No Cover Image

E-Thesis 9 views 1 download

Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses. / RACHEL HAYNES

Swansea University Author: RACHEL HAYNES

Abstract

Chemical defence is an antipredator mechanism employed by many amphibians. Despite this, chemically defended amphibians have been shown to exhibit a 60% higher contemporary extinction risk than non-defended species, with a three-times higher background extinction rate. Using structural equation mode...

Full description

Published: Swansea 2026
Institution: Swansea University
Degree level: Master of Research
Degree name: MRes
URI: https://cronfa.swan.ac.uk/Record/cronfa71780
first_indexed 2026-04-22T14:21:58Z
last_indexed 2026-04-22T14:21:58Z
id cronfa71780
recordtype RisThesis
fullrecord <?xml version="1.0" encoding="utf-8"?><rfc1807 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><bib-version>v2</bib-version><id>71780</id><entry>2026-04-22</entry><title>Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.</title><swanseaauthors><author><sid>7188d7727a9cffb6caedfa628e06a0f2</sid><firstname>RACHEL</firstname><surname>HAYNES</surname><name>RACHEL HAYNES</name><active>true</active><ethesisStudent>false</ethesisStudent></author></swanseaauthors><date>2026-04-22</date><abstract>Chemical defence is an antipredator mechanism employed by many amphibians. Despite this, chemically defended amphibians have been shown to exhibit a 60% higher contemporary extinction risk than non-defended species, with a three-times higher background extinction rate. Using structural equation models (SEMs), this phylogenetic comparative study aimed to disentangle the indirect mechanisms explaining this seemingly counterintuitive link. Three hypotheses were tested: the marginal habitats hypothesis, the slow life history hypothesis and the energetics hypothesis. Using the IUCN Red List, the second Global Amphibian Assessment, AmphiBIO and the Global Amphibian Biodiversity Project, data on chemical defence, threat status and population trajectory were compiled for 855 amphibian species.Data on habitat use, life history and body size were obtained to serve as proxies for each hypothesis. The SEMs show that the benefits of chemical defence enable species to survive in a higher proportion of marginal habitats than non-defended species. However, the intrinsic instability of these habitats will ultimately put these species at higher risk of extinction.Therefore, the marginal habitats hypothesis provides a strong explanation for the indirect effect of chemical defence on extinction risk. There was weaker support for the slow life history hypothesis and no support for the energetics hypothesis. These results underscore the importance of considering an amphibians’ full ecological context when assessing extinction risk and allocating conservation resources.</abstract><type>E-Thesis</type><journal/><volume/><journalNumber/><paginationStart/><paginationEnd/><publisher/><placeOfPublication>Swansea</placeOfPublication><isbnPrint/><isbnElectronic/><issnPrint/><issnElectronic/><keywords>comparative, phylogenetics, amphibian, extinction, conservation</keywords><publishedDay>4</publishedDay><publishedMonth>3</publishedMonth><publishedYear>2026</publishedYear><publishedDate>2026-03-04</publishedDate><doi/><url/><notes/><college>COLLEGE NANME</college><CollegeCode>COLLEGE CODE</CollegeCode><institution>Swansea University</institution><degreelevel>Master of Research</degreelevel><degreename>MRes</degreename><degreesponsorsfunders>Arbuckle, K., Wilson, R.</degreesponsorsfunders><apcterm/><funders/><projectreference/><lastEdited>2026-04-22T15:24:30.3490648</lastEdited><Created>2026-04-22T15:08:15.9700811</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Biosciences, Geography and Physics - Biosciences</level></path><authors><author><firstname>RACHEL</firstname><surname>HAYNES</surname><order>1</order></author></authors><documents><document><filename>71780__36555__b5a58d4792514c49993ac7f50d34a847.pdf</filename><originalFilename>2026_Haynes_R.final.71780.pdf</originalFilename><uploaded>2026-04-22T15:20:51.1698261</uploaded><type>Output</type><contentLength>1195787</contentLength><contentType>application/pdf</contentType><version>E-Thesis – open access</version><cronfaStatus>true</cronfaStatus><documentNotes>Copyright: the author, Rachel Haynes, 2026.</documentNotes><copyrightCorrect>true</copyrightCorrect><language>eng</language></document></documents><OutputDurs/></rfc1807>
spelling v2 71780 2026-04-22 Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses. 7188d7727a9cffb6caedfa628e06a0f2 RACHEL HAYNES RACHEL HAYNES true false 2026-04-22 Chemical defence is an antipredator mechanism employed by many amphibians. Despite this, chemically defended amphibians have been shown to exhibit a 60% higher contemporary extinction risk than non-defended species, with a three-times higher background extinction rate. Using structural equation models (SEMs), this phylogenetic comparative study aimed to disentangle the indirect mechanisms explaining this seemingly counterintuitive link. Three hypotheses were tested: the marginal habitats hypothesis, the slow life history hypothesis and the energetics hypothesis. Using the IUCN Red List, the second Global Amphibian Assessment, AmphiBIO and the Global Amphibian Biodiversity Project, data on chemical defence, threat status and population trajectory were compiled for 855 amphibian species.Data on habitat use, life history and body size were obtained to serve as proxies for each hypothesis. The SEMs show that the benefits of chemical defence enable species to survive in a higher proportion of marginal habitats than non-defended species. However, the intrinsic instability of these habitats will ultimately put these species at higher risk of extinction.Therefore, the marginal habitats hypothesis provides a strong explanation for the indirect effect of chemical defence on extinction risk. There was weaker support for the slow life history hypothesis and no support for the energetics hypothesis. These results underscore the importance of considering an amphibians’ full ecological context when assessing extinction risk and allocating conservation resources. E-Thesis Swansea comparative, phylogenetics, amphibian, extinction, conservation 4 3 2026 2026-03-04 COLLEGE NANME COLLEGE CODE Swansea University Master of Research MRes Arbuckle, K., Wilson, R. 2026-04-22T15:24:30.3490648 2026-04-22T15:08:15.9700811 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Biosciences RACHEL HAYNES 1 71780__36555__b5a58d4792514c49993ac7f50d34a847.pdf 2026_Haynes_R.final.71780.pdf 2026-04-22T15:20:51.1698261 Output 1195787 application/pdf E-Thesis – open access true Copyright: the author, Rachel Haynes, 2026. true eng
title Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
spellingShingle Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
RACHEL HAYNES
title_short Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
title_full Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
title_fullStr Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
title_full_unstemmed Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
title_sort Why chemically defended amphibians are more likely to face extinction: a phylogenetic comparative test of hypotheses.
author_id_str_mv 7188d7727a9cffb6caedfa628e06a0f2
author_id_fullname_str_mv 7188d7727a9cffb6caedfa628e06a0f2_***_RACHEL HAYNES
author RACHEL HAYNES
author2 RACHEL HAYNES
format E-Thesis
publishDate 2026
institution Swansea University
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Biosciences{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Biosciences
document_store_str 1
active_str 0
description Chemical defence is an antipredator mechanism employed by many amphibians. Despite this, chemically defended amphibians have been shown to exhibit a 60% higher contemporary extinction risk than non-defended species, with a three-times higher background extinction rate. Using structural equation models (SEMs), this phylogenetic comparative study aimed to disentangle the indirect mechanisms explaining this seemingly counterintuitive link. Three hypotheses were tested: the marginal habitats hypothesis, the slow life history hypothesis and the energetics hypothesis. Using the IUCN Red List, the second Global Amphibian Assessment, AmphiBIO and the Global Amphibian Biodiversity Project, data on chemical defence, threat status and population trajectory were compiled for 855 amphibian species.Data on habitat use, life history and body size were obtained to serve as proxies for each hypothesis. The SEMs show that the benefits of chemical defence enable species to survive in a higher proportion of marginal habitats than non-defended species. However, the intrinsic instability of these habitats will ultimately put these species at higher risk of extinction.Therefore, the marginal habitats hypothesis provides a strong explanation for the indirect effect of chemical defence on extinction risk. There was weaker support for the slow life history hypothesis and no support for the energetics hypothesis. These results underscore the importance of considering an amphibians’ full ecological context when assessing extinction risk and allocating conservation resources.
published_date 2026-03-04T15:24:31Z
_version_ 1863181005753417728
score 11.103362

Similar Items