Biology subjects

McManus, L. C.

Publications and source records attributed to McManus, L. C..

8 recordsLinked to original sources

bioRxiv2026

Contrasting patterns of seascape genetics in Acropora cf. tenuis and their symbiotic algae.

Theory suggests that pairs of mutualist species will often co-disperse and share the same dispersal patterns, though the extent to which this happens remains unclear. Photosynthetic corals constitute an example of this dynamic, as they rely on algal symbionts to meet their energetic needs, yet many acquire their symbionts environmentally after their larval dispersal phase. Consequently, corals and their symbionts may exhibit similar or contrasting patterns of genetic variation across the seascape, with implications for their evolutionary and ecological processes. Here, we densely sample corals of the key reef-building taxon Acropora cf. tenuis and their algal symbionts across a reefscape in the central Philippines to examine genetic variation across space. Four distinct coral taxa show genetic evidence of long distance dispersal, including weak or absent isolation by distance signals and parent-offspring pairs at widely spaced sites. These coral taxa all host a single group of algal symbionts from the genus Cladocopium, which shows landscape genetic structure independent from its coral hosts. In fact, Cladocopium genetics vary with both latitude and depth, potentially indicating genome-wide local adaptation at a finer spatial scale than that seen in their hosts. Genetic variation at markedly different spatial scales between host and symbiont may be beneficial for hosts if these differences enable them to acquire symbionts adapted to their settlement environments.

ecology↗

bioRxiv2025

Growth rate and adaptive capacity, not just thermal tolerance, are critical for long-term coral persistence under climate change

It is widely assumed that corals with a narrower thermal tolerance and greater bleaching susceptibility are at most risk under anthropogenic climate change. Using a simple eco-evolutionary model, we investigate coral reef futures under climate change through a factorial approach, across millions of simulations. We find that, while corals with low thermal tolerance are indeed at greatest risk of population collapse in the short term, coral population persistence beyond 2050 is instead primarily determined by the maximum population growth rate and additive genetic variance. Anthropogenic climate change exceeds the thermal tolerance of all corals, so adaptive capacity and the ability to rapidly recover from disturbance are critical for long-term persistence. As a result, it is plausible that branching corals could fare better than slower growing, stress-tolerant counterparts in the long term, but only if they can weather the greater acute threats over the coming decades. Since the response timescale of corals to climate change varies considerably across taxa, and due to the particular importance of genetic variance in facilitating evolutionary adaptation, sustainable restoration approaches should aim to conserve a broad range of coral species and genotypes, rather than aiming to optimise one particular trait.

ecology↗

bioRxiv2024

Coexistence of bacteria with a competition-colonization tradeoff on a dynamic coral host

Many macroscopic organisms enter into tightly linked symbiosis with microbial communities. Although experimental work has demonstrated the importance of these symbioses, a theoretical understanding of stable, multi-scale coexistence remains underdeveloped. Here, we explored how the competition-colonization tradeoff, a classic coexistence mechanism, operates when bacterial species compete for a dynamic biological host. Specifically, we introduce a model where corals are colonized by fast-growing mutualists and slow-growing pathogens. We found that the vital rates of the host coral influenced coexistence outcomes between bacterial types. Notably, pathogen-induced host death expanded the region of parameter space where coexistence was stable for all three species and mutualistic bacteria enabled coexistence in systems that would have otherwise collapsed. These findings provide new insights into the interplay between microbial interactions and macroscopic processes. Our work illustrates how host-microbe interactions can shape ecosystem stability, providing a theoretical framework applicable to a wide range of symbiotic systems.

ecology↗

bioRxiv2024

Marine spatial planning to enhance coral adaptive potential

Ocean warming interacts with local stressors to negatively affect coral reefs. The adaptive capacity of reefs to survive these stressors is driven by ecological and evolutionary processes occurring at multiple spatial scales. Marine protected area (MPA) networks are one solution that can address both local and regional threats, yet the impacts of MPA network design on adaptive processes remains unclear. In this paper, we used an eco-evolutionary model to simulate hypothetical MPA configurations in the Caribbean, Southwest Pacific and Coral Triangle under projected warming. We found that protecting thermal refugia (i.e., cooler reefs) largely benefited corals inside the refugia while other reefs declined. In contrast, protecting a diverse habitat portfolio led to increased coral cover both inside and outside of the MPA network. We then quantified the thermal habitat and connectivity representations of reefs both inside and outside existing MPA networks across each region. Most strikingly, reefs in current MPA networks in the Southwest Pacific and Coral Triangle are approximately 2 {degrees}C cooler than reefs outside the MPA networks, while the Caribbeans MPA network is approximately 1 {degrees}C warmer than reefs outside the network, based on mean temperatures from 2008-2018. These results suggest that the Caribbean MPA network is poised to protect sources of warm-adapted larvae but not destinations, and the opposite is true of the Southwest Pacific and Coral Triangle. Our results suggest that 1) by protecting sites with particular temperature and connectivity characteristics, marine spatial planning may alter eco-evolutionary processes to enhance or inhibit the adaptive capacity of a reef network and 2) the distribution, extent, and effectiveness of local interventions have the potential to affect regional distributions of coral cover beyond what would be expected from local benefits alone, due to the potentially wide-reaching effects of larval dispersal and gene flow.

ecology↗

bioRxiv2024

Anthropogenic climate change will likely outpace coral range expansion

Past coral range expansions suggest that high-latitude environments may serve as refugia, potentially buffering tropical biodiversity loss due to climate change. We explore this possibility for corals globally, using a dynamical metacommunity model incorporating temperature, light intensity, pH, and four distinct, interacting coral assemblages. This model reasonably reproduces the observed distribution and recent decline of corals across the Indo-Pacific and Caribbean. Our simulations suggest that there is a mismatch between the timescales of coral reef decline and range expansion under future predicted climate change. Whereas the most severe declines in coral cover will likely occur within 60-80 years, significant tropical coral range expansion requires centuries. The absence of large-scale coral refugia in the face of rapid anthropogenic climate change emphasises the urgent need to reduce greenhouse gas emissions, and mitigate non-thermal stressors for corals, both in the tropics and high-latitudes.

ecology↗

bioRxiv2024

Seeing halos: Spatial and consumer-resource constraints to landscape of fear patterns

Coral halos are algae-free space surrounding coral patches linked to the landscape of fear hypothesis, where risk-averse herbivores avoid grazing too far from coral shelter. Halo patterns thus provide insight into the state of overfished predator populations on reefs. However, halos are absent in some protected reefs and their sizes are uncorrelated with predator abundance. Here, we show that these observations are consistent with the landscape of fear hypothesis. When coral are dispersed, herbivores have more even shelter from predators across the seascape, allowing herbivores to overgraze and halos to oscillate. When coral are clustered, shelter is limited and halos can stabilize, but reducing herbivore limitation drives critical transitions to cycles that are difficult to recover from. Discordance between theory and observations may, therefore, arise from differences in underlying coral spatial distributions, with broad implications for how the landscape of fear influences pattern formation and ecological resilience in patchy ecosystems.

ecology↗

bioRxiv2021

Evolution and connectivity influence the persistence and recovery of coral reefs under climate change in the Caribbean, Southwest Pacific, and Coral Triangle

Corals are experiencing unprecedented decline from climate change-induced mass bleaching events. Dispersal not only contributes to coral reef persistence through demographic rescue but can also hinder or facilitate evolutionary adaptation. Locations of reefs that are likely to survive future warming therefore remain largely unknown, particularly within the context of both ecological and evolutionary processes across complex seascapes that differ in temperature range, strength of connectivity, network size, and other characteristics. Here, we used eco-evolutionary simulations to examine coral adaptation to warming across reef networks in the Caribbean, the Southwest Pacific, and the Coral Triangle. We assessed the factors associated with coral persistence in multiple reef systems to understand which results are general and which are sensitive to particular geographic contexts. We found that evolution can be critical in preventing extinction and facilitating the long-term recovery of coral communities in all regions. Furthermore, the strength of immigration to a reef (destination strength) and current sea surface temperature robustly predicted reef persistence across all reef networks and across temperature projections. However, we found higher initial coral cover, slower recovery, and more evolutionary lag in the Coral Triangle, which has a greater number of reefs and more larval settlement than the other regions. We also found the lowest projected future coral cover in the Caribbean. These findings suggest that coral reef persistence depends on ecology, evolution, and habitat network characteristics, and that, under an emissions stabilization scenario (RCP 4.5), recovery may be possible over multiple centuries.

ecology↗

bioRxiv2020

Geometric Analysis of Regime Shifts in Coral Reef Communities

Coral reefs are among the many communities believed to exhibit regime shifts between alternative stable states, single-species dominance, and coexistence. Proposed drivers of regime shifts include changes in grazing, spatial clustering, and ocean temperature. Here we distill the dynamic regimes of coral-macroalgal interaction into a three-dimensional geometry, akin to thermodynamic phase diagrams of state transitions, to facilitate analysis. Specific regime-shifting forces can be understood as bifurcation vectors through the cubic regime geometry. This geometric perspective allows us to understand multiple forces simultaneously in terms of the stability and persistence of interacting species. For example, in a coral-macroalgae community, grazing on macroalgae can lead to alternative stable states when there is no spatial clustering (e.g., high habitat connectivity). However, with spatial clustering, grazing can lead to coexistence because of elevated local intraspecific competition. The geometrical analysis of regime shifts is applicable to any two-species communities and can help conservation efforts navigate complexity and abrupt changes.

ecology↗