Biology subjects

Zawada, K. J. A.

Publications and source records attributed to Zawada, K. J. A..

3 recordsLinked to original sources

bioRxiv2025

Tracking morphological development in stony corals

The shape of reef-building corals largely determines how they interact with their environment and the ecosystem services they provide. However, morphology is not fixed. As corals grow and develop from singular polyps to mature adult colonies, they experience pronounced changes in their morphology. This developmental trait variation remains poorly quantified in corals, despite their importance as ecosystem engineers. To address this gap, we used photogrammetry to track the morphological development of wild coral colonies across six size-independent metrics designed to capture variation in volume compactness, surface complexity, and top-heaviness. Size-trait models and analyses of colony movement through morphological trait space revealed that small colonies shared compact morphologies and only later diverged along growth-form-specific developmental trajectories. Massive corals largely retained stable shapes as they grew, whereas non-massive colonies became less compact, more top-heavy, and in most cases, more complex. Despite these differences, there was still overlap between growth forms in their developmental trajectories through morphospace. These findings highlight that traditional categorical growth forms mask important developmental variation, particularly early in coral ontogeny. By applying a quantitative trait-based framework, this study improves understanding of coral morphological development and provides a foundation for linking individual growth trajectories to broader reef ecosystem dynamics.

ecology↗

bioRxiv2021

Coral settlement and recruitment responses to reef fish foraging and trait diversity

The process of coral recruitment is crucial to the functioning of coral reef ecosystems, as well as recovery of coral assemblages following disturbances. Fishes can be key mediators of this process by removing benthic competitors like algae, but their foraging impacts are capable of being facilitative or harmful to coral recruits depending on species traits. Reef fish assemblages are highly diverse in foraging strategies and the relationship between this diversity with coral settlement and recruitment success remains poorly understood. Here, we investigate how foraging trait diversity of reef fish assemblages covaries with coral settlement and recruitment success across multiple sites at Lizard Island, Great Barrier Reef. Using a multi-model inference approach incorporating six metrics of fish assemblage foraging diversity (foraging rates, trait richness, trait evenness, trait divergence, herbivore abundance, and sessile invertivore abundance), we found that herbivore abundance was positively related to both coral settlement and recruitment success. However, the correlation with herbivore abundance was not as strong in comparison with foraging trait diversity metrics. Coral settlement and recruitment exhibited a negative relationship with foraging trait diversity, especially with trait divergence and richness in settlement. Our findings provide further evidence that fish play a role in making benthic habitats more conducive for coral settlement and recruitment. Because of their ability to shape the reef benthos, the variation of fish biodiversity is likely to contribute to spatially uneven patterns of coral recruitment and reef recovery.

ecology↗

bioRxiv2019

Quantifying coral morphology

The morphology of coral colonies has important implications for their biological and ecological performance, including their role as ecosystem engineers. However, given that morphology is difficult to quantify across many taxa, morphological variation is typically shoehorned into coarse growth form categories (e.g., arborescent and digitate). In this study, we develop a quantitative schema for morphology by identifying three-dimensional shape variables that can describe coral morphology. We contrast six variables estimated from 152 laser scans of coral colonies that ranged across seven growth form categories and three orders of magnitude of size. We found that 88% of the variation in shape was captured by two axes of variation and three shape variables. The main axis was variation in volume compactness (cf. sphericity) and the second axis was the trade-off between surface complexity and the vertical distribution of volume (i.e., top heaviness). Variation in volume compactness also limited variation along the second axis, where surface complexity and vertical volume distribution ranged more freely when compactness was low. Traditional growth form categories occupied distinct regions within this morpho-space. However, these regions overlapped due to shape changes with colony size. Nonetheless, four of the shape variables were able to predict traditional growth form categories with 70 to 95% accuracy, suggesting that the continuous variables captured much of the qualitative variation inherently implied by these growth forms. Distilling coral morphology into geometric variables that capture shape variation will allow for better tests of the mechanisms that govern coral biology, ecology and ecosystem services such as reef building and provision of habitat.

ecology↗