More Like this

1. A pangenome analysis reveals the center of origin and evolutionary history of Phytophthora infestans and 1c clade species

   https://doi.org/10.1371/journal.pone.0314509  

   Coomber, Allison L; Saville, Amanda C; Carbone, Ignazio; Martin, Michael; Bieker, Vanessa C; Ristaino, Jean Beagle (January 2025, PLOS ONE)

   Blair, Jaime E (Ed.)

   We examined the evolutionary history ofPhytophthora infestansand its close relatives in the 1c clade. We used whole genome sequence data from 69 isolates ofPhytophthoraspecies in the 1c clade and conducted a range of genomic analyses including nucleotide diversity evaluation, maximum likelihood trees, network assessment, time to most recent common ancestor and migration analysis. We consistently identified distinct and later divergence of the two MexicanPhytophthoraspecies,P.mirabilisandP.ipomoeae, fromP.infestansand other 1c clade species.Phytophthora infestansexhibited more recent divergence from other 1c clade species ofPhytophthorafrom South America,P.andinaandP.betacei. Speciation in the 1c clade and evolution ofP.infestansoccurred in the Andes.P.andina–P.betacei–P.infestansformed a species complex with indistinct species boundaries, hybridizations between the species, and short times to common ancestry. Furthermore, the distinction between modern Mexican and South AmericanP.infestansproved less discrete, suggesting gene flow between populations over time. Admixture analysis indicated a complex relationship among these populations, hinting at potential gene flow across these regions. HistoricP.infestans, collected from 1845–1889, were the first to diverge from all otherP.infestanspopulations. Modern South American populations diverged next followed by Mexican populations which showed later ancestry. Both populations were derived from historicP.infestans. Based on the time of divergence ofP.infestansfrom its closest relatives,P.andinaandP.betaceiin the Andean region, we consider the Andes to be the center of origin ofP.infestans, with modern globalization contributing to admixture betweenP.infestanspopulations today from Mexico, the Andes and Europe. 

   more » « less
2. Bounding p-Brauer characters in finite groups with two conjugacy classes of p-elements

   https://doi.org/10.1007/s11856-024-2613-1  

   Hung, Nguyen Ngoc; Sambale, Benjamin; Tiep, Pham Huu (September 2024, Israel Journal of Mathematics)

   Abstract Letk(B₀) andl(B₀) respectively denote the number of ordinary andp-Brauer irreducible characters in the principal blockB₀of a finite groupG. We prove that, ifk(B₀)−l(B₀) = 1, thenl(B₀) ≥p− 1 or elsep= 11 andl(B₀) = 9. This follows from a more general result that for every finite groupGin which all non-trivialp-elements are conjugate,l(B₀) ≥p− 1 or elsep= 11 and$$G/{{\bf{O}}_{{p^\prime }}}(G) \cong C_{11}^2\, \rtimes\,{\rm{SL}}(2,5)$$ $G/O_{p^{\prime }}\left(G\right)\cong C_{11}^2⋊\text{SL}(2,5)$. These results are useful in the study of principal blocks with few characters. We propose that, in every finite groupGof order divisible byp, the number of irreducible Brauer characters in the principalp-block ofGis always at least$$2\sqrt {p - 1} + 1 - {k_p}(G)$$ $2\sqrt{p-1}+1-k_p\left(G\right)$, wherek_p(G) is the number of conjugacy classes ofp-elements ofG. This indeed is a consequence of the celebrated Alperin weight conjecture and known results on bounding the number ofp-regular classes in finite groups. 

   more » « less
3. Relationship between local-scale topography and vegetation on the invasive C ₄ perennial bunchgrass buffelgrass ( Pennisetum ciliare ) size and reproduction

   https://doi.org/10.1017/inp.2023.9  

   Hovanes, Katherine A.; Lien, Aaron M.; Baldwin, Elizabeth; Li, Yue M.; Franklin, Kim; Gornish, Elise S. (March 2023, Invasive Plant Science and Management)

   Abstract Buffelgrass [Pennisetum ciliare(L.) Link] is an invasive C₄perennial bunchgrass that is a threat to biodiversity in aridlands in the Americas and Australia. Topography influencesP. ciliareoccurrence at large spatial scales, but further investigation into the relationship between local-scale topography andP. ciliaregrowth and reproduction would be beneficial. Further, density-dependent effects onP. ciliaregrowth and reproduction have been demonstrated in greenhouse experiments, but the extent to which density dependence influencesP. ciliarein natural populations warrants further investigation. Here we present a study on the relationships between local-scale topography (aspect and slope gradient) and vegetation characteristics (shrub cover,P. ciliarecover, andP. ciliaredensity) and their interactions on individualP. ciliareplant size and reproduction. We measured slope gradient, aspect, shrub cover,P. ciliarecover,P. ciliaredensity, and the total number of live culms and reproductive culms of 10P. ciliareplants in 33 4 by 4 m plots located in 11 transects at the Desert Laboratory at Tumamoc Hill, Tucson, AZ, USA. We modeled the relationships at the local scale of (1)P. ciliarecover and density with aspect and slope gradient and (2)P. ciliaresize and reproduction with abiotic (slope gradient and aspect) and biotic (P. ciliarecover and density and native shrub and cacti cover) characteristics. Aspect and slope gradient were poor predictors ofP. ciliarecover and density in already invaded sites at the scale of our plots. However, aspect had a significant relationship withP. ciliareplant size and reproduction.Pennisetum ciliareplants on south-facing aspects were larger and produced more reproductive culms than plants on other aspects. Further, we found no relationship betweenP. ciliaredensity andP. ciliareplant size and reproduction. Shrub cover was positively correlated withP. ciliarereproduction. South-facing aspects are likely most vulnerable to fast spread and infilling by newP. ciliareintroductions. 

   more » « less
4. Synergistic effects of canopy chemistry and autogenic soil biota on a global invader

   https://doi.org/10.1111/1365-2745.14113  

   Majumdar, Sudipto; Kaur, Harleen; Rinella, Matthew J.; Kundu, Anish; Vadassery, Jyothilakshmi; Erbilgin, Nadir; Callaway, Ragan M.; Cadotte, Marc W.; Inderjit (July 2023, Journal of Ecology)

   Abstract Soil biota have strong effects on plants, but we have a poor understanding of how plant chemistry might modify these effects. We examined the effect of soil biota associated with an exotic invasive tree,Prosopis juliflora, versus that associated with native species, from seven sites across India on conspecifics and two other plant species. We then measured changes in species‐specific soil biota effects (identified as plant–soil feedbacks, PSFs) when leaf leachate fromP. julifloraor from native plant species was added to soil containing respective live and sterile soil inoculum.We quantified the amino acid L‐tryptophan from leaf leachate ofP. juliflora,Leucaena leucocephala(another invader), and two native species. We also tested effects ofP. julifloraor native species soil inoculum amendment of tryptophan onP. juliflora,P. cinerariaandL. leucocephalaacross seven sites. We then quantified the microbially metabolized derivatives of tryptophan, phytohormone indole‐3‐acetic acid (IAA) and intermediates after adding tryptophan intoP. julifloraand native soils.Soil biota associated withP. julifloragenerated positive effects on conspecifics andL. leucocephala, but negative effects on the native congenerP. cineraria. WhenP. julifloraleaf leachate was added to soil with liveP. juliflorainoculum, PSFs became more positive forP. julifloraand other species, compared to leaf leachate amended with sterile soil inoculum. Native leaf leachate interacted weakly with soil biota to impact biomass of conspecifics and heterospecifics.There was roughly 10× more tryptophan in the leaf leachate ofP. juliflorathan in the leaf leachate of other species. Tryptophan generally increased positive PSFs associated withP. juliflorarelative to soil biota associated with other plant species. When tryptophan was added to liveP. juliflorasoil, IAA and its intermediates were produced at five of seven sites, and at four of these sites soil biota fromP. juliflorahad positive PSFs.Synthesis. These results provide the first experimental evidence that a chemical leached from the leaves of an invader regulates PSFs. Our results indicate that canopy effects and PSFs, which are usually studied independently, can interact in ways that strongly affect conspecifics and neighbouring species. 

   more » « less
5. Statistics of Energy in Isothermal Supersonic Turbulence

   https://doi.org/10.3847/1538-4357/ad5008  

   Rabatin, Branislav; Collins, David C (July 2024, The Astrophysical Journal)

   Abstract Supersonic isothermal turbulence is a common process in astrophysical systems. In this work, we explore the energy in such systems. We show that the conserved energy is the sum of the kinetic energy (K) and Helmholtz free energy (F). We develop analytic predictions for the probability distributions,P(F) andP(K), as well as their nontrivial joint distribution,P(F,K). We verify these predictions with a suite of driven turbulence simulations, finding excellent agreement. The turbulence simulations were performed at Mach numbers ranging from 1 to 8, and three modes of driving: purely solenoidal, purely compressive, and mixed. We find thatP(F) is discontinuous atF= 0, with the discontinuity increasing with Mach number and compressive driving.P(K) resembles a lognormal with a negative skew. The joint distribution,P(F,K), shows a bimodal distribution, with gas either existing at highFand highKor at lowFand lowK. 

   more » « less