Tracing the Rise of Ants - Out of the Ground

We thank S.G. Brady, T.R. Schultz, B.L. Fisher and P.S. Ward for making original data available for re-analysis. P.S. Ward, M. Borowiec and J.K. Lattke provided input regarding habitat strata of the ant genera. J. Hunt provided input regarding the natural history of outgroup taxa. We thank J. Breinholt for technical assistance with analyses and express our appreciation to B. O'Meara, B.M. Wiegmann, Editor C.S. Moreau and two excellent reviewers for their insightful suggestions that significantly improved the manuscript.Conceived and designed the experiments: AL MDT BG MDW RRD. Performed the experiments: AL MDT. Analyzed the data: AL MDT. Contributed reagents/materials/analysis tools: AL MDT BG MDW RRD. Wrote the paper: AL MDT RRD.The evolution of ants (Hymenoptera: Formicidae) is increasingly well-understood due to recent phylogenetic analyses, along with estimates of divergence times and diversification rates. Yet, leading hypotheses regarding the ancestral habitat of ants conflict with new findings that early ant lineages are cryptic and subterranean. Where the ants evolved, in respect to habitat, and how habitat shifts took place over time have not been formally tested. Here, we reconstruct the habitat transitions of crown-group ants through time, focusing on where they nest and forage (in the canopy, litter, or soil). Based on ancestral character reconstructions, we show that in contrast to the current consensus based on verbal arguments that ants evolved in tropical leaf litter, the soil is supported as the ancestral stratum of all ants. We also find subsequent movements up into the litter and, in some cases, into the canopy. Given the global importance of ants, because of their diversity, ecological influence and status as the most successful eusocial lineage on Earth, understanding the early evolution of this lineage provides insight into the factors that made this group so successful today.Yeshttp://www.plosone.org/static/editorial#pee

Genomic Signature of Shifts in Selection in a Subalpine Ant and Its Physiological Adaptations

Understanding how organisms adapt to extreme environments is fundamental and can provide insightful case studies for both evolutionary biology and climate-change biology. Here, we take advantage of the vast diversity of lifestyles in ants to identify genomic signatures of adaptation to extreme habitats such as high altitude. We hypothesized two parallel patterns would occur in a genome adapting to an extreme habitat: 1) strong positive selection on genes related to adaptation and 2) a relaxation of previous purifying selection. We tested this hypothesis by sequencing the high-elevation specialist Tetramorium alpestre and four other phylogenetically related species. In support of our hypothesis, we recorded a strong shift of selective forces in T. alpestre, in particular a stronger magnitude of diversifying and relaxed selection when compared with all other ants. We further disentangled candidate molecular adaptations in both gene expression and protein-coding sequence that were identified by our genome-wide analyses. In particular, we demonstrate that T. alpestre has 1) a higher level of expression for stv and other heat-shock proteins in chill-shock tests and 2) enzymatic enhancement of Hex-T1, a rate-limiting regulatory enzyme that controls the entry of glucose into the glycolytic pathway. Together, our analyses highlight the adaptive molecular changes that support colonization of high-altitude environments

A New (Old), Invasive Ant in the Hardwood Forests of Eastern North America and Its Potentially Widespread Impacts

Biological invasions represent a serious threat for the conservation of biodiversity in many ecosystems. While many social insect species and in particular ant species have been introduced outside their native ranges, few species have been successful at invading temperate forests. In this study, we document for the first time the relationship between the abundance of the introduced ant, Pachycondyla chinensis, in mature forests of North Carolina and the composition, abundance and diversity of native ant species using both a matched pair approach and generalized linear models. Where present, P. chinensis was more abundant than all native species combined. The diversity and abundance of native ants in general and many individual species were negatively associated with the presence and abundance of P. chinensis. These patterns held regardless of our statistical approach and across spatial scales. Interestingly, while the majority of ant species was strongly and negatively correlated with the abundance and presence of P. chinensis, a small subset of ant species larger than P. chinensis was either as abundant or even more abundant in invaded than in uninvaded sites. The large geographic range of this ant species combined with its apparent impact on native species make it likely to have cascading consequences on eastern forests in years to come, effects mediated by the specifics of its life history which is very different from those of other invasive ants. The apparent ecological impacts of P. chinensis are in addition to public health concerns associated with this species due to its sometimes, deadly sting

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Development of a new apparatus to partition ant body size reveals their respective functional role within ant communities

The rapid decline of biodiversity is directly threatening the maintenance of important ecosystem processes. Yet, biodiversity loss is not homogeneous, with species presenting specific traits being more prone to extinction. Ultimately this can lead to potential disruption of key ecosystem functions. Ants are ubiquitous and abundant in all terrestrial ecosystems. They provide a plethora of ecosystem functions and thus are well suited for studies assessing ecological processes. Within ant communities, body size of different species can vary by several orders of magnitude reflecting different ecologies. To this point, however, our understanding of the efficiency of ecological processes by different classes in function of their body size remains largely unexplored under field conditions. This is in part due to a lack of adequate methodology for an easy and accurate assessment of their respective contributions. Here, we describe a novel approach that separates ants into three size classes based on two parameters: height of the access point and size of the entrance; and evaluated the success of this method by assessing morphometric parameters of the size classes post-filtering and quantifying the scavenging efficiency as a key ecological process. This method successfully segregated individuals based on their body size, with the large-size treatment allowing access to ants 3 times larger than ants on the medium-size treatment and 5 times larger than those on the small-size treatment. The large-size treatment was the most efficient, removing 7 times more bait per hour than the medium-size treatment and 40 times more than the small-size treatment. This approach provides a new, adjustable method for differential exclusion in the field, highlighting the role that different size classes play within a community. This opens new opportunities to study the relative role of specific functional traits, and the importance of ecological interactions in shaping ecosystem functions

Evolutionary transitions among habitat strata.

<p>Rate of transitions among six habitat states summarized across 500 trees sampled from the original likelihood distribution of Brady et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084012#pone.0084012-Brady1" target="_blank">[9]</a>. Thickness of arrows corresponds to rate of transitions. The percentages of ant genera that occupy a habitat category are indicated within each circle.</p

Influence of outgroup coding on Ancestral State Reconstruction.

<p>Influence of outgroup coding on Ancestral State Reconstructions of the habitat stratum of the root node of ants, with MCMC posterior probabilities provided as support values (performed using the Bayesian Binary Method in RASP using the model F81+G). In all cases soil was reconstructed as the ancestral habitat with the highest proportional likelihood (vs. surface dwelling or arboreal).</p

Relative proportions of extant ant genera occupying each habitat stratum and biome category.

<p>Relative proportions of the 134 included ant genera occupying each habitat stratum and biome category. Highest proportions are in bold.</p

Ancestral state reconstruction of ant habitat.

<p>Ancestral state reconstruction of ant habitat strata based on phylogram plus 500 trees sampled from the original likelihood distribution of Brady et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084012#pone.0084012-Brady1" target="_blank">[9]</a>. The outgroup in this reconstruction performed in the program RASP was coded as soil-dwelling, surface-dwelling or arboreal. The root node of ants is reconstructed as being subterranean (soil dwelling) with a posterior probability of 91.45%.</p