In a new and exciting paper in Nature Communications, we present the results of phylogenetic comparative analyses across hundreds of bat species, and demonstrate how two major forces –echolocation and diet– shaped the diversity of bat skulls over their evolutionary history. Check out this press release highlighting the main results of the paper, and the methods we used!
In collaboration with the Washington Department of Health and the Centers for Disease Control, we just published a new paper investigating spatial and temporal trends in rabies prevalence among Washington bats. We found that the highest number of positive rabies cases occur between July and August. We also found that how bats are encountered is significantly associated with rabies positivity. For example, dogs are more likely to catch a rabid bat than cats; additionally, bats found outdoors are more likely to test positive for rabies than bats found inside a house.
We also found that rabies prevalence varied among species, ranging between 2-11% positive. However, because some species (e.g., Myotis spp.) look nearly identical, they are commonly misidentified. This suggests that genetic barcoding may be necessary to accurately assess species-specific patterns.
Why do some species have larger individuals in certain parts of their range? In many animal species, body size tends to increase with latitude. This famous ecological pattern, known as Bergmann’s Rule, was originally thought to be an adaptation for heat conservation. However, several hypotheses have been proposed, such as resource availability, resistance to starvation, and heat dissipation. We evaluate which of these hypotheses best explain geographic size variation in the Pallid bat in our new paper (Kelly et al., in press). We also investigate potential consequences of size variation by testing whether skull shape (an indicator of bite performance) changes in tandem with size.
Our results suggest that primary productivity (a proxy for resource availability) and to a lesser extent, heat conservation, best explain size variation across the Pallid bat’s western range. We also found that larger individuals have cranial traits associated with greater bite force production. This may help explain why larger individuals tend to consume larger and harder prey. Our results suggest that resource availability is a major factor explaining size, morphology, and possibly feeding performance in a wide-ranging and omnivorous bat species.
Ph.D. student Katie Stanchak just published a new paper describing the variation in the membrane and limb musculature associated with the calcar – a neomorphic skeletal structure found in the hind limbs of most bats. By combining diffusible iodine-based contrast enhanced computed tomography (diceCT) and standard histological techniques, Katie found that the arrangement of the calcar musculature varies among bat species that have different flight ecologies. These results suggest that the calcar may have a functional role in flight maneuverability, an idea that Katie will be testing in later stages of her Dissertation.
Katie’s article has also been featured in the diceCT blog.
Check out the new issue of the Anatomical Record, co-edited with Adam Hartstone-Rose and Damiano Marchi! It is full of anatomical goodness, and showcases new findings and cutting-edge techniques in the study of muscle functional morphology. This issue contains several papers by Santana lab members:
Curtis A.A. and Santana S.E. 2018. Jaw-dropping: functional variation in the digastric muscle in bats. The Anatomical Record 301: 279–290. PDF
Santana S.E. 2018. Comparative anatomy of bat jaw musculature via Diffusible Iodine-Based Contrast-Enhanced Computed Tomography. The Anatomical Record 301: 267–278. PDF
Hartstone-Rose and Santana S.E. 2018. Behavioral correlates of cranial muscle functional morphology. The Anatomical Record 301: 197–201. PDF
Arbour J.A. and López-Fernández H. 2018. Intrinsic Constraints on the Diversification of Neotropical Cichlid Adductor Mandibulae Size. The Anatomical Record 301: 216–226.
Why are there bats that do not echolocate, and how has body size and morphology constrained or facilitated the evolution of sensory diversity in bats? In a collaborative paper in Nature Communications, we present a broad phylogenetic comparative analysis that illuminates the trade-offs between vision and echolocation during bat evolution. You can access the open-access paper here. Enjoy!
Why does the spectacled bear have facial stripes? Or why do canids have relatively plain faces? In a new article with the Caro and Stankowich labs, we explored the behavioral factors that might predict the diversity in facial and chest colors in carnivorans. Much to our surprise, we found that there might be different factors associated with the evolution facial and chest coloration in different lineages. Find out more by reading the full article in Behavioral Ecology and Sociobiology, or its press coverage from Science.
Ada and Leith have returned from a successful trip to La Selva Biological Station, Costa Rica! This field trip was part of our project investigating the coevolution between plant chemical signals and frugivorous bats. The team collected scent samples from fruits, and conducted behavioral experiments to measure what scents bats prefer. They were joined by our collaborators at the Dávalos and Rossiter labs, who are working on the sensory genomics of tropical bats.
Former lab undergrad Kristin Campbell has just published her study on sea otter skull and bite performance in the Journal of Mammalogy. Click here to learn whether and how differences in skull morphology and bite performance are related to diet specialization in these remarkable mammals.
For her undergraduate honors thesis, Rochelle studied bat activity in North Coast vineyards. Using acoustic equipment, she tested whether local or landscape-scale habitat diversity influenced vineyard bat activity. Rochelle and her colleagues found that local habitat diversity significantly increased overall bat activity, especially for two of the most common bat species detected (the Yuma myotis & Big brown bat).
These species are also known to consume agricultural pests. Thus, promoting their activity in agricultural landscape will not only benefit bats, but may also help suppress agricultural pests. Rochelle’s research was published last week in the journal Agriculture, Ecosystems, and the Environment.