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1. Consequences of biodiversity shift across phylogenetic scales for aspen and willow growth, survival, and herbivory

   https://doi.org/10.1111/jvs.12716  

   Grossman, Jake J. ; Cavender‐Bares, Jeannine ; Bruun, ed., Hans Henrik ( March 2019 , Journal of Vegetation Science)

   It has been established that community biodiversity has consequences for ecosystem function. Yet research assessing these biodiversity–ecosystem function (BEF) relationships usually occurs at only one phylogenetic scale; as such, the dependence ofBEFrelationships on phylogenetic scale has not been characterized. We present a novel framework for considering the consequences of biodiversity across phylogenetic scales, allowing us to ask: Do the consequences of intraspecific and interspecific diversity affect the growth, survival, and leaf herbivory of three temperate tree species?

   Salicaceous tree plantation, Minnesota, northern USA.

   We established an experimental plantation consisting of trees of three species within the willow (Salicaceae) family. Two aspen (Populus tremuloides,P. alba) and one willow (Salix nigra) species were represented by three unique genotypes such that tree neighborhoods varied both in genotype richness (intraspecific diversity) and species richness (interspecific diversity). We assessed the consequences of tree identity and diversity across these two phylogenetic scales for all trees’ aboveground productivity and survival, and for herbivore damage (onP. tremuloides) at the end of the second full growing season of the experiment.

   Diversity at any phylogenetic scale had no effect on the growth and survival ofP. albaorS. nigra. However, intraspecific diversity increased the likelihood ofP. tremuloidessurvival while interspecific diversity reducedP. tremuloidessurvival. Intraspecific diversity also reduced leaf removal and galling herbivory onP. tremuloides, while interspecific diversity had no effect on leaf removal and increased galling herbivory. Neither scale of diversity affected leaf mining.

   Tree diversity within and among populations and species affected plant performance and ecosystem properties differentially, demonstrating thatBEFrelationships shift across phylogenetic scales in a taxon‐specific manner. We call for further experiments that explicitly span these scales by measuring ecosystem and physiological responses to the manipulation of diversity within and among species.

    

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2. Extensive interlineage hybridization in the predominantly clonal Hydrilla verticillata

   https://doi.org/10.1002/ajb2.1392  

   Benoit, Lori K. ; Les, Donald H. ; King, Ursula M. ; Na, Hye Ryun ; Chen, Lei ; Tippery, Nicholas P. ( November 2019 , American Journal of Botany)

   The submersed aquatic plantHydrilla verticillata(“hydrilla”) is important ecologically and economically due to its aggressive growth in both indigenous and nonindigenous regions. Substantial morphological variation has been documented in hydrilla, including the existence of monoecious and dioecious “biotypes.” Whereas plastid sequence data have been used previously to explore intraspecific diversity, nuclear data have yet to be analyzed in a phylogenetic context. Molecular and morphological analyses were used to evaluate the genetic diversity and phylogenetic relationships of native and introduced populations.

   Nuclear (internal transcribed spacer—ITS; phytoene desaturase—PDS) and plastid (trnL‐F) sequence data were evaluated phylogenetically using likelihood and Bayesian methods. Leaf morphologies were compared among clades that were identified in phylogenetic analyses.

   Data from bothITSandPDSshow multiple instances of polymorphic sequences that could be traced to two or more lineages, including both invasive biotypes in the Americas. Leaf morphological data support the distinctness of lineages and provide a metric for distinguishing monoecious and dioecious biotypes in the United States.

   Nuclear molecular data indicate far greater genetic diversity than could be estimated using plastid markers. Substantially divergent copies of nuclear genes, found in multiple populations worldwide, likely result from interlineage hybridization. Invasive monoecious and dioecious hydrilla biotypes in the Americas are genetically distinct, with both biotypes resulting from admixture among Eurasian progenitors. Genetic similarity to populations in India and South Korea, respectively, implicates these as likely origins for the dioecious and monoecious biotypes.

    

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3. Radial growth response to climate change along the latitudinal range of the world's southernmost conifer in southern South America

   https://doi.org/10.1111/jbi.13199  

   Holz, Andrés ; Hart, Sarah J. ; Williamson, Grant J. ; Veblen, Thomas T. ; Aravena, Juan C. ( March 2018 , Journal of Biogeography)

   We examined whether and how tree radial‐growth responses to climate have changed for the world's southernmost conifer species throughout its latitudinal distribution following rapid climate change in the second half of the 20th century.

   Temperate forests in southern South America.

   New and existing tree‐ring radial growth chronologies representing the entire latitudinal range ofPilgerodendron uviferumwere grouped according to latitude and then examined for differences in growth trends and non‐stationarity in growth responses to a drought severity index (scPDSI) over the 1900–1993ADperiod and also before and after significant shifts in climate in the 1950s and 1970s.

   The radial‐growth response ofP. uviferumclimate was highly variable across its full latitudinal distribution. There was a long‐term and positive association between radial growth and higher moisture at the northern and southern edges of the distribution of this species and the opposite relationship for the core of its distribution, especially following the climatic shifts of the 1950s and 1970s. In addition, non‐stationarity in moisture‐radial growth relationships was observed in all three latitudinal groups (southern and northern edges and core) for all seasons during the 20th century.

   Climate shifts in southern South America in the 1950s and 1970s resulted in different responses in the mean radial growth ofP. uviferumat the southern and northern edges and at the core of its range. Dendroclimatic analyses document that during the first half of the 20th century climate‐growth relationships were relatively similar between the southern and northern range edges but diverged after the 1950s. Our findings imply that simulated projections of climate impacts on tree growth, and by implication on forest ecosystem productivity, derived from models of past climate‐growth relationships need to carefully consider different and non‐stationarity responses along the wide latitudinal distribution of this species.

    

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4. Contrasting effects of host tree isolation on population connectedness in two tropical epiphytic bromeliads

   https://doi.org/10.1002/ajb2.1391  

   Amici, Autumn A. ; Nadkarni, Nalini M. ; DiBlasi, Emily ; Seger, Jon ( December 2019 , American Journal of Botany)

   Conversion of primary forests to pastures is a major cause of habitat fragmentation in the tropics. Fragmentation is expected to impede gene flow for many plant species that are restricted to remaining forest fragments. Epiphytes may be especially vulnerable to this effect of forest fragmentation because they depend on host trees. However, trees that remain in pastures may enhance connectivity across the landscape for epiphyte species that can thrive on such trees. To investigate this possibility, we studied the genetic structures of two such species on isolated pasture trees and surrounding forest, in relation to their local abundances in different habitat types and aspects of their reproductive biology including pollen and seed dispersal agents, and looked for evidence of increased or diminished gene flow.

   We used microsatellite markers to assess geographic patterns of genetic diversity and differentiation in two epiphytic bromeliads,Catopsis nitidaandWerauhia tonduziana,in the Monteverde region of Costa Rica.

   About 85% of theF_STvalue forCatopsis nitidawas found among pastures within regions, while forWeruahia tonduziana,about 80% of theF_STvalue was contributed by differences between regions, indicating much more gene flow within regions, relative toC. nitida.

   Although there was substantial genetic differentiation among epiphyte populations, those on isolated pasture trees were not substantially less diverse than those in adjacent forests, suggesting that pasture trees may serve as “stepping stones” that help these species maintain their genetic connectedness and diversity at larger geographic scales.

    

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5. Lowland tapirs facilitate seed dispersal in degraded Amazonian forests

   https://doi.org/10.1111/btp.12627  

   Paolucci, Lucas N. ; Pereira, Rogério L. ; Rattis, Ludmila ; Silvério, Divino V. ; Marques, Nubia C. S. ; Macedo, Marcia N. ; Brando, Paulo M. ( February 2019 , Biotropica)

   The forests of southeastern Amazonia are highly threatened by disturbances such as fragmentation, understory fires, and extreme climatic events. Large‐bodied frugivores such as the lowland tapir (Tapirus terrestris) have the potential to offset this process, supporting natural forest regeneration by dispersing a variety of seeds over long distances to disturbed forests. However, we know little about their effectiveness as seed dispersers in degraded forest landscapes. Here, we investigate the seed dispersal function of lowland tapirs in Amazonian forests subject to a range of human (fire and fragmentation) and natural (extreme droughts and windstorms) disturbances, using a combination of field observations, camera traps, and light detection and ranging (LiDAR) data. Tapirs travel and defecate more often in degraded forests, dispersing much more seeds in these areas [9,822 seeds per ha/year (CI_95% = 9,106; 11,838)] than in undisturbed forests [2,950 seeds per ha/year (CI_95% = 2,961; 3,771)]. By effectively dispersing seeds across disturbed forests, tapirs may contribute to natural forest regeneration—the cheapest and usually the most feasible way to achieve large‐scale restoration of tropical forests. Through the dispersal of large‐seeded species that eventually become large trees, such frugivores also contribute indirectly to maintaining forest carbon stocks. These functions may be critical in helping tropical countries to achieve their goals to maintain and restore biodiversity and its ecosystem services. Ultimately, preserving these animals along with their habitats may help in the process of natural recovery of degraded forests throughout the tropics.

   Abstract in Portuguese is available with online material.

    

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