Friday, December 30, 2016

[Entomology • 2016] Selection for Predation, not Female Fecundity, Explains Sexual Size Dimorphism in the Orchid Mantises


Figure 1: Floral and disruptive camouflage in nymphal and adult Hymenopodini with varying sexual size dimorphism (SSD) of males and females.

Hymenopus (a) female nymph with monochromatic colouration (photograph by Matthew Nochisaki), (b) mating pair with pronounced SSD and monochromatic colouration (photograph by Jason Zhu). (dTheopropus with pronounced SSD, but patterned, disruptive camouflage in both male and female (photograph by Stefan Engelhardt).
(
eCreobroter sp. mating pair with low SSD and patterned colouration in both male and female (photograph by Andrew Mitchell).  


DOI:  10.1038/srep37753  

Abstract
Here we reconstruct the evolutionary shift towards floral simulation in orchid mantises and suggest female predatory selection as the likely driving force behind the development of extreme sexual size dimorphism. Through analysis of body size data and phylogenetic modelling of trait evolution, we recovered an ancestral shift towards sexual dimorphisms in both size and appearance in a lineage of flower-associated praying mantises. Sedentary female flower mantises dramatically increased in size prior to a transition from camouflaged, ambush predation to a floral simulation strategy, gaining access to, and visually attracting, a novel resource: large pollinating insects. Male flower mantises, however, remained small and mobile to facilitate mate-finding and reproductive success, consistent with ancestral male life strategy. Although moderate sexual size dimorphisms are common in many arthropod lineages, the predominant explanation is female size increase for increased fecundity. However, sex-dependent selective pressures acting outside of female fecundity have been suggested as mechanisms behind niche dimorphisms. Our hypothesised role of predatory selection acting on females to generate both extreme sexual size dimorphism coupled with niche dimorphism is novel among arthropods.



Hymenopus (a) female nymph with monochromatic colouration (photograph by Matthew Nochisaki), (b) mating pair with pronounced SSD and monochromatic colouration (photograph by Jason Zhu). (c) Helvia mating pair with pronounced SSD and monochromatic colouration (photograph by Adrian Kozakiewicz). (d) Theopropus with pronounced SSD, but patterned, disruptive camouflage in both male and female (photograph by Stefan Engelhardt). (e) Creobroter sp. mating pair with low SSD and patterned colouration in both male and female (photograph by Andrew Mitchell). 


Gavin J. Svenson, Sydney K. Brannoch, Henrique M. Rodrigues, James C. O’Hanlon and
Frank Wieland. 2016. Selection for Predation, not Female Fecundity, Explains Sexual Size Dimorphism in the Orchid Mantises.
Scientific Reports. 6:37753. DOI:  10.1038/srep37753

  Beautiful Huntresses: Scientists Explain Why Mantises Evolved To Resemble Orchids   @NPR  n.pr/2hBBdnc

  

No comments:

Post a Comment