Dry Habitats Research Articles

Sex differences in positional behavior of chimpanzees (Pan troglodytes schweinfurthii) living in the dry and open habitat of Issa Valley, Tanzania.

Many early fossil hominins are associated with savanna-mosaic paleohabitats, and high sexual dimorphism that may reflect differences in positional behavior between sexes. However, reconstructions of hominin behavior and the selective pressures they faced in an open habitat are limited by a lack of studies of extant apes living in contemporary, analogous habitats. Here, we describe adult chimpanzee positional behavior in the savanna-mosaic habitat of the Issa Valley, Tanzania, to test whether Issa chimpanzees show larger sex-differences in positional behavior than their forest-dwelling counterparts. We quantified and compared adult locomotor and postural behavior across sexes (6 females, 7 males) in the riparian forest (closed) and miombo woodland (open) vegetation types at Issa Valley (13,743 focal observations). We then compared our results to published data of chimpanzee communities living in more forested habitats. Issa females and males both spent less time arboreally in open vegetation and showed similar locomotor and postural behavior on the same substrates, notably using a high level of suspensory locomotion when arboreal. Females were, however, more arboreal than males during locomotor behavior, as well as compared with females from other communities. Issa males behaved similarly to males from other communities. Results suggest that open habitats do not elicit less arboreal behaviors in either sex, and may even select for suspensory locomotion to effectively navigate an open canopy. An open habitat may, however, increase sex differences in positional behavior by driving female arboreality. We suggest this is because of higher energetic demands and predator pressures associated with open vegetation, which are likely exaggerated for reproducing females. These results have implications for the interpretation of how sexual dimorphism may influence reconstructions of hominin positional behavior.

Two centuries of ornithological exploration of the Rio Doce Basin, southeastern Brazil. Part II—A catalogue of its birds and a gazetteer

The Rio Doce Hydrographic Basin (RDB) lies almost completely in the Brazilian Atlantic Forest, a highly threatened tropical rainforest. The RDB has suffered dramatic anthropogenic impacts during the last two centuries and is currently one of the most degraded regions in southeastern Brazil. In this paper, we gathered 140,742 bird records collected since the early 19th by more than two thousand naturalists, professional scientists, and citizen scientists. This vast database was compiled from several sources, including published literature, unpublished technical reports, natural history museums, and citizen science platforms. After checking and standardizing the database, we found high species richness in the RDB, with 689 species recorded to date, from which 675 (98%) were documented by specimens or digital vouchers. This database is presented as a detailed catalogue, including maps containing all localities in which each species has been recorded. We present text accounts for 40 noteworthy species recorded in the RDB, and a complete gazetteer for the 636 localities sampled. Preliminary analyses reveal that the RDB avifauna suffered a dramatic change in its species composition during the last two centuries, mostly due to human activity. Highly sensitive species associated to pristine forests vanished, while species associated to dry and open habitat expanded their ranges in the RDB. Finally, in addition to thoroughly characterization of the RDB avifauna, this paper provides the basis for a series of studies about the avifauna of one of the hottest hotspots of biodiversity in the entire Neotropical region.

Precipitation, solar radiation, and their interaction modify leaf hydraulic efficiency-safety trade-off across angiosperms at the global scale.

In theory, there is a trade-off between hydraulic efficiency and safety. However, the strength and direction of this trade-off at the leaf level are not consistent across studies, and habitat climate may impact this trade-off. We compiled a leaf hydraulic efficiency and safety dataset for 362 species from 81 sites world-wide, with 280 paired observations of both traits, and tested whether climate was associated with departure from the proposed trade-off. The leaf hydraulic efficiency-safety trade-off was weak (R2 = 0.144) at the global scale. Mean annual precipitation and solar radiation (SR) modified the trade-off. Species from dry and high SR habitats (e.g. desert and tropical savanna) were generally located above the trade-off line, indicating that these species tended to have higher leaf hydraulic safety and efficiency than species from wet habitats with low SR (e.g. subtropical monsoon forest and montane rainforest), which were located below the trade-off line. Leaves with high vein density, dry leaf mass per area, and osmotic regulation enhanced safety without compromising hydraulic efficiency. Variation in the hydraulic efficiency-safety trade-off at the leaf level likely facilitates plant survival in specific habitats and allows for a more nuanced view of leaf hydraulic adaption strategies at the global scale.

Speciation and evolution of growth form in Adesmia D. C. (Dalbergieae, Fabaceae): the relevance of Andean uplift and aridification.

The Andean uplift and the concomitant aridification drove the rapid diversification of several plant lineages that were able to colonize warmer and drier habitats at low elevations and wetter and colder habitats at high elevations. These transitions may be facilitated by shifts in plant strategies to cope with drought and cold, which in turn can trigger episodes of accelerated species diversification. Here, we used four nuclear DNA markers to infer phylogenetic relationships of 80 Adesmia species of annuals, perennial herbs, shrubs and small shrubs that occur in Chile and Argentina. We reconstructed ancestral states for area, climatic niche and growth form to explore how Andean uplift and aridification promoted Adesmia diversification. We also performed logistic and linear regression analyses between different components of growth form (life span, woodiness and plant height) and climate. Finally, we estimated speciation rates across the phylogeny. Our results suggest that the ancestor of Chilean Adesmia was a perennial herb that probably originated in the high Andes of northern and central Chile. The low elevations of Central Chile were colonized in the late Miocene, whereas the high latitudes of Patagonia and the hyperarid coastal Atacama Desert were colonized repeatedly since Pliocene by lineages with different growth forms. Multiple and bidirectional transitions between annual and perennial habits and between herbaceous and woody habits were detected. These shifts were not correlated with climate, suggesting that the different growth forms are alternative and successful strategies to survive unfavorable seasons of both desert and high Andes. Net diversification analysis indicated a constant rate of diversification, suggesting that the high species diversity of Adesmia that occur in Chile is due to a uniform speciation process rather than to accelerated episodes of speciation.

Vegetation Growth and Physiological Adaptation of Pioneer Plants on Mobile Sand Dunes

The Hunshandake Sandy Land is one of the largest sandy areas in China and the closest source of sand dust to the Beijing and Tianjing areas. Sand fixation by vegetation is considered the most efficient strategy for sand control and sustainable development, so clarifying the vegetation coverage and plant adaptation characteristics in the Hunshandake Sandy Land is helpful in guiding restoration and improving local sustainability. Here, we investigated the vegetation growth on the mobile sand dunes in the Hunshandake Sandy Land and specified the photosynthesis and stomatal characteristics of the pioneer plants for sand fixation. The vegetation survey showed that the windward slopes of the mobile sand dunes had far lower plant coverage (6.3%) and plant biodiversity (two species m−2) than the leeward ones (41.0% and eight species m−2, respectively). Elymus sibiricus L. and Agriophyllum squarrosum (L.) Moq. were the only two sand-fixing pioneer plants that grew on both the windward and leeward slopes of the mobile sand dunes and had higher plant heights, greater abundance, and more biomass than other plants. Physiological measurements revealed that Elymus sibiricus L. and Agriophyllum squarrosum (L.) Moq. also had higher photosynthetic rates, transpiration rates, and water use efficiency. In addition, the stomata density (151–197 number mm−2), length (18–29 μm), and area index (13–19%) of these two pioneer species were smaller than those of the common grassland species in Inner Mongolia, suggesting that they were better adapted to the dry habitat of the mobile sand dunes. These findings not only help in understanding the adaptive strategies of pioneer plants on mobile sand dunes, but also provide practical guidance for sand dune restoration and the sustainable development of local areas. Pioneer sand-fixing plant species that are well adapted to sand dunes can be used for sowing or aerial seeding in sand fixation during ecosystem restoration.

Interpreting the shifts in forest structure, plant community composition, diversity, and functional identity by using remote sensing-derived wildfire severity

BackgroundWildfires are increasingly impacting ecosystems worldwide especially in temperate dry habitats, often interplaying with other global changes (e.g., alien plant invasions). Understanding the ecological consequences of wildfires is crucial for effective conservation and management strategies. The aim of this study was to investigate the impacts of wildfire severity on plant community (both the canopy trees and herbaceous layer) and alien plant invasion, combining field observations and remotely sensed data.We conducted an observational study in the Karst forests (North-East Italy) 1 year after the large wildfire which affected the area in 2022. We assessed the impact through 35 field plots (200 m2 each) distributed among different fire severity (i.e., the loss of organic matter) classes assessed using the differenced normalized burn ratio (dNBR) calculated from satellite images. In each plot, tree species, diameter, vitality, resprouting capacity, and seedling density were measured. In addition, herb species richness (taxonomical diversity) was quantified, and plant cover was visually estimated. Functional diversity was also assessed considering six functional traits retrieved from databases.ResultsSome woody species (e.g., Quercus pubescens) showed a higher resistance to the fire (i.e., lower mortality rate), while others showed a higher resilience (i.e., recovery after fire through resprouting or seedlings, e.g., Cotinus coggygria). The transition to a shrub-dominated community (i.e., Cotinus coggygria) where fire severity was the highest underlines the dynamic nature of the post-fire succession. We detected a significant variation in the herbaceous plant community composition, diversity, and functional identity (i.e., community-weighted mean of trait) along the fire severity gradient. In particular, high-fire severity areas exhibited higher species richness compared to low-severity or unburned areas. Total alien plant cover increased with fire severity, while native cover remained constant. We also found shifts in species that enhance traits related to germination potential and growth strategy.ConclusionsOur results highlight the vulnerability of the forest stands to an increase in wildfire severity, resulting in significant mortality and changes in tree community structure. This study contributes to the understanding of ecological processes after wildfires using a novel remote sensing approach in a temperate forest, emphasizing the need for conservation strategies aimed at mitigating high severity wildfires.

The coevolution of fungus-ant agriculture.

Fungus-farming ants cultivate multiple lineages of fungi for food, but, because fungal cultivar relationships are largely unresolved, the history of fungus-ant coevolution remains poorly known. We designed probes targeting >2000 gene regions to generate a dated evolutionary tree for 475 fungi and combined it with a similarly generated tree for 276 ants. We found that fungus-ant agriculture originated ~66 million years ago when the end-of-Cretaceous asteroid impact temporarily interrupted photosynthesis, causing global mass extinctions but favoring the proliferation of fungi. Subsequently, ~27 million years ago, one ancestral fungal cultivar population became domesticated, i.e., obligately mutualistic, when seasonally dry habitats expanded in South America, likely isolating the cultivar population from its free-living, wet forest-dwelling conspecifics. By revealing these and other major transitions in fungus-ant coevolution, our results clarify the historical processes that shaped a model system for nonhuman agriculture.

Evolution of gene networks underlying adaptation to drought stress in the wild tomato Solanum chilense.

Drought stress is a key limitation for plant growth and colonization of arid habitats. We study the evolution of gene expression response to drought stress in a wild tomato, Solanum chilense, naturally occurring in dry habitats in South America. We conduct a transcriptome analysis under standard and drought experimental conditions to identify drought-responsive gene networks and estimate the age of the involved genes. We identify two main regulatory networks corresponding to two typical drought-responsive strategies: cell cycle and fundamental metabolic processes. The metabolic network exhibits a more recent evolutionary origin and a more variable transcriptome response than the cell cycle network (with ancestral origin and higher conservation of the transcriptional response). We also integrate population genomics analyses to reveal positive selection signals acting at the genes of both networks, revealing that genes exhibiting selective sweeps of older age also exhibit greater connectivity in the networks. These findings suggest that adaptive changes first occur at core genes of drought response networks, driving significant network re-wiring, which likely underpins species divergence and further spread into drier habitats. Combining transcriptomics and population genomics approaches, we decipher the timing of gene network evolution for drought stress response in arid habitats.

Speciation in the desert: A new endemic Iberus land snail restricted to the southeastern Iberian Peninsula

Arid habitats constitute harsh environments for hydrophilic animals such as land snails. Still, several land snail species appear to inhabit arid environments and such species present an array of adaptations needed to minimise water loss in dry habitats. However, different species may have found different solutions for the same problem. Here, we describe Iberus xerophilus sp. nov., a new species of arid-dwelling land snail from southeastern Spain, on the basis of phylogenetic analyses. Moreover, we show a detailed morphological description as well as a characterization of its habitat. A comparison with the shell morphology of other aridity resistant Iberus land snails casts the question of how this snail can succeed in such harsh arid environments. Southeastern Spain constitutes a hotspot for Iberus arid-dwelling species, displaying a plethora of shell morphologies. The description of this new species might contribute to our understanding of the evolution and diversification of land snails specifically adapted to drought and arid conditions.

Differential modulation of photosystem II photochemical efficiency in six C4 xero-halophytes.

Xero-halophytes are the salt-tolerant plants of dry habitats that adapt efficient strategies to endure extreme salt and water fluctuations. This study elucidated the adaptations related to PSII photochemistry, photoprotection, and photoinhibition in six C4 xero-halophytes (Atriplex stocksii , Haloxylon stocksii , Salsola imbricata, Suaeda fruticosa, Desmostachya bipinnata , and Saccharum griffithii ) grown in their native habitats. Chlorophyll a fluorescence quenching measurements suggested that S. imbricata and H. stocksii maintained efficient PSII photochemistry by downregulating heat dissipation and keeping a high fraction of open PSII centres that indicates plastoquinone (PQ) pool oxidation. Fluorescence induction kinetics revealed that S. imbricata demonstrated the highest performance index of PSII excitation to the reduction of end electron acceptors. S. fruticosa sustained photochemical efficiency through enhanced dissipation of excess energy and a low fraction of open PSII centres, indicating PQ reduced state. The large light-harvesting antenna size, deduced from the chlorophyll a /b ratio in S. fruticosa apparently led to the superior performance index of PSII excitation to the reduction of intersystem electron carriers. A. stocksii retained more open PSII centres with responsive non-photochemical quenching to safely dissipate excess energy. Despite maintaining the highest pigment contents and stoichiometry, A. stocksii remained lowest in both performance indices. The grass species D. bipinnata and S. griffithii kept fewer PSII centres open during photoinhibition, as evidenced by downregulation of PSII operating efficiency. The results provide insights into the differential modulation of PSII photochemical efficiency through dynamic control of photoprotective energy dissipation, PQ pool redox states, and photoinhibitory shutdown in these xero-halophytes.

Untangling poikilohydry and desiccation tolerance: evolutionary and macroecological drivers in ferns.

Poikilohydry describes the inability of plants to internally regulate their water content (hydroregulation), whereas desiccation tolerance (DT) refers to plants ability to restore normal metabolic functions upon rehydration. The failure to clearly separate these two adaptations has impeded a comprehensive understanding of their unique evolutionary and ecological drivers. Unlike bryophytes and angiosperms, these adaptations in ferns are sometimes uncorrelated, offering a unique opportunity to navigate their intricate interplay. We classified ferns into two syndromes: the Hymenophyllum-type (H-type), encompassing species with filmy leaves lacking stomata that experience extreme poikilohydry and varying degrees of DT, and the Pleopeltis-type (P-type), consisting of resurrection plants with variable hydroregulation but high DT. The H-type evolved during globally cool Icehouse periods, as an adaptation to low light levels in damp, shady habitats, and currently prevails in wet environments. Conversely, the P-type evolved predominantly under Greenhouse periods as an adaptation to periodic water shortage, with most extant species thriving in warm, seasonally dry habitats. Out study underscores the fundamental differences between poikilohydry and DT, emphasizing the imperative to meticulously differentiate and qualify the strength of each strategy as well as their interactions, as a basis for understanding the genetic and evolutionary background of these ecologically crucial adaptations.

Fluctuating selection in a monkeyflower hybrid zone

Abstract While hybridization was viewed as a hindrance to adaptation and speciation by early evolutionary biologists, recent studies have demonstrated the importance of hybridization in facilitating evolutionary processes. However, it is still not well-known what role spatial and temporal variation in natural selection play in the maintenance of naturally occurring hybrid zones. To identify whether hybridization is adaptive between two closely related monkeyflower species, Mimulus guttatus and Mimulus laciniatus, we performed repeated reciprocal transplants between natural hybrid and pure species’ populations. We planted parental genotypes along with multiple experimental hybrid generations in a dry (2021) and extremely wet (2023) year in the Sierra Nevada, CA. By taking fine-scale environmental measurements, we found that the environment of the hybrid zone is more similar to M. laciniatus’s seasonally dry rocky outcrop habitat than M. guttatus’s moist meadows. In our transplants hybridization does not appear to be maintained by a consistent fitness advantage of hybrids over parental species in hybrid zones, but rather a lack of strong selection against hybrids. We also found higher fitness of the drought-adapted species, M. laciniatus, than M. guttatus in both species’ habitats, as well as phenotypic selection for M. laciniatus-like traits in the hybrid habitat in the dry year of our experiment. These findings suggest that in this system, hybridization might function to introduce drought-adapted traits and genes from M. laciniatus into M. guttatus, specifically in years with limited soil moisture. However, we also find evidence of genetic incompatibilities in second generation hybrids in the wetter year, which may balance a selective advantage of M. laciniatus introgression. Therefore, we find that hybridization in this system is both potentially adaptive and costly, and that the interaction of positive and negative selection likely determines patterns of gene flow between these Mimulus species.

Taxonomic and stable isotope analyses of mammal remains from the Lateglacial site of Grotta Polesini (central Italy): Paleoenviromental implications

ABSTRACTGrotta Polesini is one of the most famous paleontological and archaeological sites of central Italy, which testifies to its human occupation during the Lateglacial. The site comprises a cave system where systematic excavation campaigns have been carried out since the 1950s. In 1974, 656 mammal remains were collected but never studied. This fossil collection is here described for the first time through taxonomic and stable isotope analyses of the enamel of selected mammal teeth. The aim is to reconstruct the paleoenvironmental and climatic conditions of the site and to offer new information on terrestrial ecosystems during the Lateglacial in central Italy. The faunal assemblage studied herein, in addition to other species reported in previous works, suggests cold climate conditions. We also describe a right radius of an adult individual of Homo sapiens, increasing the human fossil record of the site. Carbon isotope data point to a scenario dominated by C3 plants in open and dry habitats, such as grasslands and steppes, in accordance with the pollen data from central Italy. The oxygen isotope data suggest the use of water resources with a local origin, i.e. local precipitation and surface waters with a provenance from the nearby Apennine chain. The ecology of the taxa influenced the oxygen isotope values, especially in the case of semi‐obligate to non‐obligate drinker species.

Genetic structure and climate niche differentiation among populations of Leopardus geoffroyi.

Geoffroy's cat (Leopardus geoffroyi) is a small-sized felid native to South America. Given the species' distribution covering a wide variety of habitats, and the presence of high levels of anthropization in part of its range, it is possible that genetically differentiated groups exist and that they occupy different climatic niches. We assessed patterns of contemporary genetic diversity and structure in the species across most of its range, characterizing each inferred genetic group based on ecological niche models. We genotyped 11 microsatellites for 142 samples covering most of Geoffroy's cat distribution, and investigated patterns of genetic structure and diversity, applying spatial and nonspatial Bayesian clustering methods and a spatial principal component analysis. We created ecological niche models for each genetic cluster, evaluating whether these clusters occupy different climatic spaces and display differences in the suitability of different values of the climatic variables analyzed. We identified two genetic clusters, one in the north-northeast and the other in the south-southwest of the species' distribution. These clusters showed moderate FST values between them and differences in dispersal/genetic diversity. We found isolation-by-distance patterns globally and within each cluster. We observed lower expected heterozygosity compared with other studies and a north-south gradient in allelic richness. The southern cluster showed lower genetic variability and a more restricted climatic niche suggesting that this group is more vulnerable to the effects of the current context of climate change. Individuals from the southern genetic cluster are under different pressures, likely a product of the particularly dry habitat they occupy. Climatic variables associated with habitat suitability suggest the southern cluster has affinity for the arid and semiarid conditions present in its distribution. Conservation measures should consider the genetic structure observed and differences in climatic spaces to maintain the evolutionary potential of the species.

Divergent hydraulic and gas exchange strategies in two closely-related Salix species

Abstract Understanding the physiological mechanisms that trees employ to cope with drought-induced mortality is crucial for predicting their responses to a changing climate. Salix species exhibit distinct habit distributions, with Salix babylonica growing in wet habitats and S. matsudana growing in relatively dry habitats. The objective of this study was to compare hydraulic and gas exchange traits between these two closely-related Salix species with contrasting natural habitats. S. matsudana had lower photosynthesis (Amax), lower stomatal conductance (gs), and lower stem and leaf hydraulic conductance, but it exhibited higher water use efficiency (WUEi), higher hydraulic safety and wider leaf-to-stem vulnerability segmentation as well as narrower, shorter and denser conduits and a lower ratio of leaf area to sapwood area than S. babylonica. These findings suggest that variation in hydraulic vulnerability and gas exchange traits enable closely-related Salix species to adapt to different habitats.

First record of Scaphiodontophis annulatus (Duméril, Bibron & Duméril, 1854) (Squamata, Sibynophiidae) from Serranía Montes de María, department of Sucre, Colombia

We present a new record of Scaphiodontophis annulatus (Duméril, Bibron & Duméril, 1854) from Serranía Montes de María, department of Sucre, Colombia. This represents the second record of this species from the Colombian Caribbean region and the first from a tropical dry forest habitat. We discuss color variation across this species range, as the taxonomy of this species remains unresolved. 

Leaf phenotypic plasticity of European ash (Fraxinus excelsior) at its northern range in Dinaric Alps

The Dinaric Alps have been recognised on numerous occasions as a biodiversity hotspot. They host a variety of species with great importance in sustainable forestry operations and nature conservation. One such species is the European ash (Fraxinus excelsior L., Oleaceae), a broad-leaved, wind-pollinated and wind-dispersed forest tree. In this paper, we aimed to determine the morphological variability of the European ash populations of the northern Dinaric Alps. For this purpose, leaf samples from 10 individuals in seven populations were collected. Morphometric analysis of intra- and interpopulation variability was conducted using 19 morphological leaf traits. We determined great variability of trees within, and small variability among, populations. The variables that best discriminated studied populations were those relating to leaflet shape. Based on these variables, populations were grouped into two clusters. The first cluster encompassed individuals with acute leaflets, found in drier and rockier habitats, whereas the second cluster, defined by more rounded leaflets, was found in mesophilous and nutrient-rich habitats. However, this research revealed no influence of geographical or bioclimatic distances on morphological variability, which indicates that the rockiness and soil are most likely two predominant factors in shaping the phenotypic plasticity of European ash populations. These results are of great significance in the planning of future forest breeding programs, as populations from drier habitats are likely to persist and spread due to their adaptation to water scarcity, which will become more pronounced in the future.

Seasonal movements of small-island birds along habitat and elevation gradients highlights the conservation value of small-scale agroforests

Knowledge on species distributions and seasonal movement patterns within landscapes is important for understanding their ecology and roles in agroecosystems, and is critical for enabling their effective conservation and monitoring, particularly in small-island states where conservation resources are limited. We undertook bird surveys to examine species distributions across a range of agricultural land-use intensities and elevations on the Caribbean island of Grenada by collecting data over 6 repeated monthly surveys (3 wet season, 3 dry season) at sites located in a variety of habitats spread over 6–300 m elevation. We observed a gradual upslope increase in bird species diversity and abundance from the mid-wet season to the late-dry season, as well as a movement from reduced-canopy habitats to closed-canopy habitats in the dry season. The mid-elevation hillsides of Grenada consist of a diverse mosaic of closed canopy secondary forest patches, interspersed among more open agroforests and small-scale cropping and grazed areas. These agroecosystems appear to provide important habitats to birds throughout the year, especially open canopy agroforests in the wet season. We also found that open mixed agroforests contained a greater diversity of fruit, flower, and seed resources than closed canopy habitats such as secondary forest, cacao agroforests, young secondary forests, or dry forest scrub; and that plant food diversity was highest in the wet season. However, bird abundance significantly increased in closed canopy forest habitats during the dry season, suggesting that intact canopy forests provide important dry season habitat for many Grenadian birds, which may be particularly important for species in drier lowland areas experiencing more intensive agricultural land use and urban and resort development. Overall, this research demonstrates the importance of maintaining the functional connectivity of treed habitats at local and landscape scales for species conservation, as well as the contribution of diverse, small-scale agriculture to maintaining small-island bird communities.

Effects of Seasonality on the Large and Medium-Sized Mammal Community in Mountain Dry Forests

Seasonality drives natural processes, impacting environmental factors like temperature and resource availability, leading to shifts in wildlife communities. The Andean dry forests exhibit a marked seasonality, with a dry and cold season (May–September) and a warm, wet season (October–April). In a year-long remote camera survey in Southern Bolivia, we identified 29 medium to large mammal species, 18 outside their known distribution ranges. While overall species richness remained stable, photographic records varied between seasons. Capture rates, reflecting species richness and abundance, were more influenced by season and habitat. Wet season rates were lower, but higher in all other habitats compared to the mountain bush and grasslands. Rates increased with altitude and distance to hiking trails, but decreased with increasing distance from main roads. Medium to large mammals were more active during the dry season, indicating adjustments in response to seasonal changes. Our results suggest a cumulative impact of various factors beyond mere seasonality, and call for adjustments in global species distributions. Moreover, emphasize the need for biodiversity monitoring in dry forest habitats, particularly regarding responses to environmental shifts and human-induced alterations.

Home on the range: A multi-isotope investigation of ungulate resource partitioning at Ashfall Fossil Beds, Nebraska, USA

During the Miocene (ca. 23.0–5.3 Ma), North America's Great Plains were a broad mosaic of savanna-woodlands inhabited by a diverse ungulate fauna. We investigated resource partitioning among ungulates at Ashfall Fossil Beds State Historical Park (henceforth “Ashfall”) in north-central Nebraska to establish how taxa shared the landscape. This mid-Miocene (11.86 ± 0.13 Ma) site preserves a watering-hole filled with volcanic ash that entombed hundreds of skeletons of medium- and large-bodied ungulates. We analyzed carbon (δ13C), oxygen (δ18O), and strontium (87Sr/86Sr) isotopes in enamel from seven species: the rhinoceros Teleoceras major (n = 13); three horses (Cormohipparion occidentale, Pliohippus pernix, and Pseudhipparion gratum; n = 3 each); two camels (Procamelus grandis and Protolabis heterodontus; n = 1 each); and one small ruminant artiodactyl (Longirostromeryx wellsi; n = 3). Carbon isotope data indicate that all seven ungulates foraged in open habitats dominated by C3 plants (enamel δ13CVPDB range from −9.6‰ to −6.9‰) with little to no evidence of C4 plant consumption. The overall range in δ18OVPDB values is ca. 6‰ (−7.6‰ to −1.3‰), while the range for 87Sr/86Sr is narrow (0.70864–0.70898). Horses have significantly higher δ18O and 87Sr/86Sr than T. major, which we suggest indicates horses foraged in relatively dry habitats, while T. major inhabited wet habitats with different strontium sources. Both camels isotopically resemble horses, and Longirostromeryx wellsi has intermediate 87Sr/86Sr and wide-ranging δ18O values. Plotting Teleoceras and co-occurring ungulates in a model that tests for semi-aquatic behavior using δ18O suggests that T. major from Ashfall was semi-aquatic; ecology and behavior may have varied among Teleoceras species living in different places at different times. This study exemplifies how 87Sr/86Sr data complement δ13C and δ18O analyses when reconstructing ancient environments; they can provide nuanced ecological information even in landscapes with homogeneous bedrock.