Role of ecology in shaping external nasal morphology in bats and implications for olfactory tracking

Abstract

Many animals display morphological adaptations of the nose that improve their ability to detect and track odors. Bilateral odor sampling improves an animals' ability to navigate using olfaction and increased separation of the nostrils facilitates olfactory source localization. Many bats use odors to find food and mates and bats display an elaborate diversity of facial features. Prior studies have quantified how variations in facial features correlate with echolocation and feeding ecology, but surprisingly none have asked whether bat noses might be adapted for olfactory tracking in flight. We predicted that bat species that rely upon odor cues while foraging would have greater nostril separation in support of olfactory tropotaxis. Using museum specimens, we measured the external nose and cranial morphology of 40 New World bat species. Diet had a significant effect on external nose morphology, but contrary to our predictions, insectivorous bats had the largest relative separation of nostrils, while nectar feeding species had the narrowest nostril widths. Furthermore, nasal echolocating bats had significantly narrower nostrils than oral emitting bats, reflecting a potential trade-off between sonar pulse emission and stereo-olfaction in those species. To our knowledge, this is the first study to evaluate the evolutionary interactions between olfaction and echolocation in shaping the external morphology of a facial feature using modern phylogenetic comparative methods. Future work pairing olfactory morphology with tracking behavior will provide more insight into how animals such as bats integrate olfactory information while foraging.

Phylogeny and foraging behaviour shape modular morphological variation in bat humeri

“…diet and FG) and phylogeny, indicating that humeral morphological disparity has both an ecological and evolutionary signal. The magnitude of the effect of diet and FG in humeral shape mirrors patterns of cranial morphological disparity in bats, providing evidence for a correspondence between cranial and postcranial morphological disparity (Arbour et al, 2019;Brokaw & Smotherman, 2020;Hedrick et al, 2019;Leiser-Miller & Santana, 2020;Monteiro & Nogueira, 2011). Our results reveal differences between epiphyseal and diaphyseal shape in their relationship to ecology and phylogeny.…”

“…Both diet and echolocation have linked cranial phenotypic diversification and evolutionary adaptive radiations in bats (Arbour et al, 2019;Hedrick et al, 2019;Rossoni et al, 2017;Rossoni et al, 2019;Santana & Cheung, 2016;Santana et al, 2012), shedding light on the macroevolutionary trajectories that shaped modern bat diversity (Dumont et al, 2012;. Tooth row complexity, cranial shape and size, nose-leaf morphology and biomechanical performance have all been linked to the colonisation of dietary and echolocating niches during major diversification events (Arbour et al, 2019;Brokaw & Smotherman, 2020;Monteiro & Nogueira, 2011;Rossoni et al, 2019;Santana et al, 2011).…”

Dietary and body mass reconstruction of the Miocene neotropical batNotonycteris magdalenensis(Phyllostomidae) from La Venta, Colombia

“…Functional demands associated with the biomechanical processing of food has been linked to morphological adaptations of the feeding apparatus and sensory organs in bats (Arbour et al 2019, Brokaw and Smotherman 2020, Jacobs et al 2014, Leiser-Miller and Santana 2020, Nogueira et al 2009, Rossoni et al 2019, Santana et al 2010).…”

“…Traditionally, most studies on dietary ecomorphology in bats have focused on skull morphology to study the form-function link, providing crucial information to understand the range of morphological specialisations (Aguirre et al 2002, Arbour et al 2019, Monteiro and Nogueira 2011, Rossoni et al 2019, Santana and Cheung 2016, Santana and Portugal 2016. Some studies have also provided insights on the role of diet in the diversification of the postcranial skeleton (Gaudioso et al 2020, Louzada et al 2019, Norberg and Rayner 1987, Vaughan 1959) and external sensory organs (Brokaw andSmotherman 2020, Leiser-Miller andSantana 2020).…”

Olfactory tracking strategies in a neotropical fruit bat

“…Closer to the source, where the odor gradient becomes steeper, animals can also exploit the simultaneous comparisons of odor intensity ( Catania, 2013 ; Takasaki et al, 2012 ) or arrival timing ( Gardiner and Atema, 2010 ) between two or more spatially segregated receptors (tropotaxis). Morphological comparisons of nostril widths in bats suggest that the nasal emission echolocation pulses may impose an important constraint on leaf-nosed bats' abilities to exploit tropotactic mechanisms ( Brokaw and Smotherman, 2020 ), leading us to hypothesize that they may rely more heavily on different behavioral strategies to track odors.…”