Breeding system and reproductive skew in a highly polygynous ant population

Abstract.: Factors affecting relatedness among nest members in ant colonies with high queen number are still poorly understood. In order to identify the major determinants of nest kin structure, we conducted a detailed analysis of the breeding system of the ant Formica exsecta. We estimated the number of mature queens by mark-release-recapture in 29 nests and dissected a sub-sample of queens to assess their reproductive status. We also used microsatellites to estimate relatedness within and between all classes of nestmates (queens, their mates, worker brood, queen brood and male brood). Queen number was very high, with an arithmetic mean of 253 per nest. Most queens (90%) were reproductively active, consistent with the genetic analyses revealing that there was only a minimal reproductive skew among nestmate queens. Despite the high queen number and low reproductive skew, almost all classes of individuals were significantly related to each other. Interestingly, the number of resident queens was a poor predictor of kin structure at the nest level, consistent with the observation that new queens are produced in bursts leading to highly fluctuating queen number across years. Queen number also varied tremendously across nests, with estimates ranging from five to several hundred queens. Accordingly, the harmonic mean queen number (40.5) was six times lower than the arithmetic mean. The variation in queen number was the most important factor of the breeding system contributing to a significant relatedness between almost all classes of nestmates despite a high average number of queens per nes

Experimentally induced community assembly of polypores reveals the importance of both environmental filtering and assembly history

The community assembly of wood-inhabiting fungi follows a successional pathway, with newly emerging resource patches being colonised by pioneer species, followed by those specialised on later stages of decay. The primary coloniser species have been suggested to strongly influence the assembly of the later-arriving community. We created an artificial resource pulse and studied the assembly of polypores over an 11yr period to ask how the identities of the colonising species depend on the environmental characteristics and the assembly history of the dead wood unit. Our results support the view that community assembly in fungi is a highly stochastic process, as even detailed description of the characteristics of dead wood (host tree species, size, decay class of the resource unit, its bark cover and how sunken it is to the ground) and the prior community structure provided only limited predictive power on the newly colonising species. Yet, we identified distinct links between primary and secondary colonising species and showed how the spatial aggregation of dead wood had a great impact on the community assembly. © 2019 Elsevier Ltd and British Mycological SocietyPeer reviewe

Continuity of Local Time: An applied perspective

Continuity of local time for Brownian motion ranks among the most notable mathematical results in the theory of stochastic processes. This article addresses its implications from the point of view of applications. In particular an extension of previous results on an explicit role of continuity of (natural) local time is obtained for applications to recent classes of problems in physics, biology and finance involving discontinuities in a dispersion coefficient. The main theorem and its corollary provide physical principles that relate macro scale continuity of deterministic quantities to micro scale continuity of the (stochastic) local time.Comment: To appear in: "The fascination of Probability, Statistics and Their Applications. In honour of Ole E. Barndorff-Nielsen on his 80th birthday

Invasion rate of deer ked depends on spatiotemporal variation in host density

Invasive parasites are of great global concern. Understanding the factors influencing the spread of invading pest species is a first step in developing effective countermeasures. Growing empirical evidence suggests that spread rates are essentially influenced by spatiotemporal dynamics of host-parasite interactions, yet approaches modelling spread rate have typically assumed static environmental conditions. We analysed invasion history of the deer ked (Lipoptena cervi) in Finland with a diffusion-reaction model, which assumed either the movement rate, the population growth rate, or both rates may depend on spatial and temporal distribution of moose (Alces alces), the main host of deer ked. We fitted the model to the data in a Bayesian framework, and used the Bayesian information criterion to show that accounting for the variation in local moose density improved the model's ability to describe the pattern of the invasion. The highest ranked model predicted higher movement rate and growth rate of deer ked with increasing moose density. Our results suggest that the historic increase in host density has facilitated the spread of the deer ked. Our approach illustrates how information about the ecology of an invasive species can be extracted from the spatial pattern of spread even with rather limited dat

Host--parasite models on graphs

The behavior of two interacting populations, ``hosts''and ``parasites'', is investigated on Cayley trees and scale-free networks. In the former case analytical and numerical arguments elucidate a phase diagram, whose most interesting feature is the absence of a tri-critical point as a function of the two independent spreading parameters. For scale-free graphs, the parasite population can be described effectively by Susceptible-Infected-Susceptible-type dynamics in a host background. This is shown both by considering the appropriate dynamical equations and by numerical simulations on Barab\'asi-Albert networks with the major implication that in the termodynamic limit the critical parasite spreading parameter vanishes.Comment: 10 pages, 6 figures, submitted to PRE; analytics redone, new calculations added, references added, appendix remove

Design matters : an evaluation of the impact of small man-made forest clearings on tropical bats using a before-after-control-impact design

In recent years, large clearings (>1000 ha) accounted for gradually smaller amounts of total annual deforestation in the Brazilian Amazon, whereas the proportion of small clearings (<50 ha) nowadays represents more than 80% of annual deforestation. Despite the ubiquity of small clearings in fragmented Amazonian landscapes, most fragmentation research has focused on the effects of large-scale deforestation, leading to a poor understanding of the impacts of smaller barriers on Amazonian vertebrates. We capitalized on the periodical re-isolation of experimental forest fragments at the Biological Dynamics of Forest Fragments Project in the Central Amazon as a before-after-control-impact experiment to investigate the short-term effects of small clearings on bat assemblages. Over the course of three years we sampled six control sites in continuous forest, the interiors and edges of eight forest fragments as well as eight sites in the surrounding matrix. Sampling took place both before and after the experimental manipulation (clearing of a 100 m wide strip of regrowth around each fragment), resulting in ~4000 bat captures. Species were classified as old-growth specialists and habitat generalists according to their habitat affinities and a joint species distribution modeling framework was used to investigate the effect of fragment re-isolation on species occupancy. Following fragment re-isolation, species richness declined in all habitats other than fragment edges and, although responses were idiosyncratic, this decline was more pronounced for forest specialist than for generalist species. Additionally, fragment re-isolation led to a reduction in the similarity between assemblages in modified habitats (fragment interiors, edges and matrix) and continuous forest. Sampling of controls in continuous forest both prior to and after reisolation revealed that much of the variation in bat species occupancy between sampling periods did not arise from fragment re-isolation but rather reflected natural spatiotemporal variability. This emphasizes the need to sample experimental controls both before and after experimental manipulation and suggests caution in the interpretation of results from studies in which the effects of habitat transformations are assessed based solely on data collected using space-for-time substitution approaches

Design matters : an evaluation of the impact of small man-made forest clearings on tropical bats using a before-after-control-impact design

In recent years, large clearings (>1000 ha) accounted for gradually smaller amounts of total annual deforestation in the Brazilian Amazon, whereas the proportion of small clearings (<50 ha) nowadays represents more than 80% of annual deforestation. Despite the ubiquity of small clearings in fragmented Amazonian landscapes, most fragmentation research has focused on the effects of large-scale deforestation, leading to a poor understanding of the impacts of smaller barriers on Amazonian vertebrates. We capitalized on the periodical re-isolation of experimental forest fragments at the Biological Dynamics of Forest Fragments Project in the Central Amazon as a before-after-control-impact experiment to investigate the short-term effects of small clearings on bat assemblages. Over the course of three years we sampled six control sites in continuous forest, the interiors and edges of eight forest fragments as well as eight sites in the surrounding matrix. Sampling took place both before and after the experimental manipulation (clearing of a 100 m wide strip of regrowth around each fragment), resulting in ~4000 bat captures. Species were classified as old-growth specialists and habitat generalists according to their habitat affinities and a joint species distribution modeling framework was used to investigate the effect of fragment re-isolation on species occupancy. Following fragment re-isolation, species richness declined in all habitats other than fragment edges and, although responses were idiosyncratic, this decline was more pronounced for forest specialist than for generalist species. Additionally, fragment re-isolation led to a reduction in the similarity between assemblages in modified habitats (fragment interiors, edges and matrix) and continuous forest. Sampling of controls in continuous forest both prior to and after reisolation revealed that much of the variation in bat species occupancy between sampling periods did not arise from fragment re-isolation but rather reflected natural spatiotemporal variability. This emphasizes the need to sample experimental controls both before and after experimental manipulation and suggests caution in the interpretation of results from studies in which the effects of habitat transformations are assessed based solely on data collected using space-for-time substitution approaches

Direct and indirect effects of a pH gradient bring insights into the mechanisms driving prokaryotic community structures

Background: pH is frequently reported as the main driver for prokaryotic community structure in soils. However, pH changes are also linked to "spillover effects" on other chemical parameters (e.g., availability of Al, Fe, Mn, Zn, and Cu) and plant growth, but these indirect effects on the microbial communities are rarely investigated. Usually, pH also co-varies with some confounding factors, such as land use, soil management (e.g., tillage and chemical inputs), plant cover, and/or edapho-climatic conditions. So, a more comprehensive analysis of the direct and indirect effects of pH brings a better understanding of the mechanisms driving prokaryotic (archaeal and bacterial) community structures. Results: We evaluated an agricultural soil pH gradient (from 4 to 6, the typical range for tropical farms), in a liming gradient with confounding factors minimized, investigating relationships between prokaryotic communities (16S rRNA) and physical-chemical parameters (indirect effects). Correlations, hierarchical modeling of species communities (HMSC), and random forest (RF) modeling indicated that both direct and indirect effects of the pH gradient affected the prokaryotic communities. Some OTUs were more affected by the pH changes (e.g., some Actinobacteria), while others were more affected by the indirect pH effects (e.g., some Proteobacteria). HMSC detected a phylogenetic signal related to the effects. Both HMSC and RF indicated that the main indirect effect was the pH changes on the availability of some elements (e.g., Al, Fe, and Cu), and secondarily, effects on plant growth and nutrient cycling also affected the OTUs. Additionally, we found that some of the OTUs that responded to pH also correlated with CO2, CH4, and N2O greenhouse gas fluxes. Conclusions: Our results indicate that there are two distinct pH-related mechanisms driving prokaryotic community structures, the direct effect and "spillover effects" of pH (indirect effects). Moreover, the indirect effects are highly relevant for some OTUs and consequently for the community structure; therefore, it is a mechanism that should be further investigated in microbial ecology.Peer reviewe

Direct and indirect effects of a pH gradient bring insights into the mechanisms driving prokaryotic community structures

Background: pH is frequently reported as the main driver for prokaryotic community structure in soils. However, pH changes are also linked to "spillover effects" on other chemical parameters (e.g., availability of Al, Fe, Mn, Zn, and Cu) and plant growth, but these indirect effects on the microbial communities are rarely investigated. Usually, pH also co-varies with some confounding factors, such as land use, soil management (e.g., tillage and chemical inputs), plant cover, and/or edapho-climatic conditions. So, a more comprehensive analysis of the direct and indirect effects of pH brings a better understanding of the mechanisms driving prokaryotic (archaeal and bacterial) community structures. Results: We evaluated an agricultural soil pH gradient (from 4 to 6, the typical range for tropical farms), in a liming gradient with confounding factors minimized, investigating relationships between prokaryotic communities (16S rRNA) and physical-chemical parameters (indirect effects). Correlations, hierarchical modeling of species communities (HMSC), and random forest (RF) modeling indicated that both direct and indirect effects of the pH gradient affected the prokaryotic communities. Some OTUs were more affected by the pH changes (e.g., some Actinobacteria), while others were more affected by the indirect pH effects (e.g., some Proteobacteria). HMSC detected a phylogenetic signal related to the effects. Both HMSC and RF indicated that the main indirect effect was the pH changes on the availability of some elements (e.g., Al, Fe, and Cu), and secondarily, effects on plant growth and nutrient cycling also affected the OTUs. Additionally, we found that some of the OTUs that responded to pH also correlated with CO2, CH4, and N2O greenhouse gas fluxes. Conclusions: Our results indicate that there are two distinct pH-related mechanisms driving prokaryotic community structures, the direct effect and "spillover effects" of pH (indirect effects). Moreover, the indirect effects are highly relevant for some OTUs and consequently for the community structure; therefore, it is a mechanism that should be further investigated in microbial ecology.Peer reviewe

Refining predictions of metacommunity dynamics by modeling species non-independence

Abstract Predicting the dynamics of biotic communities is difficult because species? environmental responses are not independent, but covary due to shared or contrasting ecological strategies and the influence of species interactions. We used latent-variable joint species distribution models to analyse paired historical and contemporary inventories of 585 vascular plant species on 471 islands in the south-west Finnish archipelago. Larger, more heterogeneous islands were characterized by higher colonisation rates and lower extinction rates. Ecological and taxonomical species groups explained small but detectable proportions of variance in species? environmental responses. To assess the potential influence of species interactions on community dynamics, we estimated species associations as species-to-species residual correlations for historical occurrences, for colonisations, and for extinctions. Historical species associations could to some extent predict joint colonisation patterns, but the overall estimated influence of species associations on community dynamics was weak. These results illustrate the benefits of considering metacommunity dynamics within a joint framework, but also suggest that any influence of species interactions on community dynamics may be hard to detect from observational data.Peer reviewe