Biology subjects

MacColl, A.

Publications and source records attributed to MacColl, A..

3 recordsLinked to original sources

bioRxiv2026

The effect of environmental variation on the diversity and composition of the three-spined stickleback microbiome

The fish skin microbiome serves as a protective barrier, influencing host health and facilitating interactions between the host and its environment. While several studies have characterised the composition and roles of the fish skin microbiome, there remains a paucity of data on how environmental variation influences these microbes in natural populations. Here, we used 16S rRNA gene sequencing to characterise the skin microbiome of wild three-spined stickleback populations and examine how environmental factors influence microbial diversity and community composition across 17 freshwater lochs on the island of North Uist, Scotland. Analysis of 239 samples revealed a set of dominant bacterial genera commonly associated with other fish species, including Janthinobacterium, Pseudomonas, Acinetobacter, and Psychrobacter, that constituted a core skin microbiota across lochs. Microbiome composition was primarily shaped by environmental variables, particularly habitat, water pH, conductivity, and metal concentrations, with pH emerging as a key driver of community structure. Host sex also influenced microbiome variation, with several taxa differing in relative abundance between males and females. Alpha-diversity was higher among stickleback fish from lochs with a neutral pH compared with those from alkaline and acidic environments. Differential abundance analyses identified 27 and 24 amplicon sequence variants (ASVs), respectfully, associated with variations in pH and host sex, including members of Psychrobacter, Sphingobacterium, Carnobacterium, Chryseobacterium, and Arthrobacter, highlighting the combined influence of environmental and host factors on microbiome composition in wild fish populations in freshwater environments.

microbiology↗

bioRxiv2025

Developmental genetic basis of dorsal spine reduction in acidic-adapted threespine stickleback fish

The repeated emergence of similar phenotypes in independent populations is a widespread feature of evolution, yet the extent to which repeated evolution reflects shared molecular mechanisms, and the factors that determine this similarity, remain unclear. Here, we investigate the genetic basis of dorsal spine reduction in threespine stickleback fish, an adaptive trait that has evolved repeatedly in freshwater populations. Phenotypic analyses of crosses between a spine-reduced population from Scotland and the ancestral marine form reveal a major-effect locus, with the spine-reducing allele acting dominantly and influencing body patterning. Bulk segregant analysis maps this effect to a single region on chromosome VI that overlaps the hoxdb gene cluster. Transcriptomic analyses of larval stages show a gain of hoxdb expression in the developing spine region of spine-reduced fish, consistent with the dominance of the derived allele. Together, these results indicate dorsal spine reduction in threespine stickleback through cis-regulatory changes at hoxdb, a mechanism found to mediate dorsal spine evolution in a different species of stickleback fish too. These findings highlight the role of hox genes in adaptive divergence between natural populations within a species and provide a clear example of parallel evolution at the molecular level between species.

evolutionary biology↗

bioRxiv2023

Development of resident and migratory three-spined stickleback, Gasterosteus aculeatus.

The three-spined stickleback (Gasterosteus aculeatus) is a teleost fish and a model organism in evolutionary ecology, useful for both laboratory and natural experiments. It is especially valued for the substantial intraspecific variation in morphology, behaviour and genetics. Classic work of Swarup (1958) [1] has described the development in the laboratory of embryos from a single freshwater population, but this was carried out at higher temperature than many stickleback would encounter in the wild and variation between populations was not addressed. Here we describe the development of embryos from two sympatric, saltwater ecotypes of stickleback from North Uist, Scotland raised at 14{degrees}C, the approximate temperature of North Uist lochs in the breeding season. The two ecotypes were (a) a large, migratory form in which the adults are completely plated with bony armour and (b) a smaller, low-plated form that is resident year-round in saltwater lagoons. By monitoring embryos every 24-hours post fertilisation, important characteristics of development were observed and photographed to provide a reference for North Uist ecotypes at this temperature. Hatching success was greater than 85% and did not differ between resident and migratory stickleback, but migratory eggs hatched significantly earlier than the resident ecotype. Our work provides a framework that can now be used to compare stickleback populations that may also grow in distinct environmental conditions, to help understand the breadth of normal developmental features and to characterise abnormal development.

ecology↗