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Modelling the relationship between native amphibian species and the non-native marsh frog

Mackay, Aidan (2018) Modelling the relationship between native amphibian species and the non-native marsh frog. Doctor of Philosophy (PhD) thesis, University of Kent,. (KAR id:74092)

Language: English

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Due to increasing globalization the rate of non-native introductions has rapidly increased. This is likely to continue as climate change leads to increases in range of some species. In some cases, the effect of non-native species on biodiversity has been very severe. However, due to the complex nature of ecosystems it is sometimes difficult to determine if a non-native species is having a negative impact. This can be the case if interactions with other species are involved or native species are declining due to other threats such as habitat loss. This thesis investigates whether the marsh frog (Pelophylax ridibundus), a non-native species introduced to the UK in 1935, is affecting the distribution and abundance of the common frog (Rana temporaria) in Kent, south east England.


Results from an eDNA metabarcoding analysis of water samples taken in 2014 from ponds in central Kent were obtained. The data provided the presence/absences of common frogs, great crested newts, and marsh frogs. Logistic regression showed that common frogs were not negatively associated with great crested newt presence. However, there was a much higher proportion of ponds with great crested newts compared to ponds with common frogs. In contrast, the proportion of ponds occupied by marsh frogs was very low. This supported the hypothesis that marsh frogs are unlikely to be the cause of lower common frog presence in the area. Common frog spawn surveys were conducted in 2017 on a subset of the same ponds analysed by the DNA metabarcoding in 2014. These showed a change in pond occupancy between 2014 and 2017. This could be due to natural changes in occupancy or metabarcoding could be detecting non-breeding common frog ponds and missing some breeding ponds.

Both landscape and local level studies have indicated that common frog presence is lower in an area of high pond density in Kent. This is unlikely to be caused by the presence of marsh frogs because of a difference in pond preference between common frogs and marsh frogs reducing the risk of predation or competition. There was also a relatively low presence of marsh frogs in areas that were showing lower proportions of common frogs compared to great crested newts. The high proportion of ponds occupied by great crested newts is more likely to be the reason for lower common frog presence. Therefore, more active measures to control the spread of marsh frogs is not required when considering conservation measures to protect common frogs.

Item Type: Thesis (Doctor of Philosophy (PhD))
Thesis advisor: Griffiths, Richard
Thesis advisor: Davies, Zoe
Uncontrolled keywords: Amphibian, eDNA, frog, invasive, Kent, non-native, occupancy, Pelophylax, Rana temporaria, species distribution modelling, Triturus cristatus
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation
Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation > DICE (Durrell Institute of Conservation and Ecology)
SWORD Depositor: System Moodle
Depositing User: System Moodle
Date Deposited: 24 May 2019 09:20 UTC
Last Modified: 16 Feb 2021 14:04 UTC
Resource URI: (The current URI for this page, for reference purposes)
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