Is salamander arboreality limited by broad-scale climatic conditions?

Identifying the historical processes that drive microhabitat transitions across deep time is of great interest to evolutionary biologists. Morphological variation can often reveal such mechanisms, but in clades with high microhabitat diversity and no concomitant morphological specialization, the factors influencing animal transitions across microhabitats are more difficult to identify. Lungless salamanders (family: Plethodontidae) have transitioned into and out of the arboreal microhabitat many times throughout their evolutionary history without substantial morphological specialization. In this study, we explore the relationship between microhabitat use and broad-scale climatic patterns across species’ ranges to test the role of climate in determining the availability of the arboreal microhabitat. Using phylogenetic comparative methods, we reveal that arboreal species live in warmer, lower elevation regions than terrestrial species. We also employ ecological niche modeling as a complementary approach, quantifying species-level pairwise comparisons of niche overlap. The results of this approach demonstrate that arboreal species on average display more niche overlap with other arboreal species than with terrestrial species after accounting for non-independence of niche model pairs caused by geographic and phylogenetic distances. Our results suggest that occupation of the arboreal microhabitat by salamanders may only be possible in sufficiently warm, low elevation conditions. More broadly, this study indicates that the impact of micro-environmental conditions on temporary microhabitat use, as demonstrated by small-scale ecological studies, may scale up dramatically to shape macroevolutionary patterns.

Forbidden links, trait matching and modularity in plant-hummingbird networks: Are specialized modules characterized by higher phenotypic floral integration?

Background Plant-pollinator mutualistic networks show non-random structural properties that promote species coexistence. However, these networks show high variability in the interacting species and their connections. Mismatch between plant and pollinator attributes can prevent interactions, while trait matching can enable exclusive access, promoting pollinators’ niche partitioning and, ultimately, modularity. Thus, plants belonging to specialized modules should integrate their floral traits to optimize the pollination function. Herein, we aimed to analyze the biological processes involved in the structuring of plant-hummingbird networks by linking network morphological constraints, specialization, modularity and phenotypic floral integration. Methods We investigated the understory plant-hummingbird network of two adjacent habitats in the Lacandona rainforest of Mexico, one characterized by lowland rainforest and the other by savanna-like vegetation. We performed monthly censuses to record plant-hummingbird interactions for 2 years (2018–2020). We also took hummingbird bill measurements and floral and nectar measurements. We summarized the interactions in a bipartite matrix and estimated three network descriptors: connectance, complementary specialization (H2’), and nestedness. We also analyzed the modularity and average phenotypic floral integration index of each module. Results Both habitats showed strong differences in the plant assemblage and network dynamics but were interconnected by the same four hummingbird species, two Hermits and two Emeralds, forming a single network of interaction. The whole network showed low levels of connectance (0.35) and high specialization (H2’ = 0.87). Flower morphologies ranged from generalized to specialized, but trait matching was an important network structurer. Modularity was associated with morphological specialization. The Hermits Phaethornis longirostris and P. striigularis each formed a module by themselves, and a third module was formed by the less-specialized Emeralds: Chlorestes candida and Amazilia tzacatl. The floral integration values were higher in specialized modules but not significantly higher than that formed by generalist species. Conclusions Our findings suggest that biological processes derived from both trait matching and “forbidden” links, or nonmatched morphological attributes, might be important network drivers in tropical plant-hummingbird systems while morphological specialization plays a minor role in the phenotypic floral integration. The broad variety of corolla and bill shapes promoted niche partitioning, resulting in the modular organization of the assemblage according to morphological specialization. However, more research adding larger datasets of both the number of modules and pollination networks for a wider region is needed to conclude whether phenotypic floral integration increases with morphological specialization in plant-hummingbird systems.

The Ecology of Sleep in Reptiles

Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore, are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep, the ecological context of sleep in reptiles remains understudied and without systematic direction. In this review, we examine multiple aspects of reptilian sleep, including (1) habitat selection (sleep sites and their spatio-temporal distribution), (2) individual-level traits, such as behaviour (sleep postures), morphology (limb morphometrics and body colour), and physiology (sleep architecture), as well as (3) inter-individual interactions (intra- and inter-specific). Throughout, we discuss the evidence of predation, competition, and thermoregulation in influencing sleep traits and the possible evolutionary consequences of these sleep traits for reptile sociality, morphological specialization, and habitat partitioning. We also review the ways in which sleep ecology interacts with urbanisation, biological invasions, and climate change. Overall, we not only provide a systematic evaluation of the conceptual and taxonomic biases in the existing literature on reptilian sleep, we use this opportunity to organise the various ecological hypotheses for sleep characteristics. By highlighting the gaps and providing a prospectus of research directions, our review sets the stage for understanding sleep ecology in the natural world.

Systematic Position of the Enigmatic Psocid Family Lesneiidae (Insecta: Psocodea: Psocomorpha), With Description of Two New Species

The systematic placement of an enigmatic psocid family restricted to Africa, Lesneiidae, was estimated by using a multiple gene data set. The candidates for its close relatives are now classified under two different infraorders, the family Archipsocidae of the infraorder Archipsocetae or the families Elipsocidae/Mesopsocidae of the infraorder Homilopsocidea. The maximum likelihood and Bayesian analyses of the molecular data set strongly suggested that the Lesneiidae belongs to Homilopsocidea and forms a clade with Elipsocidae/Mesopsocidae/Eolachesillinae (Lachesillidae). However, the relationships among these (sub)families and Lesneiidae, including the monophyly of Elipsocidae and Mesopsocidae, were ambiguous or questionable, showing the necessity of further investigations for elucidating their relationships and validating the status of these families. Two species, L. johnsoni Yoshizawa & Lienhard, n. sp. and L. testudinata Yoshizawa & Lienhard, n. sp. (Psocodea: Lesneiidae), were described from South Africa. There appears to be a tight association between the reproductive biology and morphological specialization of this group.

Structural patterns of a coastal hermit crab-gastropod shell interaction network: new insights from a unique relationship

Hermit crabs are ideal organisms for assessing how species that share resources can coexist, as these crustacean species have an intimate relationship with gastropod shells and therefore compete for this particular resource. There is compelling evidence that hermit crabs do not interact with gastropod shells randomly, but few studies have investigated the community-level interactions between hermit crabs and shells. Here we used network analyses to present the first community-level assessment of the structure of a hermit crab-shell interaction network in a coastal region in southeastern Brazil in order to identify mechanisms that underlie hermit crab coexistence. Our results show that the hermit crab-gastropod shell interaction network was non-nested, specialized, and modular. The modular network structure revealed differences in resource use among hermit crab species. The network structure departs from those of free-living species in which the lack of interaction intimacy between species leads to a nested pattern. Thus, the morphological specialization of hermit crabs in relation to their host shells appears to play an important role in structuring the community-level interaction network. Future studies should evaluate the relative importance of abundance and functional traits in the structure of this unique interaction network.

Genomic analysis of the tryptome reveals molecular mechanisms of gland cell evolution

Background Understanding the drivers of morphological diversity is a persistent challenge in evolutionary biology. Here, we investigate functional diversification of secretory cells in the sea anemone Nematostella vectensis to understand the mechanisms promoting cellular specialization across animals. Results We demonstrate regionalized expression of gland cell subtypes in the internal ectoderm of N. vectensis and show that adult gland cell identity is acquired very early in development. A phylogenetic survey of trypsins across animals suggests that this gene family has undergone numerous expansions. We reveal unexpected diversity in trypsin protein structure and show that trypsin diversity arose through independent acquisitions of non-trypsin domains. Finally, we show that trypsin diversification in N. vectensis was effected through a combination of tandem duplication, exon shuffling, and retrotransposition. Conclusions Together, these results reveal the numerous evolutionary mechanisms that drove trypsin duplication and divergence during the morphological specialization of cell types and suggest that the secretory cell phenotype is highly adaptable as a vehicle for novel secretory products.

Genomic analysis of the tryptome reveals molecular mechanisms of gland cell evolution

Understanding the drivers of morphological diversity is a persistent challenge in evolutionary biology. Here, we investigate functional diversification of secretory cells in the sea anemone Nematostella vectensis to understand the mechanisms promoting cellular specialization across animals. We demonstrate regionalized expression of gland cell subtypes in the internal ectoderm of N. vectensis and show that adult gland cell identity is acquired very early in development. A phylogenetic survey of trypsins across animals suggests this gene family has undergone numerous expansions. We reveal unexpected diversity in trypsin protein structure and show that trypsin diversity arose through independent acquisitions of non-trypsin domains. Finally, we show that trypsin diversification in N. vectensis was effected through a combination of tandem duplication, exon shuffling, and retrotransposition. Together we reveal that numerous evolutionary mechanisms drove trypsin duplication and divergence during the morphological specialization of cell types and suggest the secretory cell phenotype is highly adaptable as a vehicle for novel secretory products.