Museum of Vertebrate Zoology

Rising temperatures and globalization are enabling widespread biotic invasions today, particularly in marine environments. While the long-term consequences of invasion are poorly understood, the fossil record can be used to assess the impacts of past invasions on ecosystem structure and functioning on evolutionary timescales. During the Late Ordovician (Katian), ~445.25 million years ago, deglaciation and subsequent rising sea level connected formerly isolated shallow epicontinental seas, facilitating the invasion of over 75 genera through larval dispersal in several pulses known as the Richmondian Invasion. Here we examine 1,139 species from these benthic marine communities of the Cincinnati Arch (USA) to quantify the effects of invasive species on functional diversity, which has been shown to influence ecosystem dynamics, stability, productivity, and functioning. Changes in functional diversity were quantified across six 3 rd -order stratigraphic sequences to assess the impacts of invasion using functional traits readily identifiable in fossil taxa: tiering above the substrate, feeding mode, motility/attachment, structural robustness, trophic rank, vision, and body form. We find that despite well documented changes in community composition, the arrival of invaders did not significantly add new functional entities or dramatically alter functional diversity, and invaders largely occupied pre-existing functions. While there were changes across the invasion, community structure ultimately returned to a state similar to the pre-invasion community. This suggests that despite changes in community composition across the Richmondian Invasion, ultimately the invasion did not substantially restructure functional diversity, as we observed little change in the number of functions, functional redundancy and over redundancy, vulnerability, and the distribution of species among functional entities. These findings emphasize the decoupling of changes in community composition and functional diversity, and the importance of functional diversity in assessing the potential ecological impacts of marine invasions today.

Understanding the extent of parallelism across adaptive radiations remains a central problem in evolutionary biology. We used whole-genome resequencing of 123 individuals to compare the adaptive radiation of Cyprinodon pupfishes in Lake Chichancanab, Mexico, to an independent radiation of San Salvador Island (SSI) pupfishes in the Bahamas, and assess the repeatability of adaptive genetic architecture, sources of adaptive variation, and stages of selection. Despite rapid craniofacial divergence of trophic specialists within 8–15 kya, only two candidate genes (0.5%; 2/426) were shared between Caribbean radiations. Although adaptive introgression played a major role in SSI, we found minimal evidence of adaptive introgression in Chichancanab, likely due to the geographic isolation of this inland lake. Instead, de novo mutations provided a substantial source of adaptive variation (30.6%) for the endemic zooplanktivore, 15 times higher than the endemic scale-eater on SSI. However, in parallel with SSI, we found strong evidence that adaptive divergence occurred in stages, first on regulatory and standing genetic variation, then on de novo and nonsynonymous mutations. Consistent with adaptive variants near opsin and spermatogenesis genes, functional categories unique to Chichancanab, we found greater visual acuity and divergent sperm morphology in lab-reared zooplanktivores relative to generalists using laboratory assays. Consistent with extensive adaptive de novo mutations in WNT10A and rapid diversification of tooth size in the zooplanktivore, we found that experimental inhibition of the Wnt pathway in generalists resulted in narrower oral teeth. We conclude that de novo mutations, not introgression, can drive rapid adaptive radiations in isolated environments.

A comprehensive study was conducted in District Dadu, Sindh, to investigate the influence of environmental variables on the prevalence and breeding patterns of two commensal rodent species. Over a standardized trapping period, a total of 256 rodent specimens were collected and identified as Bandicota bengalensis (Lesser Bandicoot Rat) and Tatera indica (Indian Gerbil). Population structure analysis revealed a significant female-biased sex ratio, with females constituting 67.2% (n = 172) of the total population, compared to males at 32.8% (n = 84). Statistical analysis confirmed this dominance was significant (χ² = 30.25, p < 0.001). The high proportion of gravid females (45% of total females) indicated active breeding, strongly correlated with seasonal fluctuations in temperature and humidity. Rodent abundance demonstrated a significant positive correlation with relative humidity (r = 0.82, p < 0.05) and a significant negative correlation with rising ambient temperatures (r = -0.75, p < 0.05). The data, expressed as mean abundance ± standard deviation (12.8 ± 3.2 individuals per site), underscore that cool, humid conditions in the Dadu district create a highly favorable environment for rodent proliferation. These findings provide critical insights for developing timely and targeted rodent management strategies in the region.

Abstract The New Mexico jumping mouse ( Zapus luteus ) is a federally endangered species reliant on riparian areas in the southwestern United States. Restoration of habitat in riparian areas would reduce threats to the species and enable recovery, and quantifying specific habitat features that support occupancy of the species throughout its range will inform management of these areas. With this objective, we surveyed for New Mexico jumping mice for 3 days each at 113 sites across Arizona and New Mexico and measured conditions of the vegetation, soil, and streams. We then constructed occupancy models to estimate detection probability and identify habitat variables important in predicting use by the species. We found that occupancy of New Mexico jumping mice was best predicted by high variability in vegetation height, tall vegetation, variation in soil moisture, stream gradient, and stream width. New Mexico jumping mice were more likely to occupy sites with consistently high soil moisture, vegetation height >60 cm with variable vegetation structure and wide streams with low gradients. Additionally, we assessed which vegetation variables were most useful in describing occupied and unoccupied sites. Reducing the number of vegetation variables that need to be measured to adequately assess conditions important to the New Mexico jumping mouse could help optimize survey protocols. This information can provide guidelines for local conditions that could be targeted for conservation and restoration to favor occupancy of the species.

Otophysans, known for their enhanced hearing enabled by the complex Weberian apparatus, comprise two-thirds of extant freshwater fish species. Previously, they were thought to have originated in fresh water before the breakup of Pangea, implying a nearly 80-million-year gap between the origin and oldest known fossil. However, the discovery of a Late Cretaceous freshwater otophysan challenges this view. Integrating fossil, morphological, and genomic data, we estimate a younger crown group origin of ~154 million years ago. Notably, ancestral range and habitat reconstructions indicate marine origins for the otophysan crown groups, with at least two transitions to fresh water. Functional simulations of the Weberian ossicles of this fossil suggest that the distinctive hearing capabilities of otophysans evolved in conjunction with fusion of hearing ossicle parts and freshwater adaptations.

Many North American game animals experienced severe population declines during the 19th century due to market hunting. However, estimates of the timing and magnitude of these declines often rely on anecdotal evidence, which makes it difficult to understand the lasting impacts of hunting pressures versus climate or landscape changes on the genetic diversity of contemporary populations. Historical reports suggest the California quail (Callipepla californica) suffered more significant hunting pressure in the late 19th century relative to either Gambel's (Callipepla gambelii) or mountain quail (Oreortyx pictus). Genomic data can help illuminate the extent to which historical exploitation moulded the genetic health of modern quail populations. We compared whole genome sequences from these three quail species to evaluate whether reported differences in hunting pressure affected contemporary patterns of genetic diversity. Contrary to our expectations, California quail did not exhibit any evidence for population declines until the late 20th century, long after the era of market hunting ended. California quail also exhibited the highest levels of genetic diversity across most analyses with evidence for population expansion over the past 500,000 years. In contrast, the mountain quail exhibited a long-term population decline beginning in the middle of the last ice age 30-40 thousand years ago. The Gambel's quail appears to have suffered a more recent bottleneck in association with a major drought that impacted the desert southwest during the mid-20th century. Gambel's quail also exhibited increased realised genetic load for mild and moderately deleterious genetic variants. Together, our results demonstrate that market hunting had little lasting impact on the genetic diversity of these quail species, whereas landscape and climate changes have led to fluctuations in effective population size (Ne) and the buildup of genetic load.

The unique geologic and biogeographic history of the island of Sulawesi in Indonesia has produced one of the world’s most endemic biota, much of which is still unknown to science. The biogeography of the island is influenced both by its unique shape, a confluence of four peninsulas, as well as its extremely mountainous topography, and its upland ecosystems are poorly understood by science. Here, we report the second full-mountain checklist from a series of herpetological surveys of Sulawesi’s Mountains conducted by an international team of researchers. During 3 weeks of work on Gunung Katopasa, a 2,825 m asl peak on Sulawesi’s Eastern Peninsula in the province of Sulawesi Tengah, we recovered 45 species of reptiles and amphibians. Among these, we believe that at least eight represent undescribed species. Our efforts to survey Gunung Katopasa highlight that greater herpetological diversity will likely be discovered upon future assessments of species richness and abundance on the Eastern Peninsula of Sulawesi.

Being naturally hyperglycemic and insulin insensitive, birds maintain plasma glucose levels twice as high as mammals of similar size. Recent evidence suggests that perturbation of myo-inositol (MI) plays a role in mammalian hyperglycemic regulation. Using an integrative approach, we identify a fundamental role of MI in avian metabolism. We show that MI transporters are highly conserved across birds and that dietary MI reduces fat accumulation in Anna’s hummingbirds. MI consumption by hummingbirds varies with seasonal changes in body mass, consistent with a regulatory role. Furthermore, MI enhances fatty acid oxidation in avian cells, via effects on pyruvate-dehydrogenase complexes, indicating a role in mitochondrial fuel selection. Our findings underscore the importance of MI in avian metabolism, offering insights into their evolutionary adaptations in the context of insulin insensitivity.

BackgroundPhagocytosis is a universal physiological process in eukaryotes with many important biological functions. In nudibranch gastropods, a novel form of phagocytosis called nematocyst sequestration is specialized for the uptake of venomous stinging organelles stolen from their cnidarian prey. This process is highly selective. Here we use the emerging model nudibranch species Berghia stephanieae and Hermissenda opalescens to identify genes enriched within the body regions where nematocyst sequestration occurs, and investigate how the expression profile of phagocytosis, immune, and digestive genes differs between nematocyst-sequestering regions relative to those where other phagocytic functions occur.ResultsWe identified 166 genes with significantly higher expression in sequestering regions in B. stephanieae, including genes associated with development, membrane transport, and metabolism. Of these, at least 31 overlap with transcripts upregulated in H. opalescens sequestering tissues. Using hybridization chain reaction in situs, we show that at least two of these genes were localized to sequestering cells in B. stephanieae, including a putative C-type lectin receptor and a collagen. Genes annotated with phagocytosis, digestion, or immunity GO terms were often expressed in both sequestering and non-sequestering tissues, suggesting that they may also play a role in sequestration processes.ConclusionOur results suggest that phagocytosis genes likely play a role in the sequestration phenotype, and that a small subset of genes (e.g., collagen) may play unique functions yet to be uncovered. We also show that genes categorized as functioning in endocytosis, immunity, and digestion have lower overall expression in sequestering tissues, supporting the hypothesis that sequestering tissues show a narrowing of function compared to digestive tissues. This study lays the foundation for further inquiry into mechanisms of organelle sequestration in nudibranchs and other organisms.