Local competition and metapopulation processes drive long-term seagrass-epiphyte population dynamics

It is well known that ecological processes such as population regulation and natural enemy interactions potentially occur over a range of spatial scales, and there is a substantial body of literature developing theoretical understanding of the interplay between these processes. However, there are comparatively few studies quantifying the long-term effects of spatial scaling in natural ecosystems. A key challenge is that trophic complexity in real-world biological communities quickly obscures the signal from a focal process. Seagrass meadows provide an excellent opportunity in this respect: in many instances, seagrasses effectively form extensive natural monocultures, in which hypotheses about endogenous dynamics can be formulated and tested. We present amongst the longest unbroken, spatially explict time series of seagrass abundance published to date. Data include annual measures of shoot density, total above-ground abundance, and associated epiphyte cover from five Zostera marina meadows distributed around the Isles of Scilly, UK, from 1996 to 2011. We explore empirical patterns at the local and metapopulation scale using standard time series analysis and develop a simple population dynamic model, testing the hypothesis that both local and metapopulation scale feedback processes are important. We find little evidence of an interaction between scales in seagrass dynamics but that both scales contribute approximately equally to observed local epiphyte abundance. By quantifying the long-term dynamics of seagrass-epiphyte interactions we show how measures of density and extent are both important in establishing baseline information relevant to predicting responses to environmental change and developing management plans. We hope that this study complements existing mechanistic studies of physiology, genetics and productivity in seagrass, whilst highlighting the potential of seagrass as a model ecosystem. More generally, this study provides a rare opportunity to test some of the predictions of ecological theory in a natural ecosystem of global conservation and economic val

New insights into the role of motion and form vision in neurodevelopmental disorders

A selective deficit in processing the global (overall) motion, but not form, of spatially extensive objects in the visual scene is frequently associated with several neurodevelopmental disorders, including preterm birth. Existing theories that proposed to explain the origin of this visual impairment are, however, challenged by recent research. In this review, we explore alternative hypotheses for why deficits in the processing of global motion, relative to global form, might arise. We describe recent evidence that has utilised novel tasks of global motion and global form to elucidate the underlying nature of the visual deficit reported in different neurodevelopmental disorders. We also examine the role of IQ and how the sex of an individual can influence performance on these tasks, as these are factors that are associated with performance on global motion tasks, but have not been systematically controlled for in previous studies exploring visual processing in clinical populations. Finally, we suggest that a new theoretical framework is needed for visual processing in neurodevelopmental disorders and present recommendations for future research

Wasting disease regulates long-term population dynamics in a threatened seagrass

The role of disease in the long-term dynamics of threatened species is poorly quantified, as well as being under-represented in ecology and conservation management. To understand persistent host–pathogen interaction operating in a vulnerable habitat, we quantified dynamics driving patterns of seagrass density using a longitudinal study in a relatively pristine site (Isles of Scilly, UK). Replicated samples of eelgrass (Zostera marina) density and wasting disease prevalence, presumably caused by Labyrinthula zosterae, were taken from five meadows at the height of the growing season, over the years 1997–2010. Data were used to parameterise a population dynamic model, incorporating density-dependent factors and sea temperature records. We found that direct density and disease-mediated feedback operate within a network of local populations. Furthermore, our results indicate that the strength of limitation to seagrass growth by disease was increased at higher temperatures. This modification of the coupled host–pathogen dynamics forms a novel hypothesis to account for dramatic die-backs of Z. marina widely reported elsewhere. Our findings highlight the importance of disease in structuring distributions of vulnerable species, as well as the application of population modelling in order to reveal ecological processes and prioritise future mechanistic investigation

Recent loss of Gibraltar seagrasses

Worldwide, seagrasses face threats including climate change, disease and anthropogenic disturbance, with populations at the extremes of species' distributions likely presaging future problems elsewhere in their geographical ranges. At the geographic limits of two marine macrophytes (Zostera marina and Posidonia oceanica) and under intense urbanization, seagrasses around Gibraltar are particularly vulnerable. However, the last published survey of Gibraltar seagrass meadows, in 1993, showed both species were abundant. We resurveyed this area and were unable to locate any seagrass in Gibraltar waters. Extensive coastal development and land reclamation make much former seagrass habitat in Gibraltar waters unsuitable, presenting substantial hurdles to any future restoration efforts

The roles of flowering, overwinter survival and sea surface temperature in the long-term population dynamics of Zostera marina around the Isles of Scilly, UK

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Development of a Campus-Wide Community Service Initiative during a Pandemic

Community service serves as a major aspect of pharmacy education; however, coronavirus disease 2019 (COVID-19) represented a significant disruption to student involvement. The College of Pharmacy student council, which serves as the local student government organization for the University of Florida College of Pharmacy, Jacksonville campus, developed a community service initiative to offer more consistent opportunities for students to participate in community service events, while adapting to COVID-19 restrictions. A retrospective, qualitative review of this initiative demonstrates the potential value of this model. Prior to this initiative, students relied on individual student organizations to provide service opportunities to their members. This excluded portions of the student body and led to sparse and inconsistent events, with limited variation in the types of service events available. Furthermore, de-centralized planning of service opportunities increased the difficulty of ensuring that COVID-19 safety restrictions were followed appropriately. This initiative resulted in 39 students logging over 200 service hours through nine events in the first seven months after its development. Despite the challenges presented by the COVID-19 pandemic, our centralized initiative serves as a model for improving community service involvement

Time series of seagrass (Zostera marina) density and epiphyte cover.

<p>Panel (a) shoot density ×100 per square metre; panel (b) seagrass density ×100 per square metre (total metres of leaf per square metre of ground); panel (c) the proportion of quadrats occupied by seagrass in a given meadow; and panel (d) the average proportion of each leaf covered by epiphytes in a given quadrat. Grey dots show individual quadrat data; black lines show meadow averages for Broad Ledges Tresco (blt), Higher Town Bay (htb), Little Arthur (la), Old Grimsby Harbour (ogh), and West Broad Ledges (wbl).</p

Data from: Fractal measures of spatial pattern as a heuristic for return rate in vegetative systems

Measurement of population persistence is a long-standing problem in ecology; in particular, whether it is possible to gain insights into persistence without long time-series. Fractal measurements of spatial patterns, such as the Korcak exponent or boundary dimension, have been proposed as indicators of the persistence of underlying dynamics. Here we explore under what conditions a predictive relationship between fractal measures and persistence exists. We combine theoretical arguments with an aerial snapshot and time series from a long-term study of seagrass. For this form of vegetative growth, we find that the expected relationship between the Korcak exponent and persistence is evident at survey sites where the population return rate can be measured. This highlights a limitation of the use of power-law patch-size distributions and other indicators based on spatial snapshots. Moreover, our numeric simulations show that for a single species and a range of environmental conditions that the Korcak–persistence relationship provides a link between temporal dynamics and spatial pattern; however, this relationship is specific to demographic factors, so we cannot use this methodology to compare between species

Phase plots of seagrass-epiphyte competition.

<p>Panel (a) average quadrat seagrass density plotted against epiphyte cover from 16 year time series, sampled at five independent <i>Zostera marina</i> meadows around the Isles of Scilly, UK; panel (b) the proportion of sampled area (quadrats) occupied by seagrass plotted against epiphyte cover (where seagrass patch occupancy proportion = 1, this was substituted with 0.99 for logit-transformation). Solid lines show epiphyte zero isoclines (no net population growth); dashed lines show <i>Z. marina</i> zero isoclines.</p

Seagrass-epiphyte population dynamic modelling.

<p>We explored three population dynamic models of intra- and inter-specific competition between seagrass and its epiphytes: (a) ln(<i>X_t/X_t</i>_-1) represents the population growth rate of local seagrass density; (b) ln(<i>X_t/X_t</i>_-1) describes the net colonization/extinction rate of available habitat by seagrass; and (c) ln(<i>Y_t/Y_t</i>_-1) represents the population growth rate of epiphytes on seagrass leaves. In each case, we compared the relative weight of evidence (AICcWt) for local, metapopulation and ‘combined’ scale (average local density including unoccupied patches) seagrass abundance as drivers of population dynamics.</p