Myxomycetes of the Caramoan Islands and an update on the species found in the Bicol Peninsula, Philippines

The main objective of this study was to characterize the assemblages of myxomycetes on isolated Philippine islands through a correlational study using geographical and ecological distance in the Caramoan Islands, including an updated checklist of the myxomycetes of the Bicol Peninsula. Four islands of varying sizes and distances from each other, but all within relatively close proximity to the mainland of the Bicol Peninsula, were surveyed. A combination of traditional and more contemporary ecological tools was used to analyze diversity indices among and between the islands. Among the four islands, Matukad Island recorded the highest species richness (46.8) and taxonomic diversity index (2.6), while ranking next to Lahos island in terms of species diversity (7.9). Pairwise comparisons using community similarity indices and clustering analysis consistently showed that Lahos and Matukad are the most similar to each other, while also being closer to one another but situated farthest from the mainland. On the other hand, the two smallest islands, which were also closest to each other and to the mainland, grouped together using clustering analysis but recorded the lowest pairwise percentage similarity value. The ecological patterns in this study appear to follow the unified neutral theory of biodiversity and biogeography more than the insular biogeography theory. In addition, this study added 16 new morphospecies to the list of myxomycetes known from the Bicol Peninsula, which brings the total to 73, including one new record for the country [Lamproderma arcyrioides (Sommerf.) Rostaf.] KEYWORDS: slime molds, insular, biodiversity, paleotropics, unified netural theory

A theoretic approach to the mode of gut microbiome translocation in SIV-infected Asian macaques

ABSTRACT Human gut microbiome could translocate to other tissues, and the relocation triggered by HIV/SIV infection has received increasing attention. However, the underlying mode of this translocation, whether it is deterministic or random (passive) process, is not clear, not to mention quantitative estimation of the relocation probability and rates. Using multi-tissue microbiome datasets collected from SIV-infected macaques, originally reported by Klase et al. (2015), we apply Hubbell's unified neutral theory of biodiversity (UNTB) implemented by Harris et al. (2017) in the form of multi-site neutral (MSN) model to explore the translocation mode and rates of the gut microbiome. We found that (i) The translocation from gastrointestinal tract to tissues was driven by stochastic (neutral) forces as revealed by 100% neutrality-passing rates with MSN testing; (ii) The translocation probability from gastrointestinal tract to tissues is significantly larger than the baseline dispersal rates occurring within gastrointestinal tract (0.234 vs. 0.006 at the phylum level, P< 0.001). (iii) Approximately, 23% of phyla and 55% of genera were migrated from gastrointestinal tract to the tissues (liver and mesenteric lymph nodes). Our findings offer the first interpretation of the microbial translocation mode from gastrointestinal tract to tissues, and the first estimates of the translocation probability and level.

How does species richness accumulate over time?

Species are units for understanding the evolution of diversity over large geographical scales and long timescales. This chapter investigates the processes causing proliferation and demise of species diversity within lineages and regions. Phylogenetic approaches have focused on documenting speciation and extinction rates, but mechanistic theory explaining variation in rates is scarce. Diversity patterns are better explained by geographical and ecological opportunity than by correlates of speciation and extinction rates per se. The neutral theory of biodiversity provides a framework that can be adapted to predict diversity patterns in terms of limits due to competition for space and resources, and species turnover (which cannot be detected directly from phylogenetic trees). These theories bring macroevolutionary and microevolutionary theories closer together. In particular, diversity patterns are the outcome of individual selection and dispersal playing out over long timescales. Some of the processes influencing species patterns can also structure diversity at higher taxonomic levels.

Quantifying the Scientific Cost of Ambiguous Terminology in Community Ecology

Fundamental terms in the field of ecology are ambiguous, with multiple meanings associated with them. While this could lead to confusion, discord, or even tests that violate core assumptions of a given theory or model, this ambiguity could also be a feature that allows for new knowledge creation through the interconnected nature of concepts. We approached this debate from a quantitative perspective, and investigated the cost of ambiguity related to definitions of ecological units in ecology related to the general term “community.” We did a meta-analysis of tests associated with two bodies of literature, Hubbell’s unified neutral theory of biodiversity and biogeography and Diamond’s assembly rules, that rely on a specific ecological unit that assumes that species are existing within a local area and that they have overlapping resource needs. We predicted that if ambiguous terminology is widespread, then researchers will have tested them with many different ecological units, that in addition some of these ecological units will violate the core assumptions of the theory, and finally that the overall level of support for a theory will be stronger if appropriate ecological units were used. We found that indeed multiple different ecological units were used in the literature to test both theories, with 65 percent appropriate ecological units for neutral theory tests, and only 6 percent for assembly rule tests. Finally, there was some evidence that the support for a theory depended on whether appropriate ecological units were used for neutral tests, but there was not enough data for the assembly rule tests. These results thus show that ambiguous terminology in ecology is having measurable effects on research and is not of solely philosophical concern. We advocate that authors be explicit in their writing and outline core assumptions of theories, that researchers apply these consistently in their tests, and that readers be attentive to what is written and cognizant of their potential biases.

Macroscale estimates of species abundance reveal evolutionary drivers of biodiversity

Evolutionary processes underpin the biodiversity on the planet. Theories advocate that the form of the species abundance distribution (SAD), presented by the number of individuals for each species within an ecological community, is intimately linked to speciation modes such as point mutation and random fission. This prediction has rarely been, however, verified empirically; the fact that species abundance data can be obtained only from local communities critically limits our ability to infer the role of macroevolution in shaping ecological patterns. Here, we developed a novel statistical model to estimate macroscale SADs, the hidden macroecological property, by integrating spatially replicated multispecies detection-nondetection observations and the data on species geographic distributions. We determined abundance of 1,248 woody plant species at a 10 km grid square resolution over East Asian islands across subtropical to temperate biomes, which produced a metacommunity (i.e. species pool) SAD in four insular ecoregions along with its absolute size. The metacommunity SADs indicated lognormal-like distributions, which were well explained by the unified neutral theory of biodiversity and biogeography (UNTB) with protracted speciation, a mode of speciation intermediate between point mutation and random fission. Furthermore, the analyses yielded an estimate of speciation rate in each region that highlighted the importance of geographic characteristics in macroevolutionary processes and predicted the average species lifetime that was congruent with previous estimates. The estimation of macroscale SADs plays a remarkable role in revealing evolutionary diversification of regional species pools.

Species diversity rises exponentially with the number of available resources in a multi-trait competition model

Theoretical studies of ecosystem models have generally concluded that large numbers of species will not stably coexist if the species are all competing for the same limited set of resources. Here, we describe a simple multi-trait model of competition where the presence of N resources will lead to the stable coexistence of up to 2 N species. Our model also predicts that the long-term dynamics of the population will lie on a neutral attractor hyperplane. When the population shifts within the hyperplane, its dynamics will behave neutrally, while shifts which occur perpendicular to the hyperplane will be subject to restoring forces. This provides a potential explanation of why complex ecosystems might exhibit both niche-like and neutral responses to perturbations. Like the neutral theory of biodiversity, our model generates good fits to species abundance distributions in several datasets but does so without needing to evoke inter-generational stochastic effects, continuous species creation or immigration dynamics. Additionally, our model is able to explain species abundance correlations between independent but similar ecosystems separated by more than 1400 km inside the Amazonian forests.