Publication
Ecologically scaled responses of forest-dwelling vertebrates to habitat fragmentation
| Summary: | Road habitat fragmentation has been identified as a major threat for biodiversity conservation. Roads induce a ‘barrier effect’ by representing a physical obstacle or promoting animal-vehicle collisions, disrupting daily and seasonal movements and consequently leading to the depletion and genetic subdivision of animal populations. However, road verges may also provide resources for some species. This thesis aimed to test for an ecologically scaled response of wildlife to road induced habitat fragmentation. The hypothesis under study is that the biological and ecological traits are determinant in predicting the road effects on species persistence. I expected to detect more pronounced negative road-related effects on species with larger body size, lower reproductive rate and greater mobility. To test this hypothesis I analyzed the responses to the road barrier effect by two model species, the wood mouse (Apodemus sylvaticus) and the stone marten (Martes foina), accounting for both potential benefits and negative consequences for species persistence. The major goal was to contribute for a sound scientific basis of road impacts on wildlife and generate advice for improving existing management practices that could benefit the maximum number of species, striving towards a better conciliation of road networks with biological conservation. I estimated the abundance of small mammals inhabiting road verges; quantified the gene flow across roadsides for wood mouse; assessed how roads affect the space use and movement of stone martens living in close vicinity of a highway; and modeled the effectiveness of wildlife-vehicle collision mitigation measures directed to medium-sized carnivores. Consistent evidences were obtained that the species’ responses to roads follow an ecological scale, where small mammals may benefit with road verge presence, although being more vulnerable to genetic isolation; and medium-sized carnivores are more prone to population depletion. I concluded that this latter group should be the focus of road mitigation plans. Highways should be upgraded with exclusionary fence impermeable to carnivores and larger species, in the most part of their length, combined with a sufficient number of open-span structures. The number of open-span passages to be installed or upgraded should consider not only the connectivity at the local scale but also at the landscape perspective in order to guarantee that the accessible habitat area is sufficient to host viable populations. |
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| Main Authors: | Ascensão, Fernando Jorge Portela Martins, 1976- |
| Subject: | Biologia da Conservação Habitat (Ecologia) Teses de doutoramento - 2013 |
| Year: | 2013 |
| Country: | Portugal |
| Document type: | doctoral thesis |
| Access type: | open access |
| Associated institution: | Universidade de Lisboa |
| Language: | English |
| Origin: | Repositório da Universidade de Lisboa |
| Summary: | Road habitat fragmentation has been identified as a major threat for biodiversity conservation. Roads induce a ‘barrier effect’ by representing a physical obstacle or promoting animal-vehicle collisions, disrupting daily and seasonal movements and consequently leading to the depletion and genetic subdivision of animal populations. However, road verges may also provide resources for some species. This thesis aimed to test for an ecologically scaled response of wildlife to road induced habitat fragmentation. The hypothesis under study is that the biological and ecological traits are determinant in predicting the road effects on species persistence. I expected to detect more pronounced negative road-related effects on species with larger body size, lower reproductive rate and greater mobility. To test this hypothesis I analyzed the responses to the road barrier effect by two model species, the wood mouse (Apodemus sylvaticus) and the stone marten (Martes foina), accounting for both potential benefits and negative consequences for species persistence. The major goal was to contribute for a sound scientific basis of road impacts on wildlife and generate advice for improving existing management practices that could benefit the maximum number of species, striving towards a better conciliation of road networks with biological conservation. I estimated the abundance of small mammals inhabiting road verges; quantified the gene flow across roadsides for wood mouse; assessed how roads affect the space use and movement of stone martens living in close vicinity of a highway; and modeled the effectiveness of wildlife-vehicle collision mitigation measures directed to medium-sized carnivores. Consistent evidences were obtained that the species’ responses to roads follow an ecological scale, where small mammals may benefit with road verge presence, although being more vulnerable to genetic isolation; and medium-sized carnivores are more prone to population depletion. I concluded that this latter group should be the focus of road mitigation plans. Highways should be upgraded with exclusionary fence impermeable to carnivores and larger species, in the most part of their length, combined with a sufficient number of open-span structures. The number of open-span passages to be installed or upgraded should consider not only the connectivity at the local scale but also at the landscape perspective in order to guarantee that the accessible habitat area is sufficient to host viable populations. |
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