Ecological causes of uneven diversification and richness in the mammal tree of life, bioRxiv, 2019-01-05

AbstractThe uneven distribution of species in the tree of life is rooted in unequal speciation and extinction among groups. Yet the causes of differential diversification are little known despite their relevance for sustaining biodiversity into the future. Here we investigate rates of species diversification across extant Mammalia, a compelling system that includes our own closest relatives. We develop a new phylogeny of nearly all ∼6000 species using a 31-gene supermatrix and fossil node- and tip-dating approaches to establish a robust evolutionary timescale for mammals. Our findings link the causes of uneven modern species richness with ecologically-driven variation in rates of speciation andor extinction, including 24 detected shifts in net diversification. Speciation rates are a stronger predictor of among-clade richness than clade age, countering claims of clock-like speciation in large phylogenies. Surprisingly, speciation rate heterogeneity in recent radiations shows limited association with latitude, despite the well-known increase in species richness toward the equator. Instead, we find a deeper-time association where clades of high-latitude species have the highest speciation rates, suggesting that species durations are shorter (turnover is higher) outside than inside the tropics. At shallower timescales (i.e., young clades), diurnality and low vagility are both linked to greater speciation rates and extant richness. We suggest that high turnover among small-ranged allopatric species has erased the signal of vagility in older clades, while diurnality has adaptively promoted lineage persistence. These findings highlight the underappreciated joint roles of ephemeral (turnover-based) and adaptive (persistence-based) processes of diversification, which manifest in recent and more ancient evolutionary radiations of mammals to explain modern diversity.Author SummaryThe over 6000 living species in the mammalian tree of life are distributed unevenly among branches so that similarly aged groups sometimes differ many fold in species richness (e.g., ∼2500 rodent species versus 8 pangolins). Why differential bursts of species diversification occur, and how long they persist, has implications for sustaining biodiversity. Here we develop a robust evolutionary timescale for most extant species, recovering signatures of rate-variable diversification linked to ecological factors. Mammals with low dispersal or that are day-active show the fastest recent speciation rates, consistent with mechanisms of allopatric isolation and ecological opportunity, respectively. Speciation is surprisingly faster in extra-tropical than tropical lineages, suggesting that longer species durations for tropical lineages underpin the latitudinal diversity gradient in mammal.

biorxiv evolutionary-biology 200-500-users 2019

Recording of sonic attacks on U.S. diplomats in Cuba spectrally matches the echoing call of a Caribbean cricket, bioRxiv, 2019-01-04

Beginning in late 2016, diplomats posted to the United States embassy in Cuba began to experience unexplained health problems including ear pain, tinnitus, vertigo, and cognitive difficulties which reportedly began after they heard strange noises in their homes or hotel rooms. In response, the U.S. government dramatically reduced the number of diplomats posted at the U.S. embassy in Havana. U.S. officials initially believed a sonic attack might be responsible for their ailments. The sound linked to these attacks, which has been described as a high-pitched beam of sound, was recorded by U.S. personnel in Cuba and released by the Associated Press (AP). Because these recordings are the only available non-medical evidence of the sonic attacks, much attention has focused on identifying health problems and the origin of the acoustic signal. As shown here, the calling song of the Indies short-tailed cricket (Anurogryllus celerinictus) matches, in nuanced detail, the AP recording in duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse. The AP recording also exhibits frequency decay in individual pulses, a distinct acoustic signature of cricket sound production. While the temporal pulse structure in the recording is unlike any natural insect source, when the cricket call is played on a loudspeaker and recorded indoors, the interaction of reflected sound pulses yields a sound virtually indistinguishable from the AP sample. This provides strong evidence that an echoing cricket call, rather than a sonic attack or other technological device, is responsible for the sound in the released recording. Although the causes of the health problems reported by embassy personnel are beyond the scope of this paper, our findings highlight the need for more rigorous research into the source of these ailments, including the potential psychogenic effects, as well as possible physiological explanations unrelated to sonic attacks.

biorxiv biophysics 200-500-users 2019

Enjoy The Violence Is appreciation for extreme music the result of cognitive control over the threat response system?, bioRxiv, 2019-01-03

Traditional neurobiological theories of musical emotions explain well why extreme music such as punk, hardcore or metal, whose vocal and instrumental characteristics share much similarity with acoustic threat signals, should evoke unpleasant feelings for a large proportion of listeners. Why it doesn't for metal music fans, however, remains a theoretical challenge metal fans may differ from non-fans in how they process acoustic threat signals at the sub-cortical level, showing deactivated or reconditioned responses that differ from controls. Alternatively, it is also possible that appreciation for metal depends on the inhibition by cortical circuits of a normal low-order response to auditory threat. In a series of three experiments, we show here that, at a sensory level, metal fans actually react equally negatively, equally fast and even more accurately to cues of auditory threat in vocal and instrumental contexts than non-fans. Conversely, cognitive load somewhat appears to reduce fans' appreciation of metal to the level reported by non-fans. Taken together, these results are not compatible with the idea that extreme music lovers do so because of a different low-level response to threat, but rather, highlight a critical contribution of higher-order cognition to the aesthetic experience. These results are discussed in the light of recent higher-order theories of emotional consciousness, which we argue should be generalized to the emotional experience of music across musical genres.

biorxiv neuroscience 200-500-users 2019

 

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