Effects of land use on butterfly (Lepidoptera: Nymphalidae) abundance and diversity in the tropical coastal regions of Guyana and Australia

Sambhu, Hemchandranauth (2018) Effects of land use on butterfly (Lepidoptera: Nymphalidae) abundance and diversity in the tropical coastal regions of Guyana and Australia. PhD thesis, James Cook University.

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Tropical forests are home to more than 50% of documented terrestrial species and provide vital ecosystem services that improve the quality of life for humankind. However, forested landscapes are being converted at an alarming rate due to expanding human populations and their associated needs and demands. The creation of urban settlements and agricultural plots to house and feed this population generally contributes to the destruction of species and habitats that are essential for the provision of these ecosystem services. There are numerous organisms that provide these ecosystem services and it is unclear how these conversions (agriculture and urban) are affecting one of the most abundant and diverse groups of organisms, insects. Given that insects make up more than half of all documented terrestrial animals, it is impossible to investigate all insects, so I chose a representative group, butterflies, to investigate the conservation impacts of these land management practices. In addition to their sensitivity to changes in habitat quality and importance for the functioning of many ecosystems, butterflies have relatively quick generational turnover, are well distributed, and are easy to sample and identify.

In this doctoral thesis, I investigated butterfly communities within agricultural (sugarcane) fields, urban settlements and forested areas in coastal sections of Guyana, South America, and the Wet Tropics Bioregion of Queensland, Australia. Specifically, I compared the abundance, richness, evenness, and diversity of butterflies within the above land management practices to evaluate the conservation potential of the modified landscapes. To conduct the respective ecological surveys in both countries, I established three 1 km transects in each of the land management practices. The transects were randomly placed and separated by at least 1–1.5 km from each other. Fruit-baited traps were placed along the transects, starting at the 0 km marker, separated by 100 m, and ending at the 1 km marker, for a total of 11 traps per transect. The traps were monitored monthly for one year to capture any seasonal trends that may exist. During the surveys in Guyana, butterflies were collected, identified and deposited in the national specimen repository (at the Centre for the Study of Biological Diversity) so as to add to the documentation of species present. In Australia, species were caught, identified and released at the trap sites (this catch-and-release method was used since Australia's butterfly diversity is well documented). I used the data from my Guyana trapping, along with comprehensive evaluation of published records over the last 153 years to develop a country checklist of butterfly species present in Guyana. This greatly improved local knowledge, which was based on the most recent checklist published in 1939. To enhance the ecological surveys and to assess people's willingness to contribute to butterfly conservation, I also conducted social surveys via semi-structured interviews with urban residents who lived on or adjacent to the property containing one of my butterfly traps.

As hypothesised, distinct groups of butterflies occupied the respective land management practices, with forests in both Guyana and Australia supporting the highest butterfly abundances. Species richness and Simpson's biodiversity index were also highest in forests in Guyana. In contrast, sugarcane and urban areas had the highest evenness in Guyana and Australia, respectively, which demonstrates the potential for conservation at local scales in human-modified landscapes. Furthermore, non-metric multidimensional scaling analysis demonstrated that each landscape in Guyana supported a distinct butterfly community, suggesting that butterfly conservation in human-modified landscapes may target species rarely found in forest habitats.

Unexpectedly, in Australia sugarcane farms supported the highest species richness of the three land uses, while species richness was lowest in the forests. This high species richness compared to Guyana farms may be due to the specific management practices used in Australian sugarcane production systems, including green harvesting and fallow schedules, mowing regime, high nutrient input and maintenance of riparian vegetation. There is growing appreciation for beta diversity, which describes the variation in community composition across space or time, and recent evidence suggests it may be highly influenced by human activity. Therefore, I compared this type of diversity (as measured by Whittaker's and Jost's metrics) among the three land uses in Australia. Whittaker's diversity was highest in forests whereas Jost's was highest in urban areas. I attribute this to greater variation in plant composition across these two habitat types relative to sugarcane farms and emphasise the importance of conserving natural areas within forests as well as urban green spaces.

The social surveys suggested that residents that were interested in learning more about butterflies, lived in areas with relatively scarce butterfly populations, and identified the benefits of butterflies were more willing to contribute to butterfly conservation. These trends were constant across both countries. Several conservation options were identified, with the majority of residents expressing a willingness to contribute in at least one way to butterfly conservation. These results suggest that to improve biological conservation, it is crucial to design activities or programs that target local enthusiasm, describe the benefits of focal species, and identify areas of local scarcity. Doing this can allow for the active involvement of residents and ensure the continuity of such initiatives which could, in turn, allow for the conservation of butterflies in human-modified spaces.

Item ID: 55977
Item Type: Thesis (PhD)
Keywords: Australia, butterfly conservation, butterfly diversity, checklist, community conservation, Guyana, insects, land management practices, land use, landscape approaches to biodiversity conservation, neotropical, south America, sugarcane cultivation, sugarcane plantation, tropical butterflies, tropical, urban green spaces, urban, Wet Tropics, willingness to contribute to conservation
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Copyright Information: Copyright © 2018 Hemchandranauth Sambhu
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 3: Sambhu, Hemchandranauth, Northfield, Tobin, Nankishore, Alliea, Ansari, Abdullah, and Turton, Steve (2017) Tropical rainforest and human-modified landscapes support unique butterfly communities that differ in abundance and diversity. Environmental Entomology, 46 (6). pp. 1225-1234.

Date Deposited: 30 Oct 2018 23:49
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060208 Terrestrial Ecology @ 25%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 75%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 40%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960804 Farmland, Arable Cropland and Permanent Cropland Flora, Fauna and Biodiversity @ 60%
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