Bringing traits back into the equation: A roadmap to understand species redistribution.

Ecological and evolutionary theories have proposed that species traits should be important in mediating species responses to contemporary climate change; yet, empirical evidence has so far provided mixed evidence for the role of behavioral, life history, or ecological characteristics in facilitating or hindering species range shifts. As such, the utility of trait-based approaches to predict species redistribution under climate change has been called into question. We develop the perspective, supported by evidence, that trait variation, if used carefully can have high potential utility, but that past analyses have in many cases failed to identify an explanatory value for traits by not fully embracing the complexity of species range shifts. First, we discuss the relevant theory linking species traits to range shift processes at the leading (expansion) and trailing (contraction) edges of species distributions and highlight the need to clarify the mechanistic basis of trait-based approaches. Second, we provide a brief overview of range shift-trait studies and identify new opportunities for trait integration that consider range-specific processes and intraspecific variability. Third, we explore the circumstances under which environmental and biotic context dependencies are likely to affect our ability to identify the contribution of species traits to range shift processes. Finally, we propose that revealing the role of traits in shaping species redistribution may likely require accounting for methodological variation arising from the range shift estimation process as well as addressing existing functional, geographical, and phylogenetic biases. We provide a series of considerations for more effectively integrating traits as well as extrinsic and methodological factors into species redistribution research. Together, these analytical approaches promise stronger mechanistic and predictive understanding that can help society mitigate and adapt to the effects of climate change on biodiversity.

Experimental evaluation of how biological invasions and climate change interact to alter the vertical assembly of an amphibian community.

While biotic-abiotic interactions are increasingly documented in nature, a process-based understanding of how such interactions influence community assembly is lacking in the ecological literature. Perhaps the most emblematic and pervasive example of such interactions is the synergistic threat to biodiversity posed by climate change and invasive species. Invasive species often out-compete or prey on native species. Despite this long-standing and widespread issue, little is known about how abiotic conditions, such as climate change, will influence the frequency and severity of negative biotic interactions that threaten the persistence of native fauna. Treefrogs are a globally diverse group of amphibians that climb to complete life-cycle processes, such as foraging and reproduction, as well as to evade predators and competitors, resulting in frog communities that are vertically partitioned. Furthermore, treefrogs adjust their vertical position to maintain optimal body temperature and hydration in response to environmental change. Here, utilizing this model group, we designed a novel experiment to determine how extrinsic abiotic and biotic factors (changes to water availability and an introduced predator, respectively) interact with intrinsic biological traits, such as individual physiology and behaviour, to influence treefrogs' vertical niche. Our study found that treefrogs adjusted their vertical niche through displacement behaviours in accordance with abiotic resources. However, biotic interactions resulted in native treefrogs distancing themselves from abiotic resources to avoid the non-native species. Importantly, under altered abiotic conditions, both native species avoided the non-native species 33 %- 70 % more than they avoided their native counterpart. Additionally, exposure to the non-native species resulted in native species altering their tree climbing behaviours by 56 % - 78 % and becoming more vertically dynamic to avoid the non-native antagonist. Our experiment determined that vertical niche selection and community interactions were most accurately represented by a biotic-abiotic interaction model, rather than a model that considers these factors to operate in an isolated (singular) or even additive manner. Our study provides evidence that native species may be resilient to interacting disturbances via physiological adaptations to local climate and plasticity in space-use behaviours that mediate the impact of the introduced predator.

Vertical stratification patterns of tropical forest vertebrates: a meta-analysis.

Tropical forests harbour the highest levels of terrestrial biodiversity and represent some of the most complex ecosystems on Earth, with a significant portion of this diversity above ground. Although the vertical dimension is a central aspect of the ecology of forest communities, there is little consensus as to prominence, evenness, and consistency of community-level stratification from ground to canopy. Here, we gather the results of 62 studies across the tropics to synthesise and assess broad patterns of vertical stratification of abundance and richness in vertebrates, the best studied taxonomic group for which results have not been collated previously. Our review of the literature yielded sufficient data for bats, small mammals, birds and amphibians. We show that variation in the stratification of abundance and richness exists within and among all taxa considered. Bat richness stratification was variable among studies, although bat abundance was weighted towards the canopy. Both bird richness and abundance stratification were variable, with no overriding pattern. On the contrary, both amphibians and small mammals showed consistent patterns of decline in abundance and richness towards the canopy. We descriptively characterise research trends in drivers of stratification cited or investigated within studies, finding local habitat structure and food distribution/foraging to be the most commonly attributed drivers. Further, we analyse the influence of macroecological variables on stratification patterns, finding latitude and elevation to be key predictors of bird stratification in particular. Prominent differences among taxa are likely due to taxon-specific interactions with local drivers such as vertical habitat structure, food distribution, and vertical climate gradients, which may vary considerably across macroecological gradients such as elevation and biogeographic realm. Our study showcases the complexity with which animal communities organise within tropical forest ecosystems, while demonstrating the canopy as a critical niche space for tropical vertebrates, thereby highlighting the inherent vulnerability of tropical vertebrate communities to forest loss and canopy disturbance. We recognise that analyses were constrained due to variation in study designs and methods which produced a variety of abundance and richness metrics recorded across different arrangements of vertical strata. We therefore suggest the application of best practices for data reporting and highlight the significant effort required to fill research gaps in terms of under-sampled regions, taxa, and environments.

Large, old trees define the vertical, horizontal, and seasonal distributions of a poison frog.

In tropical forests, large, old trees (LOTs) can be considered keystone structures for provisioning unique habitats such as decaying wood, roots, cavities, and epiphytes, including those that hold water (phytotelmata). These habitats may also be stratified in vertical space, for example, root structures occur at ground level and below, whereas epiphytes occur above-ground. Canopy habitat is utilized by a diversity of amphibians, but canopy habitat may only be viable in the wet season when epiphytes and surfaces are sufficiently saturated. Here, we examine how the provisioning of microhabitats and structures by LOTs influence the horizontal, vertical, and seasonal distribution patterns of phytotelmata-breeding poison frogs. We conducted ground-to-canopy surveys over 4 years, constituting 6 seasons, in Panama and used mark-recapture techniques on a population of the yellow-bellied poison frog, Andinobates fulguritus. We found that A. fulguritus migrated vertically, tracking seasonal rainfall, and displayed strong philopatry to individual trees. Furthermore, A. fulguritus almost exclusively inhabited the largest trees at the study location, which provided disproportionately high-quality microhabitats and epiphytes compared to other trees. LOTs, and specifically Anacardium excelsum at our site, appear to serve as keystone structures with high conservation value due to their provisioning of unique habitats. We conclude that the distribution of A. fulguritus is defined vertically by the stratification of arboreal microhabitat resources, horizontally by the presence of LOTs providing the resources, and temporally by the seasonal viability of the resources.

Cryopreservation and hormonal induction of spermic urine in a novel species: The smooth-sided toad (Rhaebo guttatus).

Global amphibian declines have fueled an increased interest in amphibian assisted reproductive technologies. Within the genus Rhaebo, half of the species are experiencing decreasing population trends; however, insufficient information is available on many of these species' reproductive biology. Using the smooth-sided toad, Rhaebo guttatus, we present effective methods for collecting and cryopreserving an example of Rhaebo sperm. Specifically, our findings show that administering 10 IU/g body weight of hCG (human chorionic gonadotropin) yields the most motile and concentrated sperm and that cryopreserving spermic urine in a solution of 5% DMFA (N,N-Dimethylformamide) and 10% trehalose returns sperm with a 33 ±â€¯3% average post-thaw motility. These findings may represent an important step forward in developing techniques that can be safely applied to other, more vulnerable species within the Rhaebo genus.

Environmental gradients in old-growth Appalachian forest predict fine-scale distribution, co-occurrence, and density of woodland salamanders.

Woodland salamanders are among the most abundant vertebrate animals in temperate deciduous forests of eastern North America. Because of their abundance, woodland salamanders are responsible for the transformation of nutrients and translocation of energy between highly disparate levels of trophic organization: detrital food webs and high-order predators. However, the spatial extent of woodland salamanders' role in the ecosystem is likely contingent upon the distribution of their biomass throughout the forest. We sought to determine if natural environmental gradients influence the fine-scale distribution and density of Southern Ravine Salamanders (Plethodon richmondi) and Cumberland Plateau Salamanders (P. kentucki). We addressed this objective by constructing occupancy, co-occurrence, and abundance models from temporally replicated surveys within an old-growth forest in the Cumberland Plateau region of Kentucky. We found that Plethodon richmondi had a more restricted fine-scale distribution than P. kentucki (mean occupancy probability [ ψ ¯ ^ ] = 0.737) and exhibited variable density, from <250 to >1000 individuals per hectare, associated with increased soil moisture and reduced solar exposure due to slope face. While more ubiquitously distributed ( ψ ¯ ^  = 0.95), P. kentucki density varied from <400 to >1,000 individuals per hectare and was inversely related to increased solar exposure from canopy disturbance and landscape convexity. Our data suggest co-occurrence patterns of P. richmondi and P. kentucki are influenced primarily by abiotic conditions within the forest, and that populations likely occur independently and without evidence of biotic interaction. Given the critical role that woodland salamanders play in the maintenance of forest health, regions that support large populations of woodland salamanders, such as those highlighted in this study-mesic forest stands on north-to-east facing slopes with dense canopy and abundant natural cover, may provide enhanced ecosystem services and support the stability of the total forest.