Influence of historical changes in tropical reef habitat on the diversification of coral reef fishes

Past environmental changes are expected to have profoundly impacted diversity dynamics through time. While some previous studies showed an association between past climate changes or tectonic events and important shifts in lineage diversification, it is only recently that past environmental changes have been explicitly integrated in diversification models to test their influence on diversification rates. Here, we used a global reconstruction of tropical reef habitat dynamics during the Cenozoic and phylogenetic diversification models to test the influence of (i) major geological events, (ii) reef habitat fragmentation and (iii) reef area on the diversification of 9 major clades of tropical reef fish (Acanthuridae, Balistoidea, Carangoidea, Chaetodontidae, Haemulinae, Holocentridae, Labridae, Pomacentridae and Sparidae). The diversification models revealed a weak association between paleo-habitat changes and diversification dynamics. Specifically, the fragmentation of tropical reef habitats over the Cenozoic was found to be a driver of tropical reef fish diversification for 2 clades. However, overall, our approach did not allow the identification of striking associations between diversification dynamics and paleo-habitat fragmentation in contrast with theoretical model’s predictions.

Uneven protection of persistent giant kelp forest in the Northeast Pacific Ocean

In most regions, the distribution of marine forests and the efficacy of their protection is unknown. We mapped the persistence of giant kelp forests across ten degrees of latitude in the Northeast Pacific Ocean and found that 7.7% of giant kelp is fully protected, with decreasing percentages from north to south. Sustainability goals should prioritize kelp mapping and monitoring, while protection and climate adaption targets should account for habitat dynamics.

Linking erosion-deposition to geomorphic units changes in a high-gradient stream in the Central Chilean Andes

<p>Geomorphic changes in rivers often happen after either single high magnitude floods or several following ordinary flood events. Erosion and deposition have been well documented in all types of rivers, as well as the formation and destruction of step-pool sequences. However, there are less evidence available on the link between erosion-deposition at the reach scale and the formation-destruction of geomorphic units. This work is based on a series of field surveys carried out in a small glacierized basin in the central Chilean Andes. The location and extent of erosion/deposition were quantified using the photogrammetric technique with a drone before and after a high magnitude flood occurred during autumn 2016. High-resolution Digital Elevation Models (DEMs) were computed to generate erosion-deposition maps (DoD; Difference of DEMs). Also, orthomosaics were used to derive maps of geomorphic units for a 100-m long study reach, before and after the studied flood event. Results show an overall deposition of sediments in the study reach, but a decrease in the number of step-pool sequences from 20 to 14. Step-pool destruction is linked to depositional patterns, whereas the formation of new step-pool sequences is more likely to occur in erosional zones. Rapids and cascades also change in number, increasing from 1 to 4 units, and their formation was related to the deposition of sediments. These results may have larger implications in terms of ecological habitat dynamics and are also important for planning and management in civil projects like bridges and hydropower water intakes</p>

Forest Climax Phenomenon: An Invariance of Scale

We can think of forests as multiscale multispecies networks, constantly evolving toward a climax or potential natural community—the successional process-pattern of natural regeneration that exhibits sensitivity to initial conditions. This is why I look into forest succession in light of the Red Queen hypothesis and focus on the key aspects of ecological self-organisation: dynamical criticality, evolvability and intransitivity. The idea of the review is that forest climax should be associated with habitat dynamics driven by a large continuum of ecologically equivalent time scales, so that the same ecological conclusions could be drawn statistically from any scale. A synthesis of the literature is undertaken in order to (1) present the framework for assessing habitat dynamics and (2) present the types of successional trajectories based on tree regeneration mode in forest gaps. In general, there are four types of successional trajectories within the process-pattern of forest regeneration that exhibits sensitivity to initial conditions: advance reproduction specialists, advance reproduction generalists, early reproduction generalists and early reproduction specialists. A successional trajectory is an expression of a fractal connectivity among certain patterns of natural regeneration in the multiscale multispecies networks of landscape habitats. Theoretically, the organically derived measures of pattern diversity, integrity and complexity, determined by the rates of recruitment, growth and mortality of forest tree species, are the means to test the efficacy of specific interventions to avert the disturbance-related decline in forest regeneration. That is of relevance to the emerging field of biocomplexity research.

Ecological constraints coupled with deep-time habitat dynamics predict the latitudinal diversity gradient in reef fishes

We develop a spatially explicit model of diversification based on palaeohabitat to explore the predictions of four major hypotheses potentially explaining the latitudinal diversity gradient (LDG), namely, the ‘time-area’, ‘tropical niche conservatism’, ‘ecological limits’ and ‘evolutionary speed’ hypotheses. We compare simulation outputs to observed diversity gradients in the global reef fish fauna. Our simulations show that these hypotheses are non-mutually exclusive and that their relative influence depends on the time scale considered. Simulations suggest that reef habitat dynamics produced the LDG during deep geological time, while ecological constraints shaped the modern LDG, with a strong influence of the reduction in the latitudinal extent of tropical reefs during the Neogene. Overall, this study illustrates how mechanistic models in ecology and evolution can provide a temporal and spatial understanding of the role of speciation, extinction and dispersal in generating biodiversity patterns.

The House and the Household

The concept of population is central to ecology, yet it has received little attention from philosophers of ecology. Furthermore, the work that has been done often recycles ideas that have been developed for evolutionary biology. We argue that ecological populations and evolutionary populations, though intimately related, are distinct, and that the distinction matters to practicing ecologists. We offer a definition of ecological population in terms of demographic independence, where changes in abundance are a function of birth and death processes alone. However, demographic independence (DI) is insufficient on its own so we supplement it with the idea of shared habitat. An ecological population is a group of organisms of the same species in a habitat that manifests DI. Given the importance of metapopulation dynamics to modern ecology, an account of ecological population must apply to this domain as well. Thus, we extend our definition of ecological population to the metapopulation. To facilitate the extension, we introduce the metahabitat—a collection of spatially segregated habitat patches shared by a single DI population. This enables us to (1) diagnose some unhelpful trends in the metapopulation literature and (2) emphasize the importance of habitat dynamics in pursuit of the goals of theoretical ecology and conservation biology.