Drivers of Geographic Variation in Exaggerated Trait in Male Giraffe Weevil (Lasiorhynchus barbicornis)

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dc.contributor.advisor Cain, K en
dc.contributor.advisor Painting, C en
dc.contributor.author Haerewa, Nicole en
dc.date.accessioned 2020-03-25T23:03:34Z en
dc.date.issued 2019 en
dc.identifier.uri http://hdl.handle.net/2292/50158 en
dc.description Full Text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Exaggerated traits are morphological features granting a greater success of obtaining a mate. Natural and sexual selection drive diversity across a species geographic range by promoting (sexual selection) or constraining (natural selection) the elaboration of exaggerated traits. However, investigations into how this selection trade-off drives variation in exaggerated traits across a species’ range are rare. Male New Zealand giraffe weevils (Lasiorhynchus barbicornis) display a positive allometry between an exaggerated weapon (rostrum) and body size, which varies in strength across its geographic range. Males in southern and colder regions have a larger body on average but do not invest as heavily into rostrum length compared to males in northern, warmer regions. My study tests the hypothesis that geographic variation of exaggerated traits is driven by a trade-off between natural and sexual selection. I conducted field observations to measure the strength of sexual selection using copulation frequencies in four North Island populations. I relate this estimate to weapon size, population density and sex ratios. I also used copulation duration and relate this to local corresponding temperatures to gain an understanding of activity levels as driven by temperature. Furthermore, to determine whether the difference in relative rostrum length is an adaptation to colder climates, I experimentally measured cooling rates of individuals from the most northern and southern populations. My results present evidence of a selection trade-off. Sexual selection pressures (sex ratio and density) alter the intensity of competition to drive exaggeration; meanwhile, temperature is found to be a thermal cost for males. Longer rostra lose heat faster than shorter rostra, while smaller bodies lose heat faster than larger bodies. This suggests that a steep positive allometric slope (longer rostrum compared to body length) has a greater thermal cost in cool environments and could partially be responsible for geographic variation in weapon size. The outcome of this thermal cost is shown to be lower copulation activity as giraffe weevils are physiologically constrained from active movement in cold temperatures. This is evident in males from Lake Papaitonga who possess a steep allometric slope yet display low copulation duration and frequency directly linked to their cold environment. The results of this thesis emphasise the intricacy and connection between natural and sexual selection and how this may drive geographic variation in exaggerated traits. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99265297514002091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights Restricted Item. Full Text is available to authenticated members of The University of Auckland only. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/nz/ en
dc.title Drivers of Geographic Variation in Exaggerated Trait in Male Giraffe Weevil (Lasiorhynchus barbicornis) en
dc.type Thesis en
thesis.degree.discipline Biological Sciences en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Masters en
dc.rights.holder Copyright: The author en
pubs.elements-id 796977 en
pubs.org-id Science en
pubs.org-id Biological Sciences en
pubs.record-created-at-source-date 2020-03-26 en
dc.identifier.wikidata Q112948662


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