Field Museum of Natural History

Molecular and morphological evidence has reshaped our understanding of oyster diversity, distributions and phylogeny, revealing widespread misidentifications and undescribed species. On Australia's east coast the Sydney rock oyster, Saccostrea glomerata , traditionally thought to be reef‐building both intertidally and subtidally, is likely a predominantly intertidal species. Examination of museum specimens and historical literature indicates that subtidal S. glomerata identifications are likely incorrect and instead represent multiple species, all with reef‐building capacity. Broadly, clarifying species identities and distributions by tidal zone and depth will be an essential first step for guiding subtidal oyster reef restoration in tropical and subtropical areas. Given this re‐interpretation, the threatened status of S. glomerata reefs should be re‐assessed to reflect their true, predominantly intertidal distribution.

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 a 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 appropriately using these two categories of distributions and their estimators. Conflating range and occurrence distributions can have serious consequences for ecological inference and conservation practice. For example, in most situations, home ranges estimated using estimators of occurrence distributions 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 estimators of range distributions to quantify home ranges and estimators of occurrence distributions to answer other questions in movement ecology, such as when and where an animal crossed a linear feature, visited a location of interest, or interacted with other animals.

Abstract All of the native terrestrial small mammals of Madagascar, comprising 59 species (Tenrecidae and Nesomyinae), are endemic and most considered as forest-dependent. However, recent fieldwork in degraded natural forest areas has found that certain species can live in disturbed habitats. Herein based on fieldwork in central eastern Madagascar and employing systematic trapping (live traps and pitfall lines), we test the importance of habitat quality for a range of species in three contiguous moist evergreen forest habitat types: relatively intact, slightly degraded, and secondary. We also employ data from two sites (slightly degraded and secondary) on levels of disturbance, presence of introduced species (Muridae and Soricidae), and soil parameters, to examine possible correlates. The two sites with relatively intact and slightly disturbed forest habitats have similar native small mammal faunas. In contrast, the secondary habitat is depauperate, although with certain tenrecid species that were previously presumed to be “forest-dependent”. Introduced species have not heavily colonized the largely intact or degraded habitats. Our survey data indicate an important level of adaptability of previously presumed “forest-dependent” or “largely forest-dependent” small mammal species to different levels of human disturbance, although at the secondary site, species diversity is notably lower.

Leptospirosis, a globally distributed, environmentally transmitted zoonosis, causes 2.9 million disability-adjusted life years annually, primarily among rural farmers in tropical regions. Infected animals' urine contaminates soils and water with Leptospira bacteria, where other individuals are then exposed. Understanding the impact of land use on the transmission of this disease is of considerable importance. In Madagascar, infection dynamics are impacted by the combined effects of converting forests to agricultural fields and colonization of these areas by non-native mammal species, which carry molecularly distinct lineages of Leptospira. We show that land use corresponds to the replacement of native species and endemic Leptospira lineages with non-native species and their cosmopolitan L. interrogans and L. kirschneri. Together, this contributes to higher infection prevalence in more disturbed habitats like flooded rice fields, where >50% of mice captured were infected, highlighting the important effects of land use on Leptospira prevalence and presence, which together impact zoonotic risk.

Host functional traits are widely used to explain patterns of parasite diversity and community structure; however, their predictive power in species-rich Neotropical freshwater systems remains poorly understood. We examined whether host traits predict helminth parasite community composition in the Lacantún River (southern Mexico), using presence/absence data for 74 helminth genera recorded from 58 fish species. We evaluated a suite of host traits related to body size, spatial ecology, migration and trophic position, together with a proxy for host phylogenetic relatedness. Multivariate analyses revealed that the first axis explained 17.9% of the total variation in parasite assemblage composition. Trophic level was the strongest contributor to this axis (23.8% of its explained variance), followed by host total length (21.3%) and position in the water column (20.6%). Notably, piscivorous hosts harboured distinct parasite communities. Nevertheless, the overall proportion of explained variation was low, reflecting the complex, multicausal nature of host-parasite systems and the influence of unmeasured factors such as host density, sampling effort and parasite life-history diversity. Consistent with this interpretation, univariate analyses showed no significant linear relationship between helminth genus richness and either host total length or trophic level. Together, these results indicate that host traits act primarily as ecological filters shaping which parasite genera occur, rather than determining the total number of parasite genera per host. Our findings highlight the importance of multivariate, trait-based approaches for understanding parasite community assembly in Neotropical rivers and caution against relying on simple richness-based predictors in highly complex host-parasite networks.

ABSTRACT Aim The isolated nature of islands makes them particularly vulnerable to climate change. The freshwater fishes of the Greater Antilles remain understudied and are further threatened by habitat fragmentation and the introduction of exotic invasive species. A practical solution to protect this diversity is to develop a spatially explicit framework to inform conservation actions. We test whether biogeographically significant subregions can be identified within the Greater Antilles. Location The Greater Antilles, Caribbean Basin. Taxa Freshwater Fishes (Atheriniformes, Cichliformes, Cyprinodontiformes, Lepisosteiformes, and Ophidiiformes). Methods We compiled a dataset of 1704 occurrence records across the Greater Antilles based on museum vouchers and the authors' fieldwork. River basins were used as analytical units for hierarchical agglomerative clustering both among and within islands. We also combined genetic data to examine phylogeographic patterns and uncover potential substructure within islands. Results Ninety‐two per cent of the freshwater fish fauna of the Greater Antilles is endemic. Although diversity is unevenly distributed among and within islands, patterns of species richness and weighted endemism partially align across islands. The region is not a single biogeographic unit but consists of multiple subregions of biogeographic significance, where river basins from the same island are more similar to each other than to basins from other islands, with Hispaniola as the only exception. Main Conclusions The Greater Antilles comprise a mosaic of biogeographically meaningful subregions, each harbouring unique, highly vulnerable, and often range‐restricted species assemblages. The patterns recovered reflect a complex interplay among the region's geological history, multiple colonization events, and diversification processes. Our proposed areas of endemism represent testable hypotheses for investigating the evolutionary history of freshwater taxa in the region. These areas also provide natural management units that can serve as geographical targets for conservation prioritisation and policymaking for freshwater ecosystems across the Greater Antilles.

ABSTRACT Mongolia's Eastern and Western Gobi Basins preserve a globally significant record of Cretaceous terrestrial vertebrates, yet their biostratigraphic correlations are complicated by a complex geological history. The Eastern Gobi Basin, a northeast‐southwest trending fault‐bounded rift system, includes several minor sub‐basins with distinct sedimentary sequences, notably the Upper Cretaceous Bayanshiree Formation. This formation hosts key localities of iconic taxa, including Segnosaurus , Erlikosaurus , Duonychus , Garudimimus , Amtocephale , Gobihadros and Adocus amtgai , yet previous correlations throughout the area lacked precision. Our sedimentological and stratigraphic campaigns (2022 to 2024) in the Bayanshiree Formation and overlying red‐bed sequences at Baishin Tsav refined these biostratigraphic and palaeoenvironmental frameworks. Field surveys at local (Baishin Tsav) and basin‐wide scales (Unegt and Zuunbayan sub‐basins) revealed a significant erosional unconformity dividing the formation into two distinct palaeoenvironmental stages: lower expansive erg (aeolian dunes) and upper mature fluvial floodplains. Additionally, this study redefines the previously misidentified red‐bed sequences above the Bayanshiree formation as the Javkhlant Formation (formerly Djadokhta or Baruungoyot formations). Taphonomic analyses indicate fossil assemblages were extensively reworked, demonstrating significant time‐averaging. This study provides evidence for climatic shifts through three successive environmental phases (erg, floodplain, alternating palaeosols) within the Bayanshiree and Javkhlant formations. These findings suggest widespread aridification in eastern Asia initiated during the Cenomanian–Turonian transition, contemporaneous with a subtropical high‐pressure shift and onset of the Cretaceous Thermal Maximum, challenging prior assumptions that placed this event later in the Late Cretaceous. This palaeoclimatic interpretation aligns with global records of past hyperthermal events and significantly refines the temporal context for interpreting regional palaeobiodiversity patterns.