Defaunation, the loss or population decline of medium and large native vertebrates represents a significant threat to the biodiversity of tropical ecosystems. Here we review the anthropogenic drivers ...of defaunation, provide a brief historical account of the development of this field, and analyze the types of biological consequences of this impact on the structure and functioning of tropical ecosystems. We identify how defaunation, operating at a variety of scales, from the plot to the global level, affects biological systems along a gradient of processes ranging from plant physiology (vegetative and reproductive performance) and animal behavior (movement, foraging and dietary patterns) in the immediate term; to plant population and community dynamics and structure leading to disruptions of ecosystem functioning (and thus degrading environmental services) in the short to medium term; to evolutionary changes (phenotypic changes and population genetic structure) in the long-term. We present such a synthesis as a preamble to a series of papers that provide a compilation of our current understanding of the impact and consequences of tropical defaunation. We close by identifying some of the most urgent needs and perspectives that warrant further study to improve our understanding of this field, as we confront the challenges of living in a defaunated world.
Is Biomass a Reliable Estimate of Plant Fitness? Younginger, Brett S; Sirová, Dagmara; Cruzan, Mitchell B ...
Applications in plant sciences,
2017-February, February 2017, 2017-Feb, 2017-02-00, 20170201, Volume:
5, Issue:
2
Journal Article
Peer reviewed
Open access
The measurement of fitness is critical to biological research. Although the determination of fitness for some organisms may be relatively straightforward under controlled conditions, it is often a ...difficult or nearly impossible task in nature. Plants are no exception. The potential for long-distance pollen dispersal, likelihood of multiple reproductive events per inflorescence, varying degrees of reproductive growth in perennials, and asexual reproduction all confound accurate fitness measurements. For these reasons, biomass is frequently used as a proxy for plant fitness. However, the suitability of indirect fitness measurements such as plant size is rarely evaluated. This review outlines the important associations between plant performance, fecundity, and fitness. We make a case for the reliability of biomass as an estimate of fitness when comparing conspecifics of the same age class. We reviewed 170 studies on plant fitness and discuss the metrics commonly employed for fitness estimations. We find that biomass or growth rate are frequently used and often positively associated with fecundity, which in turn suggests greater overall fitness. Our results support the utility of biomass as an appropriate surrogate for fitness under many circumstances, and suggest that additional fitness measures should be reported along with biomass or growth rate whenever possible.
Abscission consists in the detachment of entire vegetative and reproductive organs due to cell separation processes occurring at the abscission zones (AZs) at specific positions of the plant body. ...From an evolutionary point of view, abscission is a highly advantageous process resulting into fruit and seed dispersal as well as the shedding of no longer useful organs. In an agricultural context, however, abscission may become a major limiting factor for crop productivity. Domestication of major crops included the selection of plants that did not naturally shed ripe fruits or seeds. The understanding of abscission is of great importance to control seed and fruit production and to improve breeding and harvesting practices. Thus, advances made on model plants and crops are of major importance since they may provide potential candidate genes for further biotechnological applications. Here, we review the current knowledge of the physiological, genetic and genomic aspects related to abscission including the most recently disclosed putative regulators that appear to be implicated in the development and/or activation of the AZs.
•At harvest, glucosinolate content is higher in roots and shoots in autumn and spring, respectively.•Glucosinolate concentration is higher in roots than shoots before flowering but higher in shoots ...and inflorescences than roots after flowering in spring.•Mid and late harvest for leaves and roots, respectively, are recommended for high total glucosinolate content in radish.•Glucosinolate variation in different organs, growth stages and seasons suggests it accumulates more in inflorescences than roots, which act as organs for sexual and asexual reproduction, respectively.
Radish (Raphanus sativus L.), a root vegetable crop, contains a large amount of glucosinolate but information on its changes in field condition among different organs, growth stages and seasons is very limited. The glucosinolate composition, concentration (mmol∙kilogram−1) and content (μmol∙organ−1) of radish were analyzed among shoots, roots, inflorescences and siliques in vegetative and/or reproductive growth stages during autumn and spring to estimate sink/source relation and proper harvest time for high glucosinolate. Glucosinolates were measured weekly during autumn and spring using two autumn and one spring cultivars. All cultivars did not flower in autumn while only autumn cultivars had inflorescences in spring. Among three glucosinolates detected, glucoraphasatin was predominant, and glucobrassicin and gluconasturtiin varied in ratio among organs, growth stages and seasons. Root and shoot glucosinolate concentrations decreased as plants grow during autumn. Glucosinolate concentration in roots tended to decrease but that in shoots continuously increased during spring. Glucosinolate concentration was higher in roots than shoots during autumn and early spring but higher in shoots during late spring. Total glucosinolate content was also significantly higher in roots than shoots during autumn. However, it was higher in shoots at vegetative stage but in roots shortly at flower initiation, and then sharply increased in shoots at developmental stage during spring. The sharp increase in shoot glucosinolate content never happened in a spring cultivar without inflorescences. Glucosinolate concentration in the tenth week was significantly higher in inflorescences than other organs. These results suggest that when they co-exist, glucosinolate accumulates more in inflorescences than roots, which act as organs for sexual and asexual reproduction, respectively. Proper harvest time for leaves and roots were suggested based on the glucosinolate content and growth of radish plants.
Environmentally induced epigenetic change enables plants to remember past environmental interactions. If this memory capability is exploited to prepare plants for future challenges, it can provide a ...basis for highly sophisticated behavior, considered intelligent by some. Against the backdrop of an overview of plant intelligence, we hypothesize: (1) that the capability of plants to engage in such intelligent behavior increases with the additional level of complexity afforded by clonality, and; (2) that more faithful inheritance of epigenetic information in clonal plants, in conjunction with information exchange and coordination between connected ramets, is likely to enable especially advanced intelligent behavior in this group. We therefore further hypothesize that this behavior provides ecological and evolutionary advantages to clonal plants, possibly explaining, at least in part, their widespread success. Finally, we suggest avenues of inquiry to enable assessing intelligent behavior and the role of epigenetic memory in clonal species.
The Lower Devonian Rhynie cherts yield fossils of multiple types of fungal spores, but the systems that produced these spores are rarely preserved. Rhyniomycelium endoconidiarum gen. et sp. nov., a ...mycelium of uncertain affinity recently discovered in a degraded land plant axis from the Rhynie cherts, is characterized by endoconidia in virtually all hyphae, septa which typically occur in pairs and give off intrahyphal hyphae, and narrow hyphae ending in prominent, usually spheroidal heads that also contain, or consist of, conidia. The fossil hyphae closely resemble hyphae containing endoconidia of the extant ascomycete anamorph Geotrichum candidum (Saccharomycetales). Moreover, the fossil endoconidia appear to have originated from intrahyphal hyphae, precisely as in G. candidum. Conidiogenesis was probably thallic-arthric or thallic alternate-arthric. Rhyniomycelium endoconidiarum provides the oldest fossil evidence of endoconidia in fungi. Moreover, it links a dispersed spore type regularly encountered in the Rhynie cherts with a system in which spores of this type were produced. Documentation of such fossils contributes to our understanding of the evolution of reproductive processes in fungi.
•An unusual fungal mycelium is described from the Lower Devonian Rhynie chert.•Hyphae contain abundant endoconidia and paired septa giving off intrahyphal hyphae.•Fossil resembles extant ascomycete anamorph Geotrichum candidum (Saccharomycetales).•Endoconidia originate from intrahyphal hyphae.•Oldest fossil evidence of endoconidia formation in fungi.
Abstract
Within a few months of the year 1741, Lyonet and Trembley in Holland, Bonnet in Geneva and Réaumur in Paris all experimented industriously with the regeneration of various invertebrates, ...including the still unknown microdrile oligochaetes. Some of these worms were prone to spontaneous fragmentation as a natural mode of asexual multiplication, preceded (paratomy) or followed (architomy) by regenerative processes. Bonnet and Réaumur raised the stakes and began to study regeneration in earthworms, a challenge that, especially in Italy, inspired scholars and educated people among the clergy and aristocracy. Spallanzani conducted the most rigorous experiments and was the first to obtain consecutive regenerations of the head in one and the same megadrile. He saw detached mid-body sections becoming complete with a new head and a new tail, and he determined the points of the body where regeneration does not take place and how much length to leave for each section so that it could reintegrate. Above all, Spallanzani obtained regeneration of the gonadic segments, both in terrestrial and in freshwater megadriles, the latter today identified as Criodrilus lacuum. This and other important anatomical and physiological findings by Spallanzani, largely unpublished during his lifetime and for a long time after, preceded the discoveries of later authors by almost 50 years.
Beauveria brongniartii is a fungal pathogen that infects the beetle Melolontha melolontha, a significant agricultural pest in Europe. While research has primarily focused on the use of B. ...brongniartii for controlling M. melolontha, the genomic structure of the B. brongniartii population remains unknown. This includes whether its structure is influenced by its interaction with M. melolontha, the timing of beetle‐swarming flights, geographical factors, or reproductive mode. To address this, we analysed genome‐wide SNPs to infer the population genomics of Beauveria spp., which were isolated from infected M. melolontha adults in an Alpine region. Surprisingly, only one‐third of the isolates were identified as B. brongniartii, while two‐thirds were distributed among cryptic taxa within B. pseudobassiana, a fungal species not previously recognized as a pathogen of M. melolontha. Given the prevalence of B. pseudobassiana, we conducted analyses on both species. We found no spatial or temporal genomic patterns within either species and no correlation with the population structure of M. melolontha, suggesting that the dispersal of the fungi is independent of the beetle. Both species exhibited clonal population structures, with B. brongniartii fixed for one mating type and B. pseudobassiana displaying both mating types. This implies that factors other than mating compatibility limit sexual reproduction. We conclude that the population genomic structure of Beauveria spp. is primarily influenced by predominant asexual reproduction and dispersal.
We investigated the population genomic structure of the fungal pathogens Beauveria brongniartii and B. pseudobassiana, which were isolated from adult Melolontha melolontha beetles. We conclude that the genomic population structure of Beauveria spp. is primarily influenced by widespread clonal reproduction and long‐distance dispersal.
Sexual reproduction is widespread in eukaryotes; however, only asexual reproduction has been observed in unicellular red algae, including
Galdieria
, which branched early in Archaeplastida.
Galdieria
...possesses a small genome; it is polyextremophile, grows either photoautotrophically, mixotrophically, or heterotrophically, and is being developed as an industrial source of vitamins and pigments because of its high biomass productivity. Here, we show that
Galdieria
exhibits a sexual life cycle, alternating between cell-walled diploid and cell wall–less haploid, and that both phases can proliferate asexually. The haploid can move over surfaces and undergo self-diploidization or generate heterozygous diploids through mating. Further, we prepared the whole genome and a comparative transcriptome dataset between the diploid and haploid and developed genetic tools for the stable gene expression, gene disruption, and selectable marker recycling system using the cell wall–less haploid. The BELL/KNOX and MADS-box transcription factors, which function in haploid-to-diploid transition and development in plants, are specifically expressed in the haploid and diploid, respectively, and are involved in the haploid-to-diploid transition in
Galdieria
, providing information on the missing link of the sexual life cycle evolution in Archaeplastida. Four actin genes are differently involved in motility of the haploid and cytokinesis in the diploid, both of which are myosin independent and likely reflect ancestral roles of actin. We have also generated photosynthesis-deficient mutants, such as blue-colored cells, which were depleted in chlorophyll and carotenoids, for industrial pigment production. These features of
Galdieria
facilitate the understanding of the evolution of algae and plants and the industrial use of microalgae.
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