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Endozoochory and the Australian bluebell: Consumption of Billardiera fusiformis (Labill.) Payer (Pittosporaceae) seeds by three mammal species at Two Peoples Bay Nature Reserve, Western Australia

Authors:
  • Department of Biodiversity, Conservation and Attractions

Abstract

Animals that feed on fruits have the potential to play a key role in vegetation dynamics, assisting in plant succession and maintenance of floral diversity. Seeds may be ingested, passed through the gut and voided to the soil. Through this action seeds are dispersed to new sites (endozoochory). Removal of pulp from fleshy fruits during transport through the gut may also assist in the stimulation of germination. This study compared the germination response of seeds of the Australian bluebell, Billardiera fusiformis, retrieved from faecal pellets of three native mammals (quokka Setonix brachyurus, Gilbert's potoroo Potorous gilbertii and bush rat Rattus fuscipes) with that of freshly collected and aged, but non-ingested seeds, from Two Peoples Bay Nature Reserve, Western Australia. Ingestion of seeds of B. fusiformis by quokkas, Gilbert's potoroos and bush rats increased germination by 58%, 31% and 2% respectively over a control (seeds physically removed from freshly collected fleshy fruit). When placed in dry storage for over a year, however, both ingested and non-ingested seeds displayed significant increases in percent germination.
... Seeds form an important dietary component for many Australian mammals (Quin 1985;Murray et al. 1999;Gibson 2001;Bice & Moseby 2008). Australian seed-eating mammals are recognised as potentially important seed predators (Ballardie & Whelan 1986;Auld & Denham 1999;Mills, Gordon & Letnic 2018), but the extent to which they disperse seeds via endozoochory has received little research attention (Williams et al. 2000;Cochrane, Friend & Hill 2005). Seed predation should not automatically be equated with seed removal as some seeds may be dispersed via caching or endozoochory (Hulme 2002). ...
... penicillata) and musky rat-kangaroos (Hypsiprymnodon moschatus) are known to cache seeds, leading to increased dispersal and germination potential (Dennis 2003;Chapman 2015;Murphy et al. 2015). In addition, research on endozoochory in Australian non-volant mammals also indicates that species such as Gilbert's potoroo (Potorous gilbertii) and common brushtail possums (Trichosurus vulpecula) may pass viable seeds (Cochrane, Friend & Hill 2005;Wotton & McAlpine 2015). However, the role of most non-volant seed or fruit-eating Australian mammals in seed dispersal through endozoochory is unknown. ...
... Research on endozoochory in Australian marsupials is rare, but consumption by Potorous gilbertii and Setonix brachyurus increased germination in Billardiera fusiformis (Cochrane, Friend & Hill 2005). Similarly, we found that consumption by captive quenda increased germination in G. calycinum. ...
Technical Report
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Mammal-seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide. Many Australian mammals consume seeds, but their role in seed dispersal has not been well explored. The translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals, i.e. species that dig to obtain food or create shelter, are commonly the focus of these translocations because they are ecosystem engineers but an understanding of their role in seed dispersal is lacking. We aimed to expand the understanding of endozoochory in Australian digging mammals by determining whether seeds consumed by select species remain viable and able to germinate. Firstly, we investigated the mean retention time and the postconsumption germination capacity of Australian seeds (Acacia acuminata, Dodonaea viscosa and Gastrolobium calycinum) likely to be consumed by quenda (Isoodon fusciventer) and woylies (Bettongia penicillata ogilbyi) while in captivity. Secondly, we collected scat samples from five wild digging mammal species (boodie, B. lesueur; woylie, B. penicillata; bilby, Macrotis lagotis; golden bandicoot, I. auratus and quenda, I. fusciventer) known to consume seeds across nine sites in Western and South Australia. We searched the scat samples for seeds, identified the recovered seeds and then tested their viability and germination capacity. Mean excretion times in captive individuals were 14 hours for quenda and 24 hours for woylies, but some seeds were retained in their digestive passages for up to 39.5 and 55.5 hours, respectively. In captive settings, viable seeds of all plant species were retrieved from both quenda and woylie scats and only G. calycinum seeds ingested by quenda (62%) had a significantly higher germination percentage than control seeds (34%). In wild animals, we found that the abundance of intact seeds in scats was generally low but 70% of the retrieved seeds appeared viable. Five species of seed collected from scats of wild digging mammals germinated under laboratory conditions. Our results show that viable seeds are deposited in the scats of Australian digging mammals, indicating that these species may play a more important role in seed dispersal than previously considered. Digging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal of viable seeds but there is also a risk that non-native species could be dispersed. These costs and benefits should be considered by practitioners when planning reintroductions of digging mammals.
... The passage of the diaspore through the animal's gut can either enhance or inhibit its germination (Willson 1983;Yagihashi et al. 1998;Izhaki and Safriel 1990;Fukui 1996;Traveset et al. 2001). For example, longer retention within the digestive system can cause abrasion to the seed/fruit coat or removal of some parts of the diaspore coating (e.g., pulp), thus enhancing diaspore germination (Beveridge 1964;Barnea et al. 1990;Cochrane et al. 2005). Endozoochory also enables plants to occupy new habitats and maintain genetic diversity (Cochrane et al. 2005;Costa et al. 2014). ...
... For example, longer retention within the digestive system can cause abrasion to the seed/fruit coat or removal of some parts of the diaspore coating (e.g., pulp), thus enhancing diaspore germination (Beveridge 1964;Barnea et al. 1990;Cochrane et al. 2005). Endozoochory also enables plants to occupy new habitats and maintain genetic diversity (Cochrane et al. 2005;Costa et al. 2014). This can be understood as a process of, e.g., colonization of new habitats by annual, perennial plants and developing adaptations to a new environment. ...
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