Biological Reviews最新文献

Mitochondria are dynamic and plastic, undergoing continuous fission and fusion and rearrangement of their bioenergetic sub-compartments called cristae. These fascinating processes are best understood in animal and fungal models, which are taxonomically grouped together in the expansive Opisthokonta supergroup. In opisthokonts, crista remodelling and inner membrane fusion are linked by dynamin-related proteins (DRPs). Animal Opa1 (optical atrophy 1) and fungal Mgm1 (mitochondrial genome maintenance 1) are tacitly considered orthologs because their similar mitochondria-shaping roles are mediated by seemingly shared biochemical properties, and due to their presence in the two major opisthokontan subdivisions, Holozoa and Holomycota, respectively. However, molecular phylogenetics challenges this notion, suggesting that Opa1 and Mgm1 likely had separate, albeit convergent, evolutionary paths. Herein, we illuminate disparities in proteolytic processing, structure, and interaction network that may have bestowed on Opa1 and Mgm1 distinct mechanisms of membrane remodelling. A key disparity is that, unlike Mgm1, Opa1 directly recruits the mitochondrial phospholipid cardiolipin to remodel membranes. The differences outlined herein between the two DRPs could have broader impacts on mitochondrial morphogenesis. Outer and inner membrane fusion are autonomous in animals, which may have freed Opa1 to repurpose its intrinsic activity to remodel cristae, thereby regulating the formation of respiratory chain supercomplexes. More significantly, Opa1-mediated crista remodelling has emerged as an integral part of cytochrome c-regulated apoptosis in vertebrates, and perhaps in the cenancestor of animals. By contrast, outer and inner membrane fusion are coupled in budding yeast. Consequently, Mgm1 membrane-fusion activity is inextricable from its role in the biogenesis of fungal lamellar cristae. These disparate mitochondrial DRPs ultimately may have contributed to the different modes of multicellularity that have evolved within Opisthokonta.

Hormones mediate life-history trade-offs. In female mammals, such trade-offs have been studied predominantly in the contexts of oestrogen, progesterone and prolactin. We evaluate the hypothesis that prenatal and postnatal testosterone levels structure and regulate trade-offs in females involving components of reproduction and survival. This hypothesis is predicated on the observation that testosterone confers competition-related and survival-related benefits, but also reproduction-related costs, to female mammals. The hypothesis is supported by field and laboratory data from diverse non-human animals, and data from healthy women. Most broadly, relatively low testosterone level in females has been associated with earlier, faster and higher offspring production, greater attractiveness to males, and reduced dominance or competitiveness, whereas higher testosterone level is associated with delayed and reduced reproduction but increased dominance, status, aggression, and resource accrual. The magnitude of testosterone-mediated trade-offs is expected to depend upon the strength of female-female competition, which represents some function of species-specific ecology, behaviour and mating system. Testosterone-associated trade-offs have, until now, been virtually ignored in studies of female life history, reproductive physiology, evolutionary endocrinology, and female-limited disease, probably due to researcher biases towards conceptualizing androgens as hormones with effects mainly restricted to males.

Phytoplankton is an essential resource in aquatic ecosystems, situated at the base of aquatic food webs. Plastic pollution can impact these organisms, potentially affecting the functioning of aquatic ecosystems. The interaction between plastics and phytoplankton is multifaceted: while microplastics can exert toxic effects on phytoplankton, plastics can also act as a substrate for colonisation. By reviewing the existing literature, this study aims to address pivotal questions concerning the intricate interplay among plastics and phytoplankton/phytobenthos and analyse impacts on fundamental ecosystem processes (e.g. primary production, nutrient cycling). This investigation spans both marine and freshwater ecosystems, examining diverse organisational levels from subcellular processes to entire ecosystems. The diverse chemical composition of plastics, along with their variable properties and role in forming the "plastisphere", underscores the complexity of their influences on aquatic environments. Morphological changes, alterations in metabolic processes, defence and stress responses, including homoaggregation and extracellular polysaccharide biosynthesis, represent adaptive strategies employed by phytoplankton to cope with plastic-induced stress. Plastics also serve as potential habitats for harmful algae and invasive species, thereby influencing biodiversity and environmental conditions. Processes affected by phytoplankton-plastic interaction can have cascading effects throughout the aquatic food web via altered bottom-up and top-down processes. This review emphasises that our understanding of how these multiple interactions compare in impact on natural processes is far from complete, and uncertainty persists regarding whether they drive significant alterations in ecological variables. A lack of comprehensive investigation poses a risk of overlooking fundamental aspects in addressing the environmental challenges associated with widespread plastic pollution.

Comparative approaches in animal gut microbiome research have revealed patterns of phylosymbiosis, dietary and physiological convergences, and environment-host interactions. However, most large-scale comparative studies, especially those that are highly cited, have focused on mammals, and efforts to integrate comparative approaches with existing ecological frameworks are lacking. While mammals serve as useful model organisms, developing generalised principles of how animal gut microbiomes are shaped and how these microbiomes interact bidirectionally with host ecology and evolution requires a more complete sampling of the animal kingdom. Here, we provide an overview of what past comparative studies have taught us about the gut microbiome, and how community ecology theory may help resolve certain contradictions in comparative gut microbiome research. We explore whether certain hypotheses are supported across clades, and how the disproportionate focus on mammals has introduced potential bias into gut microbiome theory. We then introduce a methodological solution by which public gut microbiome data of understudied hosts can be compiled and analysed in a comparative context. Our aggregation and analysis of 179 studies shows that generating data sets with rich host diversity is possible with public data and that key gut microbes associated with mammals are widespread across the animal kingdom. We also show the effects that sample size and taxonomic rank have on comparative gut microbiome studies and that results of multivariate analyses can vary significantly with these two parameters. While challenges remain in developing a universal model of the animal gut microbiome, we show that existing ecological frameworks can help bring us one step closer to integrating the gut microbiome into animal ecology and evolution.

Archaeocytes are considered a key cell type in sponges (Porifera). They are believed to be multifunctional cells performing various functions, from nutrient digestion to acting as adult stem cells (ASCs). Thus, archaeocytes are mentioned in discussions on various aspects of sponge biology. As presumed ASCs of an early-diverged animal taxon, archaeocytes are of great fundamental interest for further progress in understanding tissue functioning in metazoans. However, the term 'archaeocyte' is rather ambiguous in its usage and understanding, and debates surrounding archaeocytes have persisted for over a century, reflecting the ongoing complexity of understanding their nature. This article presents a comprehensive revision of the archaeocyte concept, including both its historical development and biological features (i.e. taxonomic distribution, characteristics, and functions). The term 'archaeocyte' and its central aspects were introduced as early as the end of the 19th century based on data mainly from demosponges. Remarkably, despite the general lack of comparative and non-histological data, these early studies already regarded archaeocytes as the ASCs of sponges. These early views were readily inherited by subsequent studies, often without proper verification, shaping views on many aspects of sponge biology for more than a century. Taking into account all available data, we propose considering the archaeocytes as a cell type specific to the class Demospongiae. Clear homologues of archaeocytes are absent in other sponge classes. In demosponges, the term 'archaeocytes' refers to mesohyl cells that have an amoeboid shape, nucleolated nuclei, and non-specific inclusions in the cytoplasm. The absence of specific traits makes the archaeocytes a loosely defined and probably heterogeneous cell population, rendering the exhaustive characterisation of the 'true' archaeocyte population impossible. At the same time, the molecular characterisation of archaeocytes is only beginning to develop. Stemness and almost unlimited potency have always been at the core of the traditional archaeocyte concept. However, currently, the most consistent data on archaeocyte stem cell function come only from developing gemmules of freshwater sponges. For tissues of adult demosponges, the data favour a two-component stem cell system, in which archaeocytes may cooperate with another stem cell population, choanocytes. Simultaneously, cells with archaeocyte morphology function as macrophages in demosponges, participating in the food digestion cycle and immune defence. Such cells should be denoted with the more neutral term 'nucleolar amoebocytes', as the term 'archaeocyte' not only describes the morphology of a cell but also introduces the proposition of its stem nature. Thus, the future usage of the term 'archaeocyte' should be limited to cases where a cell is shown or at least presumed to be a stem cell.

Acoustic communication plays a prominent role in various ecological and evolutionary processes involving social interactions. The properties of acoustic signals are thought to be influenced not only by the interaction between signaller and receiver but also by the acoustic characteristics of the environment through which the signal is transmitted. This conjecture forms the core of the so-called "acoustic adaptation hypothesis" (AAH), which posits that vegetation structure affects frequency and temporal parameters of acoustic signals emitted by a signaller as a function of their acoustic degradation properties. Specifically, animals in densely vegetated "closed habitats" are expected to produce longer acoustic signals with lower repetition rates and lower frequencies (minimum, mean, maximum, and peak) compared to those inhabiting less-vegetated "open habitats". To date, this hypothesis has received mixed results, with the level of support depending on the taxonomic group and the methodology used. We conducted a systematic literature search of empirical studies testing for an effect of vegetation structure on acoustic signalling and assessed the generality of the AAH using a meta-analytic approach based on 371 effect sizes from 75 studies and 57 taxa encompassing birds, mammals and amphibians. Overall, our results do not provide consistent support for the AAH, neither in within-species comparisons (suggesting no overall phenotypically plastic response of acoustic signalling to vegetation structure) nor in among-species comparisons (suggesting no overall evolutionary response). However, when considering birds only, we found weak support for the AAH in within-species comparisons, which was mainly driven by studies that measured frequency bandwidth, suggesting that this variable may exhibit a phenotypically plastic response to vegetation structure. For among-species comparisons in birds, we also found support for the AAH, but this effect was not significant after excluding comparative studies that did not account for phylogenetic non-independence. Collectively, our synthesis does not support a universal role of vegetation structure in the evolution of acoustic communication. We highlight the need for more empirical work on currently under-studied taxa such as amphibians, mammals, and insects. Furthermore, we propose a framework for future research on the AAH. We specifically advocate for a more detailed and quantitative characterisation of habitats to identify frequencies with the highest detection probability and to determine if frequencies with greater detection distances are preferentially used. Finally, we stress that empirical tests of the AAH should focus on signals that are selected for increased transmission distance.

A comprehensive review of a full developmental sequence of eodiscinid trilobites reported in recent decades from Cambrian Series 2 and 3 strata is presented. These mostly articulated specimens exhibit detailed morphologies with preservation of even delicate structures at different growth stages, such as the bacculae, axial pores, spine pores, pygidial marginal spines and line coaptative structures. Their trunk segmentation schedules displayed a consistent developmental mode in segment generation and liberation, that is tagmosis and somitogenesis occurred heterochronously after each moulting event, providing clues regarding the potential developmental strategy in isopygous and even macropygous trilobites. The fact that the rate of segmentation obviously exceeds that of articulation results in a seemingly prolonged process of the formation of thoracic segments, which might explain why eodiscinid trilobites have a fixed and limited number of thoracic segments. In addition, the relationship between enrollment mechanism and trunk segmentation during eodiscinid ontogeny confirms this highly unusual growth pattern among the Trilobita, revealing why these early-diverging trilobites controlled the rate of segment increase and release during their life cycles, and is thus of interest with regard to the evolution of arthropod body patterning.

The growing demand for energy and the shift towards green energy solutions have led to the conversion of open spaces and agricultural fields into photovoltaic (PV) power plants, exacerbating the "food-energy-environment" trilemma. Agrophotovoltaics (APVs), a dual-use system combining agriculture and energy production on the same land, presents a potential solution to this challenge. While the environmental impacts of ground-mounted utility-scale PV (USPV) power plants and the effects of APV systems on agricultural yields have been extensively studied and reviewed, the implications for wildlife and biodiversity remain largely unexplored. This knowledge gap is pressing, given the accelerated global adoption of APV systems and the urgency of understanding their broader ecological consequences. In this concise review, we synthesise existing literature on the impacts of USPV installations on biodiversity and the effects of APV on crop production. Building on these foundations, we propose novel hypotheses concerning the potential pathways and mechanisms through which APV systems may influence biodiversity. We explore the complex interactions between agroecosystems and natural ecosystems, examining both direct and indirect effects. Our review culminates in a set of key research questions designed to guide future studies on the biodiversity outcomes of APV deployment. Future research should comprehensively address factors such as habitat type, climate, spatial scale, technology, and agricultural practices, as well as the overarching impacts of climate change. By highlighting the importance of these variables, we aim to facilitate a nuanced understanding of how APV systems can either support or undermine biodiversity. This work not only underscores the critical need for empirical studies in this emerging field but also sets the stage for more informed and sustainable implementation of APV technologies.

Mechanisms governing the migratory decisions of birds have long fascinated ecologists and sparked considerable debate. Identifying factors responsible for variation in migration distance, also known as differential migration, has been a popular approach to understanding the mechanisms underlying migratory behaviour more generally. However, research progress has been slowed by the continued testing of overlapping, non-mechanistic, and circular predictions among a small set of historically entrenched hypotheses. We highlight the body size hypothesis and suggest that the predictions commonly tested have impeded progress because body size relationships with migration distance are predictions made by several distinct hypotheses with contrasting mechanisms. The cost of migration itself has not been adequately accounted for in most hypotheses, and we propose two flight efficiency hypotheses with time- and energy-minimizing mechanisms that allow individuals to mitigate the risks inherent to longer migrations. We also advance two conceptual versions of the social dominance hypothesis based on two distinct underlying mechanisms related to distance minimization and food maximization that will help clarify the role of competition in driving migratory decisions. Overall, we describe and refine 12 mechanistic hypotheses proposed to explain differential migration (along with several other special-case hypotheses), seven of which have underlying mechanisms related to food limitation as past research has identified this to be an important driver of differential migration. We also thoroughly reviewed 145 publications to assess the amount of support for 10 critical assumptions underlying alternative hypotheses for differential migration in birds. Our review reveals that surprisingly few studies explicitly evaluate assumptions within a differential migration context. Generating and testing strong predictions and critical assumptions underlying mechanisms of alternative hypotheses will improve our ability to differentiate among these explanations of differential migration. Additionally, future intraspecific progress will be greatest if investigators continue to focus on mechanisms underlying variation in migration distance within rather than among demographic classes, as previous research has found differing mechanisms to be responsible for differential migration among demographic classes. Interspecifically, a thorough comparative analysis that seeks to explain variation in migration distance among species would broaden both our understanding of the mechanisms regulating current differential migration patterns and those that led to the evolution of migration more generally. Collectively, we provide a framework that, together with advances in animal-borne tracking and other technology, can be used to advance our understanding of the causes of differential migration distance, and migratory decisions more generally.