scholarly journals Can Differences in Symbiont Transmission Mode Explain the Abundance and Distribution of Fungus-Growing Termites in West Africa?

2020 ◽  
Vol 8 ◽  
Author(s):  
Judith Korb ◽  
Simon Kolotchèlèma Silué ◽  
N'golo Abdoulaye Koné
Keyword(s):  
Vertical Transmission ◽  
National Parks ◽  
Horizontal Transmission ◽  
Species Abundance ◽  
Transmission Mode ◽  
Termite Species ◽  
Symbiont Transmission ◽  
Ecological Dominance ◽  
Study Sites ◽  
Abundance And Distribution

Fungus-growing termites (Isoptera: Macrotermitinae) dominate African savannah ecosystems where they play important roles in ecosystem functioning. Their ecological dominance in these ecosystems has been attributed to living in an ectosymbiosis with fungi of the genus Termitomyces (Lyophyllaceae). Evolutionary theory predicts that the transmission mode of a symbiont determines cooperation and conflict between host and symbiont with vertical transmission (co-transmission of host and symbiont offspring to the next generation) leading to less conflict than horizontal transmission (symbionts are acquired by the host from the environment). Thus, one can hypothesize associations with vertical transmission to be ecological more successful than those with horizontal transmission. We tested this by analyzing whether there is an association between transmission mode and fungus-growing termite species abundance and distribution in West-African savannah and forest ecosystems. We used data from a total of 78 study sites comprising protected National Parks as well as anthropogenically disturbed ecosystems, covering Benin, Côte d'Ivoire, and Togo. Our results showed that, in contrast to expectation, species with horizontal symbiont transmission were more common. We encountered more often species with horizontal than vertical transmission. This result might be due to the fact that only five out of the 25 identified fungus-growing termite species had vertical transmission. Yet, species with horizontal transmission also had higher relative abundances within study sites than those with vertical transmission. Thus, transmission mode is unlikely to explain abundance differences between fungus-growing termite species.

scholarly journals Transmission mode is associated with environment type and taxa across bacteria-eukaryote symbioses

2018 ◽  
Author(s):  
Shelbi L Russell
Keyword(s):  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Transmission Mode ◽  
Symbiotic Associations ◽  
Transmission Modes ◽  
Symbiont Transmission ◽  
Environment Type ◽  
Full Separation ◽  
Host Evolution ◽  
Host Tissues

AbstractSymbiotic associations between bacteria and eukaryotes exhibit a range of transmission strategies. Anecdotal observations suggest that symbionts of terrestrial hosts tend to be strictly vertically inherited through host tissues, whereas symbionts of marine hosts tend towards horizontal transmission. Aside from a few cursory investigations, the rates and distributions of transmission modes have not been investigated in depth across associations, despite the consequences for symbiont and host evolution. To address this empirically and estimate the rate of each mode, I compiled data from the literature and for associations between transmission mode and the environment, transmission route, symbiont function, and taxa involved in the symbiosis. Of the 441 analyzed symbioses, 50.1% were strictly vertically transmitted, 34.0% exhibited some form of mixed mode transmission, and 15.9% were strictly horizontally transmitted. Binning symbioses by their environment revealed a significant skew towards vertical transmission on land and horizontal transmission in aquatic environments, with mixed modes abundant in both. However, host and symbiont taxa were not randomly distributed, which prevented the full separation of these variables. Overall, the data suggest that many symbiotic taxa are capable of horizontal transmission and barriers exist that reduce the rate of these events. Thus, both the environment type and host/symbiont taxa combined influence symbiont transmission mode evolution.One sentence summaryThrough an intensive analysis of the literature on symbiosis transmission modes, estimated rates for each transmission mode were calculated, revealing bias for horizontal transmission in the ocean and vertical transmission on land.

scholarly journals Evolution of symbiont transmission in conditional mutualisms in spatially and temporally variable environments

2020 ◽  
Author(s):  
Alexandra Brown ◽  
Erol Akçay
Keyword(s):  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Environmental Variation ◽  
Transmission Mode ◽  
Trade Off ◽  
Symbiotic Relationships ◽  
Physiological Constraints ◽  
Fitness Effects ◽  
Variable Environments ◽  
Symbiont Transmission

AbstractSymbiotic relationships affect the fitness and organismal function of virtually all organisms. In many cases, the fitness effects of symbiosis may be beneficial or harmful depending on the environment. The hosts of such symbionts are favored to acquire them only when the symbiont is beneficial. However, it is not clear whether such selection favors vertical or horizontal transmission, both, or neither. To address this question, we model the evolution of transmission mode in a conditional mutualism experiencing spatial and temporal environmental variation. We find that when symbionts affect host lifespan, but not fecundity, horizontal transmission can contain them to beneficial environments. Vertical transmission can produce symbiont containment when the environmental state is synchronized across locations. We also find an emergent trade-off between horizontal and vertical transmission, suggesting that physiological constraints are not required for the evolution of limits on the total amount of transmission.

scholarly journals Simulated folivory increases vertical transmission of fungal endophytes that deter herbivores and alter tolerance to herbivory in Poa autumnalis

2020 ◽  
Vol 125 (6) ◽  
pp. 981-991 ◽  
Author(s):  
Pedro E Gundel ◽  
Prudence Sun ◽  
Nikki D Charlton ◽  
Carolyn A Young ◽  
Tom E X Miller ◽  
...  
Keyword(s):  
Vertical Transmission ◽  
Transmission Rate ◽  
Horizontal Transmission ◽  
Fungal Endophytes ◽  
Natural Populations ◽  
Plant Tolerance ◽  
Hyphal Density ◽  
Symbiotic Fungi ◽  
Symbiont Transmission ◽  
Fitness Benefits

Abstract Background and Aims The processes that maintain variation in the prevalence of symbioses within host populations are not well understood. While the fitness benefits of symbiosis have clearly been shown to drive changes in symbiont prevalence, the rate of transmission has been less well studied. Many grasses host symbiotic fungi (Epichloë spp.), which can be transmitted vertically to seeds or horizontally via spores. These symbionts may protect plants against herbivores by producing alkaloids or by increasing tolerance to damage. Therefore, herbivory may be a key ecological factor that alters symbiont prevalence within host populations by affecting either symbiont benefits to host fitness or the symbiont transmission rate. Here, we addressed the following questions: Does symbiont presence modulate plant tolerance to herbivory? Does folivory increase symbiont vertical transmission to seeds or hyphal density in seedlings? Do plants with symbiont horizontal transmission have lower rates of vertical transmission than plants lacking horizontal transmission? Methods We studied the grass Poa autumnalis and its symbiotic fungi in the genus Epichloë. We measured plant fitness (survival, growth, reproduction) and symbiont transmission to seeds following simulated folivory in a 3-year common garden experiment and surveyed natural populations that varied in mode of symbiont transmission. Key Results Poa autumnalis hosted two Epichloë taxa, an undescribed vertically transmitted Epichloë sp. PauTG-1 and E. typhina subsp. poae with both vertical and horizontal transmission. Simulated folivory reduced plant survival, but endophyte presence increased tolerance to damage and boosted fitness. Folivory increased vertical transmission and hyphal density within seedlings, suggesting induced protection for progeny of damaged plants. Across natural populations, the prevalence of vertical transmission did not correlate with symbiont prevalence or differ with mode of transmission. Conclusions Herbivory not only mediated the reproductive fitness benefits of symbiosis, but also promoted symbiosis prevalence by increasing vertical transmission of the fungus to the next generation. Our results reveal a new mechanism by which herbivores could influence the prevalence of microbial symbionts in host populations.

scholarly journals Avifauna in Relation to Habitat Disturbance in Wildlife Management Areas of the Ruvuma Miombo Ecosystem, Southern Tanzania

2021 ◽  
Author(s):  
Ally K. Nkwabi ◽  
John K. Bukombe ◽  
Hamza K. Kija ◽  
Steven D. Liseki ◽  
Sood A. Ndimuligo ◽  
...  
Keyword(s):  
Wildlife Management ◽  
Species Abundance ◽  
Habitat Types ◽  
Point Count ◽  
Riverine Forest ◽  
Study Sites ◽  
Prompt Action ◽  
Abundance And Distribution ◽  
Open Woodland ◽  
Wildlife Management Areas

Understanding of relative distribution of avifauna provides insights for the conservation and management of wildlife in the community managed areas. This study examined relative diversity, abundance, and distribution of avifauna in selected habitat types across five Wildlife Management Areas of the Ruvuma landscape in miombo vegetation, southern Tanzania. Five habitat types were surveyed during the study: farmland, swamps, riverine forest, dense and open woodland. Transect lines, mist-netting, and point count methods were used to document 156 species of birds in the study sites. Descriptive statistics and Kruskal-Wallis tests were used to compare species richness and diversity across habitat types. We found differences in avifaunal species distribution in the study area whereby farmland had the highest abundance of avifauna species and lowest in the riverine forest. These results suggest that variations of avifauna species abundance, diversity, and distribution could be attributed by human activities across habitat types; due to the reason that habitats with less human encroachment had good species diversity and richness. Therefore, to improve avitourism and avoid local extinction of species, we urge for prompt action to mitigate species loss by creating awareness in the adjacent community through conservation education on the importance of protecting such biodiversity resources.

scholarly journals Evolution of transmission mode in conditional mutualisms with spatial variation in symbiont quality

2018 ◽  
Author(s):  
Alexandra Brown ◽  
Erol Akçay
Keyword(s):  
Environmental Factors ◽  
Spatial Variation ◽  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Environmental Context ◽  
Transmission Mode ◽  
Costs And Benefits ◽  
Low Frequencies ◽  
High Frequencies ◽  
Conditional Effect

AbstractWhile some symbioses are always mutualistic or parasitic, others have costs and benefits that depend on environmental factors. The environmental context may itself vary in space, in some cases causing a symbiont to be a mutualist in one location and a parasite in another. Such spatially conditional mutualisms pose a dilemma for hosts, who might evolve (higher or lower) horizontal or vertical transmission to increase their chances of being infected only where the symbiont is beneficial. To determine how transmission in hosts might evolve, we modeled transmission evolution where the symbiont had a spatially conditional effect on either host lifespan or fecundity. We found that over ecological time, symbionts that affected lifespan but not fecundity led to high frequencies of infected hosts in areas where the symbiont was beneficial and low frequencies elsewhere. In response, hosts evolved increased horizontal transmission only when the symbiont affected lifespan. We also modeled transmission evolution in symbionts, which evolved high horizontal and vertical transmission, indicating a possible host-symbiont conflict over transmission mode. Our results suggest an eco-evolutionary feedback where the component of host fitness that a conditionally mutualistic symbiont influences affects its distribution in the population, and, through this, the transmission mode that evolves.

scholarly journals Phylogenetic analysis suggests joint control of transmission mode in a grass-endophyte symbiosis

2016 ◽  
Author(s):  
Alexandra Brown ◽  
Erol Akçay
Keyword(s):  
Phylogenetic Analysis ◽  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Model System ◽  
Transmission Mode ◽  
Joint Control ◽  
Grass Endophyte ◽  
Host Phylogeny

AbstractHow symbionts are transmitted between hosts is key to determining whether symbioses evolve to be harmful or beneficial. Vertical transmission favors mutualistic symbionts, and horizontal transmission more virulent ones. Transmission mode evolution itself depends on whether the host or symbiont can respond to selection on transmission mode. When hosts control the transmission mode, vertical transmission should evolve under more restrictive circumstances than when symbionts are in control. We take a phylogenetic approach to determine whether the host, symbiont, or both control transmission mode using the pooid grass-epichloid endophyte symbiosis as a model system. This study is the first to investigate control of transmission mode evolution in a phylogenetic context. We find a signal of host phylogeny but only in conjunction with symbiont identity. This pattern suggests joint control of transmission mode by the host and symbiont. It also suggests that non-genetic or non-conserved symbiont traits may determine whether host traits lead to vertical or horizontal transmission.

scholarly journals An agent-based model of adaptation of holobionts with different microbial symbiont transmission modes

2020 ◽  
Author(s):  
Siao Ye ◽  
Zhu Liu ◽  
Evan Siemann
Keyword(s):  
Abiotic Stress ◽  
Stress Tolerance ◽  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Agent Based Model ◽  
Agent Based ◽  
Transmission Modes ◽  
Microbial Symbiont ◽  
Symbiont Transmission ◽  
Microbial Symbionts

ABSTRACTThe hologenome theory suggests that holobionts (host plus symbiont) with hosts that are only able to adapt slowly may be able to persist in deteriorating environmental conditions via rapid adaptation of their microbial symbionts. The effectiveness of such symbiont adaptation may vary depending on whether symbionts are passed directly to offspring (vertical transmission) or acquired from the environment (horizontal transmission). However, it has been suggested that holobionts with horizontal transmission cannot pass down their symbionts faithfully, preventing adaptation at the holobiont level because of host-symbiont disassociation between generations. Here we used an agent-based model to investigate whether holobionts with horizontal microbial symbiont transmission can adapt to increasing stress solely through symbiont adaptation and compared their adaptation to holobionts with vertical transmission. We found that holobionts with either transmission mode were able to adapt to increasing abiotic stress solely via symbiont adaptation. Moreover, those with horizontal transmission were more competitive than those with vertical transmission when hosts were able to selectively associate with the most suitable symbionts. However, those with horizontal transmission were less competitive than those with vertical transmission when symbiont establishment was random. Our results support the hologenome theory and demonstrate that holobionts with horizontal microbial symbiont transmission could adapt to increasing abiotic stress via their symbionts. We also showed that whether holobionts with horizontal or vertical symbiont transmission are favored in increasingly stressful conditions depends on the ability of hosts to recognize and foster microbial symbionts that confer stress tolerance.IMPORTANCESymbiotic organisms such as reef building corals are sensitive to environmental perturbations due to anthropogenic disturbances or climate change, and it is critical to understand whether they are able to adapt to previously unfavorable conditions. To date, studies have focused on the impacts of existing microbial symbiont variation on holobiont stress tolerance but here we use agent-based models to explore holobiont adaptation via symbiont adaptation. We studied both deterministic and stochastic processes in holobiont adaptation by investigating the following four factors: holobiont transmission modes, a host’s ability to recognize tolerance-conferring symbionts, a symbiont’s mutational variance, and rate of stress increase. Our simulation provides a comprehensive understanding of holobiont adaptation under stress, which not only has implications for future endangered symbiotic species management, but also provides fresh insight into species evolution as proposed by the hologenome theory.

scholarly journals Evolution of early male-killing in horizontally transmitted parasites

2015 ◽  
Vol 282 (1818) ◽  
pp. 20152068 ◽  
Author(s):  
Veronika Bernhauerová ◽  
Luděk Berec ◽  
Daniel Maxin
Keyword(s):  
Empirical Evidence ◽  
Vertical Transmission ◽  
Bacterial Strain ◽  
Horizontal Transmission ◽  
Distinct Species ◽  
High Efficacy ◽  
Infected Male ◽  
Male Killing ◽  
Wide Range ◽  
Male Killer

Early male-killing (MK) bacteria are vertically transmitted reproductive parasites which kill male offspring that inherit them. Whereas their incidence is well documented, characteristics allowing originally non-MK bacteria to gradually evolve MK ability remain unclear. We show that horizontal transmission is a mechanism enabling vertically transmitted bacteria to evolve fully efficient MK under a wide range of host and parasite characteristics, especially when the efficacy of vertical transmission is high. We also show that an almost 100% vertically transmitted and 100% effective male-killer may evolve from a purely horizontally transmitted non-MK ancestor, and that a 100% efficient male-killer can form a stable coexistence only with a non-MK bacterial strain. Our findings are in line with the empirical evidence on current MK bacteria, explain their high efficacy in killing infected male embryos and their variability within and across insect taxa, and suggest that they may have evolved independently in phylogenetically distinct species.

scholarly journals Managed and Unmanaged Pinus sylvestris Forest Stands Harbour Similar Diversity and Composition of the Phyllosphere and Soil Fungi

2020 ◽  
Vol 8 (2) ◽  
pp. 259 ◽  
Author(s):  
Jūratė Lynikienė ◽  
Diana Marčiulynienė ◽  
Adas Marčiulynas ◽  
Artūras Gedminas ◽  
Miglė Vaičiukynė ◽  
...  
Keyword(s):  
Pinus Sylvestris ◽  
National Parks ◽  
High Throughput Sequencing ◽  
Fungal Communities ◽  
Rrna Gene ◽  
Sequencing Analysis ◽  
Forest Stands ◽  
Forest Zone ◽  
The North ◽  
Study Sites

The aim was to assess fungal communities associated with living needles and soil of Pinus sylvestris in managed and unmanaged forest stands to get a better understanding of whether and how different intensities of forest management affects fungal diversity and community composition under the north temperate forest zone conditions. The study was carried out in three national parks in Lithuania. Each included five study sites in managed stands and five in unmanaged stands. At each site, three random soil cores and five random last-year needle samples were collected. Following DNA isolation, a DNA fragment of the ITS2 rRNA gene region of each sample was individually amplified and subjected to high-throughput sequencing. Analysis of 195,808 high-quality reads showed the presence of 1909 fungal taxa. Richness and composition of fungal taxa were similar in each substrate (needles and soil) in managed vs. unmanaged sites. The most common fungi in needles were Coleosporium campanulae (12.4% of all fungal sequences), Unidentified sp. 3980_1 (12.4%), Unidentified sp. 3980_4 (4.1%) and Sydowia polyspora (3.1%). In soil: Unidentified sp. 3980_21 (8.6%), Umbelopsis nana (8.2%), Archaeorhizomyces sp. 3980_5 (8.1%) and Penicillium spinulosum (6.3%). The results demonstrated that managed and unmanaged P. sylvestris stands support similar diversity and composition of fungal communities associated with living needles and soil.

scholarly journals Observation of asexual reproduction with symbiont transmission in planktonic foraminifera

2020 ◽  
Vol 42 (4) ◽  
pp. 403-410 ◽  
Author(s):  
Haruka Takagi ◽  
Atsushi Kurasawa ◽  
Katsunori Kimoto
Keyword(s):  
Life Cycle ◽  
Sexual Reproduction ◽  
Vertical Transmission ◽  
Asexual Reproduction ◽  
Planktonic Foraminifera ◽  
Gamete Release ◽  
Symbiotic Algae ◽  
Laboratory Cultures ◽  
Symbiont Transmission

Abstract Gamete release has been frequently observed in laboratory cultures of various species of planktonic foraminifera. Those observations have been taken as evidence that these organisms produce new generations exclusively by sexual reproduction. We report here the first observation of asexual reproduction in Globigerinita uvula, a small, microperforate foraminifera. The asexual phase was associated with the release of ca. 110 offspring, all of which hosted symbiotic algae that must have been passed on directly from the parent. This event was also the first observation of vertical transmission of symbionts in planktonic foraminifera. Although the trigger of the observed asexual reproduction and its frequency in nature remain unknown, our observation indicates that among the planktonic foraminifera, at least G. uvula has not abandoned the asexual phase of its life cycle.

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