New paper: Primary productivity explains size variation across the Pallid bat’s western geographic range

Pallid bat skullWhy 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.

New paper on the hindlimb membrane musculature of bats

Virtual dissections in ventral view of the calcar-depressor muscle complex of one hindlimb of (a) Myotis californicus, (b) Molossus molossus, and (c) Artibeus jamaicensis.

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.

More papers! Behavioral correlates of cranial muscle functional morphology

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.


New paper: Auditory opportunity and visual constraint enabled the evolution of echolocation in bats

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!


The evolution of anterior coloration in carnivorans

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.

Caro et al. 2017
Caro et al. 2017

Habitat diversity & bat activity in vineyards

Rochelle setting up bat acoustic monitoring equipment in a Napa Vineyard
Rochelle setting up bat acoustic monitoring equipment in a Napa Vineyard

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.

Primate faces on Discover

uakariWhy do primates have such colorful and distinct faces? We have been trying to answer this question in a broad comparative context by integrating data on the two most likely drivers of primate facial diversity: sociality and ecology. A major challenge during this research has been to quantify the facial patterns in a way that is comparable across hundreds of primates species. So, we devised  a metric, “facial complexity”, which represents how many colors there are in a primate’s face. Much to my own surprise, the evolution of facial complexity seems to be tightly linked to social group size and species sympatry. This is usually a positive relationship (Neotropical primates are the oddball), indicating that differences in the number of colors in primate faces provide cues that might be used for species and/or individual recognition.

This research has been getting a lot of media coverage (I guess everyone likes monkeys!), and a new article in Discover magazine does an excellent job at decribing our complexity scale. Check it out: