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Martin, Paul; Ghalambor, Cameron — 2022-12-15 <p><span lang="EN-US">Closely-related, ecologically-similar species often segregate their distributions along environmental gradients of time, space, and resources, but previous research suggests diverse underlying causes. Here, we review reciprocal removal studies in nature that experimentally test the role of interactions among species in determining their turnover along environmental gradients. We find consistent evidence for asymmetric exclusion coupled with differences in environmental tolerance causing the segregation of species pairs, where a dominant species excludes a subordinate from benign regions of the gradient, but is unable to tolerate challenging regions to which the subordinate species is adapted. Subordinate species were consistently smaller and performed better in regions of the gradient typically occupied by the dominant species compared to their native distribution. These results extend previous ideas contrasting competitive ability with adaptation to abiotic stress to include a broader diversity of species interactions (intraguild predation, reproductive interference) and environmental gradients, including gradients of biotic challenge. Collectively, these findings suggest that adaptation to environmental challenge compromises performance in antagonistic interactions with ecologically-similar species. The consistency of this pattern across diverse organisms, environments, and biomes suggests generalizable processes structuring the segregation of ecologically-similar species along disparate environmental gradients, a phenomenon that we propose should be named the Competitive exclusion – tolerance rule.</span></p>

Martin, Paul; Kenyon, Haley; Hayes, Leah — 2020-01-07 <p>Migrant species are commonly thought to be poor competitors in aggressive interactions with resident species. However, no studies have tested if this relationship is widespread. Here we compare the behavioural dominance of closely-related species of migratory and non-migratory birds, testing if migrants are consistently subordinate to resident species in aggressive contests. We compiled published behavioural dominance data involving migrant and resident congeners, gathering additional data on the body mass and migratory distance of each species. Focal species included a diverse array of birds (28 taxonomic families, 12 orders) from around the world. We found that migrant species are usually subordinate to resident species, but that this relationship disappears at larger body sizes. For smaller birds (&lt; 500g), resident species were behaviourally dominant in 83-88% of comparisons; for larger birds (&gt; 500g), resident species were dominant in only 25-30% of comparisons. The relative difference in body mass best predicted dominance relationships among species, with larger species dominant in 80-84% of comparisons. When migrant and resident masses were equal, however, resident species were still more likely to be dominant in smaller birds, suggesting that other factors may also contribute to the subordinate status of migrants. Overall, our results suggest that in smaller species, the evolution of migration is associated with lighter weights and other traits that compromise the competitive abilities of migrants relative to residents. In contrast, larger species appear able to evolve migration without compromising their size or competitive abilities in aggressive contests, suggesting size-dependent constraints on the evolution of migration.</p>

Collard, Allison; Wettlaufer, Jillian; Burke, Kevin; Beresford, David; Martin, Paul — 2020-09-25 <p>Body size is a key biological trait, influencing the biomechanics, physiology, behaviour, and ecology of species. Describing variation in body size within and among co-occurring species within an ecological guild can provide important context for understanding the ecology of species and the structure of ecological communities. Here, we focus on a guild of carrion beetles (Coleoptera: Silphidae) co-occurring in southeastern Ontario, Canada. We examine how body size varies (i) among species, (ii) within species, including among sexes, and (iii) across the active season, contrasting estimates of size based on mass with those based on morphological structure (elytron length). We find that body size varies significantly both within and among species. Five focal species show evidence for sexual dimorphism in size. All focal species show significant seasonal variation in size, but these patterns differ across species, and depend on our estimates of size. Overall, the observed variation in body size is most consistent with widespread environmental constraints on size and/or diverse selective pressures favouring different sizes within and among species. We discuss possible selective pressures acting on size within and among species; however, the causes and consequences of the variation in body size that we describe remain to be discovered.</p> https://creativecommons.org/publicdomain/zero/1.0/

Wettlaufer, Jillian; Burke, Kevin; Beresford, David; Martin, Paul — 2021-06-17 <p>The coexistence of ecologically similar species is thought to require resource partitioning to minimize competition. Phenological, seasonal differences in activity may provide an important axis for resource partitioning. Here, we test for evidence of seasonal differences in activity within a diverse guild of carrion beetles (Silphidae) in a habitat preserve on the Frontenac Arch, southeastern Ontario, Canada using a large-scale survey during their active seasons (April to October). We then used generalized additive models to test for differences in seasonal abundance among eight co-occurring carrion beetle species, including five species of burying beetles (Nicrophorinae: <i>Nicrophorus </i>Fabricius, 1775) and three species from the Silphinae subfamily. Consistent with previous work, all species showed seasonal variation in abundance, with peak abundance of most species occurring between June and August. All but one species (<i>Nicrophorus sayi </i>Laporte, 1840) showed positive relationships between abundance and temperature. We find evidence consistent with seasonal partitioning of resources among <i>Nicrophorus </i>habitat generalists that could potentially reduce competition for limited carrion resources. In contrast, we find little evidence for seasonal differences in abundance among <i>Nicrophorus </i>habitat specialists, which instead may partition resources spatially. Overall, our results provide evidence consistent with an important role for seasonal resource partitioning among carrion beetle species that show higher levels of spatial (habitat) overlap within a temperate beetle guild.</p>

Martin, Paul; Burke, Kevin; Bonier, Frances — 2020-08-20 <p>Habitat partitioning can facilitate the coexistence of closely related species, and often results from competitive interference inducing plastic shifts of subordinate species in response to aggressive, dominant species (plasticity), or the evolution of ecological differences in subordinate species that reduce their ability to occupy habitats where the dominant species occurs (evolutionary divergence). Evidence consistent with both plasticity and evolutionary divergence exist, but the relative contributions of each to habitat partitioning have been difficult to discern. Here we use a global dataset on the breeding occurrence of birds in cities to test predictions of these alternative hypotheses to explain previously described habitat partitioning associated with competitive interference. Consistent with plasticity, the presence of behaviorally dominant congeners in a city was associated with a 65% reduction in occurrence of subordinate species, but only when the dominant was a widespread breeder in urban habitats. Consistent with evolutionary divergence, increased range-wide overlap with dominant congeners was associated with a 56% reduction in occurrence of subordinates in cities, even when the dominant was absent from the city. Overall, our results suggest that both plasticity and evolutionary divergence play important, concurrent roles in habitat partitioning among closely related species in urban environments.</p>

Burke, Kevin; Wettlaufer, Jillian; Beresford, David; Martin, Paul — 2020-09-30 <p>The coexistence of closely related species plays an important role in shaping local diversity. However, competition for shared resources can limit the ability of species to coexist. Many species avoid the costs of coexistence by diverging in habitat use, known as habitat partitioning. We examine patterns of habitat use in seven co-occurring species of burying beetles (genus <em>Nicrophorus</em> Fabricius, 1775), testing the hypothesis that <em>Nicrophorus</em> species partition resources by occupying distinct habitats. We surveyed <em>Nicrophorus</em> abundance and 54 habitat characteristics at 100 random sites spanning an environmentally diverse region of southeastern Ontario, Canada. We found that three species occupied distinct habitat types consistent with habitat partitioning. Specifically, <em>Nicrophorus pustulatus</em> Herschel, 1807, <em>Nicrophorus hebes</em> Kirby, 1837, and <em>Nicrophorus marginatus</em> Fabricius, 1801 appear to be specialists for forest canopy, wetlands, and open fields, respectively. In contrast, <em>Nicrophorus orbicollis</em> Say, 1825, <em>Nicrophorus sayi</em> Laporte, 1840, and <em>Nicrophorus tomentosus</em> Weber, 1801 appear to be generalists with wide breadths of habitat use. We were unable to identify the habitat associations of <em>Nicrophorus defodiens</em> Mannerheim, 1846. Our findings are consistent with habitat acting as an important resource axis along which some <em>Nicrophorus </em>species partition; however, divergence along other resource axes (e.g., temporal partitioning) also appears important for <em>Nicrophorus</em> coexistence.</p>

Bouras, Emmanouil; Karhunen, Ville; Gill, Dipender; Huang, Jian; Haycock, Philip C.; Gunter, Marc J.; Johansson, Mattias; Brennan, Paul; Key, Tim; Lewis, Sarah J.; Martin, Richard M.; Murphy, Neil; Platz, Elizabeth A.; Travis, Ruth; Yarmolinsky, James; Zuber, Verena; Martin, Paul; Katsoulis, Michail; Freisling, Heinz; Nøst, Therese Haugdahl; Schulze, Matthias B.; Dossus, Laure; Hung, Rayjean J.; Amos, Christopher I.; Ahola-Olli, Ari; Palaniswamy, Saranya; Männikkö, Minna; Auvinen, Juha; Herzig, Karl-Heinz; Keinänen-Kiukaanniemi, Sirkka; Lehtimäki, Terho; Salomaa, Veikko; Raitakari, Olli; Salmi, Marko; Jalkanen, Sirpa; Jarvelin, Marjo-Riitta; Dehghan, Abbas; Tsilidis, Konstantinos K. — 2022 Additional file 2. (Supplemental Tables): Supplementary Table 1. Sources of GX instruments per cytokine &amp; genetic locus of cytokine. Supplementary Table 2. Genetic association estimates that were used in the MR analyses. Supplementary Table 3. Sources of GY instruments per cancer outcome. Supplementary Table 4. Genetic association estimates that were used in the MR analyses. Supplementary Table 5. Summary of the MR results based on the cis-pQTL instrument definition. Supplementary Table 6. Summary of the MR results based on the cis-eQTL instrument definition. Supplementary Table 7. Identification of druggable targets using publicly available repositories. Supplementary Table 8. Summary of epidemiological evidence linking prediagnostic cytokine concentrations to cancer risk. Supplementary Table 9. KeGG pathways in which significant cytokines are involved. Supplementary Table 10. Colocalization analysis. Supplementary Table 11a. Secondary cytokines associated with selected instruments, based on the gwas included in the study. Supplementary Table 11b. Secondary traits associated with selected instruments, based on a phenoscanner search. Supplementary Table 12a. Sensitivity analyses excluding potentially pleiotropic genetic variants. Supplementary Table 12b. Sensitivity analyses accounting for LD among genetic variants. Supplementary Table 13. Replication of the significant associations in the UK Biobank. https://creativecommons.org/licenses/by/4.0/legalcode