Biology subjects

Hay, E. M.

Publications and source records attributed to Hay, E. M..

5 recordsLinked to original sources

bioRxiv2026

Do microbial effects on hosts vary across life stage and vitalrate?

Interactions with microbial symbionts are widespread and can influence host fitness through effects on survival, growth, and reproduction. Demographic and evolutionary theory suggests that symbiont effects on components of host fitness should often vary in strength and even in direction as host and symbiont allocate limited resources. Through a meta-analysis of 1,736 host-symbiont effect size measurements, we evaluated how commonly the direction of symbiont effects varies across host life history stages and vital rates, and whether these effects across stages and vital rates differ across taxa. Contrary to our prediction, we found that, compared to a null expectation, published effects on host vital rates more often occurred consistently in the same direction, rather than in opposition. This finding suggests that symbiosis often provides benefits to host performance that manifest across vital rates. While the direction of symbiotic effect was often consistent, the magnitude of effects differed across fitness components and across host taxonomic groups, highlighting diverse demographic mechanisms by which symbiosis can influence host fitness. For hosts in the Poaceae family, we also found that effects of symbiosis varied across symbiont type: vertically-transmitted Epichloe fungi most strongly benefited seed germination, while the benefits of mycorrhizal fungi and bacterial endophytes were stronger for adult growth and reproduction. Importantly, this literature survey also highlights gaps in the current literature on host-microbe symbiosis. Most studies measure growth during juvenile stages for taxa from iconic, well-studied symbioses. Meta-analytic estimates of symbiotic effects on host life history provide a path towards quantitatively modeling host-symbiont demography across the tree of life.

ecology↗

bioRxiv2026

Inference of Cichlid Speciation Patterns is Dependent on Spatial Covariance and Species Delimitation

Macroevolutionary analyses typically treat species as discrete units and account for shared evolutionary history. However, speciation is a continuous process and taxa are often spatially clustered, potentially biasing inferences of diversification. Here, we investigate how species delimitation and spatial non-independence influence speciation dynamics and inferred drivers using cichlid fishes as a model system. Using a phylogeny and trait dataset of 1,712 species, we first generated a reduced dataset of 820 species by removing incipient species based on known breeding compatibilities. We then fit phylogenetic and spatiophylogenetic models using an integrated nested Laplace approximation framework to jointly account for phylogenetic and spatial covariance. We find that the treatment of incipient species and spatial non-independence both alter speciation patterns and inferred drivers. Analyses of the full phylogeny identified strong trait associations and spatial hotspots driven by young adaptive radiations in Lake Victoria and Lake Malawi, whereas removing incipient species and accounting for spatial non-independence reduced extreme speciation rates, weakened or removed trait effects, and largely eliminated spatial hotspots. These results demonstrate that macroevolutionary inference is sensitive to species delimitation and spatial structure, highlighting the need to consider the influence of incipient species and spatial covariance in comparative analyses.

evolutionary biology↗

bioRxiv2026

Mutualistic microbes drive niche expansion yet constrain diversification

Mutualistic interactions are widely hypothesized to expand ecological niches and promote diversification, yet evidence for this relationship at macroevolutionary scales remains limited. Here, we investigate how fungal seed endophytes (Epichloe) influence niche breadth and diversification across over 100 species of the globally-distributed grass genus Poa. Combining global-scale climate, environmental, phylogenetic, and symbiosis data, we constructed species distribution models for suites of symbiotic and non-symbiotic plant species, then used a range of phylogenetic comparative methods to assess the influence of these symbionts on niche breadth, niche breadth evolution, and diversification. Endophyte-positive species had [~]1.4 times broader primary niche axes (most often associated with temperature tolerances), [~]2.5 times larger geographic ranges, and >30 times faster rates of niche breadth evolution than non-symbiotic species. Endophytic plants also had significantly drier climate centroids, consistent with endophyte-mediated drought tolerance, while simultaneously showing constraints along specific niche dimensions. Despite pronounced niche expansion, hidden state speciation and extinction models revealed two modes of diversification: endophytes decrease diversification rates in young lineages, and have a neutral effect in older lineages. Together, our results demonstrate that mutualists can enhance ecological flexibility while simultaneously constraining macroevolutionary outcomes, revealing a decoupling of niche expansion and diversification, and highlighting the complex role of symbiosis in shaping host evolutionary trajectories.

evolutionary biology↗

bioRxiv2023

No evidence for song evolution influencing speciation patterns in honeyeaters

Birdsongs are acoustic signals that can play a role in sexual selection. Despite the established role of birdsong in selection and reproductive isolation at microevolutionary scales, the macroevolutionary relationships between song evolution and clade diversification remain largely unexplored. We test the hypothesis that shifts in diversification influence rates of song evolution in honeyeaters, a diverse clade of songbirds restricted to Australasia. Using a song dataset for 163 honeyeater species, we identify lineage-specific shifts in diversification, and test the influence of these shifts on song evolution with state-dependent, relaxed, multivariate Brownian motion models. We also explore the underlying patterns of song evolution and phylogenetic signal of song. Shifts to lower rates of diversification are associated with lower rates of song evolution. This suggests the two factors are correlated, but is contrary to expectations that elevated rates of diversification will be associated with elevated rates of song evolution. We also found that song follows a punctuated mode of evolution, implying that birdsong has an important role in speciation events, although this signal likely erodes over time and is subject to phylogenetic constraints.

evolutionary biology↗

bioRxiv2023

Body size shapes song in honeyeaters

Birdsongs are among the most distinctive animal signals. Their evolution is thought to be shaped simultaneously by habitat structure and by the constraints of morphology. Habitat structure affects song transmission and detectability, thus influencing song (the acoustic adaptation hypothesis), while body size and beak size and shape necessarily constrain song characteristics (the morphological constraint hypothesis). Yet, support for the acoustic adaptation and morphological constraint hypotheses remains equivocal, and their simultaneous examination is infrequent. Using a phenotypically diverse Australasian bird clade, the honeyeaters (Aves: Meliphagidae), we compile a dataset consisting of song, environmental, and morphological variables for 163 species and jointly examine predictions of these two hypotheses. Overall, we find that body size constrains song frequency and pace in honeyeaters. Although habitat type and environmental temperature influence aspects of song, that influence is indirect, likely via effects of environmental variation on body size, with some evidence that elevation constrains the evolution of song peak frequency. Our results demonstrate that morphology has an overwhelming influence on birdsong, in support of the morphological constraint hypothesis, with the environment playing a secondary role generally via body size rather than habitat structure. These results suggest that changing body size, a consequence of both global effects such as climate change, and local effects such as habitat transformation, will substantially influence the nature of birdsong.

evolutionary biology↗