Phylogenetic species recognition and hybridisation in Lasiodiplodia : a case study on species from baobabs

Lasiodiplodia species (Botryosphaeriaceae, Ascomycota) infect a wide range of typically woody plants on which they are associated with many different disease symptoms. In this study, we determined the identity of Lasiodiplodia isolates obtained from baobab (Adansonia species) trees in Africa and reviewed the molecular markers used to describe Lasiodiplodia species. Publicly available and newly produced sequence data for some of the type strains of Lasiodiplodia species showed incongruence amongst phylogenies of five nuclear loci. We conclude that several of the previously described Lasiodiplodia species are hybrids of other species. Isolates from baobab trees in Africa included nine species of Lasiodiplodia and two hybrid species. Inoculation trials with the most common Lasiodiplodia species collected from these trees produced significant lesions on young baobab trees. There was also variation in aggressiveness amongst isolates from the same species. The apparently widespread tendency of Lasiodiplodia species to hybridise demands that phylogenies from multiple loci (more than two and preferably four or more) are compared for congruence prior to new species being described. This will avoid hybrids being incorrectly described as new taxa, as has clearly occurred in the past.Members of the Tree Protection Co-operative Programme (TPCP), the NRF-DST Centre of Excellence in Tree Health Biotechnology (CTHB), and the University of Pretoria, South Africa.http://www.elsevier.com/locate/funbio2018-04-30Plant ScienceForestry and Agricultural Biotechnology Institute (FABI)Genetic

Fungi associated with black mould on baobab trees in southern Africa

There have been numerous reports in the scientific and popular literature suggesting that African baobab (Adansonia digitata) trees are dying, with symptoms including a black mould on their bark. The aim of this study was to determine the identity of the fungi causing this black mould and to consider whether they might be affecting the health of trees. The fungi were identified by sequencing directly from mycelium on the infected tissue as well as from cultures on agar. Sequence data for the ITS region of the rDNA resulted in the identification of four fungi including Aureobasidium pullulans, Toxicocladosporium irritans and a new species of Rachicladosporium described here as Rachicladosporium africanum. A single isolate of an unknown Cladosporium sp. was also found. These fungi, referred to here as black mould, are not true sooty mould fungi and they were shown to penetrate below the bark of infected tissue, causing a distinct host reaction. Although infections can lead to dieback of small twigs on severely infected branches, the mould was not found to kill trees.Members of the Tree Protection Co-operative Programme (TPCP), the NRF-DST Centre of Excellence in Tree Health Biotechnology (CTHB), and the University of Pretoria, South Africa.http://link.springer.com/journal/104822016-05-03hb201

Three new Graphium species from baobab trees in South Africa and Madagascar

Baobabs (Adansonia spp.) are iconic trees, known for their immense size, strange forms, sources of food and as the subjects of myths and mysteries. It is thus surprising that little is known regarding the fungi that infect these trees. During a survey to determine which wound infecting fungi occur on baobabs, synnematous structures were observed and Graphium-like isolates were obtained. Culture characteristics and micro-morphology, together with DNA sequence comparisons for the SSU rRNA, rRNA-ITS and TEF-1α gene regions were used to characterise these fungi. These data revealed three novel Graphium spp. and these are described as G. adansoniae, G. madagascariense and G. fabiforme.National Research Foundation (NRF), Tree Protection Co-operative Programme (TPCP), THRIP initiative of the Department of Trade and Industry (DTI

Highly transferable microsatellite markers for the genera Lasiodiplodia and Neofusicoccum

Population genetic studies play an integral role in understanding the ecology and management of fungal plant pathogens. Such studies for species of Botryosphaeriaceae are hampered by a lack of available markers. Genomic sequences are available for multiple species in this family and they provide excellent resources for the development of population genetic markers. Here we describe highly transferable microsatellite or simple sequence repeat (SSR) markers for species in Lasiodiplodia and Neofusicoccum; two important and globally distributed members of the Botryosphaeriaceae. These were developed by extracting SSR-containing sequences from available genomes. Seventy-seven markers were developed for Lasiodiplodia and 32 markers were developed for Neofusicoccum. Most of these markers were transferable between species within a genus. Twelve markers tested for fragment length polymorphism in 20 isolates of Lasiodiplodia mahajangana identified between two and nine alleles and gene diversities between 0.18 and 0.83. Eleven markers indicated between two and five alleles for 20 isolates of Neofusicoccum parvum and gene diversities between 0.26 and 0.57. The large number and high transferability of the developed markers will facilitate population studies of a wide range of Lasiodiplodia and Neofusicoccum species associated with tree diseases globally.The University of Pretoria, The Department of Science and Technology (DST) / National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology and members of the Tree Protection Cooperative Program.http://www.elsevier.com/locate/funeco2021-04-01hj2020BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

Table_2_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.xlsx

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p

Image_3_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.pdf

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p

Image_1_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.pdf

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p

Table_3_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.docx

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p

Image_2_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.pdf

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p

Data_Sheet_1_Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects.docx

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”</p