Functional diversity patterns have been thoroughly described for reef fishes across geographic gradients, but the effect of depth on these patterns remains largely unknown. Using diet, life-history, and behavioral traits, we evaluated the functional diversity of Caribbean reef-fishes from the surface to 450 m depth to test if taxonomically distinct communities along the reef slope are characterized by similar or distinct ecological traits. Core ecological traits found in shallow reef-fish communities were conserved in the upper section of deep reefs (i.e., mesophotic zone) across three taxonomically distinct assemblages. By contrast, the deepest reef communities (i.e., rariphotic zone) displayed a distinct functional structure, mainly driven by trait loss. Functional redundancy was highest in the deepest reef communities and was generated by intrageneric diversification and functional convergence across phylogenetic lineages. The decrease in functional richness and divergence combined with an increase in functional redundancy suggest that environmental filtering is the dominant evolutionary constraint shaping the functional diversity of deep-reef fishes.
In this study, we virtually reconstruct the vertebral column of Pezosiren portelli, a four-limbed stem sirenian (Pan-Sirenia, Prorastomidae) from the Eocene of Jamaica. We used three-dimensional models of various vertebrae obtained through surface scanning of fossil remains and we applied several algorithms for virtual repair, including retrodeformation of distorted vertebrae or mirroring missing processes from their bilateral counterparts. To quantify the regional morphology of P. portelli, we digitized a set of homologous landmarks, following a standardized protocol retrieved from previous morphometric studies on the evolution of the mammalian backbone. The results reveal a cervical region with relatively long spinous processes, as well as a thoracic region subdivided into prediaphragmatic and postdiaphragmatic regions with an unspecialised lumbar region. Both aspects reveal anatomical traits typical of terrestrial mammals, suggesting that P. portelli may exhibit a mosaic evolutionary pattern, showing postcranial traits typical of terrestrial taxa but also early aquatic adaptations found in its cranial skeleton. Finally, we briefly discuss the implications of morphometric analyses of the P. portelli vertebral column for understanding the evolution of axial features in other secondarily aquatic tethytherians.
Quantifying animal movements is necessary for answering a wide array of research questions in ecology and conservation biology. Consequently, ecologists have made considerable efforts to identify the best way to estimate an animal’s home range, and many methods of estimating home ranges have arisen over the past half century. Most of these methods fall into two distinct categories of estimators that have only recently been described in statistical detail: those that measure range distributions (methods such as Kernel Density Estimation that quantify the long-run behavior of a movement process that features restricted space use) and those that measure occurrence distributions (methods such as Brownian Bridge Movement Models and the Correlated Random Walk Library that quantify uncertainty in an animal movement path during a specific period of observation). In this paper, we use theory, simulations, and empirical analysis to demonstrate the importance of applying these two classes of space use estimators appropriately and distinctly. Conflating range and occurrence distributions can have serious consequences for ecological inference and conservation practice. For example, in most situations, home-range estimates quantified using occurrence estimators are too small, and this problem is exacerbated by ongoing improvements in tracking technology that enable more frequent and more accurate data on animal movements. We encourage researchers to use range estimators to estimate the area of home ranges and occurrence estimators to answer other questions in movement ecology, such as when and where an animal crosses a linear feature, visits a location of interest, or interacts with other animals. Open Research Statement Tracking data on Aepyceros melampus, Beatragus hunteri, Bycanistes bucinator, Cerdocyon thous, Eulemur rufifrons, Glyptemys insculpta, Gyps coprotheres, Madoqua guentheri, Ovis canadensis, Propithecus verreauxi, Sus scrofa, and Ursus arctos are publicly archived in the Dryad repository (Noonan et al. 2018; https://doi.org/10.5061/dryad.v5051j2), as are data from Procapra gutturosa (Fleming et al. 2014a; https://doi.org/10.5061/dryad.45157). Data on Panthera onca were taken from (Morato et al. 2018). Additional data are publicly archived in the Movebank repository under the following identifiers: Canis latrans, 8159699; Canis lupus, 8159399; Chrysocyon brachyurus, 18156143; Felis silvestris, 40386102; Gyps africanus, 2919708; Lepus europaeus, 25727477; Martes pennanti, 2964494; Panthera leo, 220229; Papio cynocephalus, 222027; Syncerus caffer, 1764627; Tapirus terrestris, 443607536; Torgos tracheliotus, 2919708; and Ursus americanus, 8170674.
Elevated temperatures pose challenges to stomatal conductance, which regulates transpiration and photosynthesis. However, the coupling of stomatal conductance, transpiration and photosynthesis may shift with warming. Here, we synthesize evidence from a meta-analysis of 207 studies to assess leaf physiological responses to warming. On average, the responses of stomatal conductance are highly variable, exhibiting no consistent directional trend, whereas transpiration increases and photosynthesis decreases, reflecting a shift towards transpirational cooling. Stomatal conductance declines until temperatures exceed 5 °C above ambient, whereas transpiration remains stable under warming <3 °C. Beyond these two thresholds, both stomatal conductance and transpiration increase with further warming. The sensitivity of stomatal conductance, photosynthesis, and water-use efficiency to warming varies substantially among plant functional types, with distinct responses across life forms, phylogenetic groups, and photosynthetic pathways. Higher mean annual temperature amplifies the positive responses of stomatal conductance and transpiration to warming, whereas greater mean annual precipitation mitigates the warming-induced declines in photosynthesis. Elevated CO2 exacerbates warming-induced declines in photosynthesis, while drought constrains transpirational cooling. Collectively, these findings highlight a progressive decoupling of stomatal conductance, transpiration and photosynthesis with warming, revealing complex trade-offs between plant water use, thermal regulation, and carbon assimilation.
Soil organic matter (SOM) is primarily derived from leaf and root inputs, but the relative contributions of each are difficult to study without the use of isotopic tracers. Furthermore, associations between trees and mycorrhizal fungi can influence the production and persistence of SOM. We quantified tree inputs and carbon and nitrogen content of three SOM fractions - free and occluded particulate organic matter (fPOM and oPOM, respectively), and mineral-associated organic matter (MAOM) - in a tree common garden in Maryland, USA, where the trees and soil have distinct isotopic signatures due to prior use of the land as a cornfield. We found that stem basal area was not associated with concentrations of carbon (C) in any SOM pool but that fine root biomass was positively related to the proportion of tree-derived MAOM-C. POM was positively associated with leaf litter carbon : nitrogen ratio (C : N), but tree-derived MAOM was not associated with fine root C : N. Tree mycorrhizal type did not influence the relative importance of leaf and root-derived SOM. Our results indicate that leaf litter and fine roots have distinct roles on POM and MAOM formation, respectively, and that these effects are consistent across tree mycorrhizal associations in early stand development.
