The global spread and invasion capacities of alien ants

Many alien species are neither cultivated nor traded but spread unintentionally, and their global movements, capacities to invade ecosystems, and susceptibility to detection by biosecurity measures are poorly known.1,2,3,4 We addressed these key knowledge gaps for ants, a ubiquitous group of stowaway and contaminant organisms that include some of the world’s most damaging invasive species.5,6,7,8,9,10 We assembled a dataset of over 146,000 occurrence records to comprehensively map the human-mediated spread of 520 alien ant species across 525 regions globally. From descriptions of the environments in which species were collected within individual regions—such as in imported cargoes, buildings, and outdoor settings—we determined whether different barriers to invasion had been overcome11 and classified alien ant species under three levels of invasion capacity corresponding to increasing biosecurity threat. We found that alien species of different invasion capacities had different sources and sinks globally. For instance, although the diversity of indoor-confined species peaked in the Palearctic realm, that of species able to establish outdoors peaked in the Nearctic and Oceanian realms, and these mainly originated from the Neotropical and Oriental realms. We also found that border interceptions worldwide missed two-thirds of alien species with naturalization capacity, many associated with litter and soil. Our study documents the vast spread of alien ants globally while highlighting avenues for more targeted biosecurity responses, such as prioritizing the screening of imports from regions that are diversity hotspots for species of high invasion capacity and improving the detection of cryptic alien invertebrates dwelling in substrates.journal articl

Developing generalized sampling schemes with known error properties: the case of a moving observer

Pattern in space and time is central to ecology, and adequately designed ecological sampling is needed to resolve those patterns, pursue ecological questions and design conservation strategies. Recently, there has been an explosion of various ecological data due to the proliferation of online data‐sharing platforms, citizen science programs and new technology such as unmanned aerial vehicles (UAVs), but data reliability, consistency and the error properties of the sampling method are usually uncertain. While there are a number of standard survey protocols for different taxa, they often subjectively designed and standardization is meant to facilitate repeatability rather than produce a quantitative evaluation of the data (e.g. error properties). Here, we describe an ecological survey scheme consisting of an ‘algorithm\u27 to be followed in the field that will result in a standard set of data as well as the error properties of the data. While many such sampling schemes could be developed that target different types of organisms, we focus on one case of a moving observer attempting to detect a species in the field (e.g. a birder, UAV, etc.) with the goal of producing a presence–absence map. The multiscale model developed is spatially explicit and accommodates inherent survey tradeoffs such as sampling speed, detectability and map resolution. Given a set of sampling parameters, the model provides estimates of the total sampling time and map accuracy translated into the probability of false negative. Additionally it also provides an actual and sampled occupancy–area curve across mapping resolutions that can be utilized to discuss sampling effects. While the proposed sampling framework is simple, the same general approach could be adapted for other conditions to meet the needs of a particular taxon. If a set of ‘canonical\u27 sampling algorithms could be developed with known mathematical properties, it would enhance reliability and usage of ecological datasets

From species sorting to mass effects: spatial network structure mediates the shift between metacommunity archetypes

Local assemblages are embedded in networks of communities connected by dispersal, and understanding the processes that mediate this local-regional interaction is central to understanding biodiversity patterns. In this network (i.e. metacommunity), the strength of dispersal relative to the intensity of environmental selection typically determines whether local communities are comprised of species well-adapted to the local environment (i.e. species sorting) or are dominated by regionally successful species that may not be locally adapted (i.e. mass effects), which by extension determines the capacity of the landscape to sustain diversity. Despite the fundamentally spatial nature of these dispersal-mediated processes, much of our theoretical understanding comes from spatially implicit systems, a special case of spatial structure in which patches are all connected to each other equally. In many real systems, both the connections among patches (i.e. network topology) and the distributions of environments across patches (i.e. spatial autocorrelation) are not arranged uniformly. Here, we use a metacommunity model to investigate how spatial heterogeneities may change the balance between species sorting versus mass effects and diversity outcomes. Our simulations show that, in general, the spatially implicit model generates an outlier in biodiversity patterns compared to other networks, and most likely amplifies mass effects relative to species sorting. Network topology has a strong effect on metacommunity outcome, with topologies of sparse connections and few loops promoting sorting of species into suitable patches. Spatial autocorrelation is another key factor; by interacting with spatial topology, intermediate-scale clusters of similar patches can emerge, leading to a reduction of regional competition, and hence maintenance of gamma diversity. These results provide a better understanding of the role that complex spatial landscape structure plays in metacommunity processes, a necessary step to understanding how metacommunity processes relate to biodiversity conservation

The Roles of Introgression and Climate Change in the Rise to Dominance of Acropora Corals

Reef-building corals provide the structural basis for one of Earth\u27s most spectacular and diverse-but increasingly threatened-ecosystems. Modern Indo-Pacific reefs are dominated by species of the staghorn coral genus Acropora, but the evolutionary and ecological factors associated with their diversification and rise to dominance are unclear. Recent work on evolutionary radiations has demonstrated the importance of introgression and ecological opportunity in promoting diversification and ecological success. Here, we analyze the genomes of five staghorn coral species to examine the roles of introgression and ecological opportunity in the rise to dominance of Acropora. We found evidence for a history marked by a major introgression event as well as recurrent gene flow across species. In addition, we found that genes with topologies mismatching the species tree are evolving faster, which is suggestive of a role for introgression in spreading adaptive genetic variation. Demographic analysis showed that Acropora lineages profited from climate-driven mass extinctions in the Plio-Pleistocene, indicating that Acropora exploited ecological opportunity opened by a new climatic regime favoring species that could cope with rapid sea-level changes. Collectively, the genomes of reef-building corals have recorded an evolutionary history shaped by introgression and climate change, suggesting that Acropora-among most vulnerable corals to stressors-may be critical for understanding how reefs track the impending rapid sea-level changes of the Anthropocene

Global biogeographic regions for ants have complex relationships with those for plants and tetrapods

On a global scale, biodiversity is geographically structured into regions of biotic similarity. Delineating these regions has been mostly targeted for tetrapods and plants, but those for hyperdiverse groups such as insects are relatively unknown. Insects may have higher biogeographic congruence with plants than tetrapods due to their tight ecological and evolutionary links with the former, but it remains untested. Here, we develop a global regionalization for a major and widespread insect group, ants, based on the most comprehensive distributional and phylogenetic information to date, and examine its similarity to regionalizations for tetrapods and vascular plants. Our ant regionalization supports the newly proposed Madagascan and Sino-Japanese realms based on tetrapod delineations, and it recovers clusters observed in plants but not in tetrapods, such as the Holarctic and Indo-Pacific realms. Quantitative comparison suggests strong associations among different groups—plants showed a higher congruence with ants than with tetrapods. These results underscore the wide congruence of diverse distribution patterns across the tree of life and the similarities shared by insects and plants that are not captured by tetrapod groups. Our analysis highlights the importance of developing global biogeographic maps for insect groups to obtain a more comprehensive geographic picture of life on Earth

Taxonomic overview of the hyperdiverse ant genus Tetramorium Mayr (Hymenoptera, Formicidae) in India with descriptions and X-ray microtomography of two new species from the Andaman Islands

With 600 described species, the ant genus Tetramorium represents one of the most species-rich ant radiations. However, much work remains to fully document the hyperdiversity of this remarkable group. Tetramorium, while globally distributed, is thought to have originated in the Afrotropics and is particularly diverse in the Old World. Here, we focus attention on the Tetramorium fauna of India, a region of high biodiversity value and interest for conservation. We overview Tetramorium diversity in India by providing a species list, accounts of all species groups present, an illustrated identification key to Indian Tetramorium species groups and notes on the Indian Tetramorium fauna. Further, we describe two new species, Tetramorium krishnani sp. n. and Tetramorium jarawa sp. n. from the Andaman Islands archipelago and embed them into currently recognized Tetramorium tonganum and Tetramorium inglebyi species groups. We also provide illustrated species level keys for these groups. Along with detailed species descriptions and high-resolution montage images of types, we provide 3D cybertypes of the new species derived from X-ray micro-computed tomography

Metacommunity ecology of Symbiodiniaceae hosted by the coral Galaxea fascicularis

Coral−algae symbiosis represents the trophic and structural basis of coral reef ecosystems. However, despite global threats to coral reefs and the dependence of coral health and stress resistance upon such mutualisms, little is known about the community ecology of endosymbiotic Symbiodiniaceae. Concepts and methods from metacommunity ecology may be used to help us understand the assembly and stability of symbiont communities and the mutualisms they comprise. In this study, we sampled colonies of the symbiont-generalist coral Galaxea fascicularis in southwestern Japan and assessed the effects of environmental and host factors on Symbiodinia ceae community composition, while simultaneously exploring residual correlations among symbiont types that may reflect non-random assembly processes such as species interactions. We metabarcoded the Symbiodiniaceae ribosomal internal transcribed spacer 2 (ITS2) region and characterized the endosymbiotic community using 2 different OTU identity cut-offs, and analyzed them with generalized dissimilarity modeling and joint species distribution modeling. We found that Symbiodiniaceae form discrete communities characterized by the dominance of ITS2 types C1, C21a, or D1, that are each associated with a different suite of co-occurring background types and tend to exclude each other in an endosymbiotic community. The communities showed modest responses to temperature, water depth, host genotype, polyp size, and bleaching status, and there was local sequence variation within the ITS2 types. After accounting for the effects of those variables, residual correlations remained in community composition, pointing to the possibility that Symbiodiniaceae community assembly in corals may be structured by interspecific competitive or facilitating interactions rather than only exogenous variables

Comparative morphology of male genital skeletomusculature in the Leptanillinae (Hymenoptera: Formicidae), with a standardized muscular terminology for the male genitalia of Hymenoptera

The male genitalia of the Insecta are famed for structural and functional diversity. Variation in this anatomical region shows ample phylogenetic signal, and this variation has proven indispensable for classification across the insects at multiple taxonomic ranks. However, in the ants (Hymenoptera: Formicidae) the male genital phenotype is ancillary to the morphology of the worker caste for systematic purposes. Ants of the enigmatic subfamily Leptanillinae are an exception, as males are easier to collect than workers. Ongoing systematic revision of the Leptanillinae must therefore rely upon the male phenotype – particularly the spectacular morphological profusion of the male genitalia. To thoroughly illuminate this anatomical region and aid comparative morphological research on ant male genitalia, we present a comparative morphological study of the male genitalia in nine exemplar lineages spanning the Leptanillinae, plus three outgroups representing other major clades of the Formicidae. We use micro-computed tomography (micro-CT) to generate 3D volumetric reconstructions of male genital skeletomusculature in these specimens. Our descriptions use new muscular terminology compatible with topographic main-group systems for the rest of the pterygote soma, and applicable to all Hymenoptera. We find that male genitalia in the Leptanillinae show an overall trend towards skeletomuscular simplification, with muscular reduction in some cases being unprecedented in ants, or even hymenopterans in general. In several lineages of the Leptanillinae we describe derivations of the male genitalia that are bizarre and unparalleled among the Hymenoptera. We conclude by discussing the functional implications of the often-extreme morphologies here observed

Additions to the taxonomy of Pheidole (Hymenoptera: Formicidae) from the southern grasslands of Brazil

The ant genus Pheidole is the most species-rich lineage of ants in the world and one of the dominant organisms in tropical regions. However, the knowledge of Pheidole diversity in the southern half of the Neotropical Region is fragmentary. Here, we offer contributions to the Pheidole taxonomy considering the species that occur in the grassland formations of South Brazil. The following species are revived from synonymy: P. idiota Santschi rev. stat., P. obscurior Forel rev. stat., P. paranana Santschi stat. rev. et n. stat. and P. strobeli Emery rev. stat. The following synonyms are proposed: P. idiota (= P. laticornis Wilson n. syn.), P. obscurior (= P. partita Mayr n. syn., = P. incisa evoluta Borgmeier n. syn.) and P. strobeli (= P. rufipilis divexa Forel n. syn., = P. nitidula daguerrei Santschi n. syn., = P. perversa Forel n. syn., = P. perversa richteri Forel n. syn., = P. strobeli misera Santschi n. syn.). Finally, six new species are described: P. abakytan n. sp., P. abaticanga n. sp., P. cangussu n. sp., P. curupira n. sp., P. mapinguari n. sp., and P. obapara n. sp

A geometric approach to scaling individual distributions to macroecological patterns

Understanding macroecological patterns across scales is a central goal of ecology and a key need for conservation biology. Much research has focused on quantifying and understanding macroecological patterns such as the species-area relationship (SAR), the endemic-area relationship (EAR) and relative species abundance curve (RSA). Understanding how these aggregate patterns emerge from underlying spatial pattern at individual level, and how they relate to each other, has both basic and applied relevance. To address this challenge, we develop a novel spatially explicit geometric framework to understand multiple macroecological patterns, including the SAR, EAR, RSA, and their relationships. First, we provide a general theory that can be used to derive the asymptotic slopes of the SAR and EAR, and demonstrates the dependency of RSAs on the shape of the sampling region. Second, assuming specific shapes of the sampling region, species geographic ranges, and individual distribution patterns therein based on theory of stochastic point processes, we demonstrate various well-documented macroecological patterns can be recovered, including the tri-phasic SAR and various RSAs (e.g., Fisher\u27s logseries and the Poisson lognormal distribution). We also demonstrate that a single equation unifies RSAs across scales, and provide a new prediction of the EAR. Finally, to demonstrate the applicability of the proposed model to ecological questions, we provide how beta diversity changes with spatial extent and its grain over multiple scales. Emergent macroecological patterns are often attributed to ecological and evolutionary mechanisms, but our geometric approach still can recover many previously observed patterns based on simple assumptions about species geographic ranges and the spatial distribution of individuals, emphasizing the importance of geometric considerations in macroecological studies