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1. Taxon pulse dynamics, episodic dispersal and host colonization across Beringia drive diversification of a Holarctic tapeworm assemblage

   https://doi.org/10.1111/jbi.13949  

   Haas, Genevieve M. S. ; Hoberg, Eric P. ; Cook, Joseph A. ; Henttonen, Heikki ; Makarikov, Arseny A. ; Gallagher, Sarah R. ; Dokuchaev, Nikolai E. ; Galbreath, Kurt E. ( September 2020 , Journal of Biogeography)

   We test the predictions of the Stockholm Paradigm, a synthesis of eco‐evolutionary theory explaining the nature of faunal assembly, host range and parasite diversification. Faunal diversification and assembly, manifested in patterns of host colonization, co‐adaptation and parasite speciation, are predicted to emerge as a consequence of alternating episodes of ecological disruption and stability. Specifically, for a diverse cestode genus (Arostrilepis), we evaluate the number and direction of Pleistocene dispersal events across Beringia, the number and relative timing of host colonization events and the relationship between host and parasite biogeographic histories and associations through time.

   Beringia and adjacent temperate to arctic biomes in North America and Eurasia.

   Arostrilepis(Cyclophyllidea: Hymenolepididae) and its rodent hosts.

   Multi‐locus phylogenetic reconstruction and biogeographic ancestral range estimation.

   Arostrilepislineages crossed Beringia eastward into North America a minimum of four times and westward into Asia twice in association with temporally disjunct geographic expansions of three major tribes of cricetid rodents (Arvicolini, Myodini, Lemmini). Inferences of ancestral host associations support at least nine instances of host colonization involving shifts from one rodent tribe or family to another. Several previously unrecognized lineages ofArostrilepisare revealed.

   Consistent with expectations of the Stockholm Paradigm, episodes of intercontinental dispersal were both frequent in the history ofArostrilepisand preceded a majority of inferred host‐colonization events. Events of historical geographic expansion created numerous opportunities for development of novel host–parasite associations through ecological fitting, as parasites tracked historically conserved resources available across diverse host taxa. Beringia played a major role in shaping rodent/parasite assemblages by mediating dispersal between the northern continents during glacial episodes of the Pleistocene, rather than by serving as a zone of refugial isolation.

    

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2. 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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3. The influence of history, geography and environment on patterns of diversification in the western terrestrial garter snake

   https://doi.org/10.1111/jbi.14146  

   Hallas, Joshua M. ; Parchman, Thomas L. ; Feldman, Chris R. ( June 2021 , Journal of Biogeography)

   A central aim of biogeography is to understand how biodiversity is generated and maintained across landscapes. Here, we establish phylogenetic and population genetic patterns in a widespread reptile to quantify the influence of historical biogeography and current environmental variation on patterns of genetic diversity.

   Western North America.

   Western terrestrial garter snake,Thamnophis elegans.

   We used double‐digest RADseq to estimate phylogenetic relationships and characterize population genetic structure across the three widespread subspecies ofT. elegans:T. e. vagrans(wandering garter snake),T. e. elegans(mountain garter snake) andT. e. terrestris(coast garter snake). We assessed patterns of dispersal and vicariance across biogeographic regions using ancestral area reconstruction (AAR) and deviations from isolation‐by‐distance across the landscape using estimated effective migration surfaces (EEMS). We identified environmental variables potentially shaping local adaptation in regional lineages using genetic‐environment association (GEA) analyses.

   We recovered three well‐differentiated genetic groups that correspond to the three subspecies. AAR analyses inferred the eastern Cascade Range as the ancestral area, with dispersal to both the east and west across western North America. Populations ofT. e. elegansdisplayed a latitudinal gradient in genetic variation across the Sierra Nevada and northern California, while populations ofT. e. terrestrisshow discrete genetic breaks consistent with well‐known biogeographic barriers. Lastly, GEA analyses identified allele frequency shifts at loci associated with a common set of environmental variables in bothT. e. elegansandT. e. terrestris.

   T. elegansis composed of distinct evolutionary lineages, each with its own geographic range and history of diversification.T. e. elegansandT. e. terrestrisshow unique patterns of diversification as populations dispersed from east to west and while adapting to the new environments they colonized. Historical events, landscape features and environmental variation have all contributed to patterns of differentiation inT. elegans.

    

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4. Repeated patterns of reptile diversification in Western North America supported by the Northern Alligator Lizard ( Elgaria coerulea )

   https://doi.org/10.1093/jhered/esad073  

   Leaché, Adam D. ; Davis, Hayden R. ; Feldman, Chris R. ; Fujita, Matthew K. ; Singhal, Sonal ; Blair, ed., Christopher ( November 2023 , Journal of Heredity)

   Understanding the processes that shape genetic diversity by either promoting or preventing population divergence can help identify geographic areas that either facilitate or limit gene flow. Furthermore, broadly distributed species allow us to understand how biogeographic and ecogeographic transitions affect gene flow. We investigated these processes using genomic data in the Northern Alligator Lizard (Elgaria coerulea), which is widely distributed in Western North America across diverse ecoregions (California Floristic Province and Pacific Northwest) and mountain ranges (Sierra Nevada, Coastal Ranges, and Cascades). We collected single-nucleotide polymorphism data from 120 samples of E. coerulea. Biogeographic analyses of squamate reptiles with similar distributions have identified several shared diversification patterns that provide testable predictions for E. coerulea, including deep genetic divisions in the Sierra Nevada, demographic stability of southern populations, and recent post-Pleistocene expansion into the Pacific Northwest. We use genomic data to test these predictions by estimating the structure, connectivity, and phylogenetic history of populations. At least 10 distinct populations are supported, with mixed-ancestry individuals situated at most population boundaries. A species tree analysis provides strong support for the early divergence of populations in the Sierra Nevada Mountains and recent diversification into the Pacific Northwest. Admixture and migration analyses detect gene flow among populations in the Lower Cascades and Northern California, and a spatial analysis of gene flow identified significant barriers to gene flow across both the Sierra Nevada and Coast Ranges. The distribution of genetic diversity in E. coerulea is uneven, patchy, and interconnected at population boundaries. The biogeographic patterns seen in E. coerulea are consistent with predictions from co-distributed species.

    

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5. Spatial phylogenetics of Fagales: Investigating drivers of temperate forest distributions

   https://doi.org/10.1111/jbi.14840  

   Folk, R. A. ; Siniscalchi, C. M. ; Doby, J. ; Kates, H. R. ; Manchester, S. R. ; Soltis, P. S. ; Soltis, D. E. ; Guralnick, R. P. ; Belitz, M. ( April 2024 , Journal of Biogeography)

   Quantifying the phylogenetic diversity of temperate trees is essential for understanding the processes that have shaped the modern distribution of temperate broadleaf forest and other major forest biomes. Here, we focus on Fagales, an iconic member of forests worldwide, to uncover global diversity and endemism patterns and investigate the distribution of root nodule symbiosis (RNS), an important morphological specialisation in this clade, as a key factor behind these patterns.

   Global.

   Fagales.

   We combined phylogenetic data covering 60.2% of living species, fine‐scale distribution models covering 90% of species, and nodulation data covering all species to investigate the distribution of species richness and phylogenetic diversity at fine spatial scales compared to the distribution of RNS. We identify abiotic environmental factors associated with RNS and with Fagales diversity in general.

   We find the highest species richness in temperate east Asia, eastern North America, and equatorial montane regions of Asia and Central America. By contrast, relative phylogenetic diversity (RPD) is highest at higher latitudes, where RNS also predominates. We found a strong spatial structuring of regionalisations of Fagales floras, reflecting distinct Northern and Southern Hemisphere floras (except a unique Afro‐Boreal region), each with distinct RNS‐environment relationships.

   Although species richness and phylogenetic regionalisation for Fagales accord well with traditional biogeographic concepts for temperate forests, this is not the case for RPD. RNS is almost universal in the highest RPD regions, which may reflect ecological filtering promoting RNS in these regions. Our results highlight the utility of global‐scale, clade‐specific spatial phylogenetics and its utility for understanding drivers of diversity in species‐rich clades.

    

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