More Like this

1. Mechanisms of community assembly explaining beta‐diversity patterns across biogeographic regions

   https://doi.org/10.1111/jvs.13032  

   Muñoz Mazón, Miguel ; Tello, J. Sebastián ; Macía, Manuel J. ; Myers, Jonathan A. ; Jørgensen, Peter M. ; Cala, Victoria ; Fuentes, Alfredo F. ; Torrez, Vania ; Arellano, Gabriel ; Price, ed., Jodi ( May 2021 , Journal of Vegetation Science)

   We examined tree beta diversity in four biogeographical regions with contrasting environmental conditions, latitude, and diversity. We tested: (a) the influence of the species pool on beta diversity; (b) the relative contribution of niche‐based and dispersal‐based assembly to beta diversity; and (c) differences in the importance of these two assembly mechanisms in regions with differing productivity and species richness.

   Lowland and montane tropical forests in the Madidi region (Bolivia), lowland temperate forests in the Ozarks (USA), and montane temperate forests in the Cantabrian Mountains (Spain).

   We surveyed woody plants with a diameter ≥2.5 cm following a standardized protocol in 236 0.1‐ha forest plots in four different biogeographical regions. We estimated the species pool at each region and used it to recreate null communities determined entirely by the species pool. Observed patterns of beta diversity smaller or greater than the null‐expected patterns of beta diversity implies the presence of local assembly mechanisms beyond the influence of the species pool. We used variation‐partitioning analyses to compare the contribution of niche‐based and dispersal‐based assembly to patterns of observed beta diversity and their deviations from null models among the four regions.

   (a) Differences in species pools alone did not explain observed differences in beta diversity among biogeographic regions. (b) In 3/4 regions, the environment explained more of the variation in beta diversity than spatial variables. (c) Spatial variables explained more of the beta diversity in more diverse and more productive regions with more rare species (tropical and lower‐elevation regions) compared to less diverse and less productive regions (temperate and higher‐elevation regions). (d) Greater alpha or gamma diversity did not result in higher beta diversity or stronger correlations with the environment.

   Overall, the observed differences in beta diversity are better explained by differences in community assembly mechanism than by biogeographical processes that shaped the species pool.

    

   more » « less
2. Integrating historical biogeography and environmental niche evolution to understand the geographic distribution of Datureae

   https://doi.org/10.1002/ajb2.1281  

   Dupin, Julia ; Smith, Stacey D. ( May 2019 , American Journal of Botany)

   The distributions of plant clades are shaped by abiotic and biotic factors as well as historical aspects such as center of origin. Dispersals between distant areas may lead to niche evolution when lineages are established in new environments. Alternatively, dispersing lineages may exhibit niche conservatism, moving between areas with similar environmental conditions. Here we test these contrasting hypotheses in the Datureae clade (Solanaceae).

   We used maximum likelihood methods to estimate the ancestral range of Datureae along with the history of biogeographic events. We then characterized the niche of each taxon using climatic and soil variables and tested for shifts in environmental niche optima. Finally, we examined how these shifts relate to the niche breadth of taxa and clades within Datureae and the degree of overlap between them.

   Datureae originated in the Andes and subsequently expanded its range to North America and non‐Andean regions of South America. The ancestral niche, and that of mostDaturaandTrompettiaspecies, is dry, whileBrugmansiaspecies likely shifted toward a more mesic environment. Nonetheless, most Datureae present moderate to high overlap in niche breadth today.

   The expansion of Datureae into North America was associated with niche conservatism, with dispersal into similarly dry areas as occupied by the ancestral lineage. Subsequent niche evolution, including the apparent shift to a mesic niche inBrugmansia, diversified the range of habitats occupied by species in the tribe Datureae but also led to significant niche overlap among the three genera.

    

   more » « less
3. Fine‐scale environmental heterogeneity and spatial niche partitioning among spring‐flowering forest herbs

   https://doi.org/10.1002/ajb2.1593  

   Beck, Jared J. ; Givnish, Thomas J. ( January 2021 , American Journal of Botany)

   Environmental heterogeneity influences plant distributions and diversity at several spatial scales. In temperate forests, fine‐scale environmental variation may promote local coexistence among herbaceous species by allowing plants to spatially partition microsites within forest stands. Here we argue that shallow soils, low soil water‐holding capacity and fertility, and reduced light near tree boles should favor short, shallow‐rooted, evergreen species likeAnemone acutilobawith low moisture, nutrient, and light requirements. Farther from trees, richer, deeper soils should favor taller, deeper‐rooted herbs with greater moisture and nutrient demands, such asSanguinaria canadensisandTrillium flexipes.

   We tested these hypotheses by mapping the fine‐scale distributions ofAnemone,Sanguinaria, andTrilliumindividuals within a 50 × 50 m plot, comparing local species’ distributions with respect to soil depth and proximity to neighboring trees, and characterizing intraspecific and interspecific spatial associations.

   Local plant distributions were consistent with our predictions based on leaf height, physiology, and phenology.Anemonewas found in microsites on shallower soils and closer to trees than eitherSanguinariaorTrillium. In all three species, individual plants were spatially aggregated within 2 m, but spatially segregated from individuals of the other species beyond 2 m.

   Differential plant responses to fine‐scale environmental heterogeneity and observed spatial associations suggest that local species‐environment associations could facilitate coexistence. These findings illustrate how fine‐scale environmental heterogeneity coupled with phenological and physiological differences likely contribute to spatial niche partitioning among spring‐flowering forest herbs and maintain high local plant diversity within temperate forests.

    

   more » « less
4. Arctic chironomids of the northwest North Atlantic reflect environmental and biogeographic gradients

   https://doi.org/10.1111/jbi.14015  

   Medeiros, Andrew S. ; Milošević, Đurađ ; Francis, Donna R. ; Maddison, Eleanor ; Woodroffe, Sarah ; Long, Antony ; Walker, Ian R. ; Hamerlík, Ladislav ; Quinlan, Roberto ; Langdon, Peter ; et al ( November 2020 , Journal of Biogeography)

   While we understand broad climate drivers of insect distributions throughout the Arctic, less is known about the role of spatial processes in determining these relationships. As such, there is a need to understand how spatial controls may influence our interpretations of chironomid environment relationships. Here, we evaluated whether the distribution of chironomids followed spatial gradients, or were primarily controlled by environmental factors.

   Eastern Canadian Arctic, Greenland, Iceland.

   Non‐biting midges (Chironomidae).

   We examined chironomid assemblages from 239 lakes in the western North Atlantic Arctic region (specifically from the Arctic Archipelago of Canada, two parts of west Greenland (the southwest and central west) and northwest Iceland). We used a combination of unconstrained ordination (Self Organizing Maps); a simple method with only one data matrix (community data), and constrained ordination (Redundancy Analysis); a canonical ordination with two datasets where we extracted structure of community related to environmental data. These methods allowed us to model chironomid assemblages across a large bioregional dimension and identify specific differences between regions that were defined by common taxa represented across all regions in high frequencies, as well as rare taxa distinctive to each region found in low frequencies. We then evaluated the relative importance of spatial processes versus local environmental factors.

   We find that environmental controls explained the largest amount of variation in chironomid assemblages within each region, and that spatial controls are only significant when crossing between regions. Broad‐scale biogeographic effects on chironomid distributions are reflected by the distinct differences among chironomid assemblages of Iceland, central‐west Greenland, and eastern Canada, defined by the presence of certain common and low‐frequency, rare taxa for each region. Environmental gradients, especially temperature, defined species distributions within each region, whereas spatial processes combine with environmental gradients in determining what mix of species characterizes each broad and geographically distinct island region in our study.

   While biogeographic context is important for defining interpretations of environmental controls on species distributions, the primary control on distributions within regions is environmental. These influences are fundamentally important for reconstructing past environmental change and better understanding historical distributions of these insect indicators.

    

   more » « less
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.

    

   more » « less