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1. Do honey badgers and greater honeyguide birds cooperate to access bees' nests? Ecological evidence and honey‐hunter accounts

   https://doi.org/10.1111/jzo.13093  

   van der Wal, J. E. M.; Afan, A. I.; Anyawire, M.; Begg, C. M.; Begg, K. S.; Dabo, G. A.; Gedi, I. I.; Harris, J. A.; Isack, H. A.; Ibrahim, J. I.; et al (June 2023, Journal of Zoology)

   Abstract In parts of Africa, greater honeyguides (Indicator indicator) lead people to bees' nests, after which people harvest the honey, and make beeswax and larvae accessible to the honeyguide. In scientific and popular literature, a similar cooperative relationship is frequently described between honeyguides and honey badgers (Mellivora capensis), yet the evidence that this occurs is unclear. Such a partnership may have implications for the origins of our own species' cooperation with honeyguides and for the ecology and conservation of both honey badgers and honeyguides. Here, we review the evidence that honey badgers and honeyguides cooperate to access bees' nests, drawing from the published literature, from our own observations whilst studying both species, and by conducting 394 interviews with honey‐hunters in 11 communities across nine African countries. We find that the scientific evidence relies on incomplete and second‐hand accounts and does not convincingly indicate that the two species cooperate. The majority of honey‐hunters we interviewed were similarly doubtful about the interaction, but many interviewees in the Hadzabe, Maasai, and mixed culture communities in Tanzania reported having seen honey badgers and honeyguides interact, and think that they do cooperate. This complementary approach suggests that the most likely scenario is that the interaction does occur but is highly localized or extremely difficult to observe, or both. With substantial uncertainty remaining, we outline empirical studies that would clarify whether and where honeyguides and honey badgers cooperate, and emphasize the value of integrating scientific and cultural knowledge in ecology. 

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2. Cycad-Weevil Pollination Symbiosis Is Characterized by Rapidly Evolving and Highly Specific Plant-Insect Chemical Communication

   https://doi.org/10.3389/fpls.2021.639368  

   Salzman, Shayla; Crook, Damon; Calonje, Michael; Stevenson, Dennis W.; Pierce, Naomi E.; Hopkins, Robin (April 2021, Frontiers in Plant Science)

   null (Ed.)

   Coevolution between plants and insects is thought to be responsible for generating biodiversity. Extensive research has focused largely on antagonistic herbivorous relationships, but mutualistic pollination systems also likely contribute to diversification. Here we describe an example of chemically-mediated mutualistic species interactions affecting trait evolution and lineage diversification. We show that volatile compounds produced by closely related species of Zamia cycads are more strikingly different from each other than are other phenotypic characters, and that two distantly related pollinating weevil species have specialized responses only to volatiles from their specific host Zamia species. Plant transcriptomes show that approximately a fifth of genes related to volatile production are evolving under positive selection, but we find no differences in the relative proportion of genes under positive selection in different categories. The importance of phenotypic divergence coupled with chemical communication for the maintenance of this obligate mutualism highlights chemical signaling as a key mechanism of coevolution between cycads and their weevil pollinators. 

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3. Auditory Communication Processing in Bats: What We Know and Where to Go

   https://doi.org/http://dx.doi.org/10.1037/bne0000308  

   Salles, A.; Bohn, K.; Moss, C.F. (June 2019, Behavioral neuroscience)

   Bats are the second largest mammalian order, with over 1,300 species. These animals show diverse behaviors, diets, and habitats. Most bats produce ultrasonic vocalizations and perceive their environment by processing information carried by returning echoes of their calls. Echolocation is achieved through a sophisticated audio-vocal system that allows bats to emit and detect frequencies that can range from ten to hundreds of kilohertz. In addition, most bat species are gregarious, and produce social communication calls that vary in complexity, form, and function across species. In this article, we (a) highlight the value of bats as model species for research on social communication, (b) review behavioral and neurophysiological studies of bat acoustic communication signal production and processing, and (c) discuss important directions for future research in this field. We propose that comparative studies of bat acoustic communication can provide new insights into sound processing and vocal learning across the animal kingdom. 

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4. Sensory-motor tuning allows generic features of conspecific acoustic scenes to guide rapid, adaptive, call-timing responses in túngara frogs

   https://doi.org/10.1098/rspb.2024.0992  

   Larter, Luke C; Ryan, Michael J (September 2024, Proceedings of the Royal Society B: Biological Sciences)

   Male frogs court females from within crowded choruses, selecting for mechanisms allowing them to call at favourable times relative to the calls of rivals and background chorus noise. To accomplish this, males must continuously evaluate the fluctuating acoustic scene generated by their competitors for opportune times to call. Túngara frogs produce highly frequency- and amplitude-modulated calls from within dense choruses. We used similarly frequency- and amplitude-modulated playback tones to investigate the sensory basis of their call-timing decisions. Results revealed that different frequencies present throughout this species’ call differed in their degree of call inhibition, and that lower-amplitude tones were less inhibitory. Call-timing decisions were then driven by fluctuations in inhibition arising from underlying frequency- and amplitude-modulation patterns, with tone transitions that produced steeper decreases in inhibition having higher probabilities of triggering calls. Interactions between the varied behavioural sensitivities to different conspecific call frequencies revealed here, and the stereotyped amplitude- and frequency-modulation patterns present in this species’ calls, can explain previously surprising patterns observed in túngara frog choruses. This highlights the importance of understanding the specific sensory drivers underpinning conspecific signalling interactions, and reveals how sensory systems can mediate the interplay between signal perception and production to facilitate adaptive communication strategies. 

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5. The geographic mosaic of arms race coevolution is closely matched to prey population structure

   https://doi.org/10.1002/evl3.184  

   Hague, Michael T. J.; Stokes, Amber N.; Feldman, Chris R.; Brodie, Jr., Edmund D.; Brodie, III, Edmund D. (August 2020, Evolution Letters)

   Abstract Reciprocal adaptation is the hallmark of arms race coevolution. Local coadaptation between natural enemies should generate a geographic mosaic pattern where both species have roughly matched abilities across their shared range. However, mosaic variation in ecologically relevant traits can also arise from processes unrelated to reciprocal selection, such as population structure or local environmental conditions. We tested whether these alternative processes can account for trait variation in the geographic mosaic of arms race coevolution between resistant garter snakes (Thamnophis sirtalis) and toxic newts (Taricha granulosa). We found that predator resistance and prey toxin levels are functionally matched in co-occurring populations, suggesting that mosaic variation in the armaments of both species results from the local pressures of reciprocal selection. By the same token, phenotypic and genetic variation in snake resistance deviates from neutral expectations of population genetic differentiation, showing a clear signature of adaptation to local toxin levels in newts. Contrastingly, newt toxin levels are best predicted by genetic differentiation among newt populations, and to a lesser extent, by the local environment and snake resistance. Exaggerated armaments suggest that coevolution occurs in certain hotspots, but prey population structure seems to be of particular influence on local phenotypic variation in both species throughout the geographic mosaic. Our results imply that processes other than reciprocal selection, like historical biogeography and environmental pressures, represent an important source of variation in the geographic mosaic of coevolution. Such a pattern supports the role of “trait remixing” in the geographic mosaic theory, the process by which non-adaptive forces dictate spatial variation in the interactions among species. 

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