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The bacterial communities of the amphibian skin (i.e., the bacteriome) are critical to the host's innate immune system. However, it is unclear how different drivers can alter this function by modulating the bacteriome's structure. Our aim was to assess the extent to which different host attributes and extrinsic factors influence the structure of the bacterial communities of the skin. Skin bacterial diversity was examined in 148 individuals of the four‐eyed frog (Pleurodema thaul) from 16 localities spanning almost 1800 km in latitude. The richness and beta diversity of bacterial families and the richness and abundance of Bd‐inhibitory bacterial genera were used to describe their structure. Predictors associated with the host (developmental stage, genetic lineage, individual Batrachochytrium dendrobatidis [Bd] infection status) and the landscape (current climate, degree of anthropogenic disturbance) were used in the statistical modeling in an information theoretical approach. Bd infection and host developmental stage were the only predictors affecting bacteriome richness, with Bd+ individuals and postmetamorphic stages (adults and juveniles) having higher richness than Bd− ones and tadpoles. High diversity in Bd+ individuals is not driven by bacterial genera with known anti‐Bd properties. Beta diversity was not affected by Bd infection and was mainly a consequence of bacterial family turnover rather than nestedness. Finally, for those bacterial genera known to have inhibitory effects on chytrid, Bd+ individuals had a slightly higher diversity than Bd− ones. Our study confirms an association between Bd infection and the host developmental stage with the bacterial communities of the skin of P. thaul. Unexpectedly, macroclimate and human impact factors do not seem to play a role in shaping the amphibian skin microbiome. Our study exemplifies that focusing on a single host–parasite system over a large geographic scale can provide essential insights into the factors driving host–parasite–bacteriome interactions. [ABSTRACT FROM AUTHOR]

Assessing the heat tolerance (CTmax) of organisms is central to understand the impact of climate change on biodiversity. While both environment and evolutionary history affect CTmax, it remains unclear how these factors and their interplay influence ecological interactions, communities and ecosystems under climate change. We collected and reared caterpillars and parasitoids from canopy and ground layers in different seasons in a tropical rainforest. We tested the CTmax and Thermal Safety Margins (TSM) of these food webs with implications for how species interactions could shift under climate change. We identified strong influence of phylogeny in herbivore–parasitoid community heat tolerance. The TSM of all insects were narrower in the canopy and parasitoids had lower heat tolerance compared to their hosts. Our CTmax‐based simulation showed higher herbivore–parasitoid food web instability under climate change than previously assumed, highlighting the vulnerability of parasitoids and related herbivore control in tropical rainforests, particularly in the forest canopy. [ABSTRACT FROM AUTHOR]

Abstract: There have been over 25 independent unicellular to multicellular evolutionary transitions, which have been transformational in the complexity of life. All of these transitions likely occurred in communities numerically dominated by unicellular organisms, mostly bacteria. Hence, it is reasonable to expect that bacteria were involved in generating the ecological conditions that promoted the stability and proliferation of the first multicellular forms as protective units. In this study, we addressed this problem by analyzing the occurrence of multicellularity in an experimental phylogeny of yeasts (Sacharomyces cerevisiae) a model organism that is unicellular but can generate multicellular clusters under some conditions. We exposed a single ancestral population to periodic divergences, coevolving with a cocktail of environmental bacteria that were inoculated to the environment of the ancestor, and compared to a control (no bacteria). We quantified culturable microorganisms to the level of genera, finding up to 20 taxa (all bacteria) that competed with the yeasts during diversification. After 600 generations of coevolution, the yeasts produced two types of multicellular clusters: clonal and aggregative. Whereas clonal clusters were present in both treatments, aggregative clusters were only present under the bacteria treatment and showed significant phylogenetic signal. However, clonal clusters showed different properties if bacteria were present as follows: They were more abundant and significantly smaller than in the control. These results indicate that bacteria are important modulators of the occurrence of multicellularity, providing support to the idea that they generated the ecological conditions‐promoting multicellularity. [ABSTRACT FROM AUTHOR]

A number of hypotheses about compensatory mechanisms that allow ectothermic animals to cope with the latitudinal decrease in ambient temperature ( T A ) have been proposed during the last century. One of these hypotheses, the 'metabolic homeostasis' hypothesis (MHH), states that species should show the highest thermal sensitivity of the metabolic rate ( Q 10-SMR ) at the colder end of the range of T A s they usually experience in nature. This way, species should be able to minimize maintenance costs during the colder hours of the day, but quickly take advantage of increases in T A during the warmer parts of the day. Here, we created a dataset that includes Q 10-SMR values for 58 amphibian species, assessed at four thermal ranges, to evaluate three predictions derived from the MHH. In line with this hypothesis, we found that: (i) Q 10-SMR values tended to be positively correlated with latitude when measured at lower T A s, but negative correlated with latitude when measured at higher T A s, (ii) Q 10-SMR measured at lower T A s were higher in temperate species, whereas Q 10-SMR measured at higher T A s were higher in tropical species, and (iii) the experimental T A at which Q 10-SMR was maximal for each species decreased with latitude. This is the first study to our knowledge showing that the relationship between Q 10-SMR and latitude in ectotherms changes with the T A at which Q 10-SMR is assessed, as predicted from an adaptive hypothesis. This article is part of the theme issue 'Physiological diversity, biodiversity patterns and global climate change: testing key hypotheses involving temperature and oxygen'.

Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomical measure of the aerobic power of an animal. Although several authors have compared heart masses across bird species, a phylogenetic comparative analysis is still lacking. By compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g. model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart size is consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e. hummingbirds) have substantially larger hearts than other groups, species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study reveals that on a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)