Host functional and phylogenetic composition rather than host diversity structure plant-herbivore networks

Declining plant diversity alters ecological networks, such as plant-herbivore interactions. However, our knowledge of the potential mechanisms underlying effects of plant species loss on plant-herbivore network structure is still limited. We used DNA barcoding to identify herbivore-host plant associations along declining levels of tree diversity in a large-scale, subtropical biodiversity experiment. We tested for effects of tree species richness, host functional and phylogenetic diversity, and host functional (leaf trait) and phylogenetic composition on species, phylogenetic and network composition of herbivore communities. We found that phylogenetic host composition and related palatability/defence traits but not tree species richness significantly affected herbivore communities and interaction network complexity at both the species and community levels. Our study indicates that evolutionary dependencies and functional traits of host plants determine the composition of higher trophic levels and corresponding interaction networks in species-rich ecosystems. Our findings highlight that characteristics of the species lost have effects on ecosystem structure and functioning across trophic levels that cannot be predicted from mere reductions in species richness.

Dramatic Remodeling of the Gut Microbiome Around Parturition and Its Relationship With Host Serum Metabolic Changes in Sows

Perinatal care is important in mammals due to its contribution to fetal growth, maternal health, and lactation. Substantial changes in host hormones, metabolism, and immunity around the parturition period may be accompanied by alterations in the gut microbiome. However, to our knowledge, changes in the gut microbiome and their contribution to the shifts in host metabolism around parturition have not been investigated in pigs. Furthermore, pigs are an ideal biomedical model for studying the interactions of the gut microbiota with host metabolism, due to the ease of controlling feeding conditions. Here we report dramatic remodeling of the gut microbiota and the potential functional capacity during the late stages of pregnancy (5 days before parturition, LP) to postpartum (within 6 h after delivery, PO) in both experimental and validated populations of sows (n = 107). The richness of bacteria in the gut of both pregnant and delivery sows significantly decreased, whilst the β-diversity dramatically expanded. The ratio of Bacteroidetes to Firmicutes, and the relative abundance of Prevotella significantly decreased, whilst the relative abundance of the predominant genus Lactobacillus significantly increased from LP to PO state. The predicted functional capacities of the gut microbiome related to amino acid metabolism, the metabolism of cofactors and vitamins, and glycan biosynthesis were significantly decreased from LP to PO state. However, the abundance of the functional capacities associated with carbohydrate and lipid metabolism were increased. Consistent with these changes, serum metabolites enriched at the LP stage were associated with the metabolism of amino acids and vitamins. In contrast, metabolites enriched at the PO stage were related to lipid metabolism. We further identified that the richness and β-diversity of the gut microbiota and the abundance of Lactobacillus accounted for shifts in the levels of bile acid metabolites associated with lipid metabolism. The results suggest that host-microbiota interactions during the perinatal period impact host metabolism. These benefit the lactation of sows by providing energy from lipid metabolism for milk production.

Area and distance from mainland affect in different ways richness and phylogenetic diversity of snakes in Atlantic Forest coastal islands

AIM

The Theory of Island Biogeography posits that ecological and evolutionary processes regulate species richness of isolated areas. We assessed the influences of an island area and distance from the mainland on species richness, phylogenetic diversity, and phylogenetic composition of snakes on coastal islands.

LOCATION

Coastal islands of the megadiverse Atlantic Forest in southeastern Brazil.

METHODS

We compiled the species composition of 17 coastal islands in southeastern Brazil. Species richness and phylogenetic diversity were calculated for each island. Phylogenetic composition was measured using principal coordinates of phylogenetic structure. We then employed generalized linear models to test the influence of area and distance from the mainland on the diversity metrics.

RESULTS

We found a prominent influence of area on species richness, whereas phylogenetic diversity was more affected by distance from the mainland. Snake clades were distinctly associated with area and distance. The Boidae family was associated with nearer and larger islands, whereas Elapidae was broadly distributed. Distance from the mainland was associated with the distribution of Dipsadidae, whereas Colubridae was influenced by both the area and distance. The Viperidae family attained higher values of phylogenetic diversity in smaller and more remote islands.

MAIN CONCLUSIONS

This island system conserved a considerable piece of snake richness from southeastern Brazil, including island endemic species. Area and distance from the mainland were important drivers of snake diversity in the Atlantic Forest coastal islands. However, these predictors affected the different components of diversity in different ways. Phylogenetic composition analysis enables us to understand how basal nodes contributed to high levels of phylogenetic diversity on smaller and farther islands regardless of the decrease in species richness.

Evidence for phylogenetic correlation of plant-AMF assemblages?

BACKGROUND AND AIMS

Specificity in biotic interactions is mediated' by functional traits inducing shifts in the community species composition. Functional traits are often evolutionarily conserved, resulting in closely related species tending to interact with similar species. This tendency may initially shape the phylogenetic composition of coexisting guilds, but other intraguild ecological processes may either blur or promote the mirroring of the phylogenetic compositions between guilds. The roles of intra- and interguild interactions in shaping the phylogenetic community composition are largely unknown, beyond the mere selectivity in the interguild interactions. Plant facilitation is a phylogenetically structured species-specific process involving interactions not only between the same guild of plants, but also between plants and other guilds such as arbuscular mycorrhizal fungi (AMF). In this study it is hypothesized that reciprocal plant-AMF interactions will leave an interdependent phylogenetic signal in the community composition of both plants and AMF.

METHODS

A correlation was used to test for a relationship between the phylogenetic composition of plant and AMF assemblages in a patchy xeric shrubland environment shaped by plant facilitation. In addition, a null model was used to test whether this correlation can be solely explained by selectivity in plant-AMF interactions.

KEY RESULTS

A significant correlation was observed between the phylogenetic composition of plant and AMF assemblages. Plant phylogenetic composition in a patch was related to the predominance of plant species with high nursery quality that can influence the community assembly. AMF phylogenetic composition was related to the AMF phylogenetic diversity in each patch.

CONCLUSIONS

This study shows that shifts in the phylogenetic composition of plants and AMF assemblages do not occur independently. It is suggested that besides selectivity in plant-AMF interactions, inter-related succession dynamics of plants and AMF within patches could be an ecological mechanism driving community assembly. Future lines of research might explore whether interlinked above- and below-ground dynamics could be occurring across multiple guilds simultaneously.