About

Diana Rennison is an Associate Professor and the Gordon H. Sato Endowed Fellow in the School of Biological Sciences at the University of California San Diego, where she joined the faculty in 2019. She completed her M.Sc. at the University of Victoria in 2010, focusing on opsin gene duplication and divergence in Poeciliid fish. In 2016, she earned her Ph.D. from the University of British Columbia, studying the genetics of adaptation in the threespine stickleback. For her postdoctoral research, Diana was awarded a Marie Sklodowska-Curie Fellowship at the University of Bern, where she investigated parallel genomic differentiation and genetic sources of evolutionary constraint. Her research integrates evolution, ecology, and genomics to understand adaptive processes and evolutionary patterns in natural populations.

Research topics

• Biology
• Ecology
• Evolutionary biology
• Genetics
• Fishery
• Mathematics
• Geography
• Statistics
• Economic geography
• Zoology

Selected publications

• The genome assemblies of the Tui chub, <i>Siphateles bicolor</i> , and Arroyo chub, <i>Gila orcuttii</i>

  Journal of Heredity · 2026-01-09

  articleOpen access

  We present genome assemblies for two cyprinoid fishes, the tui chub (Siphateles bicolor) and the arroyo chub (Gila orcuttii). These fishes are ecologically important representatives of native fish assemblages in the western United States and are both species of conservation concern. The two species hybridize where introductions bring them into contact, with potentially important ecological and evolutionary implications that have not yet been thoroughly examined from a genomic perspective. We present de novo assemblies for both species, representing the first scaffold-level genomes within their respective genera, which were developed as part of the California Conservation Genomics Project (CCGP) using Pacific Biosciences HiFi and Omni-C data. Our tui chub assembly consists of 258 scaffolds spanning 1 148 084 093 base pairs, has a scaffold N50 of 45.9 Mb, a contig N50 of 23.7 Mb, and a BUSCO completeness score of 98.1%. Our arroyo chub assembly consists of 179 scaffolds spanning 1 263 410 250 base pairs, has a scaffold N50 of 50.5 Mb, a contig N50 of 13.1 Mb, and a BUSCO completeness score of 97.8%. A comparative analysis of the two species revealed relatively conserved genomes, with the exception of two inversions at chromosome 20. We annotated a total of 34 090 genes with a BUSCO completeness score of 98.1% for the tui chub, and 28 193 genes with a score of 97.4% for the arroyo chub. These assemblies will be valuable resources for characterizing the species' phylogeographic histories and delineating the role of hybridization in their evolution.

  PublisherDOI

• Speciation with gene flow

  Plants People Planet · 2026-01-01 · 1 citations

  articleOpen access

  Societal Impact Statement Biodiversity is threatened by human activities, with extinction debt accumulating rapidly. Many of these activities change the connectivity of populations, fragmenting existing population systems or bringing previously isolated populations or species into contact. Speciation research offers insights into both the short‐ and long‐term outcomes of changes in isolation and connectivity and thus provides fundamental knowledge that can inform biodiversity management. Here, we review what is known about the role of gene flow in speciation, highlighting that gene flow does not appear to be a major impediment to speciation in plants and instead often contributes to diversification. Summary The likelihood of speciation with gene flow represents one of the longest running debates in evolutionary biology. Gene flow can hamper speciation by disrupting associations between loci under divergent natural selection and those causing assortative mating. Conversely, variation introduced by gene flow can facilitate speciation, and some modes of speciation require interspecific gene flow. Here, we first describe the history of this debate. Next, we review theoretical models of speciation with gene flow, along with empirical evidence, emphasizing studies of plants. Our review includes both primary divergence with gene flow, as well as gene flow following secondary contact, including different forms of hybrid speciation. We find that plants have several characteristics that can promote the formation of associations between ecological and assortative mating traits, including magic traits (divergently selected traits that also cause assortative mating) and abundant recombination suppressors, such as inversions. Biogeographic studies of several plant groups show patterns of greater range overlap and range asymmetry in sister species compared with more distantly related species. This pattern suggests that geographic isolation is not required for speciation in plants and also that speciation by budding may be important. Genomic data further indicate that gene flow is frequent, but often intermittent, during the speciation process in plants and that speciation triggered by secondary gene flow (introgression) is common. We conclude that Darwin's skepticism about the necessity of geographic isolation in speciation is warranted, especially in the plant kingdom.

  PublisherDOI

• Consistent, scale-dependent differences in the biogeography of host-associated and free-living microbiomes across systems

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-04-21

  articleOpen access

  ABSTRACT Microbial communities are critical to the functioning of ecosystems and shape the ecology and evolution of host organisms. However, we have a limited understanding of how host-associated and free-living microbes differ in their structure and biogeography. Here, we test whether host-associated (fish gut) and free-living (lake bacterioplankton) microbes exhibit different metacommunity structure, spatial turnover, and consistency with neutral expectations using two independent lake systems. We characterized microbial communities in lake water (Vancouver Island and Sierra Nevada) and guts in two fish species (stickleback and brook trout) using 16S amplicon sequencing. We compared alpha and beta diversity within lakes, quantified spatial turnover (distance-decay), and tested for departure from neutral abundance-occurrence expectations between bacterioplankton and fish gut microbiomes. Fish microbiomes had lower alpha diversity compared to bacterioplankton, but higher beta diversity within lakes. Bacterioplankton were more similar across lakes yet showed stronger patterns of spatial turnover with distance than fish gut microbiomes. A neutral model explained a substantial proportion of abundance-occurrence relationships in bacterioplankton communities but performed poorly for fish-associated microbes. Our study indicates that host-associated and free-living microbes have disparate patterns of metacommunity structure and spatial turnover consistent with differences in the strength of neutral ecological processes. Fish microbiomes were less diverse at the local scale but more variable across space and time than bacterioplankton communities, suggestive of potentially strong local selection and/or reduced microbial exchange among hosts compared to environmental communities. Importantly, we observed highly consistent patterns across both lake systems despite differences in host species, sampling design, and region, demonstrating that differences in the distribution of host and environmental microbes are potentially widespread. This study demonstrates how host association fundamentally alters the diversity and spatial distribution of microbes, emphasizing the need to incorporate hosts into broader frameworks of microbial biogeography.

  PublisherDOI

• GLUEing the World: The GLobal Urban Evolution Project and Its Importance to Urban Biodiversity Conservation

  2025-01-01 · 3 citations

  book-chapter
  PublisherDOI

• Contrasting alpha, beta, and gamma diversity in the littoral zones of mountain lakes: effects of habitat size and within-lake community structuring on bacterial biogeography

  FEMS Microbiology Ecology · 2025-03-17 · 3 citations

  articleOpen accessSenior author

  Research on microbial biogeography has revealed key patterns like the diversity-area relationship and distance-decay of similarity. However, how habitat size affects bacterial diversity in freshwater environments remains largely unclear. Here, we characterize bacterial communities in the littoral zones of 10 mountain lakes in the Sierra Nevada, CA, ranging in surface area from 0.92 to 71.72 ha. Despite significant habitat size effects on community composition, dominant bacterial phyla were shared across lakes. We found no evidence for diversity-area relationships, either in single samples (alpha diversity) or cumulative lake-level samples (within-lake gamma diversity), when accounting for environmental variation. Moreover, within-lake beta diversity showed little spatial structuring, with similar bacterial community composition across samples regardless of geographic distance. Gamma diversity did not reach saturation with our sample size, and lake size had no effect on the predicted sample size necessary to reach gamma diversity saturation. Our findings offer new insights into diversity-area dynamics and spatial structuring by investigating alpha, beta, and gamma diversity in freshwater environments. Notably, individual water samples captured much of the bacterial community, with strong correlations between alpha and gamma diversity. These results advance our understanding of microbial biogeography and inform sampling designs for characterizing bacterial diversity in freshwater ecosystems.

  PublisherOA PDFDOI

• Host traits and environmental variation shape gut microbiota diversity in wild threespine stickleback

  Animal Microbiome · 2025-06-18 · 3 citations

  articleOpen accessSenior author

  BACKGROUND: Despite the growing recognition of the importance of gut microbiota in host ecology and evolution, our understanding of the relative contributions of host-associated and environmental factors shaping gut microbiota composition within and across wild populations remains limited. Here, we investigate how host morphology, sex, genetic divergence, and environmental characteristics influence the gut microbiota of threespine stickleback fish populations from 20 lakes on Vancouver Island, Canada. RESULTS: Our findings reveal substantial variation in gut microbiota composition and diversity among populations, with host traits exerting a relatively stronger influence on bacterial alpha diversity than environmental characteristics. Previous studies have suggested a link between stickleback body shape and niche specialization, and our results indicate that aspects of host morphology may be associated with gut microbiota divergence among populations, though whether this is related to trophic ecology remains to be explored. Within and across populations, we only observed a weakly defined core microbiota and limited sharing of amplicon sequence variants (ASVs) among hosts, indicating that gut microbiota composition is individualized. Additionally, we detected sex-dependent differences in microbial diversity, opening avenues for future research into the mechanisms driving this variation. CONCLUSIONS: In sum, our study emphasizes the need to consider both host-associated and environmental factors in shaping gut microbiota dynamics and highlights the complex interplay between host organisms, their associated microbial communities, and the environment in natural settings. Ultimately, these insights add to our understanding of the eco-evolutionary implications of host-microbiota interactions while underscoring the need for further investigation into the underlying mechanisms.

  PublisherOA PDFDOI

• Ecology of Gene Expression

  Molecular Ecology · 2025-07-17 · 2 citations

  editorialOpen access

  The fundamental importance of the expression of genes has long been recognised in biology, but understanding its role in ecology and evolution has only recently begun to gain traction. This Special Issue highlights recent developments in this field, with 43 papers focusing on transcriptional variation in ecological processes, responses to environmental gradients or stressors, and as an important phenotype affecting other measurable traits, including fitness. This issue also highlights the rapid advancements in methods that will continue to improve our understanding of this molecular phenotype. In this Editorial, we highlight the diversity of authors in these papers and how they contribute to an improved understanding of molecular ecology. We hope that this discussion will inspire and drive progress towards equity, diversity and inclusion in ecology and evolutionary biology. Finally, we suggest some recommendations for Molecular Ecologists to advance the research area of ecology of gene expression.

  PublisherOA PDFDOI

• Haploblocks contribute to parallel climate adaptation following global invasion of a cosmopolitan plant

  Nature Ecology & Evolution · 2025-07-08 · 8 citations

  articleOpen access

  The role of rapid adaptation during species invasions has historically been minimized with the assumption that introductions consist of few colonists and limited genetic diversity. While overwhelming evidence suggests that rapid adaptation is more prevalent than originally assumed, the demographic and adaptive processes underlying successful invasions remain unresolved. Here we leverage a large whole-genome sequence dataset to investigate the relative roles of colonization history and adaptation during the worldwide invasion of the forage crop, Trifolium repens (Fabaceae). We show that introduced populations encompass high levels of genetic variation with little evidence of bottlenecks. Independent colonization histories on different continents are evident from genome-wide population structure. Five haploblocks-large haplotypes with limited recombination-on three chromosomes exist as standing genetic variation within the native and introduced ranges and exhibit strong signatures of parallel climate-associated adaptation across continents. Field experiments in the native and introduced ranges demonstrate that three of the haploblocks strongly affect fitness and exhibit patterns of selection consistent with local adaptation across each range. Our results provide strong evidence that large-effect structural variants contribute substantially to rapid and parallel adaptation of an introduced species throughout the world.

  PublisherOA PDFDOI

• Effect of Marine Reference on Inferred Evolutionary Patterns of Freshwater Stickleback

  Ecology and Evolution · 2025-05-29

  articleOpen accessSenior authorCorresponding

  Threespine stickleback are a model system for studying rapid and parallel evolution. Studies characterizing freshwater evolution often use contemporary marines as an ancestral proxy, an approach that relies on untested assumptions about the lack of phenotypic variance in these marine fish. Here, we survey marine individuals collected from several sites, asking whether there is evidence of phenotypic variation. We identified considerable phenotypic variation among fish from different sites. Thus, we investigated the impact of this phenotypic variance on the inferred pattern of freshwater evolution. We tested whether estimates of the magnitude of phenotypic divergence or parallelism were affected by the choice of marine reference. We found that for freshwater populations, the magnitude of phenotypic divergence was dependent on marine sampling location-with divergence estimates differing by up to 65% with the substitution of marine reference site. Geographic distance and environmental similarity between marine and freshwater sites explained some of the variance in these divergence estimates. In contrast, across marine sites, neither geographic distance nor environmental similarity predicted morphological similarity, suggesting other factors drive morphological divergence among marine fish. The magnitude of phenotypic parallelism, estimated using a multivariate vector-based approach, also differed significantly depending on the marine reference used. Together these results suggest that the choice of marine reference population, particularly its geographic distance from the focal population, is an important consideration when trying to characterize patterns of evolution in freshwater stickleback.

  PublisherOA PDFDOI

• Coexistence in Sympatry With Gene Flow Before Speciation Has Completed

  Molecular Ecology · 2025-08-13 · 8 citations

  articleOpen accessSenior author

  Incipient species often coexist in sympatry before complete reproductive isolation has evolved between them. How do they persist in the face of hybridization and gene flow? The challenge is more acute than ordinary ecological coexistence not only because gene flow erodes and recombines genetic differences, but also because selection against hybrids can destabilise population sizes. We estimated gene flow and selection against hybrid genotypes between sympatric limnetic and benthic species of threespine stickleback in two British Columbia lakes. First-generation hybrids are present at a rate of about 2%. To estimate selection, we compared the frequency distribution of ancestry proportions between juvenile and adult samples. We also used genomic simulation with assortative mating in an ecological model to determine how much selection is required to reproduce observed genotype frequencies. Results from the two approaches were comparable and yielded estimated selection coefficients S against the least fit ancestry proportion (within backcross range) between 0.5 and 0.6. Surprisingly, selection was found to be only slightly weaker than that leading readily to collapse and fusion in our simulations, suggesting that sympatric stickleback species are close to a coexistence boundary. Moderately strong selection appears to be required for coexistence with even low levels of gene flow. We suggest that larger niche differences are required to stabilise coexistence with gene flow than without gene flow. This helps to explain why successful sympatric species that hybridise often show conspicuous ecological and phenotypic differences.

  PublisherOA PDFDOI

Frequent coauthors

• Andreas Härer

  University of California, San Diego

  19 shared

• Seth M. Rudman

  Washington State University Vancouver

  16 shared

• Dolph Schluter

  University of British Columbia

  15 shared

• Gregory L. Owens

  University of Victoria

  15 shared

• Tim Vines

  12 shared

• Ken Thompson

  Stanford University

  12 shared

• Sébastien Renaut

  Université Laval

  10 shared

• Thor Veen

  Quest University Canada

  10 shared

Labs

• Rennison LabPI

Education

• PhD, Zoology

  University of British Columbia

  2016

• MSc, Biology

  University of Victoria

  2010

• BSc, Biology

  University of Victoria

  2008