When fossil clades ‘compete’: local dominance, global diversification dynamics and causation

Examining the supposition that local-scale competition drives macroevolutionary patterns has become a familiar goal in fossil biodiversity studies. However, it is an elusive goal, hampered by inadequate confirmation of ecological equivalence and interactive processes between clades, patchy sampling, few comparative analyses of local species assemblages over long geological intervals, and a dearth of appropriate statistical tools. We address these concerns by reevaluating one of the classic examples of clade displacement in the fossil record, in which cheilostome bryozoans surpass the once dominant cyclostomes. Here, we analyse a newly expanded and vetted compilation of 40 190 fossil species occurrences to estimate cheilostome and cyclostome patterns of species proportions within assemblages, global genus richness and genus origination and extinction rates while accounting for sampling. Comparison of time-series models using linear stochastic differential equations suggests that inter-clade genus origination and extinction rates are causally linked to each other in a complex feedback relationship rather than by simple correlations or unidirectional relationships, and that these rates are not causally linked to changing within-assemblage proportions of cheilostome versus cyclostome species.

Which Class Matters? Juxtaposing Multiple Class Environments as Frames-of-Reference for Academic Self-Concept Formation

Equally able students have lower academic self-concept in high achieving schools or classes, a phenomenon known as the big fish little pond effect (BFLPE). The class (more so than the school) has been shown to be the pivotal frame-of-reference for academic self-concept formation—a local dominance effect. However, many school systems worldwide employ forms of course-by-course tracking, thus exposing students to multiple class environments. Due to the high correlation between multiple student environments, the frame-of-reference used for academic self-concept formation in course-by-course tracked systems is unclear to date. We addressed this unresolved issue by using data from a comprehensive survey that measured the entire population of Austrian eighth-grade students in the domain of mathematics in 2012. General secondary school students were in the core subjects (i.e., mathematics, German, and English) grouped according to ability, whereas regular class composition was the same in all other subjects. Using cross-classified multilevel models, we regressed math self-concept on average math achievement of students’ school, math class, and regular class. Consistent with the local dominance effect, we found the BFLPE on the school level to be weak after controlling for the class levels. We found a stronger BFLPE on the regular class level and the strongest BFLPE on the math class level. Our study demonstrates the importance of multiple class environments as frames-of-reference for academic self-concept formation.

The Interplay of Macrofauna Functional Groups Shapes Nitrogen Cycling in Oligotrophic Estuarine Sediments

The effects of single macrofauna species on benthic nitrogen (N) cycling has been extensively studied, whereas the effect of macrofauna communities on N-related processes remains poorly explored. In this study, we characterized benthic N-cycling in bioturbated sediments of an oligotrophic northern Baltic waters (Öre estuary). Solute fluxes and N transformations (N2 fixation, denitrification and DNRA) were measured in sediments and in macrofauna-bacteria holobionts to partition the role of three dominant macrofauna taxa (Limnecola balthica, Marenzelleria sp. and Monoporeia affinis) in shaping N-cycling, and to disentangle the contribution of different functional groups within the community. In the studied area, benthic macrofauna comprised a low diversity community with extremely high local dominance of three macrofauna taxa, which are widespread and dominant in the Baltic. The biomass of these three taxa in the benthic community explained up to 30% of variation in measured biogeochemical processes, confirming their role in ecosystem functioning. The results also show that these taxa significantly contributed to the benthic metabolism and N-cycling (direct effect) as well as reworked sediments with positive feedback to dissimilative nitrate reduction (indirect effect). Taken together, these functions promoted a re-use of nutrient at the benthic level, limiting net losses (e.g. denitrification) and effluxes to bottom water. Finally, the detection of multiple N transformations in dominating macrofauna holobionts suggested a community-associated active and versatile microbiome, which alternatively contributes to the biogeochemical processes. The present study highlights hidden and interactive effects among microbes and macrofauna, which should be considered in analysing benthic functioning.

Object-Based Predictive Modeling (OBPM) for Archaeology: Finding Control Places in Mountainous Environments

This contribution examines the potential of object-based image analysis (OBIA) for archaeological predictive modeling starting from elevation data, by testing a ruleset for the location of “control places” on two test areas in the Alpine environment (northern Italy). The ruleset was developed on the western Asiago Plateau (Vicenza Province, Veneto) and subsequently re-applied (semi)automatically in the Isarco Valley (South Tirol). Firstly, we considered the physiographic, climatic, and morphological characteristics of the selected areas and we applied 3 DTM processing techniques: Slope, local dominance, and solar radiation. Subsequently, we employed an object-based approach to classification. Solar radiation, local dominance, and slope were visualized as a three-layer RGB image that was segmented with the multiresolution algorithm. The classification was implemented with a ruleset that selected only image–objects with high local dominance and solar radiation, but low slope, which were considered more suitable parameters for human occupation. The classification returned five areas on the Asiago Plateau that were remotely and ground controlled, confirming anthropic exploitation covering a time span from protohistory (2nd-1st millennium BC) to the First World War. Subsequently, the same model was applied to the Isarco Valley to verify the replicability of the method. The procedure resulted in 36 potential control places which find good correspondence with the archaeological sites discovered in the area. Previously unknown contexts were further controlled using very high-resolution (VHR) aerial images and digital terrain model (DTM) data, which often suggested a possible (pre-proto)historic human frequentation. The outcomes of the analysis proved the feasibility of the approach, which can be exported and applied to similar mountainous landscapes for site predictivity analysis.

Enhancing subtle seafloor relief variation: relief visualisation techniques for bathymetric data

<p>Bathymetric data is commonly visualized as a simple shaded relief, where features oriented parallel to the light source are prone to false topographic perception or are even obscured to the viewer. On the other hand, many relief visualisation techniques developed in past decades are extensively used in visualisation and analysis of high-resolution digital elevation models, especially in geomorphological and archaeological studies. We tested and assessed the suitability of relief visualisation techniques provided by the Relief Visualisation Toolbox (RVT) software for representation of bathymetric data. We used a multibeam-sonar derived bathymetric model with a 10 x 10 m cell size from the Gulf of Trieste (northern Adriatic) characterised by a shallow low-relief seabed. Our results clearly demonstrate the effectiveness of relief visualisation techniques for exposing subtle relief variation in bathymetric data. We find that small-scale features (outcrops, wrecks, pockmarks, reefs, etc.) and negative linear features are best highlighted by “visualization for archaeological topography” (VAT) and “openness” techniques. High-relief features and topographic infection points are pronounced by “hillshade from multiple directions” and “sky-view factor” (SVF). Finally, “principal components analysis” (PCA), “prismatic openness”, “simple local relief model”, “anisotropic SVF” and “local dominance” algorithms show best results when we want to highlight both high- and low-relief features in one image. The tested techniques are far superior to a simple hillshade visualisation especially when imaging low-gradient relief (common on continental shelves and abyssal plains) where topographic details are often not adequately pronounced by hillshading. To our knowledge, this study represents the first attempt to test and compare several relief visualisation techniques for bathymetric data.  </p>

Graph matching

This chapter explores parallel algorithms for graph matching. Here, a graph is the mathematical representation of a network, with vertices representing the nodes of the network and edges representing their connections. The edges have positive weights, and the aim is to find a matching with maximum total weight. The chapter first presents a sequential, parallelizable approximation algorithm based on local dominance that guarantees attaining at least half the optimal weight in near-linear time. This algorithm, coupled with a vertex partitioning, is the basis for developing a parallel algorithm. The BSP approach is shown to be especially advantageous for graph problems, both in developing a parallel algorithm and in proving it correct. The basic parallel algorithm is enhanced by giving preference to local matches when breaking ties and by adding a load-balancing mechanism. The scalability of the parallel algorithm is put to the test using graphs of up to 150 million edges.

Are local dominance and inter-clade dynamics causally linked when one fossil clade displaces another?

Disputing the supposition that ecological competition drives macroevolutionary patterns is now a familiar goal in many fossil biodiversity studies. But it is an elusive goal, hampered by patchy sampling, few assemblage-level comparative analyses, unverified ecological equivalence of clades and a dearth of appropriate statistical tools. We address these concerns with a fortified and vetted compilation of 40190 fossil species occurrences of cyclostome and cheilostome bryozoans, a canonical example of one taxonomically dominant clade being displaced by another. Dramatic increases in Cretaceous cheilostome genus diversification rates begin millions of years before cheilostomes overtake cyclostomes in local species proportions. Moreover, analyses of origination and extinction rates over 150 Myr suggest that inter-clade dynamics are causally linked to each other, but not to changing assemblage-level proportions.One Sentence SummaryGlobal fossil diversification rates and local taxonomic dominance are not causally linked.