Functional trait diversity of Cyclanthaceae and its convergent evolution with Araceae in Neotropical forests

The Cyclanthaceae comprise a relatively small family of about 230 species and 12 genera in the Pandanales that is widespread in wet Neotropical forests. The great majority of species can be divided into three growth forms (understory herbs, epiphytes, and root-climbing hemiepiphytes) that share functional traits with similar growth forms present in the Araceae, a member of the Alismatales and not closely related. Our objectives were first to characterize the diversity, functional growth forms, and ecological traits of Cyclanthaceae at the La Selva Biological Station. Specific functional leaf and canopy traits of terrestrial herbs and epiphytes are very similar and associated with ecological success in both families. We further examined the functional traits of root-climbing hemiepiphytes, a specialized growth form that links the two families but rare in other families and argue that their specialized functional traits allow them to be considered as a distinct functional growth form. A key trait in distinguishing hemiepiphytes which are rare outside of the Cyclanthaceae and Araceae is the severance of the main stem hydraulic connection to the soil early in plant development. We used field data to examine the possible evolutionary pathways of developmental and ecological transition from terrestrial to hemiepiphyte growth forms. The broader ecological success of hemiepiphytic Araceae compared to Cyclanthaceae is hypothesized to result from the presence of heteroblasty in developing stems and leaves which allows more efficient utilization of complex canopy light environments of wet tropical forests.

Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms

Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.

Locomotion of an adult female and juvenile male aye-aye (Daubentonia madagascariensis) in Torotorofotsy, Madagascar

Aye-ayes (Daubentonia madagascariensis) locate and acquire invertebrates from within woody substrates at all levels of the rainforest; yet how their locomotion helps them accommodate this diet has not been explored in detail. We studied the locomotor behavior of an adult female (N = 1,085) and juvenile male (N = 708) aye-aye in the undisturbed forest of Torotorofotsy, Madagascar from May to December 2017. We used bout sampling to record locomotion during foraging and travel of the two radio-collared individuals. We used χ ² tests to compare overall locomotion, travel, and foraging, as well as strata and support use. We performed a correspondence analysis to examine relationships between individual behaviors, strata, and support types. Leaping accounted for 47.9% and 50.1% of all locomotor activity in the adult female and juvenile male, respectively. Leaping was the most common behavior during travel in both individuals (59.2% and 53.9%, respectively), whereas head-first descent was most frequent during foraging (35.0% and 48.0%, respectively). For all three locomotor categories, the main canopy (40.3%-79.6%) was used most frequently and trunks were the most frequently used support type (50.7%-60.0%). There is a strong association between strata and support use overall and during travel. Quadrupedal walking was significantly associated with the main canopy, as was head-first descent with the low canopy. Our analysis demonstrates that aye-ayes use a variety of locomotor behaviors to forage for invertebrates. Aye-ayes' ability to repurpose their positional repertoire to acquire other resources in degraded forests should not obscure the importance of invertebrates to this species.

Seeing beyond the trees: a comparison of tropical and temperate plant growth forms and their vertical distribution

Forests are the most diverse and productive terrestrial ecosystems on Earth, so sustainably managing them for the future is a major global challenge. Yet, our understanding of forest diversity relies almost exclusively on the study of trees. Here, we demonstrate unequivocally that other growth forms (shrubs, lianas, herbs, epiphytes) make up the majority of vascular plant species in both tropical and temperate forests. By comparing the relative distribution of species richness among plant growth forms for over 3,400 species in 18 forests in the Americas, we construct the first high-resolution quantification of plant growth form diversity across two ecologically important regions at a near-continental scale. We also quantify the physical distribution of plant species among forest layers, that is, where among the vertical strata plants ultimately live their adult lives, and show that plants are strongly downshifted in temperate forests vs. tropical forests. Our data illustrate a previously unquantified fundamental difference between tropical and temperate forests: what plant growth forms are most speciose, and where they ultimately live in the forest. Recognizing these differences requires that we re-focus ecological research and forest management plans to encompass a broader suite of plant growth forms. This more holistic perspective is essential to conserve global biodiversity.

Temporal variation in the spider assemblage (Arachnida, Araneae) in canopies of Callisthene fasciculata (Vochysiaceae) in the Brazilian Pantanal biome

ABSTRACT Spiders are generalist predators and present a high diversity of capturing and foraging, as well as considerable species richness in tropical habitats. Although, generally, not presenting specific relations to the host plant, they can be influenced by its phenology, structure and resource availability. So, this study analyzed temporal variation on the structure and composition of Araneae assemblage in Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) canopies, in an area of monodominant vegetation, in the periods of high water, receding water, dry season and rising water in Pantanal of Mato Grosso, Brazil. The collection was performed on 24 individuals of C. fasciculata, six in each seasonal period, in 2010 and 2011, making use of canopy fogging with insecticide. For that, ten nylon funnels were distributed under each canopy of C. fasciculata individuals, in a total of 240 m² of sampled canopies. In all, 3,610 spiders were collected and distributed in 24 families and 55 species. Anyphaenidae (43.3%; 6.5 ind./m2), Pisauridae (16.2%; 2.4 ind./m2), Araneidae (12.7%; 1.9 ind./m2) and Salticidae (12.4%; 1.9 ind./m2) were the most representative. Osoriella tahela Brescovit, 1998 was the most abundant species (12.2%). The nocturnal aerial runners of foliage (45.6%; 6.9 ind./m2), nocturnal aerial ambushers of foliage (17.3%; 2.6 ind./m2), aerial orb weavers (13.3%; 2.0 ind./m2) and the diurnal aerial runners of foliage (12.5%; 1.9 ind./m2) spiders represented the most abundant guilds. Significant differences were observed in the composition of families and behavioral guilds, as well as abundance and richness among seasonal periods. The assemblage showed the highest abundance in receding water and highest species richness in high water period, probably related to the hydrologic cycle of the area and its influence on C. fasciculata phenology, indicating the importance of this plant species for spider’s diversity maintenance in the Pantanal.

LONG HINDLIMBS CONTRIBUTE TO AIR-RIGHTING PERFORMANCE IN FALLING TREE FROGS

Tree frogs are able to climb or even jump on leaves and branches using their toe pads adhering to and detaching from surfaces, but have to be in the face of the risk of falling down due to fatigue or a slip. While falling down from a great height, air-righting response was observed, which prevents tree frogs from injury caused by back hitting the ground, however the mechanism underlying is unknown. Using a high-speed camera with a plane mirror, we captured the body and limb kinematics of falling tree frogs as they performed rapid air-righting response in three-dimension. The kinematics were then characterized into three stages and substituted into a mathematical multi-body model to simulate the air-righting dynamics caused by the kinematics. The results show that a head-down tree frog performs rapid air-righting with specific series of actions in hindlimb motion, which generates sufficient local angular momentum for the frog to rotate its body upright and keep the total moment of momentum conserved. The applications of these results to small landing robots and multi-segment spacecraft are anticipated.