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Over the past century, ecologists have attempted to understand patterns of species diversity by showing stable coexistence arising from a baseline expectation of competitive exclusion. This expectation stems from an explicit assumption of resource scarcity and implicit assumptions of Malthusian struggle and winner-takes-all dynamics. Fidelity to the competitive exclusion principle (CEP) presents species diversity as a paradox: if species compete for limited resources, how can they coexist? In this article, we investigate the contradiction between the theoretical expectation of competitive exclusion and the empirical prevalence of multispecies communities. We trace the persistence of the CEP in ecological research despite numerous challenges and explore publishing trends suggesting that this framework has resulted in a disproportionate focus on competition and exclusion in contemporary research. From a critical science studies perspective, we analyze the sociopolitical factors that have contributed to these patterns. We argue that we must excavate the ideological foundation on which competition-based coexistence research has been built to move beyond the current perceived "diversity paradox." To that end, we propose shifting the baseline expectation of coexistence research, introducing the notion of a coexistence principle, which positions the persistence of multispecies communities as the rule rather than the exception in nature. [ABSTRACT FROM AUTHOR]

Biotic specialization holds information about the assembly, evolution, and stability of biological communities. Partner availabilities can play an important role in enabling species interactions, where uneven partner availabilities can bias estimates of biotic specialization when using phylogenetic diversity indices. It is therefore important to account for partner availability when characterizing biotic specialization using phylogenies. We developed an index, phylogenetic structure of specialization (PSS), that avoids bias from uneven partner availabilities by uncoupling the null models for interaction frequency and phylogenetic distance. We incorporate the deviation between observed and random interaction frequencies as weights into the calculation of partner phylogenetic α‐diversity. To calculate the PSS index, we then compare observed partner phylogenetic α‐diversity to a null distribution generated by randomizing phylogenetic distances among the same number of partners. PSS quantifies the phylogenetic structure (i.e., clustered, overdispersed, or random) of the partners of a focal species. We show with simulations that the PSS index is not correlated with network properties, which allows comparisons across multiple systems. We also implemented PSS on empirical networks of host–parasite, avian seed‐dispersal, lichenized fungi–cyanobacteria, and hummingbird pollination interactions. Across these systems, a large proportion of taxa interact with phylogenetically random partners according to PSS, sometimes to a larger extent than detected with an existing method that does not account for partner availability. We also found that many taxa interact with phylogenetically clustered partners, while taxa with overdispersed partners were rare. We argue that species with phylogenetically overdispersed partners have often been misinterpreted as generalists when they should be considered specialists. Our results highlight the important role of randomness in shaping interaction networks, even in highly intimate symbioses, and provide a much‐needed quantitative framework to assess the role that evolutionary history and symbiotic specialization play in shaping patterns of biodiversity. PSS is available as an R package at https://github.com/cjpardodelahoz/pss. [ABSTRACT FROM AUTHOR]

The new genus Sinuicella, an early successional lichen, was found on bare soil in Oregon, USA. The thallus is minute fruticose, grey to nearly black, branching isotomic dichotomous, branches round, 20–90 μm wide in water mount. The cortex is composed of interlocking cells shaped like jigsaw puzzle pieces. Spores are hyaline, 1-septate, 25–40(–50) × 6.5–9(–11) μm. Maximum likelihood phylogenetic analyses on multilocus data sets, first spanning the entire order Peltigerales and then restricted to Peltigeraceae with extended sampling from Solorina and Peltigera, revealed the placement of Sinuicella outside of currently recognized genera, sister to Peltigera, with high support. Based on the phylogenetic, morphological and ecological distinctness of Sinuicella, we formally introduce a new genus represented by the single species S. denisonii. The cyanobiont of S. denisonii is Nostoc from phylogroup XL, Clade 2, Subclade 3 based on the rbcLX marker. [ABSTRACT FROM AUTHOR]

Peltigera globulata Miadl. & Magain, a new species in the P. ponojensis/monticola species complex of section Peltigera , is formally described. This clade was previously given the interim designation Peltigera sp. 17. It is found in sun-exposed and xeric habitats at high altitudes in Peru and Ecuador. Peltigera globulata can be easily recognized by its irregularly globulated margins covered mostly by thick, white pruina, somewhat resembling the sorediate thallus margins of P. soredians , another South American species from section Peltigera. The hypervariable region of ITS1 (ITS1-HR), which is in general highly variable among species of section Peltigera , does not have diagnostic value for species identification within the P. ponojensis/monticola complex. Nevertheless, no significant level of gene flow was detected among eight lineages representing a clade of putative species (including P. globulata) within this complex. ITS sequences from the holotype specimens of P. monticola Vitik. (collected in 1979) and P. soredians Vitik. (collected in 1981) and lectotype specimens of P. antarctica C. W. Dodge (collected in 1941) and P. aubertii C. W. Dodge (collected in 1952) were successfully obtained through Sanger and Illumina metagenomic sequencing. BLAST results of these sequences revealed that the type specimen of P. monticola falls within the P. monticola/ponojensis 7 clade, which represents P. monticola s. str., and confirmed that the type specimen of P. aubertii falls within a clade identified previously as P. aubertii based on morphology. The ITS sequence from the type specimen of P. soredians , which superficially resembles P. globulata , confirms its placement in the P. rufescens clade. Finally, we discovered that the name P. antarctica was erroneously applied to a lineage in the P. ponojensis/monticola clade. The ITS sequence from the type specimen of P. antarctica represents a lineage within the P. rufescens clade, which is sister to the P. ponojensis/monticola clade. [ABSTRACT FROM AUTHOR]