Ecology and Evolution最新文献

In the West Antarctic Peninsula, global warming has led to severe alterations in community composition, species distribution, and abundance over the last decades. Understanding the complex interplay between structure and stability of marine food webs is crucial for assessing ecosystem resilience, particularly in the context of ongoing environmental changes. In this study, we estimate the interaction strength within the Potter Cove (South Shetland Islands, Antarctica) food web to elucidate the roles of species in its structure and functioning. We use these estimates to calculate food web stability in response to perturbations, conducting sequential extinctions to quantify the importance of individual species based on changes in stability and food web fragmentation. We explore connections between interaction strength and key topological properties of the food web. Our findings reveal an asymmetric distribution of interaction strengths, with a prevalence of weak interactions and a few strong ones. Species exerting greater influence within the food web displayed higher degree and trophic similarity but occupied lower trophic levels and displayed lower omnivory levels (e.g., macroalgae and detritus). Extinction simulations revealed the key role of certain species, particularly amphipods and the black rockcod Notothenia coriiceps, as their removal led to significant changes in food web stability and network fragmentation. This study highlights the importance of considering species interaction strengths in assessing the stability of polar marine ecosystems. These insights have crucial implications for guiding monitoring and conservation strategies aimed at preserving the integrity of Antarctic marine ecosystems.

Microsatellites or simple sequence repeats (SSRs) are prevalent across various organisms' genomes. However, their distribution patterns and evolutionary dynamics in reptile genomes are rarely studied systematically. We herein conducted a comprehensive analysis of SSRs in the genomes of 36 reptile species. Our findings revealed that the total number of SSRs ranged from 1,840,965 to 7,664,452, accounting for 2.16%–8.19% of the genomes analyzed. The relative density ranged from 21,567.82 to 81,889.41 bp per megabase (Mbp). The abundance of different SSR categories followed the pattern of imperfect SSR (I-SSR) > perfect SSR (P-SSR) > compound SSR (C-SSR). A significant positive correlation was observed between the number of SSRs and genome size (p = 0.0034), whereas SSR frequency (p = 0.013) or density (p = 0.0099) showed a negative correlation with genome size. Furthermore, no correlation was found between SSR length and genome size. Mononucleotide repeats were the most common P-SSRs in crocodilians and turtles, whereas mononucleotides, trinucleotides, or tetranucleotides were the most common P-SSRs in snakes, lizards, and tuatara. P-SSRs of varying motif sizes showed nonrandom distribution across different genic regions, with AT-rich repeats being predominant. The genomic SSR content of the squamate lineage ranked the highest in abundance and variability, whereas crocodilians and turtles showed a slowly evolving and reduced microsatellite landscape. Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that genes harboring P-SSRs in the coding DNA sequence regions were primarily involved in the regulation of transcription and translation processes. The SSR dataset generated in this study provides potential candidates for functional analysis and calls for broader-scale analyses across the evolutionary spectrum.

With about 1700 described species, the mining bee genus Andrena is a rapidly diversifying lineage and one of the most species-rich groups of bees. Recent phylogenomic advances have greatly improved our understanding of the phylogeny of the genus, yet many species still await description, subgeneric assignments that are in line with their evolutionary history, as well as study of their morphology and behavior. Here we provide a comprehensive account of a newly discovered species, Andrena androfovea n. sp. We sequence the genome of the new species and include it in the presently most comprehensive phylogenomic analysis of Andrena using ultraconserved element (UCE) sequence data, comprising 264 samples and 249 species. Given the recovered phylogenetic position of the new species, we establish a new subgenus, Foveoandrena, provide a detailed morphological description, and discuss the antiquity and historical biogeography of the lineage in light of molecular divergence time estimates. Lastly, we study and document the foraging behavior of the new species with photos and video footage, and discuss the species' unusual host plant associations with Chamaesaracha and Quincula, both Solanaceae. Being likely oligolectic on these plants, we present the first documented case of an Andrena species being narrowly associated with members of this plant family. By integrating multiple lines of documentation, our study provides a particularly detailed account of species discovery and description.

Mutualisms, reciprocally beneficial interactions between two or more species, are ubiquitous in nature. A common feature of mutualisms is extensive context-dependent variation in fitness outcomes. This context-dependency is hypothesized to stem from the environment's mediation of the relative costs and benefits associated with mutualisms. However, traits related to the exchange of goods and services in mutualisms have received little attention in comparison to net fitness outcomes. In this study, we quantified the contribution of host and symbiont genotypes to variation in resource exchange, use, and production traits measured in the host using the model mutualism between legumes and nitrogen-fixing rhizobia. We predicted that plant genotype × rhizobia genotype (G × G) effects would be common to resource exchange traits because resource exchange is hypothesized to be governed by both interacting partners through bargaining. On the other hand, we predicted that plant genotype effects would dominate host resource use and production traits because these traits are only indirectly related to the exchange of resources. Consistent with our prediction for resource exchange traits, but not our prediction for resource use and production traits, we found that rhizobia genotype and G × G effects were the most common sources of variation in the traits that we measured. The results of this study complement the commonly observed phenomenon of G × G effects for fitness by showing that numerous mutualism traits also exhibit G × G variation. Furthermore, our results highlight the possibility that the exchange of resources as well as how partners use and produce traded resources can influence the evolution of mutualistic interactions. Our study lays the groundwork for future work to explore the relationship between resource exchange, use and production traits and fitness (i.e., selection) to test the competing hypotheses proposed to explain the maintenance of fitness variation in mutualisms.

Round goby (Neogobius melanostomus) is an invasive fish present in all five Great Lakes and is becoming increasingly common in their tributaries. Johnny darter (Etheostoma nigrum) is a native species that often coexists with N. melanostomus. In this work, historic factors are addressed as a source of genomic variation in study populations of these species. To do this, patterns of variation in the mitochondrial gene NADH dehydrogenase subunit 2 (ND2) were characterized for both species throughout Lower Michigan. Populations of N. melanostomus and E. nigrum were sampled from 17 localities representing both eastern and western basins of Lower Michigan to test the hypothesis that populations differ between the eastern and western basins of the Great Lakes. Neogobius melanostomus populations were largely homogenous with no significant differences detected among populations or between the eastern and western basins. Additionally, N. melanostomus exhibited no evidence of overarching historical genetic structure, consistent with the recent invasion and rapid expansion of this species. Etheostoma nigrum exhibited significant differentiation among local populations; however, similarity among mtDNA haplotypes indicated that differences among populations are recent, suggesting that local forces are a more important factor in shaping patterns of variation than historical factors. Contrary to predictions, there were no significant differences detected between the eastern and western basins of the Great Lakes; however, construction of a neighbor-joining tree with F_ST estimates revealed clustering of populations by basin with some anomalies. These anomalies may be the result of recent stream capture events facilitating gene flow between the two basins.

Tree growth–survival relationships link two demographic processes that individually dictate the composition, structure and functioning of forest ecosystems. While these relationships vary intra-specifically, it remains unclear how this reflects environmental variation and disturbance. We examined the influence of a 700-m elevation gradient and an Mw = 6.7 earthquake on intra-specific variability in growth–survival relationships. We expected that survival models that incorporated recent growth would be better supported than those only using other factors known to influence tree survival. We used a permanent plot network that representatively sampled a monodominant Nothofagus forest in New Zealand's Southern Alps in 1974 and that was remeasured seven times through to 2009. The relationships were assessed using pre-earthquake growth and survival, pre-earthquake growth and post-earthquake survival (0–5 years post-earthquake), and post-earthquake growth and survival (5+ years post-earthquake). Survival was related to growth of 4504 trees on 216 plots using Bayesian modelling. We hypothesised there would be a positive, logistic relationship between growth and survival. Pre-earthquake, we found a positive, logarithmic growth–survival relationship at all elevations. At higher elevations, trees grew more slowly but had higher survival than trees at lower elevations, supporting our hypothesised demographic trade-off with elevation. The earthquake altered growth–survival relationships from those found pre-earthquake and 0–5 years post-earthquake survival held little relationship with growth. A strong, logarithmic growth–survival relationship developed 5+ years post-earthquake because of enhanced survival of fast-growing trees yet low survival of slow-growing trees. Synthesis. Our findings demonstrate a trend in growth–survival relationships along an elevation gradient. If we assume a gradual climate warming is the equivalent of a forest stand shifting to a lower elevation, then data from our pre-earthquake period suggest that tree growth–survival relationships at any elevation could adjust to faster growth and lower survival. We also show how these novel growth–survival relationships could be altered by periodic disturbance.

The role of biotic interactions, such as interspecific competition, in driving geographical range evolution is still poorly understood. For instance, lineages distributed across regions with a large number of potential competitors might experience some level of geographical packing of their range limits, so that changes in their geographical distributions are hampered. Conversely, a large number of competitors could instead lead to accelerated rates of geographical range evolution, with lineages shifting their ranges to avoid competition. We recently introduced the concept of clade density (CD; the sum of the areas of overlap between a species and other members of its higher taxon, weighted by their phylogenetic distance) as a proxy of the potential for interspecific competition across the geographical distribution of a given species. In this study, we used a large dataset with 5936 terrestrial vertebrate species to test whether CD is significantly associated with variation in the rate of geographical range evolution using two alternative approaches. First, we tested if there is a significant relationship between CD and the geographical distance between sister species. In addition, we estimated tip rates of geographical range evolution and tested if they were consistently associated with variation in CD. We found no evidence for an effect of CD on geographical range evolution in either of the tested approaches, even after accounting for phylogenetic uncertainty. These results are inconsistent with equilibrial models of species diversification and suggest that interspecific competition might not play a pervasive role in geographical range evolution of terrestrial vertebrates.

The microfossil record contains abundant, diverse, and well-preserved fossils spanning multiple trophic levels from primary producers to apex predators. In addition, microfossils often constitute and are preserved in high abundances alongside continuous high-resolution geochemical proxy records. These characteristics mean that microfossils can provide valuable context for understanding the modern climate and biodiversity crises by allowing for the interrogation of spatiotemporal scales well beyond what is available in neo-ecological research. Here, we formalize a research framework of “micropaleoecology,” which builds on a holistic understanding of global change from the environment to ecosystem level. Location: Global. Time period: Neoproterozoic-Phanerozoic. Taxa studied: Fossilizing organisms/molecules. Our framework seeks to integrate geochemical proxy records with microfossil records and metrics, and draws on mechanistic models and systems-level statistical analyses to integrate disparate records. Using multiple proxies and mechanistic mathematical frameworks extends analysis beyond traditional correlation-based studies of paleoecological associations and builds a greater understanding of past ecosystem dynamics. The goal of micropaleoecology is to investigate how environmental changes impact the component and emergent properties of ecosystems through the integration of multi-trophic level body fossil records (primarily using microfossils, and incorporating additional macrofossil data where possible) with contemporaneous environmental (biogeochemical, geochemical, and sedimentological) records. Micropaleoecology, with its focus on integrating ecological metrics within the context of paleontological records, facilitates a deeper understanding of the response of ecosystems across time and space to better prepare for a future Earth under threat from anthropogenic climate change.

The Ogasawara Islands, representing an oceanic island ecosystem in Japan, have a notably high rate of endemic species akin to other oceanic islands globally. Pittosporum parvifolium is a critically endangered shrub with only four remaining individuals in its natural habitat on the Ogasawara Islands. Current conservation efforts encompass both in situ and ex situ approaches for P. parvifolium. However, these efforts face challenges stemming from the lack of critical conservation information. Therefore, we explored P. parvifolium's genetic diversity and implications for conservation. We utilized simple sequence repeat markers to scrutinize genetic diversity within both in situ and ex situ populations, revealing notably rich diversity among both. The in situ genetic diversity was significantly high despite the few extant individuals. In addition, many of the ex situ peculiar genotypes were absent in individuals conserved in situ. This investigation also provides insights into the reproductive strategies and combinations of selfing and outcrossing. The results of the present study recommend conservation to maximize genetic diversity in P. parvifolium by promoting cross-pollination among in situ individuals and by introducing individuals with unique genotypes into ex situ stocks.

Global climate change and agricultural practices have increased atmospheric nitrogen (N) deposition, significantly affecting the nitrogen cycling process in grasslands. The impact of different N forms on key soil enzyme activities involved in N nitrification, particularly in the saline-alkali grasslands of the Hexi Corridor, using natural grassland as a control (CK) and adding three N treatments: inorganic N (IN), organic N (ON) and a mixed N treatment (MN, with a 4:6 ratio of organic to inorganic N). Our study assessed the effects of these N forms on soil properties and enzyme activities crucial for N cycling. The findings indicate that different N forms significantly enhance soil mineral N content, with ON treatment leading to the highest increases in nitrate and ammonium content 92.44% and 35.6%, respectively, compared to CK. Both IN and ON treatments significantly boosted soil nitrate reductase and urease activities (p < 0.05), while MN treatment decreased nitrate reductase activity, with ON treatment showing the greatest sensitivity to enzyme activity changes. Soil pH slightly increased with N addition, but soil nitrite reductase activity remained relatively unchanged (0.372–0.385 mg g⁻¹). Correlation analysis revealed that soil mineral N content and pH are key regulators of enzyme activities in saline-alkaline grasslands. These results suggest that different N forms should be considered in nutrient cycling models, with organic N addition potentially enhancing soil N conversion and mitigating nutrient limitations in grassland ecosystems.