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1. Niche conservatism over deep timescales and diverse niche axes in land vertebrates

   https://doi.org/10.1111/geb.13715  

   Saban, Kristen E. ; Qu, Yan‐Fu ; Wiens, John J. ( June 2023 , Global Ecology and Biogeography)

   There has been considerable interest in niche conservatism, the idea that ecological variables are similar among related species. Much research has focused on climatic niches of recently diverged species, rather than deeper timescales or non‐climatic niche axes. Furthermore, it has been suggested that conservatism disappears over deeper timescales, and is greater in alpha niche traits (like diet and microhabitat) than beta niche variables (like climate). Here, we test these latter two ideas by comparing patterns of phylogenetic conservatism among 10 niche variables across major clades of land vertebrates.

   Global.

   Present to 350 million years ago.

   Tetrapods, including amphibians, mammals, lepidosaurs (including lizards and snakes), turtles, crocodilians and birds.

   The 10 niche variables included four alpha niche components (diet, diel activity, habitat, body temperature) and six beta niche components (related to climatic temperature and precipitation). We analysed these variables on time‐calibrated phylogenies with similar taxon sampling (~1700 species), using phylogenetic signal (lambda) to estimate conservatism, along with theDstatistic and estimates of evolutionary rates.

   Phylogenetic signal was generally strong across all variables, with lambda generally >0.80 (with 1.0 representing maximum signal). Nevertheless, mean phylogenetic signal was lower in beta niche traits than alpha niche traits (based on lambda and especially theDstatistic), and alpha niche traits showed significantly slower rates of evolution.

   We address two long‐held views in the literature on niche conservatism, rejecting one but supporting the other. We show that phylogenetic signal does not disappear over deep timescales for many important niche variables, even over 350 million years. We also generally support greater conservatism in alpha niche traits than beta niche traits over hundreds of millions of years, a pattern that was previously suggested (but not explicitly tested) based on closely related species.

    

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2. Have Niche, Will Travel. New Means of Linking Diet and Ecomorphology Reveals Niche Conservatism in Freshwater Cottoid Fishes

   https://doi.org/10.1093/iob/obz023  

   Buser, T J ; Finnegan, D L ; Summers, A P ; Kolmann, M A ( January 2019 , Integrative Organismal Biology)

   Synopsis Evolutionary transitions between habitats have been catalysts for some of the most stunning examples of adaptive diversification, with novel niches and new resources providing ecological opportunity for such radiations. In aquatic animals, transitions from saltwater to freshwater habitats are rare, but occur often enough that in the Neotropics for example, marine-derived fishes contribute noticeably to regional ichthyofaunal diversity. Here, we investigate how morphology has evolved in a group of temperate fishes that contain a marine to freshwater transition: the sculpins (Percomorpha; Cottoidea). We devised a novel method for classifying dietary niche and relating functional aspects of prey to their predators. Coupled with functional measurements of the jaw apparatus in cottoids, we explored whether freshwater sculpins have fundamentally changed their niche after invading freshwater (niche lability) or if they retain a niche similar to their marine cousins (niche conservatism). Freshwater sculpins exhibit both phylogeographical and ecological signals of phylogenetic niche conservatism, meaning that regardless of habitat, sculpins fill similar niche roles in either saltwater or freshwater. Rather than competition guiding niche conservatism in freshwater cottoids, we argue that strong intrinsic constraints on morphological and ecological evolution are at play, contra to other studies of diversification in marine-derived freshwater fishes. However, several intertidal and subtidal sculpins as well as several pelagic freshwater species from Lake Baikal show remarkable departures from the typical sculpin bauplan. Our method of prey categorization provides an explicit, quantitative means of classifying dietary niche for macroevolutionary studies, rather than relying on somewhat arbitrary means used in previous literature. 

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3. What explains patterns of species richness? The relative importance of climatic‐niche evolution, morphological evolution, and ecological limits in salamanders

   https://doi.org/10.1002/ece3.2301  

   Kozak, Kenneth_H ; Wiens, John_J ( July 2016 , Ecology and Evolution)

   A major goal of evolutionary biology and ecology is to understand why species richness varies among clades. Previous studies have suggested that variation in richness among clades might be related to variation in rates of morphological evolution among clades (e.g., body size and shape). Other studies have suggested that richness patterns might be related to variation in rates of climatic‐niche evolution. However, few studies, if any, have tested the relative importance of these variables in explaining patterns of richness among clades. Here, we test their relative importance among major clades of Plethodontidae, the most species‐rich family of salamanders. Earlier studies have suggested that climatic‐niche evolution explains patterns of diversification among plethodontid clades, whereas rates of morphological evolution do not. A subsequent study stated that rates of morphological evolution instead explained patterns of species richness among plethodontid clades (along with “ecological limits” on richness of clades, leading to saturation of clades with species, given limited resources). However, they did not consider climatic‐niche evolution. Using phylogenetic multiple regression, we show that rates of climatic‐niche evolution explain most variation in richness among plethodontid clades, whereas rates of morphological evolution do not. We find little evidence that ecological limits explain patterns of richness among plethodontid clades. We also test whether rates of morphological and climatic‐niche evolution are correlated, and find that they are not. Overall, our results help explain richness patterns in a major amphibian group and provide possibly the first test of the relative importance of climatic niches and morphological evolution in explaining diversity patterns.

    

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4. Stable isotopes reveal limited Eltonian niche conservatism across carnivore populations

   https://doi.org/10.1111/1365-2435.13266  

   Manlick, Philip J. ; Petersen, Shelby M. ; Moriarty, Katie M. ; Pauli, Jonathan N. ; McArthur, ed., Clare ( January 2019 , Functional Ecology)

   Niche conservatism—the retention of ecological traits across space and time—is an emerging topic of interest because it can predict responses to global change. The conservation of Grinnellian niche characteristics, like species‐habitat associations, has received widespread attention, but the conservation of Eltonian traits such as consumer–resource interactions remains poorly understood.

   The inability to quantify Eltonian niches through space and time has historically limited the assessment of Eltonian niche conservatism and the dynamics of foraging across populations. Consequently, the relative influence of endogenous factors like phylogeny versus exogenous features like environmental context has rarely been addressed.

   We tested Eltonian niche conservatism using a paired design to compare foraging among four populations of American martensMartes americanaand Pacific martensMartes caurina, morphologically and ecologically similar sister taxa that are allopatrically distributed throughout western North America. We developed a three‐stage isotopic framework and then quantified dietary niche overlap between the sister species and paired island‐mainland sites to assess the relative influence of endogenous (i.e., species) versus exogenous (i.e., environment) factors on Eltonian niches. First, we calculated pairwise dietary overlap in scaled δ‐space using standard ellipses. We then estimated proportional diets (“p‐space”) for individuals using isotopic mixing models and developed a novel utilization distribution overlap approach to quantify proportional dietary overlap. Lastly, we estimated population‐level proportional diets and quantified the differential use of functional prey groups across sites.

   We detected no pairwise overlap of dietary niches in δ‐space, and distributions of individual diets in p‐space revealed little overlap in core diets across populations. All pairwise comparisons of individuals revealed significant differences in diet, and population‐level comparisons detected contrasting use of functional prey groups.

   We developed a multi‐faceted isotopic framework to quantify Eltonian niches and found limited evidence of Eltonian niche conservatism across carnivore populations. Our findings are consistent with the growing recognition of dietary plasticity in consumers and suggest that consumer–resource dynamics are largely driven by exogenous environmental factors like land cover and community composition. These results illustrate the context‐dependent nature of foraging and indicate consumer functionality can be dynamic.

   Aplain language summaryis available for this article.

    

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5. Trait evolution rates shape continental patterns of species richness in North America's most diverse angiosperm genus ( Carex , Cyperaceae)

   https://doi.org/10.1111/jse.12739  

   Pender, Jocelyn_E ; Hipp, Andrew_L ; Hahn, Marlene ; Starr, Julian_R ( July 2021 , Journal of Systematics and Evolution)

   Ecological opportunity has been associated with increases in diversification rates across the tree of life. Under an ecological diversification model, the emergence of novel environments is hypothesized to promote morpho‐ and ecospace evolution. Whether this model holds at the clade level within the most species‐rich angiosperm genus found in North America (Carex, Cyperaceae) is yet to be tested. Recent works demonstrate a temporal coupling of climate cooling and widespread colonization ofCarexin North America, implicating ecological diversification. In addition, research has consistently found asymmetric patterns of lineage‐level diversification in the genus. Why does variation in clade sizes exist in the genus? Is ecological diversification involved? In this study, we tested whether rates of morphological and ecological trait evolution are correlated with clade‐level species richness inCarexof North America north of Mexico. We constructed a phylogeny of 477 species—an almost complete regional sample. We estimated rates of evolution of morphological traits, habitat, and climatic niche and assessed whether differences in rates of evolution correlate with species richness differences in replicate non‐nested sister clades. Our work demonstrates significant positive correlations between climatic niche rates, habitat and reproductive morphological evolution, and species richness. This coupling of trait and niche evolution and species richness in a diverse, continental clade sample strongly suggests that the ability of clades to explore niche and functional space has shaped disparities in richness and functional diversity across the North American flora region. Our findings highlight the importance of the evolutionary history of trait and niche evolution in shaping continental and regional floras.

    

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