Mycorrhizal Switching and the Role of Fungal Abundance in Seed Germination in a Fully Mycoheterotrophic Orchid, Gastrodia confusoides

Mycorrhizal associations are essential for orchid germination and seedling establishment, and thus may constrain the distribution and abundance of orchids under natural conditions. Previous studies have shown that germination and seedling establishment in several orchids often decline with increasing distance from adult plants, resulting in non-random spatial patterns of seedling establishment. In contrast, individuals of the fully mycoheterotrophic orchid Gastrodia confusoides often tend to have random aboveground spatial patterns of distribution within bamboo forests. Since G. confusoides is parasitic on litter-decaying fungi, its random spatial patterns of distribution may be due to highly scattered patterns of litter-decaying fungi within bamboo forests. To test this hypothesis, we first identified the main mycorrhizal fungi associating with developing seeds and adult plants at a bamboo forest site in Taiwan using Miseq high-throughput DNA sequencing. Next, we combined seed germination experiments with quantitative PCR (qPCR) analyses to investigate to what extent the abundance of mycorrhizal fungi affected spatial patterns of seed germination. Our results show that seed germination and subsequent growth to an adult stage in G. confusoides required a distinct switch in mycorrhizal partners, in which protocorms associated with a single Mycena OTU, while adults mainly associated with an OTU from the genus Gymnopus. A strong, positive relationship was observed between germination and Mycena abundance in the litter, but not between germination and Gymnopus abundance. Fungal abundance was not significantly related to the distance from the adult plants, and consequently germination was also not significantly related to the distance from adult plants. Our results provide the first evidence that the abundance of litter-decaying fungi varies randomly within the bamboo forest and independently from G. confusoides adults.

Toward Empowering Conversational Agency in Aphasia: Understanding Mechanisms of Topic Initiation in People With and Without Aphasia

Purpose: This study examined topic initiation (TI) in conversations involving people with aphasia (PWA), matched people without aphasia (M-PWoA), and speech-language pathologists who were their conversation partners (SLP-Ps). For each speaker type, we analyzed patterns of distribution of typical mechanisms of TI and patterns of simultaneous use of multiple TI mechanisms. Lastly, we examined associations between use of simultaneous TI mechanisms and communicative success. Method: Twenty PWA and 20 M-PWoA each participated in two conversations with SLP-Ps. Conversation samples were analyzed for TI locations and mechanisms, with results tallied for each speaker type following a published typology. A measure of communicative success was applied to TI utterances. Rank-order correlations were conducted to evaluate the patterns of distribution of the TI mechanisms between speaker types and the patterns of multiple mechanism usage between speaker types. Descriptive analysis was conducted to provide additional insight to the TI behaviors of each speaker type and to evaluate the relationship between multiple TI mechanisms and communicative success. Results: All speaker types used cohesion most often to achieve TI. PWA used an abrupt method of TI (noncoherent TI) more often than other speaker types. A single mechanism of TI was used most often by all speaker types, except for SLP-Ps when they were in conversations with PWA. In this case, SLP-Ps most often used two or more layered mechanisms of TI. SLP-Ps also used a highly salient TI mechanism with greater frequency when speaking with PWA than observed between other speaker types. When PWA layered mechanisms of TI, they appeared to be more likely to achieve better communicative success. Conclusions: Specific, teachable behaviors such as favoring certain TI mechanisms and using multiple TI mechanisms may improve communicative success during TI for PWA. Furthermore, findings suggest that SLP-Ps modify their TI behaviors when speaking to PWA. Supplemental Material: https://doi.org/10.23641/asha.17699423

Better Alone Than in Bad Company: New Species of Caudofoveate Limifossorid (Mollusca, Aplacophora) Unravels Patterns of Distribution Hidden in the Deep Atlantic

Aplacophorans are common inhabitants of the deep-sea, where many places remain unexplored regarding their biodiversity. Filling a gap in knowledge about these animals from the South Atlantic, Scutopus variabilis sp. nov. (Caudofoveata, Limifossoridae) is described; further, species distribution modelling (SDM) was performed to elucidate the distribution patterns of Atlantic species of Scutopus. The type materials of S. megaradulatusSalvini-Plawen (1972) and S. chilensisSalvini-Plawen (1972), were examined and a search was performed for specimens of Scutopus held in museum collections. Scutopus variabilis sp. nov. has a slender and highly variable body form and a very distinct suture line is present midventrally. Two dominant types of trunk sclerites were observed by Scanning Electron Microscopy (SEM): one elongated with lateral margins slightly concave in medial portion, and another longer, with narrower base; its radula bears up to eight rows of heavily sclerotized teeth bearing 12–16 small denticles. The species occurs in a wide bathymetric range (40–1300 m), being more abundant at the edge between the continental shelf and upper slope. Outside the areas from where these samples were obtained, suitable areas for S. variabilis sp. nov. were found in the Southern Caribbean Sea (from where S. megaradulatus is recorded) and in the Brazilian Northern coast; the Gulf of Mexico and the Brazilian Northeastern coasts were found as unsuitable. Species of Scutopus appear to exhibit different patterns of geographical distribution: the European S. ventrolineatusSalvini-Plawen (1968) and S. robustusSalvini-Plawen (1970) are known as widely distributed, while non-European representants, the American S. megaradulatus, S. chilensis and S. variabilis sp. nov., and the Japanese S. schanderiSaito and Salvini-Plawen (2014) and S. hamatamiiSaito and Salvini-Plawen (2014) have more restricted distributions. However, clear and definite patterns of distribution of some of these species are probably blurred by sampling bias, for the European area is better studied. In the Atlantic, the SDM showed that species of Scutopus occur in a way that overlapping is minimized. Great sampling efforts combined with detailed descriptions based on SEM have revealed an interesting, abundant and up to now undescribed Brazilian deep-sea malacofauna.

Redes de pendularidade estudantil dos polos sub-regionais do interior de Minas Gerais

<p>No interior do estado de Minas, o crescimento total bruto de matrículas no ensino superior, entre 1991 e 2010, foi de 371,82%, relativamente maior do que o nacional (309,41%). Cabe, portanto, uma análise sobre as formas de polarização e as características da mobilidade pendular de estudantes na rede de centros regionais no estado. Neste artigo, avaliam-se os fluxos e os padrões de distribuição das redes de pendularidade de estudantes entre os centros regionais do interior do estado de Minas Gerais, tendo como base os dados do Censo Demográfico de 2010. Foram analisados os movimentos de pendularidade de estudantes de vinte e dois centros considerados de alta centralidade, aqui denominados sub-regionais. A interpretação foi elaborada por meio da avaliação das redes de distribuição espacial, conjugada com a mensuração de indicadores como a Distância Média ponderada (DMp) e a Razão de pendularidade escolar (RPe), o que permitiu a distinção dos movimentos estudantil e laboral. Os resultados indicam a magnitude de deslocamentos intrarregionais e maior abrangência espacial de polarização de cinco sub-centros regionais. Quinze municípios apresentaram RPe maior que um, ou seja, possuem a prevalência na atração da pendularidade estudantil, o que mostra a relevância do papel das instituições de ensino na atração populacional.</p><p><span>Abstract</span></p><p>NETWORKS OF STUDENTS’ PENDULAR MOVEMENTS FOR THE SUBREGIONAL POLES OF THE COUNTRYSIDE OF MINAS GERAIS</p><p>In the countryside of Minas Gerais state (MG), the absolute growth in the period between 1991 and 2010 was of 371,82%, which is a bit higher than the National growth (309,41%). Such context raises questions about the forms of polarization and the students’ pendular fluxes between regional centres. In this article I evaluate these fluxes and the patterns of distribution of the networks of students’ pendular motion among the regional centres of the countryside of MG based on the data of the Demographic Census of 2010. I analysed students’ pendular movements from 22 centres located in the exact centre of the state, which I named “subregionals” for the purposes of this paper. My interpretation was built through the evaluation of the networks of spatial distribution compared with the measurement of the Average Weighed Distance (DMp in Portuguese) and with the Rate of Students’ Pendular Movements (RPe in Portuguese), which allowed me to distinguish between the students’ and workers’ movements. The results I obtained reveal the magnitude of the interregional movements and a higher spatial encompassment of the polarization of five regional centres, seats of Federal Universities. Fifteen municipalities have shown an RPe higher than 1, which means they present a prevalence of students’ pendular movements, revealing the importance of theeducational institutions’ role in the spatial dynamics of the population.</p>

Seasonal use of bridges as day-roosts by bats in the Trans-Pecos of Texas

Bats commonly use highway infrastructure as day- or night-roosts. Nonetheless, little is known regarding how regularly bats use these structures or whether they do so only on a seasonal basis. We surveyed 13 parallel box beam bridges along 15 km of State Highway 17 in Jeff Davis County, Texas monthly for 12 months to examine seasonality of day-roost use. Bats using bridges, ranked based on abundance, were: Tadarida brasiliensis, Myotis velifer, M. californicus/ciliolabrum, M. yumanensis, Antrozous pallidus, and M. thysanodes. Myotis velifer, M. californicus/ciliolabrum, and M. yumanensis exhibited significant differences among bridges and significant seasonality in roost use. Tadarida brasiliensis exhibited significant differences among bridges but no significant seasonality of bridge use. Seasonality of use of bridges as day-roosts likely reflects seasonal patterns of distribution of species in the Trans-Pecos. Moreover, these results suggest that surveys of bats roosting in highway infrastructure should be planned carefully and consider the seasonal nature of roost use

Increasing fungal abundance in the substrate enhances seed germination in a fully mycoheterotrophic orchid

Mycorrhizal associations are essential for orchid germination and seedling establishment, and thus may constrain the distribution and abundance of orchids under natural conditions. Previous works have shown that germination and seedling establishment in several orchids often decline with increasing distance from adult plants, resulting in nonrandom spatial patterns of seedling establishment. In contrast, individuals of the fully mycoheterotrophic orchid Gastrodia confusoides often tend to have random spatial patterns of distribution within bamboo forests. Since G. confusoides is parasitic on litter-decaying fungi, its random spatial patterns of distribution may be due to highly scattered patterns of litter-decaying fungi within bamboo forests. To test this hypothesis, we first identified the main mycorrhizal fungi associating with developing seeds and adult plants using Miseq high-throughput sequencing. Next, we combined seed germination experiments with quantitative PCR (qPCR) analyses to investigate to what extent the abundance of mycorrhizal fungi affected spatial patterns of seed germination. Our results show that seed germination and subsequent growth to an adult stage in G. confusoides required a distinct switch in mycorrhizal partners, in which protocorms associated with a single Mycena fungus, while adults associated with a fungus from the genus Gymnopus. A strong, positive relationship was observed between germination and Mycena abundance in the litter, but not between germination and Gymnopus abundance. Fungal abundance was not significantly related to the distance from the adult plants, and consequently germination was also not significantly related to the distance from adult plants. Our results provide the first evidence that the spatial distribution and abundance of litter-decaying fungi are distributed randomly within the bamboo forest and independently from G. confusoides adults.

THE CHILD POPULATION OF BELARUS AND THE SPECIFICS OF ITS GEOGRAPHICAL DISTRIBUTION

В статье рассмотрены основные закономерности распределения детей до 16 лет по регионам Беларуси по результатам переписи населения 2019 г. Сделан вывод о том, что на размещение детей в регионах Беларуси определяющее влияние оказывают центр-периферийные процессы. Концентрация детей в районах центрального типа (экономического ядра) в последние годы растёт более высокими темпами, чем концентрация в них всего населения страны и, вероятно, эта тенденция сохранится в будущем. В размещении детей в Беларуси выявлен также градиент север-юг. В этом направлении заметно увеличивается доля детей до 16 лет и снижается уровень регрессивности возрастной структуры населения. Это свидетельство того, что регионы Белорусского Подвинья имеют наиболее сложную демографическую ситуацию, которая в обозримой перспективе будет только ухудшаться. The article considers the main patterns of distribution of children under 16 years of age in the regions of Belarus according to the results of the 2019 census. It is concluded that the placement of children in the regions of Belarus is determined by the center-peripheral processes. The concentration of children in the central type (economic core) areas has been growing at a higher rate in recent years than the concentration of the entire population in them, and this trend is likely to continue in the future. A north-south gradient has also been identified in the placement of children in Belarus. In this direction, the proportion of children under 16 years of age is significantly increasing and the level of demographic aging of the population is decreasing. This is evidence that the regions of the Belarusian Podvinya region have the most difficult demographic situation, which will only worsen in the foreseeable future.