influence of patch density on meta-population persistence and provides insight on the effects of probabilistic dispersal events on species persistence. Importantly, our formalism makes it possible to capture the transient nature of inter-patch connections, and can thereby provide short term predictions on species distribution, which might be highly relevant for projections on how climate and land use changes influence species distribution patterns.
... Combined negative effects of high temperature and food limitation may occur for instance after warm winters, which are known to impact recruitment in S. balanoides (Polaczanska et al., 2008;Abernot-Le Gac et al., 2017). More generally, larvae tend to be highly sensitive to environmental fluctuations (Pandori and Sorte, 2019) and make a strong contribution to the recovery and persistence of marine populations following disturbance (Cowen and Sponaugle, 2009;Pineda et al., 2009;Giménez et al., 2020). We therefore quantify the effect of food level and temperature on survival of larvae, cyprid size, rate of development and the subsequent metamorphic success. ...
A critical question in marine ecology is understanding how organisms will cope with environmental conditions under climate change. Increasing temperatures not only have a direct effect on marine organisms but may also lead to food limitation through for example trophic mismatches, or by the increased metabolic demands imposed by developing at high temperatures. Using barnacles from a population of North Wales, we studied the combined effect of temperature and food density on the survival, settlement success, developmental time and body size of larvae of the native barnacle Semibalanus balanoides and its exotic competitor, the barnacle Austrominius modestus. Larvae were reared at similar food levels but at temperature ranges which varied among species reflecting their different phenology and tolerances. For S. balanoides (spring larval release) we used a lower temperature of 9 °C, reflecting spring temperatures from N Wales to SW England, and 15 °C representing warmer conditions; for A. modestus (summer larval release) a typical summer temperature for this geographic range of 15 °C was used with a raised temperature of 18 °C. Larvae were reared under controlled conditions in automated, computer programmable incubators and fed diatoms (Skeletonema costatum) at three food levels. We found stress effects of food limitation on larval performance of S. balanoides. While survival during naupliar development was little affected by food and temperature, low food levels strongly depressed survival and settlement during the cyprid stage of S. balanoides at both tested temperatures, but especially at 15 °C. By contrast, at the tested temperatures little effects were found on survival and settlement success in the exotic A. modestus. Both species delayed development in response to low food levels while S. balanoides cyprids showed decreased body size at the high tested temperature. The main impact occurred as a delayed effect, at the time when cyprids attempt to settle, rather than as an effect on naupliar survival or metamorphosis to the cyprid stage. Response in body size and developmental time may have costs at the time of metamorphosis (delayed settlement) or after metamorphosis. Overall, our experiments suggest that as temperature increases, settlement success of S. balanoides larvae (but not that of its competitor A. modestus) will become more sensitive to conditions of food limitation, imposed for instance by phenological mismatches with periods of phytoplankton peak.
Connectivity between populations is important when considering conservation or the management of exploitation of vulnerable species. We investigated how populations of a broadcast‐spawning marine species (scallop, Pecten maximus) that occur in discrete geographic locations were connected to each other. Population genetic insights were related to the outputs from a three‐dimensional hydrodynamic model implemented with scallop larval behaviour to understand the extent to which these areas were linked by oceanographic processes and how this was altered by season and two contrasting years that had strongly different average temperature records (warm vs cold) to provide contrasting oceanographic conditions. Our results span from regional to shelf scale. Connectivity was high at a regional level (e.g. northern Irish Sea), but lower at scales >100 km between sites. Some localities were possibly isolated thus dependent on self‐recruitment to sustain local populations. Seasonal timing of spawning and inter‐annual fluctuations in seawater temperature influenced connectivity patterns, and hence will affect spatial recruitment. Summer rather than spring spawning increased connectivity among some populations, due to the seasonal strengthening of temperature‐driven currents. Furthermore, the warm year resulted in higher levels of modelled connectivity than the cold year. The combination of genetic and oceanographic approaches provided valuable insights into the structure and connectivity at a continental shelf scale. This insight provides a powerful basis for defining conservation management units and the appropriate scale for spatial management. Temporal fluctuations in temperature impact upon variability in connectivity, suggesting that future work should account for ocean warming when investigating population resilience.
Predicting range expansion of invasive species is one of the key challenges in ecology. We modelled the phenological window for successful larval release and development (WLR) in order to predict poleward expansion of the invasive crab Hemigrapsus sanguineus along the Atlantic coast of North America and north Europe. WLR quantifies the number of opportunities (in days) when larval release leads to a successful completion of the larval phase; WLR depends on the effects of temperature on the duration of larval development and survival. Successful larval development is a necessary requirement for the establishment of self‐persistent local populations. WLR was computed from a mechanistic model, based on in situ temperature time series and a laboratory–calibrated curve predicting duration of larval development from temperature. As a validation step, we checked that model predictions of the time of larval settlement matched observations from the field for our local population (Helgoland, North Sea). We then applied our model to the North American shores because larvae from our European population showed, in the laboratory, similar responses to temperature to those of a North American population. WLR correctly predicted the northern distribution limit in North American shores, where the poleward expansion of H. sanguineus appear to have stalled (as of 2015). For north Europe, where H. sanguineus is a recent invader, WLR predicted ample room for poleward expansion towards NE England and S Norway. We also explored the importance of year‐to‐year variation in temperature for WLR and potential expansion: variations in WLR highlighted the role of heat waves as likely promoters of recruitment subsidising sink populations located at the distribution limits. Overall, phenological windows may be used as a part of a warning system enabling more targeted programs for monitoring.
