A new species group of Strumigenys (Hymenoptera, Formicidae) from Ecuador, with a description of its mandible morphology

Strumigenys is one of the most diverse ant genera in the world and arguably the most morphologically diverse, exhibiting an exceptional range of mandible shape and function. A new species, Strumigenys ayersthey sp. nov., discovered in the Chocó region of Ecuador is described. With two morphological characters, this species is shown to be a morphologically unique outlier among Strumigenys globally, having predominately smooth and shining cuticle surface sculpturing and long trap-jaw mandibles. Using μCT scans, we produced 3D images of the worker ant and static images to examine and compare mandible articular morphologies with most morphologically similar members of the mandibularis species group. Cuticular, pilosity, and articular mandible morphological differences supports placing the new species in its own new species group

Colonize, radiate, decline: Unraveling the dynamics of island community assembly with Fijian trap‐jaw ants

The study of island community assembly has been fertile ground for developing and testing theoretical ideas in ecology and evolution. The ecoevolutionary trajectory of lineages after colonization has been a particular interest, as this is a key component of understanding community assembly. In this system, existing ideas, such as the taxon cycle, posit that lineages pass through a regular sequence of ecoevolutionary changes after colonization, with lineages shifting toward reduced dispersal ability, increased ecological specialization, and declines in abundance. However, these predictions have historically been difficult to test. Here, we integrate phylogenomics, population genomics, and X-ray microtomography/3D morphometrics, to test hypotheses for whether the ecomorphological diversity of trap-jaw ants (Strumigenys) in the Fijian archipelago is assembled primarily through colonization or postcolonization radiation, and whether species show ecological shifts toward niche specialization, toward upland habitats, and decline in abundance after colonization. We infer that most Fijian endemic Strumigenys evolved in situ from a single colonization and have diversified to fill a large fraction of global morphospace occupied by the genus. Within this adaptive radiation, lineages trend to different degrees toward high elevation, reduced dispersal ability, and demographic decline, and we find no evidence of repeated colonization that displaces the initial radiation. Overall these results are only partially consistent with taxon cycle and associated ideas, while highlighting the potential role of priority effects in assembling island communities

Estimating species relative abundances from museum records

Funding: C.F., U.B. and D.J.R. acknowledge COST Action ‘European Soil-Biology Data Warehouse for Soil Protection’ (EUdaphobase), CA18237, supported by COST (European Cooperation in Science and Technology). AEM thanks the Leverhulme Trust (RPG-2019-401). D.B.B. was supported by an NSF Postdoc Research Fellowship in Biology (NSF 000733206), S.M.R. was supported by an NSERC Discovery Grant Author Contributions, A.V.S. was supported by NSF 1755336, C.S.M was supported by NSF 1398620 and N.J.G was supported by NSF 2019470.1. Dated, geo-referenced museum specimens are a rich data source for reconstructing species' distribution and abundance patterns. However, museum records are potentially biased towards over-representation of rare species, and it is unclear whether museum records can be used to estimate relative abundance in the field. 2. We assembled 17 coupled field and museum datasets to quantitatively compare relative abundance estimates with the Dirichlet distribution. Collectively, these datasets comprise 73,039 museum records and 1,405,316 field observations of 2,240 species. 3. Although museum records of rare species overestimated relative abundance by 1-fold to over 100-fold (median study = 9.0), the relative abundance of species estimated from museum occurrence records was strongly correlated with relative abundance estimated from standardized field surveys (r2 range of 0.10-0.91, median study = 0.43). 4. These analyses provide a justification for estimating species relative abundance with carefully curated museum occurrence records, which may allow for the detection of temporal or spatial shifts in the rank ordering of common and rare species.Publisher PDFPeer reviewe

The Rts1 Regulatory Subunit of Protein Phosphatase 2A Is Required for Control of G1 Cyclin Transcription and Nutrient Modulation of Cell Size

The key molecular event that marks entry into the cell cycle is transcription of G1 cyclins, which bind and activate cyclin-dependent kinases. In yeast cells, initiation of G1 cyclin transcription is linked to achievement of a critical cell size, which contributes to cell-size homeostasis. The critical cell size is modulated by nutrients, such that cells growing in poor nutrients are smaller than cells growing in rich nutrients. Nutrient modulation of cell size does not work through known critical regulators of G1 cyclin transcription and is therefore thought to work through a distinct pathway. Here, we report that Rts1, a highly conserved regulatory subunit of protein phosphatase 2A (PP2A), is required for normal control of G1 cyclin transcription. Loss of Rts1 caused delayed initiation of bud growth and delayed and reduced accumulation of G1 cyclins. Expression of the G1 cyclin CLN2 from an inducible promoter rescued the delayed bud growth in rts1Δ cells, indicating that Rts1 acts at the level of transcription. Moreover, loss of Rts1 caused altered regulation of Swi6, a key component of the SBF transcription factor that controls G1 cyclin transcription. Epistasis analysis revealed that Rts1 does not work solely through several known critical upstream regulators of G1 cyclin transcription. Cells lacking Rts1 failed to undergo nutrient modulation of cell size. Together, these observations demonstrate that Rts1 is a key player in pathways that link nutrient availability, cell size, and G1 cyclin transcription. Since Rts1 is highly conserved, it may function in similar pathways in vertebrates

The Structure and Assembly of Ant Communities: Patterns and Processes

Measured in species richness and abundance, ants are globally successful in temperate to tropical latitudes. Explaining the origin, success, and maintenance of diversity at both global and local scales has proven challenging because patterns of diversity and processes that drive patterns of diversity often differ between global and local scales. In this thesis, I study the patterns and processes driving ant diversity over a gradation of geographic levels. Chapter 1 compares and describes the density and dispersion of nut-nesting ants in southeastern United States temperate deciduous forests under nut producing trees. Species diversity and nut occupancy rates do not differ among sites or states and that ant-occupied nuts are spatially aggregated across ant species, a pattern inconsistent with spatial segregation of species that might arise in a competition-assembled community. In Chapter 2, through the development of new rapid sampling methods, I determine Strumigenys ant communities are feasible to study. I found 0.20 ha habitats and 1.0 m2 microsites are appropriate spatial scales for investigating abiotic factors and general habitat characteristics important for Strumigenys communities. I concluded that an even finer scale (< 1.0 m2) would be necessary to investigate community patterns on spatial scales on which Strumigenys are likely to interact or compete. Chapter 3 focuses on broad scale diversity patterns and describes the biogeographic origins of Nearctic Strumigenys. I produce a molecular based phylogeny to describe phylogenetic relationships of species and infer likely biogeographic histories of Nearctic species. I tested two alternative hypotheses for the assembly of biogeographic patterns in Nearctic Strumigenys, the adaptive radiation hypothesis verses the evolutionary conservatism hypothesis. Ranges of migrant or introduced species within the U.S. are consistent with average annual temperature and rainfall of ranges they occupy outside of the U.S. Results of climate and phylogenetic comparisons support predictions of the evolutionary conservatism hypothesis. Chapter 4 examines patterns and processes in the ant genus Strumigenys. I examined the phylogenetic and trait relationships of co-occurring Strumigenys species at very small to very large geographic spatial scales to test predictions of a competition hypothesis against three alternative community assembly hypotheses. The largest geographic scale included 60,000km2 bioregions across North America North of Mexico, to southeastern U.S. local communities of 2000m2 and 25m2, and 0.1m2 microsites. Patterns of biodiversity of Strumigenys differed as a function of scale and suggested processes are differentially important depending on the geographic scale of pattern investigation. However, there was no evidence that competition had influenced assemblage patterns of Strumigenys communities at any geographic scale

Taxonomic clarification of two Nearctic Strumigenys (Hymenoptera: Formicidae)

Booher, Douglas B. (2019): Taxonomic clarification of two Nearctic Strumigenys (Hymenoptera: Formicidae). Zootaxa 4664 (3): 401-411, DOI: https://doi.org/10.11646/zootaxa.4664.3.

FIGURE 16 in The ant genus Strumigenys Smith, 1860 (Hymenoptera: Formicidae) in western North America North of Mexico

FIGURE 16. Clypeus in face view of representative Strumigenys species.Published as part of Booher, Douglas B., 2021, The ant genus Strumigenys Smith, 1860 (Hymenoptera: Formicidae) in western North America North of Mexico, pp. 201-248 in Zootaxa 5061 (2) on page 211, DOI: 10.11646/zootaxa.5061.2.1, http://zenodo.org/record/564937

A new species group of Strumigenys (Hymenoptera, Formicidae) from Ecuador, with a description of its mandible morphology

Strumigenys is one of the most diverse ant genera in the world and arguably the most morphologically diverse, exhibiting an exceptional range of mandible shape and function. A new species, Strumigenys ayersthey sp. nov., discovered in the Chocó region of Ecuador is described. With two morphological characters, this species is shown to be a morphologically unique outlier among Strumigenys globally, having predominately smooth and shining cuticle surface sculpturing and long trap-jaw mandibles. Using µCT scans, we produced 3D images of the worker ant and static images to examine and compare mandible articular morphologies with most morphologically similar members of the mandibularis species group. Cuticular, pilosity, and articular mandible morphological differences supports placing the new species in its own new species group