title: Sensory Drive Mediated by Climatic Gradients Partially Explains Divergence in Acoustic Signals in Two Horseshoe Bat Species, Rhinolophus swinnyi and Rhinolophus simulator.
abstract: Geographic variation can be an indicator of still poorly understood evolutionary processes such as adaptation and drift. Sensory systems used in communication play a key role in mate choice and species recognition. Habitat-mediated (i.e. adaptive) differences in communication signals may therefore lead to diversification. We investigated geographic variation in echolocation calls of African horseshoe bats, Rhinolophus simulator and R. swinnyi in the context of two adaptive hypotheses: 1) James' Rule and 2) the Sensory Drive Hypothesis. According to James' Rule body-size should vary in response to relative humidity and temperature so that divergence in call frequency may therefore be the result of climate-mediated variation in body size because of the correlation between body size and call frequency. The Sensory Drive Hypothesis proposes that call frequency is a response to climate-induced differences in atmospheric attenuation and predicts that increases in atmospheric attenuation selects for calls of lower frequency. We measured the morphology and resting call frequency (RF) of 111 R. simulator and 126 R. swinnyi individuals across their distributional range to test the above hypotheses. Contrary to the prediction of James' Rule, divergence in body size could not explain the variation in RF. Instead, acoustic divergence in RF was best predicted by latitude, geography and climate-induced differences in atmospheric attenuation, as predicted by the Sensory Drive Hypothesis. Although variation in RF was strongly influenced by temperature and humidity, other climatic variables (associated with latitude and altitude) as well as drift (as suggested by a positive correlation between call variation and geographic distance, especially in R. simulator) may also play an important role.
authors.affiliation: Animal Evolution and Systematics Group (AES), Biological Sciences Department, University of Cape Town, Cape Town 7701, South Africa.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Mutumi
authors.affiliation: Animal Evolution and Systematics Group (AES), Biological Sciences Department, University of Cape Town, Cape Town 7701, South Africa.
authors.forename: David S
authors.initials: DS
authors.lastname: Jacobs
authors.affiliation: Centre for Statistics in Ecology, Environment and Conservation (SEEC), South African National Biodiversity Institute (SANBI), Cape Town, South Africa.
authors.forename: Henning
authors.initials: H
authors.lastname: Winker
mesh_terms: D000222:Adaptation, Physiological; D000349:Africa; D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002685:Chiroptera / Q000033:anatomy & histology / Q000502:physiology*; D002980:Climate; D004455:Echolocation; D017753:Ecosystem; D005260:Female; D006813:Humidity; D008297:Male; D013045:Species Specificity; D013696:Temperature
references.citation: J Exp Biol. 1999 Dec;202(Pt 23):3359-67
references.pmid: 10562518
references.citation: Proc Biol Sci. 2005 Apr 7;272(1564):751-7
references.pmid: 15870037
references.citation: Oecologia. 2007 Jun;152(3):583-94
references.pmid: 17345101
references.citation: PLoS One. 2008;3(11):e3715
references.pmid: 19005563
references.citation: PLoS One. 2010 Sep 17;5(9):null
references.pmid: 20862252
references.citation: J Acoust Soc Am. 2010 Oct;128(4):2204-11
references.pmid: 20968390
references.citation: J Acoust Soc Am. 2012 Feb;131(2):1650-8
references.pmid: 22352535
references.citation: J Acoust Soc Am. 2012 Sep;132(3):1765-75
references.pmid: 22978903
references.citation: Proc Biol Sci. 2012 Dec 7;279(1748):4827-35
references.pmid: 23034703
references.citation: J R Soc Interface. 2013 Dec 11;11(91):20130961
references.pmid: 24335559
references.citation: BMC Evol Biol. 2014 Mar 27;14(1):60
references.pmid: 24674227
references.citation: PLoS One. 2014 Jul 30;9(7):e103452
references.pmid: 25075972
references.citation: Integr Zool. 2015 May;10(3):241-56
references.pmid: 25664901
references.citation: Oecologia. 1989 Aug;80(2):178-186
references.pmid: 28313104
references.citation: Evolution. 1999 Dec;53(6):1898-1914
references.pmid: 28565459
references.citation: J Mammal. 2016 Jun 9;97(3):663-688
references.pmid: 29692469
references.citation: J Zool. 1974 Jun;173(2):264-71
references.pmid: 4468893
references.citation: J Acoust Soc Am. 1982 Mar;71(3):585-90
references.pmid: 7085967