Biology subjects

Million, W. C.

Publications and source records attributed to Million, W. C..

5 recordsLinked to original sources

bioRxiv2026

Genomic variation associated with endosymbiont shuffling and areal growth in the endangered elkhorn coral, Acropora palmata

Biodiversity losses continue to outpace traditional management, underscoring the need to understand adaptive capacity and the potential for interventions to increase fitness under climate change. We undertook a genome-wide association study on 156 Acropora palmata genets to investigate the genomic basis of areal growth, endosymbiont association, and thermal tolerance. Seven peaks on chromosomes 1, 3 and 14 were associated with endosymbiont shuffling and two peaks on chromosome 4 were associated with areal growth. As variants were located in non-coding regions we incorporated additional data from an independent field-transplant experiment to investigate their relationship with patterns of gene expression. Intersection of these datasets implicated melanocortin-like receptor activity and Ran GTPase activating protein 1 in endosymbiont composition and surface area growth, respectively. Results indicate that growth and endosymbiont associations may represent more viable intervention targets than temperature tolerance and highlight the need to better understand the role of non-coding variation in basic biology and development of restoration interventions.

genomics↗

bioRxiv2026

Reproductive Trade-offs in Caribbean Corals: Plasticity Accelerates While Fragmentation Delays Reproductive Capacity

In modular organisms, where growth and fragmentation blur the boundaries between individuals, the interplay between asexual and sexual reproduction creates complex fitness trade-offs. Life-history theory predicts that resources allocated to one fitness component necessarily reduce investment in others, yet detecting these trade-offs in wild populations of clonal organisms remains challenging. Phenotypic plasticity can enhance survival, yet its influence on reproductive capacity and life history trade-offs remains poorly understood. Using a fully crossed reciprocal transplant design, we tracked 263 colonies of the branching coral Acropora cervicornis across nine reef sites over 42 months, investigating relationships between fragmentation, morphological plasticity, and the capacity for sexual reproduction. Breakage patterns reflected both environmental and genetic factors. Primary branch breaks created a "double negative" effect--simultaneously more than doubling mortality risk and delaying attainment of a validated reproductive size class by [~]40%. Conversely, higher morphological plasticity in surface area-to-volume ratio accelerated sexual maturation up to 6-fold, counteracting the negative effects of fragmentation. In parallel, a simple demographic model parameterized with published fecundity data estimated that primary breakage reduces expected cumulative reproductive output by [~]58%, a result robust across a wide range of parameter assumptions. These results demonstrate a fundamental reproductive trade-off in which asexual reproduction through fragmentation undermines sexual reproductive potential by reducing colony size. Moreover, our findings reveal that fragmentation susceptibility is broadly heritable and subject to selection, and identify a compensatory mechanism through which plasticity enhances fitness beyond immediate survival.

evolutionary biology↗

bioRxiv2023

Microhabitat acclimatization shifts physiological baselines and thermal tolerance of the symbiotic anemone, Anthopleura elegantissima

Contemporary organisms in extreme environments can give insight into how species will respond to environmental change. The intertidal forms an environmental gradient where stress increases with tidal height. Here, we explore the contribution of fixed genotypic and plastic environmental effects on thermal tolerance of the intertidal anemone Anthopleura elegantissima and its algal symbionts using a laboratory-based tank experiment. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline maximum quantum yield compared to low intertidal anemone symbionts, despite identical symbiont communities. High intertidal anemones maintained greater maximum quantum yield and symbiont-to-host cell ratios under heat stress compared to low intertidal anemones, suggesting that high intertidal holobionts have greater thermal tolerance. However, thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating emersion duration is not the sole environmental driver of physiological variation. Fixed genotypic effects also influenced physiological baselines, but did not modulate thermal tolerance, demonstrating thermal tolerance is largely driven by environmental history. These results indicate that this symbiosis is highly plastic and may be able to rapidly acclimatize to climate change, defying the convention that symbiotic organisms are more susceptible to environmental stress.

ecology↗

bioRxiv2022

Long term maintenance of heterologous symbiont association in Acropora palmata on natural reefs

The sensitivity of reef-building coral to elevated temperature is a function of their symbiosis with dinoflagellate algae in the family Symbiodiniaceae. Changes in the composition of the endosymbiont community in response to thermal stress can increase coral thermal tolerance. Consequently, this mechanism is being investigated as a human-assisted intervention for rapid acclimation of coral in the face of climate change. Successful establishment of novel symbioses that increase coral thermal tolerance have been demonstrated in laboratory conditions; however, it is unclear how long these heterologous relationships persist in nature. Here, we show that Acropora palmata can form a novel symbiosis with Durusdinium spp. when reared in land-based aquaria. We tested the stability of this heterologous relationship by outplanting clonal replicates (ramets) of five A. palmata host genotypes to natural reefs in the lower Florida Keys. Amplicon sequencing analysis of ITS2-type profiles revealed that the majority of surviving ramets remained dominated by Durusdinium spp. two years after transplantation. However, 15% of ramets, including representatives of all genotypes, did exhibit some degree of symbiont shuffling or switching at six of eight sites, including complete takeover by site-specific strains of the native symbiont, Symbiodinium fitti. The predominant long-term stability of the novel symbiosis supports the potential effectiveness of symbiont modification as a management tool. However, the finding that 6-7 year-old coral can alter symbiont community composition in the absence of bleaching indicates that Symbiodiniaceae communities are indeed capable of greater flexibility under ambient conditions.

microbiology↗

bioRxiv2022

Evidence for adaptive morphological plasticity in the Caribbean coral, Acropora cervicornis.

Genotype-by-environment interactions (GxE) indicate that variation in organismal traits cannot be explained by fixed effects of genetics or site-specific plastic responses alone. For tropical coral reefs experiencing dramatic environmental change, identifying the contributions of genotype, environment, and GxE on coral performance will be vital for both predicting persistence and developing restoration strategies. We quantified the impacts of G, E, and GxE on the morphology and survival of the endangered coral, A. cervicornis, through an in situ transplant experiment exposing common garden (nursery) raised clones of ten genotypes to nine reef sites in the Florida Keys. By fate-tracking outplants over one year with colony-level 3D photogrammetry, we uncovered significant GxE on coral size and survivorship indicating that no universal winner exists in terms of colony performance. Moreover, the presence of GxE also implies the existence of intraspecific variation in phenotypic plasticity. Rather than differences in mean trait values, we find that individual-level morphological plasticity is adaptive in that the most plastic individuals also exhibited the fastest growth and highest survival. This indicates that adaptive morphological plasticity may continue to evolve, influencing the success of A. cervicornis and resulting reef communities in a changing climate. As focal reefs are active restoration sites, the knowledge that variation in phenotype is an important predictor of performance can be directly applied to restoration planning. Taken together, these results establish A. cervicornis as a system for studying the eco-evolutionary dynamics of phenotypic plasticity that also can inform genetic- and environment-based strategies for coral restoration.

ecology↗