Plant-pollinator interactions are essential for maintaining biodiversity and ecosystem functioning. Their analysis through ecological networks enables the assessment of the structure, resilience, and temporal dynamics of these mutualistic systems. However, research on the temporal variation of pollination networks is scarce for arid and semi-arid environments, where biological communities are highly dynamic due to climate variability. Here, we characterized the temporal variation of plant-pollinator networks in a semi-arid scrubland of the southern Chihuahuan Desert across two years with contrasting precipitation. We conducted monthly surveys of pollination interactions, reconstructed temporally discrete networks for three seasons of each year, and evaluated intra- and inter-annual changes in network composition, structure, and robustness to species loss. Interaction variability was modulated by precipitation dynamics, more pronounced among seasons of the same year than between years, and mainly driven by temporal turnover of the plant species in bloom. Greater rainfall was linked to higher plant and pollinator richness and a greater number of connectors, module hubs, and network hubs, especially herbs, dipterans, and lepidopterans. We recorded substantial temporal variation in species' structural roles, yet highlight the importance of generalist bees for network cohesion over time. Seasonal networks showed a persistent compound topology, where nestedness occurs within modules rather than at the whole-network scale. Specialization and modularity tended to increase under drought conditions, accompanied by a decrease in network robustness to species loss. Our results underscore the remarkable diversity and plasticity of plant-pollinator networks in semi-arid environments and provide valuable insights for their conservation under climate change scenarios.
Global change reshapes biodiversity through shifts in species composition, richness, and body size. How these shifts combine to alter higher-level ecological processes within food webs can have important implications for entire ecosystems. However, the strength and direction of these shifts will depend on combinations of ways that species and trait compositions change through time. We combine long-term data from ~15,000 freshwater and marine fish communities (1949-2019) with information about their size, diets, and trophic status to evaluate how food webs change through time at local spatial scale. We found that selective species turnover driven by body size reductions is associated with widespread alteration to fish food web topology and function, including increased connectance and generalism, leading to higher predation pressure and increased prey vulnerability. Food webs were also less modular. These changes extend across food web trophic structures, causing a cascading shift in the proportion of species across trophic levels. Our study highlights complex biodiversity responses to confluent changes across multiple facets.
Plants are essential components of ecosystems and depend on various interactions with animals, among which mutualistic associations with ants stand out. Defensive mutualisms mediated by extrafloral nectaries (EFNs) create complex networks that shape species coexistence and contribute to ecological stability. Understanding how these networks respond to environmental disturbances is essential for predicting ecosystem dynamics. We investigated how fire influences the structure of ecological networks between ants and plants with EFNs in an area of the Cerrado affected first by frost and then by a high-intensity forest fire. Over the course of a year, we monitored ant richness and abundance, along with ant-plant interaction patterns involving regenerating plants. We observed that fire initially promoted more widespread networks, driven by an increase in resources and the synchronized growth of plant species. The ant species Camponotus crassus emerged as a central element of the network, playing a key role in the organization and stability of the network. However, tree fauna was more sensitive to disturbance, showing a marked decline in ant species dependent on branches and trunks. In summary, fires and frosts temporarily reshape ant-plant interactions, requiring adequate long-term monitoring.
A. hybridus tolerance to salinity depends on constitutively active mechanisms, whereas A. hypochondriacus tolerance to salt and water deficit depends on a constitutive protection and a robust transcriptional response. Drought and soil salinity are two environmental factors that significantly affect crop production. To gain a better understanding of how amaranth responds to these abiotic stresses, we analyzed the transcriptomic and metabolomic changes in the leaves of Amaranthus hybridus, a wild species, and A. hypochondriacus, a cultivated species used for seed production. We identified differentially expressed genes (DEGs) between the two species and under different stress conditions. Control plants of A. hypochondriacus exhibited higher expression levels of genes associated with photosynthesis, amino acid metabolism, fatty acid metabolism, sulfur metabolism, thiamine metabolism, and secondary metabolism. Notably, A. hybridus under salt stress showed an up-regulation of genes related to phosphonate and phosphinate metabolism and steroid biosynthesis. In contrast, the response of A. hypochondriacus to salt stress was characterized by increased expression of ABC transporters and genes involved in fructose, mannose, trehalose, porphyrin, thiamine, and monoterpenoid metabolism. When subjected to both types of stresses, A. hypochondriacus showed up-regulation of MAPK signaling pathways, ABC transporters, galactose, branched-chain amino acid (BCAA) degradation, and the production of defense compounds. Both amaranth species modulated their metabolic processes in response to drought and salinity stress towards cell wall modification, as well as the metabolism of pectin and lignin, while also producing antimicrobial and antifungal metabolites. Additionally, we detected differential accumulation of compounds, including methylphosphonate, 2-hydroxyethylphosphonate, and several metabolites related to fatty acid metabolism in the leaves of both amaranth species.
Background: Bletia comprises 56 species distributed throughout the Americas, with its principal center of diversity in Mexico. Among them are Bletia concolor and B. similis, two rare species for which information on morphology, distribution, and ecology is limited. Neither species had been recorded for the last 13 and 62 years, respectively, since their most recent collections. Questions: How do the new records of Bletia concolor and B. similis contribute to the knowledge of their distribution and to the assessment of their conservation status? Studied species: Bletia concolor and B. similis. Study site: San Ángel Zurumucapio, Michoacán, Mexico. Methods: Field explorations were conducted in Michoacán to collect specimens and prepare detailed morphological descriptions. Additionally, specimens in herbaria and digital databases were reviewed. Distribution maps were generated, and the conservation status was assessed following the criteria of the IUCN. Results: New localities in Michoacán were confirmed for Bletia similis, previously known only from Uruapan and now recorded in San Ángel Zurumucapio, as well as for B. concolor, located west of this locality. These records expand the known distribution range and represent the rediscovery of B. similis after 62 years without confirmed records. More complete morphological descriptions were prepared, including characters that had not been previously documented. Both species have restricted distributions and are classified as endangered according to criterion B of the IUCN. Conclusions: The new records expand current knowledge of the distribution, morphology, and ecology of both species, which are considered endangered.
